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| Djeghri, Nicolas; Stibor, Herwig; Lebeau, Oanez; Pondaven, Philippe. |
| Some jellyfish host zooxanthellae in their tissues (mostly from the family Symbiodiniaceae; Dinophyceae) and supplement their heterotrophic nutrition with their symbiont's photosynthates. The mixotrophy of zooxanthellate jellyfishes (as holobionts) renders the study of their nutrition, growth, and population dynamics complicated. Here, we used an experimental approach to assess how carbon and nitrogen stable isotopes (δ13C and δ15N) as well as the elemental composition (C:N ratios) of zooxanthellate jellyfishes are affected by variations in nutrition sources: i. e. predation (heterotrophic) versus photosynthesis (autotrophic). Our laboratory experiment, conducted on the zooxanthellate jellyfish Cassiopea sp. medusae (including symbionts) in the presence or... |
| Tipo: Text |
Palavras-chave: Stable isotopes; C:N ratios; Photosymbiosis; Mixotrophy; Scyphozoa; Zooxanthellae. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00591/70348/68448.pdf |
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| Djeghri, Nicolas; Atkinson, Angus; Fileman, Elaine S.; Harmer, Rachel A.; Widdicombe, Claire E.; Mcevoy, Andrea J.; Cornwell, Louise; Mayor, Daniel J.. |
| There has been an upsurge of interest in trait-based approaches to zooplankton, modelling the seasonal changes in the feeding modes of zooplankton in relation to phytoplankton traits such as size or motility. We examined this link at two English Channel plankton monitoring sites south of Plymouth (L4 and El). At L4 there was a general transition from diatoms in spring to motile microplankton in summer and autumn, but this was not mirrored in the succession of copepod feeding traits; for example the ambushing Oithona similis dominated during the spring diatom bloom. At nearby El we measured seasonality of food and grazers, finding strong variation between 2014 and 2015 but overall low mesozooplankton biomass (median 4.5 mg C m(-3)). We also made a seasonal... |
| Tipo: Text |
Palavras-chave: Copepod; Zooplankton biomass; Feeding; Selectivity; Intraguild predation; Predator-prey size ratio; Western Channel Observatory; Sloppy feeding. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00616/72783/83484.pdf |
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| Djeghri, Nicolas; Pondaven, Philippe; Stockenreiter, Maria; Behl, Stephan; Huang, Jessica Y. T.; Hansen, Thomas; Patris, Sharon; Ucharm, Gerda; Stibor, Herwig. |
| Mixotrophic organisms are increasingly recognized as important components of ecosystems, but the factors controlling their nutrition pathways (in particular their autotrophy–heterotrophy balance) are little known. Both autotrophy and heterotrophy are expected to respond to density‐dependent mechanisms but not necessarily in the same direction and/or strength. We hypothesize that the autotrophy–heterotrophy balance of mixotrophic organisms might therefore be a function of population densities. To investigate this relationship, we sampled mixotrophic jellyfish holobionts (host, Mastigias papua etpisoni; symbiont, Cladocopium sp.) in a marine lake (Palau, Micronesia) on six occasions (from 2010 to 2018). Over this period, population densities varied ~100... |
| Tipo: Text |
Palavras-chave: Density dependence; Jellyfish; Marine lakes; Mixotrophy; Stable isotopes; Symbiosis; Zooxanthellae. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00663/77469/79159.pdf |
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| Djeghri, Nicolas; Pondaven, Philippe; Stibor, Herwig; Dawson, Michael N.. |
| Many marine organisms form photosymbioses with zooxanthellae, but some, such as the medusozoans, are less well known. Here, we summarize the current knowledge on the diversity of zooxanthellate jellyfishes, to identify key traits of the holobionts, and to examine the impact of these traits on their ecology. Photosymbiosis with zooxanthellae originated at least seven times independently in Medusozoa; of these, five involve taxa with medusae. While most zooxanthellate jellyfishes are found in clades containing mainly non-zooxanthellate members, the sub-order Kolpophorae (Scyphozoa: Rhizostomeae) is comprised-bar a few intriguing exceptions-of only zooxanthellate jellyfishes. We estimate that 20-25% of Scyphozoa species are zooxanthellate (facultative... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00604/71661/70246.pdf |
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