Finding Nemo’s clock reveals switch from nocturnal to diurnal activity

• Published in: Scientific reports Vol. 11; no. 1; p. 6801
• Main Authors: Schalm, Gregor, Bruns, Kristina, Drachenberg, Nina, Geyer, Nathalie, Foulkes, Nicholas S., Bertolucci, Cristiano, Gerlach, Gabriele
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24-03-2021; Nature Publishing Group; Nature Portfolio
• Subjects: 631/158/2039; 631/208/199; 631/601/18; 631/80/105; Amphiprion percula; BMAL1 protein; Circadian rhythm; Circadian rhythms; Coral reefs; Dispersal; Diurnal; Embryos; Endosymbionts; Gene expression; Hatching; Humanities and Social Sciences; Juveniles; Larvae; multidisciplinary; Nocturnal; Period 2 protein; Period 3 protein; Science; Science (multidisciplinary); Zooxanthellae
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-86244-9

Timing mechanisms play a key role in the biology of coral reef fish. Typically, fish larvae leave their reef after hatching, stay for a period in the open ocean before returning to the reef for settlement. During this dispersal, larvae use a time-compensated sun compass for orientation. However, the timing of settlement and how coral reef fish keep track of time via endogenous timing mechanisms is poorly understood. Here, we have studied the behavioural and genetic basis of diel rhythms in the clown anemonefish
Amphiprion ocellaris
. We document a behavioural shift from nocturnal larvae to diurnal adults, while juveniles show an intermediate pattern of activity which potentially indicates flexibility in the timing of settlement on a host anemone. qRTPCR analysis of six core circadian clock genes (
bmal1
,
clocka
,
cry1b
,
per1b
,
per2
,
per3
) reveals rhythmic gene expression patterns that are comparable in larvae and juveniles, and so do not reflect the corresponding activity changes. By establishing an embryonic cell line, we demonstrate that clown anemonefish possess an endogenous clock with similar properties to that of the zebrafish circadian clock. Furthermore, our study provides a first basis to study the multi-layered interaction of clocks from fish, anemones and their zooxanthellae endosymbionts.