Darwin's Pyrgoma (Cirripedia) revisited: Revision of the Savignium group, molecular analysis and description of new species

Darwin recognized the coral inhabiting barnacles as congeneric belonging to Pyrgoma. Ross and Newman (1973) assigned those with fused shell and elongated scuta to the genus Savignium. Later those with tooth like articular projection on tergum were assigned to Trevathana dentata. We sequenced and analyzed the divergence of three mithochondrial genes (12S rDNA, 16S rDNA, COI) of Savignium crenatum from two host coral, of Neotrevathana elongata from Echinopra and of T. dentata from five host corals genera, Leptastrea, Platygyra, Favia, Favites, and Cyphastrea. Based on the molecular analysis of these genes we show that members of populations of the nominal species T. dentata occupying different host corals display clear genetic differences, suggesting that the barnacles from these five different coral genera represent five distinct biological species. These species display host specificity at the generic level. Barnacles colleted from the same host genus but different geographical regions, clustered in the same clades. We described morphological characters of the shell, opercular valves, and limb characteristics, trophi and cirri, of barnacles from these host coral. We concluded that the material extracted from Leptastrea conform with Darwin's type and the specific epithet of Trevathana from Leptastrea should continue to be dentata, specimens from the four other host corals are four new species of Trevathana; namely T. mizrachae n. sp. from Platygyra, T. margaretae n. sp. from Favia, T. jensi n. sp. from Favites, and T. sarae n. sp. from Cyphastrea. The morphological data confirm the results of the molecular analysis that species of coral inhabiting barnacles are highly genus-level host-specific.