Mar Environ Res 2025 Dec 23;215:107814. doi: 10.1016/j.marenvres.2025.107814.

Habitat preference and physiological characteristics of sea urchins: the case of Tripneustes gratilla.

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Tripneustes gratilla is an economically important sea urchin species that is found in the tropics and has great potential for market development. However, owing to habitat loss, overfishing, climate change and other factors, the natural resources of this species have experienced serious decline. Understanding the habitat selection patterns and physiological responses of this species is highly important for promoting the sustainability of its resources. In this study, we investigated the preferences of T. gratilla for three habitat types, including a Sargassum habitat, natural sand habitat and coral reef rock habitat; on the basis of the results of the selection experiments, we further resolved the effects of combined habitats (Sargassum-coral rock) and the size of the sea urchins (large, medium and small) on their behavioural patterns. The results of this study revealed that sea urchins preferred the Sargassum habitat, followed by the coral reef rock habitat. The sea urchins in the Sargassum habitat exhibited the highest activities of catecholamine hormones and digestive enzymes. In the combined habitat, the small sea urchins exhibited higher activities, with higher reef-finding rates and longer travel distances. Temperature was negatively correlated with the distances travelled by the medium and small sea urchins, whereas there was not a significant correlation with the large sea urchins. There was no significant correlation between light intensity and the distance travelled by individuals in any of the three size classes. However, during the 5:00-15:00 period, regression analyses revealed some relationships between the distance travelled by sea urchins temperature and light. The results of this study may provide a reference for enhancing the resources of T. gratilla and its sustainable development and utilization.

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