Podcasts about Daphnia

Die Themen in den Wissensnachrichten: +++ Auch als sicher geltende Weichmacher können sich negativ auf Fische auswirken +++ Nicht zu eng, sondern zu verdreht - deshalb kommen Menschen-Babys so schwer durch den Geburtskanal +++ Wie Kokumi Käse richtig herzhaft macht +++**********Weiterführende Quellen zu dieser Folge:Exposure to phthalate plasticizer compromises normal brain function in an adult vertebrateGradual exacerbation of obstetric constraints during hominoid evolution implied by re-evaluation of cephalopelvic fit in chimpanzeesTowards prediction of maturation-dependent kokumi taste in cheese by comprehensive high throughput quantitation of glutamyl dipeptides, in: Food Chemistry 15.01.2025Combined toxicity of perfluoroalkyl substances and microplastics on the sentinel species Daphnia magna: Implications for freshwater ecosystems, In: Environmental Pollution 15.12.2024Health impact of urban green spaces: a systematic review of heat-related morbidity and mortalityAlle Quellen findet ihr hier.**********Ihr könnt uns auch auf diesen Kanälen folgen: Tiktok, Tiktok und Instagram.

¿Cuáles son la violencias que enfrentan las personas gordas en el día a día que han sido normalizadas? Daphnia, creadora de La Cuerpa, se une al espacio para ayudarnos a comprender la importancia de erradicar la gordofobia, empezando desde las pequeñas acciones. Sigue a La Cuerpa https://instagram.com/_lacuerpa?igshid=NTc4MTIwNjQ2YQ== --- Support this podcast: https://podcasters.spotify.com/pod/show/espacio-sin-censura/support

June 1 marks the start of meteorological summer and that sunny and warm weather makes you want to go into the water. You're also - hopefully - putting on sunscreen in order to reduce the risk of skin cancer, but in the last few years there's been some reason to question whether sunscreen is as safe for our waterways even while it protects you from UV light. Should everyone still be free to wear sunscreen? In fall 2020 there was a study out of the University of Alberta that suggested that the active ingredients found in sunscreen have detrimental effects on freshwater ecosystems. The researchers exposed water fleas, Daphnia magna to be more precise, to three common ingredients in sunscreen and the results showed that exposure to ultraviolet filters (UVFs) over a 48-hour period prevented the fleas from navigating through their environment. This was kind of a big deal. Other studies showed that ultraviolet filters were having an effect on very sensitive sea water life forms like coral, but these are water fleas, one of the most common creatures found in almost every freshwater everywhere; if they're feeling the effects of sunscreen ingredients leaching from people's skin, then what is the total environmental impact from UVFs? That same team has been working on answering that question, and they recently released new findings. The lead author of both studies, Aaron Boyd, is the guest on this week's podcast. Boyd's a grad student and researcher in the Department of Biology at the University of Alberta, and he will tell you about the ingredients in sunscreen, the difference between studying the effects of sunscreen in salt water versus freshwater, and why Daphnia magna are the chosen test subjects for these experiments. Also, where will the research go next and is it okay to wear sunscreen without killing a lake? So let's talk about sunscreen on this week's edition of the Guelph Politicast! This is a link to an article on the University of Alberta for the original 2020 study and this link will take you to an article about the latest research. For the scientifically literate, you can read the original research paper published in the March issue of the Journal of Hazardous Materials. TL;DR - It's definitely okay to wear sunscreen while you're out there having summer fun. Don't leave home without it. The host for the Guelph Politicast is Podbean. Find more episodes of the Politicast here, or download them on your favourite podcast app at Apple, Stitcher, Google, TuneIn and Spotify . Also, when you subscribe to the Guelph Politicast channel and you will also get an episode of Open Sources Guelph every Monday, and an episode of End Credits every Friday.

Romi talks about her research with Daphnia, invasive snails and environmental DNA. She also shares her journey as a chocolate educator! Enjoy!

A new research perspective was published in Aging (listed as "Aging (Albany NY)" by MEDLINE/PubMed and "Aging-US" by Web of Science) Volume 14, Issue 20, entitled, “Rapamycin treatment early in life reprograms aging: hyperfunction theory and clinical practice.” On October 24, 2022, Mikhail Blagosklonny, M.D., Ph.D. from Roswell Park Comprehensive Cancer Center published a riveting research perspective discussing the clinical application of early-life rapamycin treatment and its ability to reprogram aging, based on the hyperfunction theory. “Making provocative headlines, three outstanding publications demonstrated that early-life treatment with rapamycin, including treatments during developmental growth, extends lifespan in animals, confirming predictions of hyperfunction theory, which views aging as a quasi-program (an unintended continuation of developmental growth) driven in part by mTOR. Despite their high theoretical importance, clinical applications of two of these studies in mice, Drosophila and Daphnia cannot be implemented in humans because that would require growth retardation started at birth. A third study demonstrated that a transient (around 20% of total lifespan in Drosophila) treatment with rapamycin early in Drosophila adult life is as effective as lifelong treatment, whereas a late-life treatment is not effective. However, previous studies in mice demonstrated that a transient late-life treatment is highly effective. Based on hyperfunction theory, this article attempts to reconcile conflicting results and suggests the optimal treatment strategy to extend human lifespan.” DOI: https://doi.org/10.18632/aging.204354 Corresponding Author: Mikhail V. Blagosklonny - Corresponding Email: Blagosklonny@oncotarget.com Video - https://www.youtube.com/watch?v=Br7iD48fKF4 Keywords: senescence, gerostatics, geroscience, sirolimus, healthspan Sign up for free Altmetric alerts about this article: https://aging.altmetric.com/details/email_updates?id=10.18632%2Faging.204354 About Aging-US: Launched in 2009, Aging (Aging-US) publishes papers of general interest and biological significance in all fields of aging research and age-related diseases, including cancer—and now, with a special focus on COVID-19 vulnerability as an age-dependent syndrome. Topics in Aging go beyond traditional gerontology, including, but not limited to, cellular and molecular biology, human age-related diseases, pathology in model organisms, signal transduction pathways (e.g., p53, sirtuins, and PI-3K/AKT/mTOR, among others), and approaches to modulating these signaling pathways. Please visit our website at www.Aging-US.com​​ and connect with us: SoundCloud – https://soundcloud.com/Aging-Us Facebook – https://www.facebook.com/AgingUS/ Twitter – https://twitter.com/AgingJrnl Instagram – https://www.instagram.com/agingjrnl/ YouTube – https://www.youtube.com/agingus​ LinkedIn – https://www.linkedin.com/company/aging/ Reddit – https://www.reddit.com/user/AgingUS Pinterest – https://www.pinterest.com/AgingUS/ For media inquiries, please contact media@impactjournals.com Aging (Aging-US) Journal Office 6666 E. Quaker Str., Suite 1B Orchard Park, NY 14127 Phone: 1-800-922-0957, option 1

Jazz Ahead 156 - Playlist: 1. Aka tombo, Akira Sakata, Aka tombo, Daphnia, 2020..2. Nobody Else But Me (Jerome Kern), Alessandro Lanzoni, Mirage, Fresh Sound, 2021..3. A la Bougie, Alban Darche, Le Gros Cube #2, Yolk Records, 2021..4. Que te Pedi, Miguel Zenon/Luis Perdomo, El Arte del Bolero, Miel Music, 2021..5. Não Negue Ternura, Zé Manoel, Do Meu Coração Nu, Joia Moderna, 2020..6. Caroline no, Sam Gendel e Sam Wilkes, Saxofone & Bass Guitar More Songs, Leaving Records, 2021..7. Fallen Lowers, James Brandon Lewis Red Lily Quintet, Jasup Wagon,TAO..8. Valse des Papillons de Nuit, Florian Weiss Woodoism, Alternate Reality, NWog Records, 2021..9. Bumpers Cars, Alfa Mist, Two For Mistake, Anti-Records, 2021

