Cymothoa Fabricius, 1793

Hadfield, Kerry A., Bruce, Niel L. & Smit, Nico J., 2011, Cymothoa hermani sp. nov. (Isopoda, Cymothoidae, Crustacea), a parasitic isopod, collected off the Zanzibar coast, Tanzania from the mouth of a parrotfish (Scaridae), Zootaxa 2876, pp. 57-68 : 58

Genus Cymothoa Fabricius, 1793

Restricted synonymy

Cymothoa .– Kussakin, 1979: 289.– Brusca, 1981: 185.– Trilles, 1994: 137.

Diagnosis of adult female. Body elongate, bilaterally symmetrical. Cephalon immersed in pleonite 1. Antennae slender, basal articles widely separated and not expanded, antennule more stout than antenna. Pereonites with lateral margins rounded. Pereonite 1 with anterolateral angles produced to some extent around cephalon. Pereonite 7 laterally encompassing pleon. Coxae 5–7 not extending beyond posterior margin of pereonite. Pereopods 1–3 shorter than 4–7 with no carina, pereopods 4–7 each with carina on basis. Pleon narrowest at pleonite 1, pleonites increasing in length and width from anterior to posterior. Pleotelson without median point. Pleopods without setae, exopod larger than endopod. Pleopods with exopod and endopods generally distally broadly rounded, peduncle without retinaculae.

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

Remarks. Brusca (1981) considered Cymothoa to be one of the most poorly understood genera in the Cymothoidae with only two or three of the then thirty known species that could be regarded as being fully described at the time of writing. Only five more species of Cymothoa have been described since the 1980s, and thus Brusca’s (1981) statement is still relevant as no attempt has yet been made to revise this genus.

The other common buccal cavity inhabiting genera in the south-western Indian Ocean are Ceratothoa Dana, 1852 and Cinusa Schioedte and Meinert, 1884 . Cymothoa has widely seperated antenna bases, while Cinusa has narrowly separated bases; Ceratothoa has contiguous antennal bases and the antennae are also conspicuously expanded ( Hadfield et al. 2010).

Of the current 48 known Cymothoa species (see Schotte et al. 2010) only three have been reported from the south-western Indian Ocean namely C. borbonica Schioedte & Meinert, 1884 , C. eremita ( Brünnich, 1783) and C. rotundifrons Haller, 1880 ( Kensley 2001) . Cymothoa borbonica has been recorded from Reunion Island ( Schioedte and Meinert 1884, Monod 1934), Maldives ( Stebbing 1904), South Africa ( Barnard 1920), Mozambique ( Barnard 1926), Madagascar ( Barnard 1960, Trilles 1975, Trilles 1979) and Mauritius ( Trilles 1975). Cymothoa eremita has been recorded from Mauritius ( Leach 1818), the Seychelles Islands ( Milne Edwards 1840), and Zanzibar ( Stebbing 1910), and C. rotundifrons is known only from the type locality, Mauritius ( Haller 1880).