MEPS 608:165-182 (2019)  -  DOI: https://doi.org/10.3354/meps12797

ABSTRACT: Increased temperature and storminess will render nearshore tropical organisms more vulnerable to climate change. The sea urchin Tripneustes gratilla lives in a wide range of habitats and can survive even in harsh conditions, but the mechanisms underlying its resilience are not well understood. We investigated the somatic and reproductive phenotypic traits of adults (66.78 ± 0.22 mm test diameter) from seagrass- and seaweed-dominated sites during 2 monsoon seasons in a location frequently disturbed by strong cyclones and northeasterly winds in the northeastern Philippines (NE Phil). These were compared with seagrass sites in a less exposed location in the northwest portion of the islands (NW Phil). Populations from NE Phil had significantly thicker and heavier body walls, but significantly smaller Aristotle’s lanterns, guts and gonads regardless of season compared to those from NW Phil. Moreover, the body walls in individuals from the seaweed-dominated sites were thicker and heavier. Allocation of the body wall to body weight was 62.2 and 53.7% in the NE Phil seaweed and seagrass sites, respectively, both of which were significantly greater than those from the NW Phil seagrass sites (44.74%). In contrast to other studies, plasticity in the Aristotle’s lantern was not related to food availability. The differences in the Aristotle’s lantern, gonad and body wall weights indicate a trade-off in resource allocation for feeding (growth) and reproduction in favor of maintenance. Comparative analysis of multiple phenotypic traits of T. gratilla populations provides substantive empirical field evidence and insights into the resilience of tropical species to increased storminess and wave exposure.

KEY WORDS: Resource allocation · Trade-offs · Phenotypic plasticity · Tripneustes gratilla · Storminess · Monsoon winds · Seaweed-, Seagrass-habitats