Jazz Ahead 156 - Playlist: 1. Aka tombo, Akira Sakata, Aka tombo, Daphnia, 2020..2. Nobody Else But Me (Jerome Kern), Alessandro Lanzoni, Mirage, Fresh Sound, 2021..3. A la Bougie, Alban Darche, Le Gros Cube #2, Yolk Records, 2021..4. Que te Pedi, Miguel Zenon/Luis Perdomo, El Arte del Bolero, Miel Music, 2021..5. Não Negue Ternura, Zé Manoel, Do Meu Coração Nu, Joia Moderna, 2020..6. Caroline no, Sam Gendel e Sam Wilkes, Saxofone & Bass Guitar More Songs, Leaving Records, 2021..7. Fallen Lowers, James Brandon Lewis Red Lily Quintet, Jasup Wagon,TAO..8. Valse des Papillons de Nuit, Florian Weiss Woodoism, Alternate Reality, NWog Records, 2021..9. Bumpers Cars, Alfa Mist, Two For Mistake, Anti-Records, 2021

What on earth is a 'blob' and why should you fish them?Before we go TOO far, you can still grab the remaining two lessons from Phil Rowley and I's 'Stillwater Ice-Off Tactics' free mini-course HERE. You will learn ice-off fishing tactics, ice-off equipment and our TOP 20 patterns for fishing the pre-turnover window. Moving on...What are blob flies and why should you fish them?Originated in the UK, blob patterns are incredibly effective both as an attractor and as an imitative pattern when fish are keyed in on micro-organisms like Daphnia (Zooplankton). There was a time when we would curse the presence of Daphnia, but thanks to blob flies we are able to routinely catch fish when fish are keyed in on them. Find it all and more in today's episode below... enjoy!

Jazz Ahead 111 - Playlist: 1. Paniniwala (Belief), Susie Ibarra, Talking Gong, New Focus Recordings, 2021..2. Dancesteps, Susie Ibarra, Talking Gong, New Focus Recordings, 2021..3. Sunbird, Susie Ibarra, Talking Gong, New Focus Recordings, 2021..4. My dear son, Jacopo Ferrazza, Wood Tales, Autoproduzione, 2021..5. Waiting, Jacopo Ferrazza, Wood Tales, Autoproduzione, 2021..6. Hope, Jacopo Ferrazza, Wood Tales, Autoproduzione, 2021..7. Memories from a farmer, Jacopo Ferrazza, Wood Tales, Autoproduzione, 2021..8. The Message Continues (Mark de Clive-Lowe Remix), Nubya Garcia, The Message Continues (Mark de Clive-Lowe Remix), Concord Jazz, 2021..9. Aka tombo, Akira Sakata, Aka tombo, Daphnia, 2020..10. Tsonmbon Tuuraitai Kheren, Akira Sakata, Aka tombo, Daphnia, 2020..11. Going home, Akira Sakata (Antoni Dvorek), Aka tombo, Daphnia, 2020

Jazz Ahead 111 - Playlist: 1. Paniniwala (Belief), Susie Ibarra, Talking Gong, New Focus Recordings, 2021..2. Dancesteps, Susie Ibarra, Talking Gong, New Focus Recordings, 2021..3. Sunbird, Susie Ibarra, Talking Gong, New Focus Recordings, 2021..4. My dear son, Jacopo Ferrazza, Wood Tales, Autoproduzione, 2021..5. Waiting, Jacopo Ferrazza, Wood Tales, Autoproduzione, 2021..6. Hope, Jacopo Ferrazza, Wood Tales, Autoproduzione, 2021..7. Memories from a farmer, Jacopo Ferrazza, Wood Tales, Autoproduzione, 2021..8. The Message Continues (Mark de Clive-Lowe Remix), Nubya Garcia, The Message Continues (Mark de Clive-Lowe Remix), Concord Jazz, 2021..9. Aka tombo, Akira Sakata, Aka tombo, Daphnia, 2020..10. Tsonmbon Tuuraitai Kheren, Akira Sakata, Aka tombo, Daphnia, 2020..11. Going home, Akira Sakata (Antoni Dvorek), Aka tombo, Daphnia, 2020

Catherine Searle, Assistant Professor in the Department of Biological Sciences at Purdue University, researches disease ecology. Searle discusses native and invasive species, pathogens, and two specific systems that her lab studies: amphibians and daphnia. 

Learn a bit about genomic sequencing and annotation of Daphnia magna (water fleas) with Nick as he talks about finding his thesis topic and advisor, and how he switched directions after the pandemic shutdown interrupted his lab work.

En el episodio de hoy hablo de unos cuantos indicios que observamos, tanto en la naturaleza como experimentalmente, de las hipótesis sobre la existencia del sexo de las que hablamos la semana pasada. Además, hablo de la hipótesis de la Reina Roja, cuyo nombre me parece bastante mal. Una pulga de agua del género Daphnia: https://upload.wikimedia.org/wikipedia/commons/b/b3/Rodz%C4%85ca_dafnia.jpgUn bonito rotífero: https://upload.wikimedia.org/wikipedia/commons/e/ec/Mikrofoto.de-Raedertier-14.jpgCatalina la Gusana Elegante, también conocida como Caenorhabditis elegans:https://upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Adult_Caenorhabditis_elegans.jpg/1920px-Adult_Caenorhabditis_elegans.jpg La publicación de la que hablo hoy: https://science.sciencemag.org/content/333/6039/216.full

Was verraten Wasserflöhe darüber, wie gut es einem Gewässer geht? Eine Wissenschaftlerin aus Indonesien erforscht die kleinen Lebewesen im Bodensee und beobachtet, wie sie sich an ihre Umwelt anpassen - und damit auch an den Einfluss der Menschen.  

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.27.222653v1?rss=1 Authors: Mora-Castro, R., Alfaro-Cordoba, M., Hernandez-Jimenez, M., Fernandez Otarola, M., Mendez-Rivera, M., Ramirez-Morales, D., Rodriguez-Rodriguez, C. E., Duran-Rodriguez, A., Hanson, P. E. Abstract: Many small parasitoid wasps have a black-orange-black (BOB) color pattern, which is usually present in both sexes. A likely function of this widespread pattern is aposematic (warning) coloration, but this has never been investigated. To test this hypothesis, we presented spider predators (Lyssomanes jemineus), both field-captured and lab-reared individuals, to a species with the BOB pattern and a congeneric all-black species in each of four scelionid genera (Baryconus, Chromoteleia, Macroteleia and Scelio). Each spider/wasp trial was filmed for 40 minutes under controlled conditions and three behavioral responses (detect, attack, avoid) were recorded in each of 136 trials, never using the same predator and prey more than once. In order to better understand the results obtained, two additional studies were performed. First, the reflection spectrum of the cuticle of the wasp and a theoretical visual sensibility model of the spider were used to calculate a parameter we called "absorption contrast" that allowed us to compare the perception contrast between black and orange in each wasp genus as viewed by the spider. Second, acute toxicity trials with the water flea, Daphnia magna, were performed to determine toxicity differences between BOB and non-BOB wasps. By combining the results from the three types of experiments, together with a statistical analysis, we confirmed that BOB color pattern plays an aposematic role. Copy rights belong to original authors. Visit the link for more info

