Two New Species of Spheroid Ectoparasitic Isopods (Epicaridea: Dajidae) Attached to the Antennules of Brachyuran Crab Hosts, with Description of a New Genus and Species of Hyperparasite (Epicaridea: Cryptoniscoidea)

In this paper, we describe two new species of dajid isopods found enveloping the antennules decapod hosts: Akrophryxus acinaces sp. nov. parasitizing Pycnoplax surugensis (Rathbun, 1932) (off Pacific coast central Japan, approximately 200 m depth) and A. pallipalicus Parapalicus armatus Castro, 2000 (South China Sea, 410 depth). Females both exhibit characteristic spheroid shape in genus Williams Boyko, 2021. three can be distinguished by several characters, including form pleon oostegite 5. Males head/pereomere 1 to pereomere 2 ratio posterolateral margin shape, pereopod 6 dactylus ischium size. The not only differ morphological characters but parasitize belonging different heterotreme brachyuran families. first described cryptoniscus larval stage for any is We also a cryptoniscoid, Chimaeroniscus spheramator gen. et nov., hyperparasite from host (A. on Pa. armatus). This putative egg predator its exhibits unique combination generic level including: markedly narrower than pereon, antennule with large teeth basal segment setal brush, 3 or 4 coxal all pereomeres, pereopods 3–7 isomorphic dissimilar 2, telson smooth distomedial projection, uropodal exopods half-length endopods. Finally, address some taxonomic issues within Cryptoniscoidea, moving genera (Neritoniscus Schultz, 1977 Cryptocisus 1977) known Cryptoniscoidea incertae sedis Dajidae synonymize Cryptonus Holophryxus Richardson, 1905.