Psammechinus miliaris

Psammechinus miliaris occurs in a diverse range of habitats, frequently at high densities, particularly in shallow or littoral locations. There is now a significant body of literature examining its reproduction, diet and trophic ecology, as well as the way in which these interactions are reflected in its gonad biochemistry. Hence, the species lends itself well as a model to better understand a variety of processes of the inshore ecosystem. Its omnivory is well documented. Observations that a diet rich in encrusting invertebrates support high gonad indices in this species have been confirmed by examination of the fatty acid profile of the gonad tissue. It is likely the grazing activity of P. miliaris has a profound impact on the biodiversity and distribution of subtidal and intertidal encrusting invertebrates, as well as the flora. As they ingest and process macroalgae, they radically alter its fatty acid signature. Fecal output is low in long chain polyunsaturated fatty acids (LC-PUFAs), whereas the sea urchin gonad and the gametes and larvae, which enter the pelagic food web, are relatively high in LC-PUFA. The consistent differences in fatty acid profile between males and females suggest a functional significance that has yet to be elucidated. This species shows phenotypic plasticity, both morphologically and in its behavior in response to changes in diet. This is relevant to our wider understanding of how sea urchins persist through ecosystem phase shifts from macroalgal dominated communities to urchin barrens. The fate of ingested carotenoid pigments and their transformation and expression as gonad color have been investigated. As it is relatively robust in culture, P. miliaris is increasingly used as a model for the study of developmental embryology, the impact of climate change and environmental pollutants. ?? 2013 Elsevier B.V.