After extracting a feckless but well-meaning youth from a 3-way gang fight, the newly-christened Twilight Patrol attend to personal matters before becoming tangled with the supernatural snuff trade. Dr. Ravenglass comes face to face with an aristocratic foe, Solomon basks in some well-earned tabloid applause, Daphnia attends to the comfort of her girls, Basil helps to enact reform in Doskvol's streets and Victoria swears to stay her blade, if only for at least one job. The Gauntlet, and everything related, can be found at http://gauntlet-rpg.com/ Blades in the Dark, by John Harper, can be found at https://bladesinthedark.com/ Vigilantes, by Sean Nittner, can be found at https://www.dropbox.com/sh/3tt8i4czfnlfsgo/AACzQRVMZaw6kJV17Rd9AEm-a?dl=0 The Lark Brigade, an RPG index by Robert Angus, can be found at https://twitter.com/larkbrigade

Desde este miércoles, 12 de febrero, y hasta el jueves 20, Bilbao BBK Talent Sarriko acoge la iniciativa “Estación de Microscopía Ciudadana”. Además de jóvenes en edad escolar, el público general podrán sumarse a los diversos talleres y actividades que incluyen la fabricación de microscopios láser y microscopios para smartphones, fotografía microscópica, preparación de muestras de célula vegetal (cebolla) y animal (epitelio bucal) o la posibilidad de comprobar el efecto de algunas sustancias sobre la frecuencia cardíaca en Daphnia (pulga de agua).

Desde este miércoles, 12 de febrero, y hasta el jueves 20, Bilbao BBK Talent Sarriko acoge la iniciativa “Estación de Microscopía Ciudadana”. Además de jóvenes en edad escolar, el público general podrán sumarse a los diversos talleres y actividades que incluyen la fabricación de microscopios láser y microscopios para smartphones, fotografía microscópica, preparación de muestras de célula vegetal (cebolla) y animal (epitelio bucal) o la posibilidad de comprobar el efecto de algunas sustancias sobre la frecuencia cardíaca en Daphnia (pulga de agua).

Join us for a tour of the galaxy to discover how research here at the University of Birmingham relates to the Star Wars universe and discover why the Force is strong with our academics . . . Dr Luisa Orsini PhD, Senior Lecturer in Biosystems and Climate Change and PhD Students Muhammad Abdullahi and Niamh Eastwood discuss how, like Han Solo, water flea Daphnia can survive being frozen and also help tell us important information about biodiversity. www.birmingham.ac.uk /the-rise-of-research

For our one year anniversary episode, we celebrate with drinks, discuss model organisms (fun, weird and without a spine), and talk about how we would act on the bachelor franchise. With model organisms, we discuss Daphnia's heartbeat, Loligo pealei's giant axon, and Aequorea victoria's glowing green protein. Then we move on to yeast, where the Nobel prizes are a plenty. We discuss discoveries of cell cycle regulators and autophagy. Finally, we talk about Aplysia californica (a sea slug). We discuss a reflex that taught people about the physiology and molecular basis underlying short term memory in the brain.HAPPY ONE YEAR ANNIVERSARY LISTENERS!

Welcome to Episode 26 of Slightly Evolved! This week our guest is Dr Luisa Orsini, lecturer at the University of Birmingham, UK. Luisa talks to us about her work on Daphnia, a fascinating system where you able to "resurrect" dormant individuals that are sometimes 100s of years old. We talk about how you can use the system to test for recent adaptation, and discuss the importance of taking a multi -omics approach for studying evolution. As always you can contact us via email (slightlyevolvedpod@gmail.com), Twitter (twitter.com/slightlyevolpod) or join on our Facebook group (www.facebook.com/groups/664596143711550/). Remember you can also subscribe on iTunes (itunes.apple.com/us/podcast/sligh…d1197890502?mt=2), and we would really appreciate it if you could leave a rating/comment there! You can read more about Luisa's research here (https://lorsini5.wixsite.com/luisaorsini) and follow her on Twitter (twitter.com/luorgen).

In this podcast I'll be exploring Epigenetics: I’ll explain the difference between genetics and epigenetics I’ll talk about how your environment impacts the activation and expression of your genes Finally, I’ll give a few holistic tips on how to activate and express health-boosting and life-affirming genes CLICK HERE TO LEARN WHAT ARE THE BEST HEALING FOODS FOR YOUR GUT The study of how genes control life is called genetics. Genetic looks at genetic differences, mutations, heredity, and of course of lot of today’s genetic research looks into genetic diseases. Genetics and the study of genes is a very important and valid science, but the belief behind genetics is outdated old-school thinking and that belief is that genes control life. This belief came from the hypothesis that there is a gene for every protein. The more complex an organism, the more cells and proteins there are, the more genes there would be. That was the idea. This idea turns out to be incorrect. The Human Genome Project, which started back in the late 1980s, was setup to uncover the entire sequence of genetic information found in human DNA with the side benefit of discovering the genetics of every disease and how to prevent and cure them. The human body has about 100,000 protein molecules, so science expected to find about 100,000 genes. Fast forward 15 years and guess how many genes they found at the end of the project in 2001 – only 35,000. Fast forward another 15 years to today and after further study and research that initial number has shrunk to about 20,000 genes. There was a lot of hype in the science community about the Human Genome Project, but funnily enough when the scientist’s expectations proved to be wrong, very wrong, there was no big deal made about the unexpected results. This massively incorrect assumption about a gene coding for a protein fell off the radar. Science tends to work this way unfortunately where the good news is reported and the bad news is swept under the rug. So now we know that there are only 20,000 genes in the human genome and these 20,000 genes code for over 100,000 proteins and alongside this fact is the news that the largest number of genes found in a single animal is 31,000 genes and that animal is the near-microscopic water flea Daphnia. Imagine that, a near-microscopic simple organism with hardly any cells and proteins compared to the 35 trillion cells and 100,000 proteins in your human body and yet this tiny little life form has 11,000 more genes than humans do. What this shows you is that genes do not control life. No matter the complexity of an organism the number of genes present will vary a lot. It’s not the genes that say how life will be from birth to death. It’s the life that is lived that will determine which genes get expressed or activated or switched on and which genes don’t. Say goodbye to the old belief that your genes control your life and hello to the new way of thinking – that your life controls your genes. This new way of thinking is actually 50 years old and is called the science of epigenetics, which looks at how environmental signals affect gene expression. Epigenetics means above the genes and studies how your environment affects the biochemical and physiological processes that are happening outside of your genetic code, but have a direct effect on which sequence of your genetic code to read and which genes to express or not. Remember the old way of thinking says that genes are in control like a foreman of a construction site. Genes dictate what gets built and so decide the health or disease of your cells. The new way of thinking, epigenetics, says genes are actually just simple blueprints. They don’t do anything at all. It’s all the proteins and enzymes and cellular signals and every other process that’s going on in and outside of your cell that dictate which blueprints to read (gene expressio...

Organisms respond to changes in their environment affecting their physiological or ecological optimum by reactions called stress responses. These stress responses may enable the organism to survive by counteracting the consequences of the environ- mental change, the stressor, and usually consist of plastic alterations of traits related to physiology, behaviour, or morphology. In the ecological model species Daphnia, the waterflea, stressors like predators or parasites are known to have an important role in adaptive evolution and have been therefore studied in great detail. However, although various aspects of stress responses in Daphnia have been analysed, molecu- lar mechanisms underlying these traits are not well understood so far. For studying unknown molecular mechanisms, untargeted ‘omics’ approaches are especially suit- able, as they may identify undescribed key players and processes. Recently, ‘omics’ approaches became available for Daphnia. Daphnia is a cosmo- politan distributed fresh water crustacean and has been in research focus for a long time because of its central role in the limnic food web. Furthermore, the responses of this organism to a variety of stressors have been intensively studied e.g. to hypoxic conditions, temperature changes, ecotoxicological relevant substances, parasites or predation. Of these environmental factors, especially predation and interactions with parasites have gained much attention, as both are known to have great influence on the structure of Daphnia populations. In the work presented in this thesis, I characterised the stress responses of Daphnia using proteomic approaches. Proteomics is particularly well suited to analyse bio- logical systems, as proteins are the main effector of nearly all biological processes. However, performing Daphnia proteomics is a challenging task due to high proteolytic activity in the samples, which most probably originate from proteases located in the gut of Daphnia, and are not inhibited by proteomics standard sample pre- paration protocols. Therefore, before performing successful proteomic approaches, I had to optimise the sample preparation step to inhibit proteolytic activity in Daph- nia samples. After succeeding with this task, I was able to analyse stress responses of Daphnia to well-studied stressors like predation and parasites. Furthermore, I stud- ied their response to microgravity exposure, a stressor not well analysed in Daphnia so far. My work on proteins involved in predator-induced phenotypic plasticity is de- scribed in chapter 2 and 3. Daphnia is a textbook example for this phenomenon and is known to show a multitude of inducible defences. For my analysis, I used the system of Daphnia magna and its predator Triops cancriformis. D. magna is known to change its morphology and to increase the stability of its carapace when exposed to the pred- ator, which has been shown to serve as an efficient protection against T. cancriformis predation. In chapter 2, I used a proteomic approach to study predator-induced traits in late-stage D. magna embryos. D. magna neonates are known to be defended against Triops immediately after the release from the brood pouch, if mothers were exposed to the predator. Therefore, the formation of the defensive traits most probably oc- curs during embryonic development. Furthermore, embryos should have reduced protease abundances, as they do not feed inside the brood pouch until release. To study proteins differing in abundance between D. magna exposed to the predator and a control group, I applied a proteomic 2D-DIGE approach, which is a gel based method and therefore enables visual monitoring of protein sample quality. I found differences in traits directly associated with known defences like cuticle proteins and chitin-modifying enzymes most probably involved in carapace stability. In addition, enzymes of the energy metabolism and the yolk protein vitellogenin indicated alterations in energy demand. In chapter 3, I present a subsequent study supporting these results. Here, I analysed responses of adult D. magna to Triops predation at the proteome level using an optimised sample preparation procedure, which was able to generate adult protein samples thereby inhibiting proteolysis. Furthermore, I established a different proteomic approach using a mass-spectrometry based label- free quantification, in which I integrated additional genotypes of D. magna to create a more comprehensive analysis. With this approach, I was able to confirm the results of the embryo study, as similar biological processes indicated by cuticle proteins and vi- tellogenins were involved. Furthermore, additional calcium-binding cuticle proteins and chitin-modifying enzymes and proteins involved in other processes, e.g. protein biosynthesis, could be assigned. Interestingly, I also found evidence for proteins in- volved in a general or a genotype dependent response, with one genotype, which is known to share its habitat with Triops, showing the most distinct responses. Genotype dependent changes in the proteome were also detectable in the study which I present in chapter 4. Here, I analysed molecular mechanisms underlying host-parasite interactions using the well characterised system of D. magna and the bacterial endoparasite Pasteuria ramosa. P. ramosa is known to castrate and kill their host and the infection success is known to depend strongly on the host’s and the para- site’s genotype. I applied a similar proteomic approach as in chapter 3 using label- free quantification, but contrastingly, I did not use whole animal samples but only the freshly shed cuticle. It has been shown, that the genotypic specificity of P. ramosa infection is related to the parasite’s successful attachment to the cuticle of the host and is therefore most probably caused by differences in cuticle composition. Hence, I analysed exuvia proteomes of two different genotypes known to be either suscept- ible to P. ramosa or not. Furthermore, I compared exuvia proteomes of susceptible Daphnia exposed to P. ramosa to a control group for finding proteins involved in the infection process and in the stress response of the host. The proteomes of the different genotypes showed indeed very interesting abundance alterations, connected either to cuticle proteins or matrix metalloproteinases (MMPs). Additionally, the cuticle pro- teins more abundant in the susceptible genotype showed a remarkable increase in predicted glycosylation sites, supporting the hypothesis that P. ramosa attaches to the host’s cuticle by using surface collagen-like proteins to bind to glycosylated cuticle proteins. Most interestingly, in all replicates of the susceptible genotype exposed to P. ramosa, such a collagen-like protein was found in high abundances. Another group of proteins found in higher abundance in the non-susceptible genotype, the MMPs, are also connected to this topic, as they may have collagenolytic characteristics and therefore could interfere with parasite infection. Furthermore, the data indicate that parasite infection may lead to retarded moulting in Daphnia, as moulting is known to reduce the infection success. Contrastingly to the work presented so far, the study described in chapter 5 invest- igated the protein response of Daphnia to a stressor not well studied on other levels, namely microgravity. As gravity is the only environmental parameter which has not changed since life on earth began, organisms usually do not encounter alterations of gravity on earth and cannot adapt to this kind of change. Daphnia has been part of one mission to space, however, responses of the animals to microgravity are not well described so far. In addition, as Daphnia are an interesting candidate organisms for aquatic modules of biological life support systems (BLSS), more information on their response to microgravity is necessary. For this reason, proteomics is an interesting ap- proach, as biological processes not detectable at the morphological or physiological level may become apparent. Therefore, a ground-based method, a 2D-clinostat, was used to simulate microgravity, as studies under real microgravity conditions in space need high technical complexity and financial investment. Subsequently, a proteomic 2D-DIGE approach was applied to compare adult Daphnia exposed to microgravity to a control group. Daphnia showed a strong response to microgravity with abundance alterations in proteins related to the cytoskeleton, protein folding and energy meta- bolism. Most interestingly, this response is very similar to the reactions of a broad range of other organisms to microgravity exposure, indicating that the response to altered gravity conditions in Daphnia follows a general concept. Altogether, the work of my thesis showed a variety of examples of how a proteomic approach may increase the knowledge on stress responses in an organisms not well- established in proteomics. I described both, the analysis of molecular mechanisms underlying well-known traits and the detection of proteins involved in a response not well characterised. Furthermore, I gave examples for highly genotype dependent and also more general stress responses. Therefore, this thesis improves our understanding of the interactions between genotype, phenotype and environment and, moreover, offers interesting starting points for studying the molecular mechanisms underlying stress responses of Daphnia in more detail.

Wed, 20 May 2015 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/18319/ https://edoc.ub.uni-muenchen.de/18319/1/Rabus_Max.pdf Rabus, Max ddc:570, ddc:500, Fakultät für Biologie

Tue, 18 Mar 2014 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/18558/ https://edoc.ub.uni-muenchen.de/18558/1/Engel_Katharina.pdf Engel, Katharina

In episode 31 we talk to Stu Auld about host-parasite coevolution in Daphnia.  If you like tales about crustaceans with parasites and gender issues, then this is the podcast for you!  If not, it's probably still the podcast for you, because Stu is awesome and funny.

HEARTFEELS RADIOSHOW # 23 on Megaport.FMДвадцать третий выпуск  "HEARTFEELS RADIOSHOW". Гостевой микс для выпуска подготовил музыкант с именем Daphnia, владелец лейблов ADRO Records и Callote.  

HEARTFEELS RADIOSHOW # 23 on Megaport.FMДвадцать третий выпуск  "HEARTFEELS RADIOSHOW". Гостевой микс для выпуска подготовил музыкант с именем Daphnia, владелец лейблов ADRO Records и Callote.  

Gary's got his feet wet again, watching a Swamp Sparrow, Gordon tells tales of American Beech, and Joann's second graders found a Daphnia. We interview Sam Droege of the USGS about native bees.

