Chemical Analysis of Holothurian Sclerites

Abstract

THE Holothuroidea differ from all other echinoderm classes in having a greatly reduced skeletal system. Typically, external plates are absent, while a peripharyngeal crown, anal plates, madreporite and spicules are usually present. Of these, the endoskeletal spicules (or ossicles), formed in superficial dermal layers, constitute the outstanding character of the class, and are of paramount importance in the specific identification of Recent forms. Although it has been continually stated that such holothurian spicules, as with all other echinoderm skeletal elements, consist entirely of calcium carbonate, few accurate attempts to analyse them chemically have been made¹. It seems of interest, therefore, to record results obtained by a chemical examination of spicules from a typical aspidochirote holothuroid, Holothuria impatiens (Forskäl), a littoral species of circumtropical to subtropical distribution.