A new species and record of branchial parasitic isopods (Crustacea: Isopoda: Bopyridae: Pseudioninae) of porcellanid crabs from the Philippines.

Branchial bopyrids infesting porcellanid crabs from the Philippines were investigated based on intertidal collections made in 1999-2000. Crabs of the genus Petrolisthes collected from sites in the northern Philippines were examined and two parasite species were found. One new pseudionine species found infesting Petrolisthes sp. [cf. Petrolisthes asiaticus (Leach)] is described as Aporobopyrus galleonus (prevalence 6.1%); this species is distinguished from other members of the genus by a setose palp on the maxilliped of the females, barbula morphology, and male characters including the possession of pleopods. This represents the second described species of Aporobopyrus from the Philippines, and the first from porcellanid crabs. In addition, Pleurocrypta macrocephala Nierstrasz and Brender à Brandis, 1923 (originally described from Indonesia) was found infesting the same unidentified Petrolisthes sp. (prevalence 2.6%); this is the first report of the species from the Philippines.