Ryukyua Williams & Bunkley-Williams, 1994

Ravichandran, S., Vigneshwaran, P. & Rameshkumar, G., 2019, A taxonomic review of the fish parasitic isopod family Cymothoidae Leach, 1818 (Crustacea: Isopoda: Cymothooidea) of India, Zootaxa 4622 (1), pp. 1-99 : 73

Genus Ryukyua Williams & Bunkley-Williams, 1994

Ryukyua Williams & Bunkley-Williams, 1994: 155–161 .— Vigneshwaran, Ravichandran & Martin, 2018d: 199 .

Livoneca — Pillai, 1954: 17 ; 1964: 218–220 [partim].

Type species. Ryukyua globosa Williams & Bunkley-Williams, 1994 , by holotype.

Diagnosis. A detailed diagnosis was given by Williams & Bunkley-Williams (1994) and Vigneshwaran et al. (2018d).

Remarks. Williams & Bunkley-Williams (1994) provided the provisional diagnosis of the genus Ryukyua . Ryukyua can be identified by the strongly hunched and spherical body; mandibular palp all distinct article 3 short; coxae partially visible dorsally; uropods small relative to body size, rami elongate-oval, subequal in length.

Ryukyua shares several characters with Cterissa Schiöedte & Meinert, 1884 . Both genera are similar with regard to their cephalon and pereon morphology, cephalon small deeply immersed into pereonite 1, posterior margin not trilobed; pereonite 1 short, lateral margins convex, wider than two thirds the length of pereonite 2; pereonites 6 and 7 decreasing in width and length posteriorly, widest at pereonites 4 and 5; pereonite 7 posterior margin deeply concave, lateral margin produced posteriorly and overlapping lateral margin of pleonites 3–5. Ryukyua can be distinguished from Cterissa in having symmetrical body coxae 2–3 narrow with posteroventral angles rounded; coxae 4–7 acute, partially visible in dorsal view (vs coxae of pereonites all wide rounded and visible in dorsal view in Cterissa ) and pleonites 1–3 lateral margins which are not bilobed. The genus Ryukyua distinguished from other known cymothoid genera by hunched and spherical body.