Studies on Decapod Crustacea From the Indian River Region of Florida. Xxiii. The Laboratory Cultured Zoeal Stages of the Coral Gall-forming Crab Troglocarcinus Corallicola Verrill, 1908 (Brachyura: Hapalocarcinidae) and Its Familial Position

The first 5 zoeal stages of the brachyuran, coral-inhabiting, gall-forming crab Troglocarcinus corallicola Verrill, 1908, are described and illustrated. Based on the sequential appearance of morphological characters, this species passes through at least 5, and perhaps 6 or 7 larval stages before metamorphosing to megalopa. The zoeae can be easily recognized in the plankton by a combination of lateral aliform expansions on the fourth, and a distinct dorsal caplike process on the second abdominal somite. The number of abdominal somites (5) remains constant throughout the first 5 (and probably subsequent) zoeal stages. Evidence from larval morphology supports the contention based on adult characters, that the Hapalocarcinidae are closely related to the Pinnotheridae, as well as having close affinities to the Hymenosomatidae and Leucosiidae. The family Hapalocarcinidae is a widespread group of approximately 27 species in at least 8 genera (Fize and Serene, 1957; Takeda and Tamura, 1979). The major distribution is throughout the Pacific and Indian Oceans, with only 3 species presently recorded from the Atlantic Ocean (2 from the western Atlantic and one from the eastern Atlantic). The family is unique in that the members symbiotically associate with scleractinian corals by forming galls, dens, or depressions within the substratum of the living corallum. Previous studies have been primarily taxonomic in nature, but the group is so taxonomically confusing that its phylogenetic position within the brachyuran Decapoda has not been established with certainty. Within the family, first zoeal larvae have been briefly described and inadequately illustrated for only 3 species (Potts, 1915; Edmondson, 1933; Fize, 1956; Al-Kholy, 1963; as reviewed in Castro, 1976), so that the larval development within the family can be considered practically unknown. Of the 2 species known from the western Atlantic Ocean, Troglocarcinus corallicola is the most widespread, being recorded from Bermuda (the type-locality of Verrill, 1908), Straits of Florida, northeastern Gulf of Mexico, and Dominica, British West Indies (Rathbun, 1937; Shaw and Hopkins, 1977). The species is a known symbiont of madreporarian hermatypic corals, in which it forms lunate galls or dens. However, our collections made off the central eastern Florida coast showed the species to be an associate of the Ivory Tree Coral Oculina varicosa Lesueur, 1820, as well. Among specimens obtained were several ovigerous females. These offered an opportunity to study the larval development of the species, and perhaps clarify systematic relationships within the family. Accordingly, this paper reports on the first 5 larval stages of Troglocarcinus corallicola, and (as far as previously published data allow) compares morphological characters of the zoeae with those noted for the Pacific species Hapalocarcinus marsupialis Stimpson, 1859 (Potts, 1915; Al-Kholy, 1963) and Cryptochirus minutus Edmondson, 1933 [=C. coralliodytes Heller, 1861, fide Utinomi, 1944].