Diogenioninae, Detorre & Williams & Boyko, 2023

Detorre, Marissa, Williams, Jason D. & Boyko, Christopher B., 2023, A review of the endoparasitic isopods (Epicaridea: Entoniscidae) from hermit crabs, including description of the new subfamily Diogenioninae and a new species of Paguritherium Reinhard, 1945 from the Philippines, Zootaxa 5249 (1), pp. 12-40 : 16

Subfamily Diogenioninae n. subfam.

Type genus: Diogenion Codreanu, Codreanu & Pike, 1960

Diagnosis: As for genus, see below.

Included genera: Diogenion Codreanu, Codreanu & Pike, 1960 (1 species).

Remarks: As discussed by Adkison (1990), Diogenion exhibits two apomorphic characters among entoniscids: females with seven pairs of pereopods and lack of pleopods. This genus appears to be the most primitive group of entoniscids and sister taxon to the other two subfamilies, Entoniscinae (apomorphies: females with host derived sheath and oostegites forming brood pouch, first oostegite not different from others, males with unsegmented pereopods) and Entionine (apomorphies: females with heart in pleomere 3 and at least some pleural lamellae complexly folded). Specimens belonging to Diogenion contain characters found in both previously recognized subfamilies; specifically, they share characters with species in Entioninae (presence of a maxilliped in females, and males with segmented pereopods) and Entoniscinae (heart in pleomere 1, absence of pleural lamellae and uropods in females). In terms of larval development, the sole species of Diogenion exhibits synchronous development as is found in species of Entioninae, in contrast to the asynchronous development (i.e., multiple stages at one time in brood chamber) in species of Entoniscinae .Although Adkison (1990) concluded that Diogenion should belong in its own subfamily, he referred to the taxon only as “Subfamily A” throughout the work and his dissertation was never published. In addition, Adkison (1990) never examined any specimens of Diogenion ; his conclusions were made solely from analysis of the original description ( Codreanu et al. 1960). Based on our examination of new material of Diogenion cf. vermifactus from the Philippines and confirmation of the unique suite of characters, we conclude that the genus should be placed in its own subfamily as designated herein.