Different as night and day: Behavioural and life history responses to varied photoperiods in Daphnia magna

Abstract

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.

Circadian Rhythm in Feeding Behavior of Daphnia dentifera

“…The nocturnal feeding rhythm shown in D. dentifera is temperature compensated and is consistent with the well-studied DVM behavior of many zooplanktons. Circadian rhythms in Daphnia have been shown to impact behavior and life history traits (Coldsnow et al, 2017; Gust et al, 2019; Schwarzenberger et al, 2020). The observed circadian rhythm in feeding behavior could alter the timing of energetically demanding processes like metabolism and immunity.…”

Transcriptome analysis of different life-history stages and screening of male-biased genes in Daphnia sinensis

“…Usually, under worse conditions (such as fish predation, unsuited temperature and photoperiod), Daphnia transforms from parthenogenesis to sexual reproduction, producing male and sexual female, which mate and form resting eggs [24][25][26]. Colbourne et al (2011) reported the detailed genomes information of D. pulex, the amount of genomic and transcriptomic database greatly promoted our understanding of sex-biased genes for Daphnia.…”

Transcriptome analysis of different developmental stages of Daphnia similoides sinensis and screening of male sex determination candidate genes

“…Usually, under worse conditions (such as sh predation, unsuited temperature and photoperiod), Daphnia transforms from parthenogenesis to sexual reproduction, producing male and sexual female, which mate and form resting eggs [24][25][26]. Previous studies have shown that several genes (Dsx, antp, Tra and DMRT93B) could play important roles in the male sex determination of Daphnia [11][12][13][14].…”