Microalgae have higher growth rates and higher lipid content than terrestrial plants and the yield per unit area is even higher by several orders of magnitude. Furthermore, the production of microalgae does not compete for fertile land for food production. Therefore, microalgae are in the focus of research for biodiesel production, nutritional supplements and aquaculture approaches. However, after almost half a century of research the full promise of microalgae as a feedstock for biofuel production has remained largely unfulfilled. My research was motivated by the obvious gaps in the application of ecological pros of microalgae. DIVERSITY-PRODUCTIVITY RELATIONSHIPS: THE ROLE OF DIVERSITY FOR MICROALGAL LIPID PRODUCTION The relationship between diversity and productivity within terrestrial and algal primary producers has been well documented in ecology. However, the importance of diversity for lipid production for biofuel remains limited. Hence, I set out to investigate, experimentally, whether diversity may also affect lipid production in microalgae. Microalgae from all major algal groups were grown in a large number of treatments differing in their diversity level. Additionally, I compared the growth and lipid production of laboratory communities with the lipid production of natural lake and pond phytoplankton communities along a diversity gradient. This comparison showed that the lipid production of selected laboratory monocultures was not significantly higher than that of natural phytoplankton communities. The lipid production in general increased with increasing diversity in both natural and laboratory microalgal communities. The underlying reason for the observed ‘diversity-productivity’ relationship seems to be resource use complementarity. Additionally, a very important observation was that diversity also influences the specific lipid production of each microalgae in the high diverse communities. DIVERSITY- LIGHT- LIPID RELATIONSHIPS: LIPID PRODUCTION IN THE RIGHT LIGHT The knowledge about the relationship between diversity and biomass/lipid production in primary producer communities for biofuel production is underestimated. However, basic ecological research studies on the growth of microalgal communities provide evidence of a positive relationship between diversity and biomass production and show that the observed positive diversity-productivity-relationships are related to an increase in the efficiency of light use by diverse microalgal communities. I cultivated microalgae from all major freshwater algal groups in treatments that differed in their species richness and functional group richness. Polycultures with high functional group richness showed higher light use and algal lipid content with increasing species richness. Additionally, I could show a clear correlation between light use and lipid production in functionally diverse communities. Therefore, a powerful and cost effective way to improve biofuel production might be accomplished by incorporating diversity related resource-use-dynamics into algal biomass production. DIVERSITY AND FOOD QUALITY: ADVANTAGES FOR AQUACULTURE FOOD WEBS Determining the factors that control the energy transfer at the plant-animal interface is a key issue in ecology, because this transfer is highly variable and despite its global importance it is still not well understood. Food quality of primary producers seems to be a crucial factor influencing the transfer efficiency towards higher trophic levels. One major aspect of food quality is the biomass fatty acid composition in terms of essential ω3-polyunsaturated fatty acids (ω3-PUFAs) of primary producers, because all animals are incapable to synthesize them de novo. However, the influence of diversity on phytoplankton food quality in terms of lipid composition (e.g. ω3-PUFAs) remains unclear. I tested via a series of experiments controlled for diversity how the diversity of microalgal communities influences their fatty acid composition. My study shows the significant influence of diversity of primary producer communities on their fatty acid composition; especially on essential ω3-PUFA content. MICROALGAL BIOMASS CONTROL VIA GRAZING: IMPACT OF MICROALGAL SIZE The direction and strength of phytoplankton community responses to zooplankton grazing most probably depend on the size of phytoplankton species. To examine the influence of migrating (diel vertical migration, DVM) and non migrating zooplankton communities on different sized phytoplankton communities, I designed an experiment where I manipulated the size distribution of a natural phytoplankton community a priori in field mesocosms. Comparison of “migration” and “no migration” zooplankton treatments showed that nutrient availability and total phytoplankton biovolume were higher in “no migration” treatments with phytoplankton communities comprising mainly small algae and in “migration” treatments with phytoplankton communities of a broader size spectrum of algae. Additionally my results showed experimentally that food size selection and migration behavior of Daphnia hyalina can cause a shift from small sized microalgae towards larger species. NEW CULTIVATION TECHNIQUES FOR BIOMASS AND LIPID YIELD OPTIMIZATION IN MICROALGAE For the installation of infrastructure for the large-scale production of biofuel from microalgae is essential to establish cultivation methods that maximize lipid production but which are also economically viable in terms of energy demand and resource supply. For this purpose, I compared different cultivation systems (semi-batch, continuous) to optimize simultaneously growth and biomass lipid content of Botryococcus braunii. To enhance both, biomass accumulation and lipid production at the same time I further investigated a two-stage cultivation method to replace one stage semi-batch cultivation systems. In the first step of this cultivation method a full growth medium allows an enhancement of biomass accumulation. In the next step, the culture was transferred into nitrogen limited growth medium, where a further accumulation of photosynthetic products in the form of lipids occurred. Two-stage cultivation cultures resulted in higher nutrient specific biomass production and lipid content of B. braunii compared to one stage cultivation. If a continuous cultivation of cultures with high biomass in stage one can be assured, an almost constant supply of huge amounts of algae with even high lipid content in the second step could be guaranteed. My results clearly show that a better understanding of general ecological principles for biomass and lipid production of microalgae provides a cost effective and environmental friendly way to cultivate high yielding microalgal communities for commercial approaches. The enhancement of the yield efficiency of lipid production in diverse microalgal communities would be difficult to do only by technical means such as increasing resource supply. In addition, increasing the supply of resources is usually correlated with high energy requirements and therefore cost intensive. It is therefore important for biomass production systems to utilize all possible ecological options to increase the efficiency of the use of the supplied resources by integrating basic ecological principles into the cultivation systems.

Background: Although inducible defences have been studied extensively, only little is known about how the presence of parasites might interfere with these anti-predator adaptations. Both parasites and predators are important factors shaping community structure and species composition of ecosystems. Here, we simultaneously exposed Daphnia magna to predator cues (released by the tadpole shrimp, Triops, or by a fish) and spores of the yeast parasite Metschnikowia sp. to determine how life history and morphological inducible defences against these two contrasting types of predators are affected by infection. Results: The parasite suppressed some Triops-induced defences: Daphnia lost the ability to produce a greater number of larger offspring, a life-history adaptation to Triops predation. In contrast, the parasite did not suppress inducible defences against fish: induction (resulting in smaller body length of the mothers as well as of their offspring) and infection acted additively on the measured traits. Thus, fish-induced defences may be less costly than inducible defences against small invertebrate predators like Triops; the latter defences could no longer be expressed when the host had already invested in fighting off the parasite. Conclusions: In summary, our study suggests that as specific inducible defences differ in their costs, some might be suppressed if a target prey is additionally infected. Therefore, adding parasite pressure to predator-prey systems can help to elucidate the costs of inducible defences.

Natural hybridization, the interbreeding of species, can contribute to understanding the processes of maintaining biodiversity. There are different theories to explain the coexistence of hybrids with their parental species. Some models assume that hybrids are temporarily more or equally successful as parental taxa in a specific environment; but even in case of lower fitness of hybrids, a dynamic equilibrium between natural selection against hybrids and dispersal explains the maintenance of hybrid zones. Although the long-term significance of hybridization in animals is poorly understood, it is common among cyclical parthenogens, especially in zooplankton species of the genus Daphnia. In the first part of my thesis (Chapters 2-4), I investigated the population structure of Daphnia longispina assemblages under different selection pressures. First of all, in Chapter 2, I detected a nearly perfect correspondence in the assignment of Daphnia individuals to different parental and hybrid taxa based on microsatellite markers (15 loci) when examining reference clones which had been previously classified by different markers (allozymes, mtDNA). This allowed me to identify species and different hybrid classes from field samples by microsatellite markers alone and their assignment was verified by a set of statistical approaches (Factorial Correspondence Analysis and two Bayesian methods). Secondly, by applying microsatellite markers on Daphnia samples isolated from eight different lakes, I explored the dynamics of the hybridizing system (Chapter 2). Within taxa, replicated genotypes were of clonal origin but clonal lineages rarely persisted in subsequent years suggesting that populations must go through sexual reproduction to be re-established in spring, from sexually produced diapause eggs. In addition, I also observed a complete replacement of taxa between two spring seasons (Chapter 2). Such a year-to-year taxon replacement has not been reported for the D. longispina complex before. I additionally detected that the genotypic diversity is lower in hybrids than in parental species (Chapters 2 and 3), supporting the existence of reproductive incompatibilities between the parental genomes. Thirdly, in order to understand the impact of cyclically parthenogenetic reproduction on populations, I explored the changes in taxon and clonal composition of Daphnia populations, across time (generation-to-generation) and space (between sampling stations), during a period of seasonal environmental change (Chapter 3). I observed that clonal diversity increased with time, as a few dominant clones were replaced by a higher number of less common clones. I assumed that a loss in selective advantage for the dominant clones may have been due to parasite selection acting in a negative frequency-dependent manner. Therefore, in Chapter 4, I investigated the possibility of parasite-mediated selection in D. longispina populations. I found significant differences in clonal composition between random and infected parts of the host population. This suggests that parasite-driven selection might operate in natural Daphnia populations, as parasites influence the clonal structure of host population. In the second part of my thesis (Chapters 5), I investigated how host-parasite interactions could be altered by predation. Specifically, I tested the potential costs of simultaneous prey exposure to enemies from different functional levels (i.e. predators and parasites). I found that the proportion of successful infections and the number of parasite spores were higher among defended (against predators) than undefended Daphnia, demonstrating a previously unknown and environmentally relevant cost to inducible defences. These results enhance our understanding of how epidemiology can be integrated into the concept of phenotypic plasticity.

Habitat selection is an important behavior of many organisms. The direction and strength of this behavior is often characterized as a result of a trade off between predator avoidance and obtaining resources. A characteristic example of this trade off may be seen in organisms in the pelagic ecosystem in the form of vertical migrations. Diel vertical migration (DVM) is a predator avoidance behavior of many zooplankton species, which is marked by a significant shift in the vertical distribution of the zooplankton where night time is spent in the epilimnion and day time in the hypolimnion While the causes of DVM and its ecophysiological consequences for the zooplankton are well studied, little is known about the consequences of DVM for the pelagic food ecosystem. Vertical migrations are not only restricted to zooplankton but are often exhibited by phytoplankton species, which respond to vertical gradients of light and nutrient availability. Many phytoplankton species cope with light and nutrient gradients by changing their position in the water column through active movement or buoyancy adjustment. The costs and consequences of this phytoplankton behavior are hardly studied. In my thesis, I studied the consequences of zooplankton DVM for the pelagic food web and the consequences of phytoplankton vertical migrations on individual growth and biomass composition through both field and laboratory experiments. I, Upward phosphorus transport by Daphnia DVM: During stagnation periods of the water column, physical upward transport processes are very unlikely and nutrients become scarce in the photic zone of many lakes. DVM of zooplankton could be a mechanism of nutrient repletion in the epilimnion. I experimentally examined the upward transport of phosphorus by Daphnia DVM. Results revealed that Daphnia DVM caused an upward nutrient transport. The amount of phosphorus transported and released by Daphnia in my study was within a biologically meaningful range: five percent of the estimated daily maximum phosphorus uptake of the phytoplankton community in the epilimnion. Therefore, nutrient transport by Daphnia DVM could be a significant mechanism in fuelling primary production in the phosphorus limited epilimnion. II, Daphnia DVM: implications beyond zooplankton: DVM creates a temporal and spatial predator-free niche for the phytoplankton, and theoretical models predict that parts of the phytoplankton community could use this niche. I experimentally investigated the influence of Daphnia DVM on the phytoplankton community of an oligotrophic lake in field mesocosms. My results suggest that Daphnia DVM had significant effects on quantitative and qualitative characteristics of the phytoplankton community. Phytoplankton biomass was higher in “no DVM” treatments. DVM also increased diversity in the phytoplankton community. The analyses showed that the gelatinous green algae Planktosphaeria gelatinosa was the main species influencing phytoplankton dynamics in the experiment, and therefore the effects of Daphnia DVM were highly species specific. III, Initial size structure of natural phytoplankton communities determines the response to Daphnia DVM: Previous studies have shown that the direction and strength of phytoplankton responses to zooplankton DVM most likely depends on the size of the phytoplankton species. To examine the influence of DVM on different sized phytoplankton communities, I manipulated the size distribution of a natural phytoplankton community a priori in field mesocosms. The results reveal that DVM oppositely affected the two different phytoplankton communities. A comparison of “DVM” and “no DVM” treatments showed that nutrient availability and total phytoplankton biovolume was higher in “no DVM” treatments of phytoplankton communities consisting mainly of small algae, whereas it was higher in “DVM” treatments of phytoplankton communities with a wide size spectrum of algae. It seemed that two different mechanisms on how DVM can influence the phytoplankton community were at work. In communities of mainly small algae nutrient recycling was important, seemed to be important, whereas in communities with a wide size spectrum of algae the refuge effect played the dominant role. IV, Carbon sequestration and stoichiometry of motile and non-motile green algae: The ability to move actively should entail costs in terms of increased energy expenditure and the provision of specific cell structures for movement. In a laboratory experiment, I studied whether motile, flagellated and non-motile phytoplankton taxa differ with respect to their energetic costs, phosphorus requirements, and structural carbon requirements. The results show that flagellated taxa had higher respiration rates and higher light requirements for growth than non-motile taxa. Accordingly, both short-term photosynthetic rates and long-term biomass accrual were lower for flagellated than for non-motile taxa. My results point at significant costs of motility, which may explain why flagellated taxa are often outcompeted by non-motile taxa in turbulently mixed environments, where active motility is of little use. The data in this study also suggest that motility alone may not be sufficient to explain the lower C: P ratios of flagellates. In summary, my results show that migrating phytoplankton and zooplankton species can act as a vector transporting energy, organic matter and ecological interaction. The complex consequences for the pelagic ecosystem are thereby determined by the organisms´ activity and characterized by their life history.

