Thyroid hormones link habitat conditions to developmental changes in reef fish

Researchers from the Okinawa Institute of Science and Technology, CNRS, and CRIOBE studied convict surgeonfish (Acanthurus triostegus) around Moorea Island to test how coastal habitats shape the transition from open-ocean larvae to reef-dwelling juveniles. The fish settle in mangroves, beach rock zones, and sandy beaches that differ in temperature, oxygen, salinity, and predator pressure.

Previous observations had shown that fish in mangroves grow more slowly and develop darker pigmentation than those in other habitats. The new work combined transcriptomics, metabolomics, and hormone measurements across the first eight days after settlement, repeated over two years, to capture the underlying biological mechanisms.

Thyroid hormone levels peaked at the end of the oceanic phase and then varied significantly among habitats. Gene expression for thyroid hormone synthesis and downstream targets, including pigmentation genes, also differed by site. Metabolic profiles shifted from aerobic to anaerobic energy production during metamorphosis, with sandy beach fish showing patterns consistent with higher energy expenditure.

In field enclosures placed in each habitat type, the same developmental differences appeared, confirming that local conditions drive the variation rather than genetic differences among populations. The researchers describe thyroid hormones as a biological interface that integrates environmental cues such as resource availability and shelter to adjust physiology and metabolism.

The findings illustrate a mechanism by which a single species can produce habitat-specific developmental outcomes within a single generation. This plasticity may influence how resilient populations are to rapid environmental change, though the study does not project future climate scenarios.

The research was published in Science Advances on August 7, 2026, under the title "Environmental Tuning of Thyroid Hormone Signaling Drives Developmental Plasticity" (DOI: 10.1126/sciadv.aec5359).