Evans, C.W. (1977). The ultrastructure of larvae from marine sponge Halichondria moorei Bergquist (Porifera, Demospongiae). Cahiers de Biologie Marine. 18 (4): 427-432.

390307

Evans, C.W.

1977

18 (4): 427-432

Publication

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Larvae from the marine sponge Halichondria moorei Bergquist have been examined by ultrastructural techniques both within the adult sponge and in situ after attachment to an artificial substrate. Settled larvae undergoing metamorphosis were found to possess a complex and unique glycocalyx lining the cells of their upper surface. This unique structure, which has been referred to as the sponge larval coat, was not present on adult sponges nor was it found on unsettled larvae. The ultrastructure and possible mode of synthesis of the larval coat have been discussed, and its similarity in some respects to the amoeba fuzzy surface coat has been noted. In examining the possible functions of the larval coat, no evidence could be obtained to suggest a role in ingestion and thus it is postulated that the main functions of this structure may be to confer protection and support to the settled larvae during metamorphosis. Adhesion of sponge larvae to an artificial substrate has also been examined and it is suggested that the mechanism of attachment bears some similarity to the adhesion of many cultured cells to their substrates. This hypothesis is supported by the absence in sponge larvae of specialized cement glands which are known to be involved in substrate attachment in other marine invertebrates. It is postulated that substrate attachment in sponge larvae involves two sets of interactions: the first is between the cell coat and a groundmat secreted by the larvae and the second involves the attachment of the groundmat to the substrate. The ground mat is thus seen to mediate between the basal cells of the larvae and the substrate to which the larvae are attached.

Indo West Pacific Region

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Porifera

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