On Air With Daphnia (Ukraine) 01.Kosmorama - Sunset (Daphnia remix) [Historus Records] 02.Daphnia & Tlbn - The Drunk Driver (Tlbn Remix) [Comfortable music] 03.Daphnia - V.V. [NEW] 04.Daphnia - Katrin [Carica Limited] 05.Daphnia - In Depth [NewBorn Records] 06.Daphnia - The Secret [Kyoto Records] 07.Daphnia - The Galaxy Born [NewBorn Records] 08.Daphnia - Lonesome [Historus Records] 09.Daphnia - Albania [Kyoto Records] 10.Daphnia - Atomic Touch [Carica Records] 11.Daphnia - Give Me Chance [Historus Records] 12.Daphnia - MicroHeart [Historus Records] 13.Daphnia - My Ego [Renno Records] 14.Daphnia - Switched Off Telephone [Carica Records] 15.Simak De Litvin - City Light (Daphnia Remix) 16.Daphnia - 36.6 [NEW] 17.Daphnia - Windfall [Carica Records] 18.Daphnia & Tlbn - The Drunk Driver (Daphnia Remix) [Comfortable music] 19.Daphnia - Impossible [Historus Records]

On Air With Daphnia (Ukraine) 01.Kosmorama - Sunset (Daphnia remix) [Historus Records] 02.Daphnia & Tlbn - The Drunk Driver (Tlbn Remix) [Comfortable music] 03.Daphnia - V.V. [NEW] 04.Daphnia - Katrin [Carica Limited] 05.Daphnia - In Depth [NewBorn Records] 06.Daphnia - The Secret [Kyoto Records] 07.Daphnia - The Galaxy Born [NewBorn Records] 08.Daphnia - Lonesome [Historus Records] 09.Daphnia - Albania [Kyoto Records] 10.Daphnia - Atomic Touch [Carica Records] 11.Daphnia - Give Me Chance [Historus Records] 12.Daphnia - MicroHeart [Historus Records] 13.Daphnia - My Ego [Renno Records] 14.Daphnia - Switched Off Telephone [Carica Records] 15.Simak De Litvin - City Light (Daphnia Remix) 16.Daphnia - 36.6 [NEW] 17.Daphnia - Windfall [Carica Records] 18.Daphnia & Tlbn - The Drunk Driver (Daphnia Remix) [Comfortable music] 19.Daphnia - Impossible [Historus Records]

Background: Daphniids, commonly known as waterfleas, serve as important model systems for ecology, evolution and the environmental sciences. The sequencing and annotation of the Daphnia pulex genome both open future avenues of research on this model organism. As proteomics is not only essential to our understanding of cell function, and is also a powerful validation tool for predicted genes in genome annotation projects, a first proteomic dataset is presented in this article. Results: A comprehensive set of 701,274 peptide tandem-mass-spectra, derived from Daphnia pulex, was generated, which lead to the identification of 531 proteins. To measure the impact of the Daphnia pulex filtered models database for mass spectrometry based Daphnia protein identification, this result was compared with results obtained with the Swiss-Prot and the Drosophila melanogaster database. To further validate the utility of the Daphnia pulex database for research on other Daphnia species, additional 407,778 peptide tandem-mass-spectra, obtained from Daphnia longicephala, were generated and evaluated, leading to the identification of 317 proteins. Conclusion: Peptides identified in our approach provide the first experimental evidence for the translation of a broad variety of predicted coding regions within the Daphnia genome. Furthermore it could be demonstrated that identification of Daphnia longicephala proteins using the Daphnia pulex protein database is feasible but shows a slightly reduced identification rate. Data provided in this article clearly demonstrates that the Daphnia genome database is the key for mass spectrometry based high throughput proteomics in Daphnia.

Phytoplankton growth is controlled by the balance between reproduction and mortality. Phytoplankton reproduction is determined by environmental factors (such as temperature and pH) and by essential resources (such as light and nutrients). In my thesis, I investigated the importance of the essential resources light and nutrients for phytoplankton dynamics in laboratory and field experiments. Research questions involved topics such as: the resource use efficiency of phytoplankton communities, the role of resources for phytoplankton stoichiometry, aspects of phytoplankton food quality and grazing by zooplankton, costs of behavioural strategies of mobile phytoplankton species and the establishment of new methods to quantify growth and loss processes of phytoplankton in situ. EFFECTS OF DIVERSITY ON PHYTOPLANKTON RESOURCE UPTAKE AND GROWTH The resource use efficiency of terrestrial plant communities has been related to taxonomic diversity and a recent metaanalysis of freshwater and brackish phytoplankton communities shows that this relationship also exists in phytoplankton communities. Our experiments with natural and assembled phytoplankton communities showed a clear effect of phytoplankton biodiversity on carbon incorporation. Phytoplankton functional groups differ in their resource use attributes and exhibit different constituents of photosynthetic active pigments. We have shown that the diversity of wavelength specific photosynthetically active pigments was a function of the taxonomic diversity of the phytoplankton communities. The effect of biodiversity on carbon incorporation was related to the functional (biochemical) diversity of phytoplankton communities (Paper 1). Increasing biodiversity and thereby increasing pigment diversity resulted in a higher absorbance of light within the photosynthetic active radiation spectrum and thereby higher carbon assimilation. EFFECTS OF DIVERSITY ON PHYTOPLANKTON RESOURCE UPTAKE AND BIOMASS COMPOSITION (STOICHIOMETRY) Phytoplankton carbon assimilation and nutrient uptake are not tightly coupled. As a result of fluctuating resources, autotrophs can exhibit variable biomass compositions (biomass carbon to nutrient ratios). The increased efficiency of resource use in highly diverse phytoplankton communities (Paper 1) also has consequences for the biomass composition of those communities (Paper 2). Increasing biodiversity resulted in increasing carbon assimilation, but not in a comparable increase of phosphorus uptake. This resulted in increasing biomass carbon to phosphorous ratios. Phytoplankton with high biomass carbon to phosphorus ratios are considered to be low quality food for cladoceran zooplankton such as Daphnia. Although the stoichiometry of Daphnia varies somewhat with algae and diet, they maintain a relatively homeostatic composition with low carbon to nutrient (phosphorus) biomass composition compared to their food. Phytoplankton biodiversity could therefore also have consequences for freshwater phytoplankton-zooplankton interactions. The mismatch in the biomass composition between phytoplankton and Daphnia could lead to changed trophic transfer efficiencies between phytoplankton and zooplankton and hence affect the entire pelagic food web. THE SUPPLY OF LIGHT AND NUTRIENTS AND ITS CONSEQUENCES FOR PHYTOPLANKTON-ZOOPLANKTON INTERACTIONS Both, low and high light to nutrient (phosphorus) ratios in the environment can restrict herbivore growth rates by either the quantity (photosynthetically fixed carbon) of phytoplankton at low light to nutrient ratios or the nutritional quality (biomass carbon to phosphorus ratios) of phytoplankton at high light to nutrient ratios. This can result in an unimodal relationship between light intensity and zooplankton growth. In mesocosm experiments with natural phytoplankton communities from different lakes, we established gradients of light to nutrient ratios by manipulating the light availability for phytoplankton. After two weeks we added the herbivorous zooplankter Daphnia magna to the mesocosms. Indeed, in treatments from phosphorus limited oligotrophic and mesotrophic lakes we found unimodal relationships between light intensity and Daphnia growth rates (Paper 3). At low light levels Daphnia growth rates were limited by food quantity and at high light levels they were limited by food quality. Light dependent variations of natural phytoplankton biomass carbon to phosphorus ratios can effect zooplankton growth. COSTS OF BEHAVIOURAL STRATEGIES FOR PHYTOPLANKTON RESOURCES UPTAKE In pelagic environments, light and nutrients are not equally distributed within the water column and show vertical gradients of availability. While light intensity is higher in upper water layers, nutrient concentrations are, during periods of stratification, generally higher in deeper water layers. A possibility for phytoplankton species to optimize resource uptake is mobility. Mobile species can (at least to a certain degree) migrate within the water column to choose an optimal position for nutrient uptake and photosynthesis. Mobility involves costs in terms of energy to develop, maintain and operate mobility structures. We conducted laboratory growth experiments with mobile and non-mobile green algal species along a gradient of light availability (Paper 4). Phytoplankton biomass (determined as particulate organic carbon) and biomass carbon to phosphorus ratios of non-mobile species were higher than those of mobile species. This indicates that the efficiency of resource use of mobile species was worse than that of non-mobile species. Mobile species had higher energy requirements to balance the costs of basic metabolism. Thus, the advantages of mobility are restricted to specific environmental conditions. NEW METHODS TO ESTIMATE GROWTH AND MORTALITY OF PHYTOPLANKTON COMMUNITIES It is difficult to measure phytoplankton growth and mortality (grazing by micro- and mesozooplankton) in situ in natural phytoplankton communities. However, these are important parameters to understand the dynamics of natural phytoplankton communities. We established a new method to estimate phytoplankton growth and mortality by combining existing dilution (to measure mortality) and dialysis (to measure growth) techniques (Paper 5). Experiments showed that the combination of these methods can be successfully used to quantify phytoplankton gross growth rates and micro- and mesozooplankton grazing in situ.

