A CORAL-EATING BARNACLE, REVISITED (CIRRIPEDIA, PYRGOMATIDAE)

The coral-eating barnacle Hoekia monticulariae (Gray, 1831), the only internal parasite among the Thoracica described to this day, is charac terized by an irregularly-shaped shell nestled cryptically between the polyps of the hermatypic coral Hydnophora Fischer, 1807, which occurs throughout most of the Indo-West Pacific. Because of its protean form , cirripedologists have failed to appreciate the diversity of taxa rel ated to Hoekia, a presumed monotypic genus. We describe seven new spec ies divided between Hoekia and three new genera, Eohoekia, Parahoekia, and Ahoekia for which the Tribe Hoekiini is proposed. As in other pyr gomatids, calcareous overgrowth by the coral is inhibited around the e dge of the wall and aperture. But in Hoekiini a pseudopolyp, upon whic h the barnacle feeds with modified trophi, covers the wall and apertur e. Furthermore, rather than articulating with a calcareous basis, the wall is suspended in coral tissue. Its hypertrophied lateral margin (= basal margin), in contact with the host's tissue, is the site where m etabolic activities are inferred to take place. In Hoekia and Ahoekia, the wall develops simple or connecting tubes that lead to openings in the margin, which serve as circulatory pathways. A hypertrophied marg in and elaborated circulatory system suggests that the Hoekiini may no t be wholly dependent on feeding directly on host tissue and/or coelen teronic material, but may also be absorptive parasites. Although other pyrgomatids, in the tribes Pyrgopsellini nov. and Pyrgomatini nov., e xercise some control over their hosts by an apertural frill and throug h discontinuities between the shell and basis, they are still planktot rophic.