Ceratothoa Dana, 1852

Martin, Melissa B., Bruce, Niel L. & Nowak, Barbara F., 2013, Redescription of Ceratothoa carinata (Bianconi, 1869) and Ceratothoa oxyrrhynchaena Koelbel, 1878 (Crustacea: Isopoda: Cymothoidae), buccal-attaching fish parasites new to Australia, Zootaxa 3683 (4), pp. 395-410 : 396

Genus Ceratothoa Dana, 1852

Ceratothoa Dana, 1852: 203 ; 1853: 747.— Miers, 1876: 104 –105.— Schioedte and Meinert, 1883: 322.— Richardson, 1905: 233.— Bowman, 1978: 217 –218.— Brusca, 1981: 177.— Bruce and Bowman, 1989: 1.— Horton, 2000: 1041.

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

Rhexana Schioedte and Meinert, 1883: 289 .

Cteatessa Schioedte and Meinert, 1883: 296 .

Meinertia Stebbing, 1893: 354 ; 1900: 642; 1910: 103.— Richardson, 1905: 236.— 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 Schioedte and Meinert, 1883 ].

Type species. The type species for Ceratothoa can only be Cymothoa gaudichaudii Milne Edwards, 1840 or Cymothoa parallela Otto, 1828 , these being the two species included in the genus by Dana (1852). The type specimen of Ceratothoa parallela was originally deposited in Museum of Göttingen ( Schioedte & Meinert 1883) but is no longer extant ( Bruce and Bowman 1989; Horton 2000; Hadfield 2012). Trilles (1972b) examined a female (no.48) and male (no.49) Ceratothoa gaudichaudii held at the MNHN and labelled as M. Gaudichaud’s material. The male specimen (labeled ‘type’), cannot be the specimen (2 pouces, c. 25 mm) described by Milne Edwards (1840) according to Trilles (1972b) and Horton (2000) due to its small size (19 mm). Horton (2000) cites the female examined by Trilles as a lectotype, although no author has made a lectotype desgination. According to Hadfield (2012), both specimens attributed to M. Gaudichaud should be regarded as syntypes, with the male being the accompanying male to the female. Milne Edwards did not (for any of this species) indicate the number of specimens that he had at hand, and we agree with Hadfield’s (2012) interpretation. The female ‘syntype’ for Ceratothoa gaudichaudii is apparently missing ( Hadfield 2012) or near destroyed ( Trilles 1972b), the bottle containing only the male syntype collected in Chile, Coquimbo (MNHN-Is315).

Remarks. Characters that define Ceratothoa include contiguous antennal bases, pereonite 1 longest, body widest at pereonite 4 or 5 and subequal uropod rami that are equal in length or extend to the posterior margin of the pleotelson. Ceratothoa is closely related to other buccal-attaching isopods such as Cinusa Schioedte and Meinert, 1884 , Glossobius Schioedte and 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; pereonite 3 to 4 widest anteriorly; pereonite 1 and antennae bases close-set, almost contiguous ( Hadfield et al. 2010). Cymothoa differs from Ceratothoa by having basal articles of the antennule widely separated and not expanded ( Hadfield et al. 2011), and in having fleshy and thick folds on the pleopods.

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 recommended that species records of Ceratothoa found on flying fish should be transferred to Glossobius Schioedte and Meinert, 1883 . Bruce and Bowman (1989) considered the characters that separate adult females of the two genera to be unambiguous. Ceratothoa has the anterolateral margins of pereonite 1 projecting forward, the anterior margin of pereonite 1 recessed, and pereonite 6 longer than Glossobius .