Cymothoa Fabricius, 1793

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 : 17-18

Genus Cymothoa Fabricius, 1793

Cymothoa Fabricius, 1793: 503 .— Milne Edwards, 1840: 264.— Schiöedte & Meinert, 1884: 223.— Kussakin, 1979: 289.— Brusca, 1981: 185.— Brusca & Iverson, 1985: 45.— Trilles, 1994: 137.— Hadfield, Bruce & Smit, 2011: 58.— Hadfield, Bruce & Smit, 2013: 153:— Martin, Bruce & Nowak, 2016; 5.

Type species. Oniscus oestrum Fabricius, 1793 ; by subsequent designation ( Kussakin 1979).

Diagnosis. The genus diagnosis has been comprehensively revised by Hadfield et al. (2011, 2013).

Remarks. Cymothoa is may be identified by the strongly vaulted body; widest at pereonite 3; cephalon with wide, subtruncate rostrum folded back deeply immersed in pereonite 1, widely separated and slender antenna and antennula; coxae 5–7 dorsally partially visible; pereonite 7 posterolateral margins extending past pleonite 1; wide pleotelson; pleonite 1 as wide as other pleonites; and uropod rami which are shorter than the pleotelson; pereopods 5–7 basis with broad blade-like carina.

The other common buccal cavity inhabiting genera in the north-eastern Indian Ocean are Ceratothoa Dana, 1852 and Cinusa Schiöedte & Meinert, 1884 . Cymothoa has widely separated antenna bases, while Cinusa has narrowly separated bases; Ceratothoa has contiguous antennal bases and the antenna are also conspicuously expanded ( Martin et al. 2015a). The genus Cymothoa has not been reviewed for many years; although brief notes on the generic characteristics have been provided by several researchers ( Brusca 1981; Brusca & Iverson 1985; Hadfield et al. 2011; Hadfield 2012; Martin et al. 2015a). Smit et al. (2014) showed that the highest cymothoid diversity is found in the tropics and rapidly drops as latitude increases. This is relevant to Cymothoa , where nine species are each found in the central Indo–Pacific and tropical Atlantic region and eight species in the western Indo–Pacific. Five species of Cymothoa were known from Indian waters, and this number has not changed despite the current review for the genus, suggesting that perhaps different cymothoid genera have different levels of diversity or distribution.