Clownfish larvae exhibit faster growth, higher metabolic rates and altered gene expression under future ocean warming

Increasing ocean temperatures have been demonstrated to have a range of negative impacts on coral reef fishes. How-ever, despite a wealth of studies of juvenile/adult reef fish, studies of how early developmental stages respond to ocean warming are limited. As overall population persistence is influenced by the development of early life stages, detailed studies of larval responses to ocean warming are essential. Here, in an aquaria-based study we investigate how temper-atures associated with future warming and present-day marine heatwaves (+3 degrees C) impact the growth, metabolic rate, and transcriptome of 6 discrete developmental stages of clownfish larvae (Amphiprion ocellaris). A total of 6 clutches of larvae were assessed, with 897 larvae imaged, 262 larvae undergoing metabolic testing and 108 larvae subject to tran-scriptome sequencing. Our results show that larvae reared at +3 degrees C grow and develop significantly faster and exhibit higher metabolic rates than those in control conditions. Finally, we highlight the molecular mechanisms underpinning the response of larvae from different developmental stages to higher temperatures, with genes associated with metab-olism, neurotransmission, heat stress and epigenetic reprogramming differentially expressed at +3 degrees C. Overall, these results indicate that clownfish development could be altered under future warming, with developmental rate, meta-bolic rate, and gene expression all affected. Such changes may lead to altered larval dispersal, changes in settlement time and increased energetic costs.

Automated summary

In this study, the researchers examine the impacts of ocean warming on the growth, metabolic rate, and gene expression of clownfish larvae. They find that larvae reared at higher temperatures grow and develop faster, exhibit higher metabolic rates, and have differential gene expression. These results indicate that future warming could alter clownfish development and have implications for larval dispersal and settlement time.