Holopneustes purpurascens

Williamson, J.E., de Nys, R., Kumar, N., Carson, D.G., and Steinberg, P.D., Induction of metamorphosis in the sea urchin Holopneustes purpurascens by a metabolite complex from the algal host Delisea pulchra, Biol. Bull., 198, 332, 2000. 

A recent study has identified the substances that induce metamorphosis in the sea urchin Holopneustes purpurascens.n Although adult urchins live in the canopy of several different subtidal algae, including the red alga Delisea pulchra and the kelp Ecklonia radiata, recent recruits were found predominantly on D. pulchra. Competent larvae metamorphosed in the presence of D. pulchra, seawater surrounding this alga, and polar extracts of D. pulchra. The cue for metamorphosis was isolated by reverse-phase HPLC from an aqueous partition of the MeOH extract of D. pulchra. It was characterized primarily by NMR and found to be a water-soluble complex... 

Several studies now point to the importance of carbohydrates as settlement cues. Many species of coral larvae that settle on crustose coralline algae metamorphose in response to an algal cell wall polysaccharide.17132 The sacoglossan Alderia modesta metamorphoses in response to carbohydrates of different size classes from its algal food Vaucheria longicaulis.144 The sea urchin Holopneustes purpurascens metamorphoses in response to a complex of the sugar floridoside and isethionic acid from the red alga Delisea pule hr a.11 In this case, the combination of compounds was important because neither induced metamorphosis alone. 

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