Zooplankton populations which perform diel vertical migration (DVM) only spend the night in surface water layers but migrate downwards into the lower water layers during the day. The intention of this study was to investigate effects of DVM of Daphnia on phytoplankton dynamics and Daphnia life history parameters in a lake. I conducted field and laboratory experiments in which I compared ‘migration’ with ‘no-migration’ situations. It is generally assumed that phytoplankton communities in the epilimnion of stratified lakes profit from the presence of DVM. This might be caused by less grazing due to intermittent grazing and/or less grazing due to lower population densities of migrating Daphnia populations (as they migrate into the colder, lower hypolimnion during the day which leads to a lower temperature-dependent population growth). In a first laboratory experiment I showed that an enhanced phytoplankton biomass could develop under a migration regime solely due to intermittent grazing. I further showed that edible phytoplankton species with higher intrinsic growth rates benefited more from intermittent grazing than edible species with lower intrinsic growth rates. Field experiments also indicated that phytoplankton biomass in the epilimnion was higher when subject to a migrating zooplankton population and that additionally different phytoplankton community compositions arose from different migration regimes (‘migration’/’no-migration’). For example edible algae were at an advantage when zooplankton migrated, whereas large, inedible algae species had an advantage when zooplankton populations did not migrate. In an additional laboratory experiment I also showed that these changes in phytoplankton composition had strong feedback effects on life history parameters of daphnids and that food conditions experienced by migrating daphnids were advantageous. In a further laboratory experiment I exposed two Daphnia species to either constant or regularly changing temperature regimes to study whether a fluctuating temperature regime – as experienced by migrating daphnids – implies costs for daphnids. Somatic growth rates of juvenile Daphnia in the regularly changing temperature regime were almost as low as under constant low temperature conditions indicating that a regular change in temperature involves high costs. The results of my study indicate that DVM has a strong modulating effect on zooplankton-phytoplankton interactions in a lake.

The aim of this study was to reveal factors affiliated with morphological plasticity in Daphnia cucullata. This planktonic crustacean shows a seasonal variation in body shape that is commonly known as cyclomorphosis. Here I show that both predator-released chemicals and water-soluble “alarm” signals from wounded Daphnia can induce certain morphological features in Daphnia cucullata. Specifically, the inductive effect of the “alarm” signals is minute compared to the predator-exposed animals. Moreover, laboratory-generated small-scale turbulence was identified to be a proximate factor in cyclomorphosis. This special kind of turbulence is compared to turbulence evoked by the movement of other organisms. A distinct protective effect of the morphological traits against invertebrate predation was revealed as the likely ultimate factor of cyclomorphosis. Furthermore, a unique method of ultrasonic microscopy reveals “hidden” morphological plasticity in daphnids. The armor of predator-exposed animals is much stronger than that of those not exposed to predators. I developed a new SEM-preparation method to get detailed insight in ontogenesis in Daphnia. I detected morphological defenses in predator-chemical-induced Daphnia cucullata already in the last embryonic stage. Induction experiments on transgenerational effects in Daphnia cucullata show that defended mothers release offspring that are better defended than the descendants of unthreatened parents. Furthermore, daphnids could asses their actual predation risk by taking both predator and prey density into account. Thereafter the degree of a defense is adjusted to the individual hazard, thus saving unnecessary costs associated with the development of a particular defense. The combined results of this study indicate that cyclomorphosis in Daphnia cucullata has evolved as an adaptation to variable environments.

Fri, 1 Jan 1993 12:00:00 +0100 http://epub.ub.uni-muenchen.de/5119/ http://epub.ub.uni-muenchen.de/5119/1/Gabriel_wilfried_5119.pdf Taylor, B. E.; Gabriel, Wilfried Taylor, B. E. und Gabriel, Wilfried (1993): Optimal adult growth of Daphnia in a seasonal environment. In: Functional Ecology, Vol. 7: pp. 513-521. Biologie

Wed, 1 Jan 1992 12:00:00 +0100 http://epub.ub.uni-muenchen.de/5090/ http://epub.ub.uni-muenchen.de/5090/1/5090.pdf Taylor, B. E.; Gabriel, Wilfried Taylor, B. E. und Gabriel, Wilfried (1992): To grow or not to grow. Optimal resource allocation for Daphnia. In: American Naturalist, Vol. 139, Nr. 2: pp. 248-266. Biologie 0

I. Birth and death rates of natural cladoceran populations cannot be measured directly. Estimates of these population parameters must be calculated using methods that make assumptions about the form of population growth. These methods generally assume that the population has a stable age distribution. 2. To assess the effect of variable age distributions, we tested six egg ratio methods for estimating birth and death rates with data from thirty-seven laboratory populations of Daphnia pulicaria. The populations were grown under constant conditions, but the initial age distributions and egg ratios of the populations varied. Actual death rates were virtually zero, so the difference between the estimated and actual death rates measured the error in both birth and death rate estimates. 3. The results demonstrate that unstable population structures may produce large errors in the birth and death rates estimated by any of these methods. Among the methods tested, Taylor and Slatkin's formula and Paloheimo's formula were most reliable for the experimental data. 4. Further analyses of three of the methods were made using computer simulations of growth of age-structured populations with initially unstable age distributions. These analyses show that the time interval between sampling strongly influences the reliability of birth and death rate estimates. At a sampling interval of 2.5 days (equal to the duration of the egg stage), Paloheimo's formula was most accurate. At longer intervals (7.5–10 days), Taylor and Slatkin's formula which includes information on population structure was most accurate.

Tue, 1 Jan 1985 12:00:00 +0100 http://epub.ub.uni-muenchen.de/5014/ http://epub.ub.uni-muenchen.de/5014/1/5014.pdf Taylor, B. E.; Gabriel, Wilfried Taylor, B. E. und Gabriel, Wilfried (1985): Reproductive strategies of two similar Daphnia species. In: Verhandlungen / International Association of Theoretical and Applied Limnology, Vol. 22, Nr. 5: pp. 3047-3050. Biologie

Sun, 1 Jan 1984 12:00:00 +0100 http://epub.ub.uni-muenchen.de/5011/ http://epub.ub.uni-muenchen.de/5011/1/5011.pdf Lampert, W.; Gabriel, Wilfried Lampert, W. und Gabriel, Wilfried (1984): Tracer kinetics in Daphnia. an improved two compartment model and experimental test. In: Archiv für Hydrobiologie, Vol. 100: pp. 1-20. Biologie 0

Fri, 1 Jan 1982 12:00:00 +0100 http://epub.ub.uni-muenchen.de/5008/ http://epub.ub.uni-muenchen.de/5008/1/5008.pdf Gabriel, Wilfried Gabriel, Wilfried (1982): Modelling reproductive strategies of Daphnia. In: Archiv für Hydrobiologie, Vol. 95: pp. 69-80. Biologie

Mon, 1 Jan 1877 12:00:00 +0100 http://epub.ub.uni-muenchen.de/11827/ http://epub.ub.uni-muenchen.de/11827/1/8Zool.349_153.pdf Spangenberg, Friedrich Spangenberg, Friedrich: Das Centralnervensystem von Daphnia Magna und Moina Rectirostris. München: Oldenbourg, 1877