Cymothoa frontalis Milne Edwards, 1840

Martin, Melissa B., Bruce, Niel L. & Nowak, Barbara F., 2016, Review of the fish-parasitic genus Cymothoa Fabricius, 1793 (Crustacea: Isopoda: Cymothoidae) from Australia, Zootaxa 4119 (1), pp. 1-72 : 24-25

Cymothoa frontalis Milne Edwards, 1840

Cymothoa frontale (Cymothoé frontal) Milne Edwards, 1840: 271.

Cymothoa frontalis .— White, 1847: 110.— Heller, 1868: 146.— Schioedte & Meinert, 1884: 226, tab. VI (Cym. XXIV) figs. 1, 2.— Gerstaecker, 1901: 261.— Nierstrasz, 1931: 136.— Avdeev, 1978b: 282; 1990: 32, figs. 1–6.— Trilles, 1975: 980, pl. I (3–5). — Bruce, Lew Ton & Poore, 2002: 175.— Trilles & Bariche, 2006: 228: figs. 1–3.

Identity uncertain

Cymothoa frontalis .— Dana, 1853: 750, pl. 49, fig. 12 (a–b).— Trilles, 1994: 143. Cymothoa frontalis .— Rameshkumar, Ravichandran, Sivasubramanian & Trilles, 2013: 42, fig. 1(B).

Type material. Syntypes: 2 ovig. ♀ (17, 22 mm, not examined), from the Indian Ocean; precise location and host not known ( MNHN –IU–2007–4059).

Diagnosis and description. We provide a brief diagnosis of the species. For a detailed description of the type material see Hadfield (2012).

Body subparallel, 2.0 times as long as greatest width, smooth and polished in appearance, laterally sub-parallel, widest at pereonite 5, most narrow at pereonite 1. Cephalon subtriangular, 0.7 times longer than wide, visible from dorsal view. Frontal margin subacute. Eyes partially visible. Pereonite 1 anterolateral margins minute, not reaching anterior margin of cephalon; pereonites 1–4 subequal in length, posterior margin moderately concave, with small medial point; pereonites 5–7 subequal in length. Coxae 2–3 posteroventral margins subtruncate; 6 and 7 with moderately acute carinae. Pleonites subequal in width, visible in dorsal view; pleonites posterior margin irregular. Pleotelson subtruncate, 0.7 times as long as anterior width, anterior margin irregular, lateral margin straight, posterior margin irregular, without median point. Antennula comprised of 8 articles. Antenna comprised of 9 articles. Pereopods 1 and 2 dactyli slender; carpus with straight proximal margin; merus proximal margin without bulbous protrusion; basis superior proximal basis broad, without acute carinae. Pereopods 3–5 similar to pereopod 2, gradually increasing in size, without robust or simple setae. Pereopods 6 and 7 superior proximal basis with broad and raised carinae; merus proximal margin without bulbous protrusion; dactyli stout. Uropod not extending beyond pleotelson posterior margin, peduncle 0.9 times longer than exopod rami, apices narrowly rounded.

Size. Ovigerous females: 24–28 mm; non-ovigerous female: 20 mm ( Schioedte & Meinert 1884).

Remarks. Cymothoa frontalis has a narrow and elongate body; subtriangular cephalon not immersed in pereonite 1; pereonite 1 with minute anterolateral margins; posterior margins of pereonites weakly trisinuate; pereonite 7 deeply arched and appearing to overlap pleonites 1–3; pleon narrow; pleonites subequal in width; uropods half the length of the pleotelson; and pleotelson posterior margin subtruncate. Cymothoa frontalis also appears to have the posterolateral margins of pereonites more curved than Trilles’s (1975) specimen.

Cymothoa frontalis closely resembles C. indica in the subtriangular cephalon and pereonite 1 with minute anterolateral margins that do not reach beyond the anterior half of the cephalon. Cymothoa indica differs from C. frontalis in having a moderately broad and weakly subparallel body [2.2 times longer than wide in Hale’s (1926) illustration and 2.3 times longer than wide in Trilles & Bariche’s (2006) illustrations of C. indica ]; uropod reaching or extending beyond pleotelson posterior margin and pereopod 7 basis without raised carina.

Dana’s (1853) illustration of C. frontalis showed a rounded rostrum, coxae on pereonites 3–7 visible from dorsal view, and posterior margin of pereonites evenly curved. Nearly all of Dana’s collections were lost with the wreck of the USS Peacock on the bar of the Colombia River ( Dana 1852b), so the identity of his specimen(s) cannot be established and we have excluded the record from the synonymy.

A single female specimen of C. frontalis from one of 14 Strongylura leiura (Bleeker, 1850) was recorded from Mathupettai, India ( Rameshkumar et al. 2013). The Indian specimen is very similar to the syntype in the subtriangular cephalon not being immersed in pereonite 1 and pereonite 1 with minute anterolateral margins that do not reach beyond the anterior half of the cephalon, but differs from the syntype in having a more rounded pleotelson posterior margin, uropodal rami not reaching half of pleotelson length, and a subtruncate cephalon anterior margin. This is the only specimen reported from Strongylura (family Belonidae ) and without further description of the Indian specimen, we regard this record as of uncertain identity.

Distribution. Known from the Indian Ocean ( White 1847; Schioedte & Meinert 1884; Trilles 1975); Singapore ( Heller 1868); Bangkok ( Schioedte & Meinert 1884; Trilles 1975); and off west coast of Australia ( Avdeev 1978b).

Hosts. Only known from the family Cyclopteridae : on the gills of Cyclopterus (see White 1847).