Habitat-dependent growth in a Caribbean sea urchin Tripneustes ventricosus: the importance of food type

Abstract

The sea urchin Tripneustes ventricosus is a common, yet relatively poorly known, grazer of seagrass beds and coral reefs throughout the Caribbean. We compared the size and abundance of urchins between adjacent seagrass and coral reef habitats (where macroalgae are the dominant primary producers). We also conducted a laboratory experiment comparing the growth rate of juvenile urchins fed a diet of either macroalgae or seagrass. Reef urchins had signiWcantly larger test diameter than those in the seagrass on some sampling dates. This size diVerence may be at least partially explained by diet, because laboratory-reared urchins fed macroalgae grew signiWcantly faster than those fed seagrass. The seagrass population, however, was stable over time, whereas the reef population exhibited strong Xuctuations in abundance. Overall, our study indicates that both the seagrass and coral reef habitats are capable of supporting healthy, reproductive populations of T. ventricosus. Each, however, appears to oVer a distinct advantage: faster growth on the reef and greater population stability in the seagrass.

Shifts in biodiversity and physical structure of seagrass beds across 5 decades at Carriacou, Grenadines

“…Ordination analysis showed that these patterns in seagrass community composition across years may be related to an inverse pattern in the frequency of occurrence of sea urchins ( Tripneustes ventricosus group), which was minimal in 1994 compared to 1969 and 2016. The importance of sea urchins as major grazers of seagrass and macroalgae is well established [ 67 , 68 ] and some species are known to graze coral recruits [ 69 – 71 ]. Sea urchins were intensively harvested in Grenada (less so in Carriacou) for export in the early 1990s, leading to the collapse and closure of the fishery by 1995 [ 72 ].…”

The Epibiotic Microbiota of Wild Caribbean Sea Urchin Spines Is Species Specific

“…We had previously reported a similar trend for sea urchin gut samples [ 4 ]. The species E. lucunter and D. antillarum inhabit hardgrounds where corals, sponges, and other cnidarians are dominant [ 22 ], while L. variegatus and T. ventricosus usually graze on turtle grass blades ( Thalassia testudinum ) [ 37 ]. The unexpected difference in external microbiota between T. ventriocus and L. variegatus , and the relative similarity between T. ventricosus and the two reefs’ species, could be explained somehow due to the migration behavior of this species [ 70 ].…”

“…Individuals of this species were found and collected close to the limit between the seagrass and back reef zones, at approximately 5 m from the border between the two biotopes. T. ventricosus is a common herbivore of seagrass throughout the Caribbean [ 37 ]. Although T. ventricosus is typically associated with seagrass habitats, it has been observed to migrate to the backreef zone where D. antillarum and E. lucunter inhabit [ 70 ], which could explain their relative similarity in gut bacterial composition [ 4 ] and now their epibionts communities too.…”

“…Furthermore, L. variegatus and T. ventricosus are usually inhabitants of the back-reef biotope dominated by seagrass meadows of Thalassia testudinum . These omnivorous echinoids forage on T. testudinum leaves, but also on macroalgae and small invertebrates [ 37 , 38 ].…”

Features of group growth for gray sea urchin (Strongylocentrotus interme¬dius) at the northwestern coast of the Japan Sea

“…Второй метод -исследование особенностей роста путем периодических измерений ежей, содержащихся в садках или в аквариумах, либо меченых животных, выпущенных в естественную среду (Pearse and Pearse, 1975;Мина, Клевезаль, 1976;Найденко, Дзюба, 1982;Macia, Robinson, 2008). Этот метод также весьма трудоемок, кроме того, данные по росту, полученные при содержании ежей в контролируемых условиях, не позволяют судить о локальных особенностях их роста в естественной среде.…”