New Records of Parasitic Crustaceans (Isopoda and Rhizocephala) on Hermit Crabs from Northeastern Venezuela

Rhizocephalans (Thecostraca: Cirripedia) are parasitic crustaceans that infect a wide range of decapod hosts, including hermit crabs, crabs, and shrimps. These parasites exert profound effects on their hosts, inducing parasitic castration, suppressing the development of secondary sexual characteristics, feminizing male crabs, and altering male behavior that resembles that of females. In this study, we examined the secondary sexual characteristics of two hermit crabs– Pagurus lanuginosus from Asari Town (Hokkaido, Japan) on the Sea of Japan coast and Pagurus filholi from Chikura Town (Chiba, Japan) on the Pacific coast–both parasitized by Peltogasterella gracilis andPeltogaster sp., respectively. Specifically, we assessed the presence of secondary pleopods and the length of the right large cheliped. Our findings demonstrate that male P. lanuginosus and P.filholi parasitized by P. gracilis and Peltogaster sp. exhibit morphological changes and characteristics of females, confirming morphological feminization. Moreover, the magnitude of parasitic effect on morphological feminization varies between the two host species depending on the rhizocephalan genus. It indicates that the extent of feminization varied depending on the parasite genus. Notably, different parasite genera induced varying degrees of host modification, even within the same host species. Similarly, the level of feminization caused by a single parasite genus differed between host species. Our study highlights the importance to understand the characteristics of both the hermit crab host and rhizocephalan parasite to offer a crucial insights into the morphological feminization of the parasite within its host.

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.

Rhizocephalans (Thecostraca: Cirripedia) are parasitic crustaceans that infect a wide range of decapod hosts, including hermit crabs, crabs, and shrimps. These parasites exert profound effects on their hosts, inducing parasitic castration, suppressing the development of secondary sexual characteristics, feminizing male crabs, and altering male behavior to resemble that of females. In the present study, we examined the secondary sexual characteristics of two hermit crab species– Pagurus lanuginosus from Asari (Hokkaido, Japan) on the Sea of Japan coast and Pagurus filholi from Chikura (Chiba, Japan) on the Pacific coast–parasitized by Peltogasterella gracilis and Peltogaster sp., respectively. Specifically, we assessed the presence of secondary pleopods and the length of the right large cheliped. Our findings demonstrate that male P. lanuginosus and P. filholi parasitized by P. gracilis and Peltogaster sp. exhibit morphological changes and characteristics of females, confirming morphological feminization. The magnitude of parasitic effects on morphological feminization varies between the two host species depending on the rhizocephalan genus. Thus, the extent of feminization varies depending on the parasite genus. Notably, different parasite genera induced varying degrees of host modification, even within the same host species. Similarly, the level of feminization caused by a single parasite genus differed between host species. These results highlight the importance of understanding the characteristics of both the hermit crab host and rhizocephalan parasite in developing insights into parasitically induced morphological feminization.

Markham, J.C., 2003. A worldwide list of hermit crabs and their relatives (Anomura: Paguroidea) reported as hosts of Isopoda Bopyridae. In: Lemaitre, R., and Tudge, C.C. (eds), Biology of the Anomura. Proceedings of a symposium at the Fifth International Crustacean Congress, Melbourne, Australia, 9‐13 July 2001. Memoirs of Museum Victoria 60(1): 71‐77. Hermit crabs and their relatives in the anomuran superfamily Paguroidea are among the most frequently reported hosts of bopyrid isopods, all species of which are parasites of decapod crustaceans in general. This report serves, for the first time, to collect the widely scattered records of paguroid infestation into a single list with both host and parasite names updated to conform with the currently accepted nomenclature; each entry includes the geographical locality for the occurrence of each species of parasite on each species of host and the citation of the publication in which it was reported. The known host paguroids are in the Diogenidae (48 species plus 3 others not identified to species), Lithodidae (6), Paguridae (52 + 7), and Parapaguridae (3 + 1). Their parasites belong to three bopyrid subfamilies, the Pseudioninae (32 species occurring in the branchial chambers of hosts), the Athelginae (41 species clinging to the abdomens of their hosts), and the Bopyrophryxinae (one species attached simultaneously to branchiae and abdomen of their hosts).

First 3D reconstruction of the rhizocephalan root system using MicroCT

Transcriptomic analysis of sexually dimorphic cypris larvae of the rhizocephalan barnacle Peltogasterella gracilis