Coral-Eating Barnacles: Wall Morphology and the Descriptions of Two New Species

抄録

Among the species of the zooxanthellate stony coral Hydnophora Fischer, which are found throughout most of the Indo-West Pacific faunal province, only a few are known to be parasitized by the coral-eating barnacles comprising the tribe Hoekiini ROSS and NEWMAN, 1995. The single-plated wall in these sessile cirripeds, nestled cryptically between and tending to mimic the hydnons of the host, assumes an unrivaled spectrum of outlines and overall shapes that seemingly defy description. Indeed, the range of disparate morphological features as well as the number of species in this poorly known taxon are far greater than previously believed.
The present collection includes Hoekia monticulariae (GRAY, 1831) from Singapore, and two species from unspecified localities in the Philippine Archipelago, Hoekia philippensis n. sp. and Ahoekia microtrema n. sp. The latter provide insights into the lacuno-circumferential system and structural organization of the marginal fringe, or inner lamina of the wall. Fringe width, height and density, or ratio of solid to void, as well as how the fringe is accessed, varies with each genus, but the net effect is that the surface area covered by tissue, through which it is believed these barnacles mediate their relationship with the host coral, is essentially comparable in all of the species. In a manner similar to certain other invertebrates, such as corallivorous gastropods, these barnacles likely foster the development of energy sink sites that promote regeneration of the tissue consumed by the barnacle.