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Abstract

Grossly enlarged corallites, which had earlier been interpreted as tumors, epibionts, or parasitic galls, on colonies of deep-sea scleractinians of the genus Madrepora from various Indo-Pacific localities, were recognized as galls in 1996 by Grygier and Cairns on account of the new species of ascothoracidan crustacean, Petrarca madreporae Grygier, they had found inside enlarged corallites from a site in Indonesia. Here we report the confirmatory recovery of living specimens of P. madreporae from an enlarged corallite of a possibly undescribed variant of Madrepora oculata Linnaeus in Japan. Two affected coral colonies were taken by fishermen off Katsuura, Chiba Prefecture, at ca. 480 m depth. A fully living colony had one enlarged corallite (18.3 × 13.8 mm) containing two specimens of P. madreporae within its basal part, along with eggs that hatched into nauplius larvae. The first and second naupliar stages resembled those of the confamilial ascothoracidan Zibrowia ?auriculata Grygier. The second, partly dead colony had four slightly or considerably enlarged corallites with a spongy columella and no fossa; these lacked coral tissue at the time of collection and had only empty cavities inside. Photographs of the corals, their enlarged corallites and internal cavities, and the parasites, as well as a morphological account of the successive stages of gall formation and illustrations of the parasites’ nauplius larvae, are presented here. A comparison is made to enlarged corallites in another deep-sea coral, Lophelia pertusa (Linnaeus), attributed to infection by sponges, along with a suggestion of a possible mutualistic benefit to the host of infection by P. madreporae and a full list of records of Petrarcidae and presumed petrarcid galls from Japan.

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