The distribution and host utilization of scleractinian coral-infesting Ascothoracida (Crustacea, Thecostraca), including the discovery of a new species of Petrarca from Dongsha Island, Taiwan

Petrarca is a genus of specialized crustacean ascothoracidan endoparasites that inhabit scleractinian corals and form galls on the corals’ surface. In the present study, we identified a new species, Petrarca chengi sp. nov., within external galls on the deepwater coral Deltocyathus magnificus collected off Dongsha Island, Taiwan. We provide a description of the new species based on light and scanning electron microscopy.

This species is diagnosed using the morphology of the carapace, mouthparts, and penis. Diagnostic morphological characters for Petrarca include: carapace shape, the morphology of carapace papillae and spines, the structure of the rudimentary abdomen, the shape of the distal part of the penis, the morphology of thoracopod 1, the cutting margins of the mandibles and maxillules, and the ultrastructure of the distal part of the aesthetasc of the antennular claw guard.

The study also compares host specificity interactions among members of the family Petrarcidae, including the genera Introcornia, Petrarca, and Zibrowia, offering new insights into the biology of these parasitic crustaceans. We provide a comprehensive summary of existing records for these genera; the resulting data on localities, depths, and host taxonomy reveal the parasites’ vast geographical ranges and diverse host associations.