Crustacean parasites associated with hermit crabs from the western Mediterranean Sea, with first documentation of egg predation by the burrowing barnacle Trypetesa lampas (Cirripedia: Acrothoracica: Trypetesidae).

Parasitic isopods (family Bopyridae) and burrowing barnacles (family Trypetesidae) infesting hermit crabs were investigated from shallow subtidal collections made along the southeastern coast of Spain in 2009. A total of 713 specimens of Clibanarius erythropus (Latreille, 1818) and 82 Calcinus tubularis (L., 1767) were examined. Gastropod shells and worm tubes inhabited by hermit crabs were collected by hand while snorkeling and were cracked to determine host species, size, sex and presence of eggs. Two species of bopyrid isopods were found on C. erythropus: the branchial parasite Bopyrissa fraiseii (Carayon, 1943) and the abdominal parasite Parathelges cardonae Codreanu and Codreanu in Codreanu, 1968. Among all C. erythropus examined, Bopyrissa fraiseii was found on 0.6% of hermit crabs and P. cardonae was found on 0.3%. A redescription of P. cardonae is provided and the species is documented with light and scanning electron microscopy for the first time. No Calcinus tubularis harbored parasitic isopods, but one specimen was parasitized by an unidentified rhizocephalan barnacle of the genus Septosaccus (1.2%). The burrowing barnacle Trypetesa lampas (Hancock, 1849) was found associated with both hermit crab species and evidence of predation on host eggs by this barnacle is shown for the first time. Trypetesa lampas was found in 4.2% of the shells collected. The present study expands our knowledge of the parasite fauna of hermit crabs from the Mediterranean Sea and indicates that additional research is needed to determine the impact of trypetesid egg predators on hermit crab populations.