Project description:Across evolutionary time, nearly all animal species have harnessed photoperiod to initiate processes that ultimately influence seasonal behavior and life history traits. In the freshwater cladoceran Daphnia magna, the effect of photoperiod on various life history traits has generally been investigated in conjunction with additional environmental stimuli. In the present study, we sought to untangling responses directly attributable to photoperiod in D. magna and identify the molecular processes underlying resultant behavioral and life history responses using functional analysis of global transcriptomic expression. D. magna were exposed to five different photoperiods immediately post-hatch for 21d where a standard long-day photoperiod of 16 hours light and 8 hours dark (16L:8D) served as the control relative to 4L:20D, 8L:16D, 12L:12L, and 20L:4D photoperiods. Entrainment to short-day photo-periods (4L:20D, 8L:16D, and 12L:12L) resulted in significantly increased light-avoidance behaviors relative to the control photoperiod where young Daphnia (7d old) displayed the most pronounced avoidance responses. Correspondingly, functional transcriptomics identified differential transcriptional expression of genes involved in glutamate signaling, which is critical in arthropod light-avoidance responses, as well as period circadian protein and proteins coding F-box/LRR-repeat domains, all of which contribute to establishing circadian rhythms in arthropods. Short-day photoperiods also induced increased metabolic rates which corresponded with broad-scale changes in transcriptional expression across multiple systems-level energy metabolism pathways. The most striking observation was increased male production across short-day photoperiods (4L:20D, 8L:16D, and 12L:12D). Transcriptional expression consistent with multiple putative mechanisms of male production were observed including expression suggestive of increased glutamate signaling; a response observed to induce male production in D. pulex via photo-period sensitive mechanisms. Overall, the results demonstrate the importance of photoperiod on behavior and life history trajectories in D. magna where we have now established multiple putative mechanistic pathways underlying several critical responses.

Project description:Nearly all animal species have utilized photoperiod to cue seasonal behaviours and life history traits. We investigated photoperiod responses in keystone species, Daphnia magna, to identify molecular processes underlying ecologically important behaviours and traits using functional transcriptomic analyses. Daphnia magna were photoperiod-entrained immediately posthatch to a standard control photoperiod of 16 light/ 8 dark hours (16L:8D) relative to shorter (4L:20D, 8L:16D, 12L:12L) and longer (20L:4D) day length photoperiods. Short-day photoperiods induced significantly increased light-avoidance behaviours relative to controls. Correspondingly, significant differential transcript expression for genes involved in glutamate signalling was observed, a critical signalling pathway in arthropod light-avoidance behaviour. Additionally, period circadian protein and proteins coding F-box/LRR-repeat domains were differentially expressed which are recognized to establish circadian rhythms in arthropods. Indicators of metabolic rate increased in short-day photoperiods which corresponded with broadscale changes in transcriptional expression across system-level energy metabolism pathways. The most striking observations included significantly decreased neonate production at the shortest day length photoperiod (4L:20D) and significantly increased male production across short-day and equinox photoperiods (4L:20D, 8L:16D and 12L:12D). Transcriptional expression consistent with putative mechanisms of male production was observed including photoperiod-dependent expression of transformer-2 sex-determining protein and small nuclear ribonucleoprotein particles (snRNPs) which control splice variant expression for genes like transformer. Finally, increased transcriptional expression of glutamate has also been shown to induce male production in Daphnia pulex via photoperiod-sensitive mechanisms. Overall, photoperiod entrainment affected molecular pathways that underpin critical behavioural and life history traits in D. magna providing fundamental insights into biological responses to this primary environmental cue.

Dataset Information

Dopamine mediates life-history responses to food abundance in Daphnia.

Publications

Dopamine mediates life-history responses to food abundance in <i>Daphnia</i>.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets