Ceratothoa Dana, 1852

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 : 15-16

Genus Ceratothoa Dana, 1852

Ceratothoa Dana, 1852: 303 ; 1853: 752.—Miers, 1876: 104–105.—Haswell, 1882: 282.— Schiöedte & Meinert, 1883: 322– 323.— Richardson, 1905: 233–234.— Bowman, 1978: 217–218.— Brusca, 1981: 177–178.— Bruce & Bowman 1989: 1–2.—Horton 2000: 1041.— Martin, Bruce & Nowak, 2013: 396; 2015a: 253–254.— Hadfield, Bruce, Szinetár & Smit, 2014b: 449–450.— Hadfield, Bruce & Smit, 2014a: 3–4; 2016: 41–42.— Martin, Bruce & Nowak, 2015a: 253–254.

Codonophilus Haswell, 1881: 471 .—1882: 283.— Hale, 1926: 201, 223.

Rhexana Schiöedte & Meinert, 1883: 289–290 .

Cteatessa Schiöedte & Meinert, 1883: 296–297 .

Meinertia Stebbing, 1893: 354 ; 1900: 642; 1910: 103.— Richardson, 1905: 236–237.—Menzies, 1962: 116.— Schultz, 1969: 156.

Rhexanella Stebbing, 1911: 179 .

Not Ceratothoa .— Dana, 1853: 747.— Richardson, 1905: 236.— Schultz, 1969: 155.— Kussakin, 1979: 287 [= Glossobius Schiöedte & Meinert, 1883].

Type species. Cymothoa parallela Otto, 1828 (by subsequent designation, see Martin et al. 2015a).

Diagnosis. Bruce & Bowman (1989) provided a provisional diagnosis; a detailed diagnosis was provided by Hadfield et al. (2014a).

Remarks. Ceratothoa can be identified by the contiguous swollen antennal bases, antennula more stout than antenna; triangular cephalon, elongate body, widest at pereonite 4 or 5; pleotelson and pleonite 1 which are narrower than the other pleonites, and subequal rami short, not extending past posterior margin of pleotelson, subequal; and the pereopods have a large carinae on basis. Hadfield et al. (2016) revised the poorly known species of Ceratothoa Dana, 1852 with redescriptions based on their type material. The Australian species of Ceratothoa were recently revised by Martin et al. (2015a).

The most recent reviews of this genus are those of Bruce & Bowman (1989), Martin et al. (2013, 2015a) and Hadfield et al. (2014 b, 2016). Meinertia Stebbing, 1893 and Codonophilus Haswell, 1881 were placed into synonymy with Ceratothoa , the senior available name by Bowman (1978), and Bruce & Bowman (1989) synonymised Cteatessa Schiöedte & Meinert, 1883 and Rhexanella Stebbing, 1911 with Ceratothoa . Glossobius and Ceratothoa are very similar and have in the past been considered synonymous by Stebbing (1893). Bowman (1978) resolved the nomenclature ambiguities of Ceratothoa and Glossobius and is considered a valid genus which includes species associated with pelagic beloniform fishes ( Exocoetidae , Hemirhamphidae ). Bruce & Bowman (1989) considered the characters that separate adult females of the two genera to be unambiguous.

Ceratothoa is closely related to other buccal-attaching isopods such as Cinusa Schiöedte & Meinert, 1884 , Glossobius Schiöedte & Meinert, 1883 and Cymothoa Fabricius, 1793 . Cinusa differs from Ceratothoa in the following characters: body ovoid, asymmetrical; pereonite 1 short, with rounded anterolateral margins that do not project anteriorly; pereonites 3 and 4 widest anteriorly; pereonite 1 and antenna bases close-set, almost contiguous ( Hadfield et al. 2010). Cymothoa differs from Ceratothoa by having basal articles of the antennula widely separated and not expanded ( Hadfield et al. 2011), and in having fleshy and thick folds on the pleopod. Ceratothoa has the anterolateral margins of pereonite 1 projecting forward, the anterior margin of pereonite 1 recessed, and pereonite 6 longer than Glossobius .