Ceratothoa carinata Bianconi 1869

Ceratothoa carinata (Bianconi, 1869)

Figures 1–3

Cymothoa carinata Bianconi, 1869: 210, pl. II, figs. 2 (a, b).— Gerstaecker, 1901: 258.

Cymothoa (Ceratothoa) carinata.— Hilgendorf, 1879: 846.

Ceratothoa carinata.— Schioedte and Meinert, 1883: 327, pl. XIII (Cym. XX) figs. 1–2.– Trilles, 1986: 623, tab. 1; 1994: 116; 2008: 23.— Kensley, 2001: 232.— Bruce, 2007: 278. —Trilles 2008: 23.

Meinertia carinata.— Lanchester, 1902: 378.— Stebbing, 1910: 103.— Trilles, 1972b: 1244, 1256, pl. I, photos 5–7; 1972c: 3, photos 1–4.

Codonophilus carinatus.— Nierstrasz, 1931: 132.

Ceratothoa curvicauda Nunomura, 2006: 36, figs. 12–13. [new synonymy]

Ceratothoa sp.— Saito, 2009: 7, photos 1, 2.

Material examined. Ƥ (31 mm ovig., dissected), Arafura Sea, Northern Territory, 22 November 1980, from buccal cavity of Selar crumenophthalmus (Bloch, 1793) (host registration QM I219506-006), coll. CSIRO Soela (MTQ W30409).

Ovigerous female. Length 31 mm, width 11 mm.

Body 2.5 times as long as greatest width, dorsal, median longitudinal ridge present; cuticle smooth and polished in appearance, widest at pereonites 4 and 5, narrowest at pereonite 1; dorsolaterally concave. Cephalon 0.6 times longer than wide, visible in dorsal view. Frontal margin subacute, simple, not folded. Eyes trapezoid, narrow, 0.1 times width of head. Pereonite 1 smooth with slight indentations produced medially, anterolateral angle with small distinct produced point. Coxae 2–3 with posteroventral angles rounded; 4–7 with small, distinct point. Pereonites 5–7 progressively narrower in length and 7 is one third the length pereonite 6. Pereonite 5–7 posteriorly arched, with pereonite 7 posterior end hidden under pleonite 2. Pleonite 1 visible in dorsal view; pleonites 2–5 progressively wider; pleonite posterior margins smooth, mostly concave; posterolateral angles of pleonite 2 narrowly rounded. Pleonite 5 with posterolateral angles overlapped by lateral margins of pleonite 4, posterior margin bisinuate. Pleotelson 0.4 times as long as anterior width, dorsal surface with 2 sub-medial depressions; lateral margins convex, posterior margin emarginate.

Antennule more stout than antenna, comprised of 7 articles; peduncle articles 1 and 2 distinct and articulated; article 2 0.8 times as long as article 1; article 3 0.4 times as long as combined lengths of articles 1 and 2, 0.8 times as long as wide; flagellum with 4 articles, extending to posterior margin of eye. Antenna comprised of 9 articles. Antenna peduncle article 3 1.8 times as long as article 2, 1.0 times as long as wide; article 4 1.2 times as long as wide, 1.2 times as long as article 3; article 5 0.5 times as long as article 4, 1.1 times as long as wide; flagellum with 5 articles, terminal article without setae, extending to posterior margin of head. Labrum lateral margins concave, with small median point. Mandibular process ending in acute incisor, mandible palp article 2 and 3 with fine ‘pectinate scales’. Maxillule simple with 4 terminal robust spines. Maxilla mesial lobe with 8 recurved spines, partly fused to lateral lobe with 9 recurved spines. Maxilliped oostegite lobe lamellar. Maxilliped article 3 with 4 curved spines. Oostegite smooth, with setae.

Pereopod 1 basis 1.5 times as long as greatest width; ischium 0.8 times as long as basis; merus proximal margin without bulbous protrusion; carpus with straight proximal margin; propodus 1.6 times as long as wide; dactylus slender, 1.3 as long as propodus, 4.5 times as long as basal width. Pereopod 2 propodus 1.4 times as long as wide; dactylus 1.2 times as long as propodus; similar to pereopod 3. Pereopod 6 basis 1.0 times as long as greatest width; ischium 1.0 times as long as basis, propodus 1.0 as long as wide, dactylus 1.4 times as long as propodus. Pereopod 7 basis 1.1 times as long as greatest width; ischium 0.8 times as long as basis, with large proximal flattened protrusion; merus proximal margin with slight bulbous protrusion, merus 0.3 times as long as ischium, 0.5 times as long as wide; carpus 0.3 times as long as ischium, without bulbous protrusion, 0.5 times as long as wide; propodus 0.5 times as long as ischium, 1.0 times as long as wide; dactylus slender, 1.2 times as long as propodus, 1.8 times as long as basal width.

Pleopod 1 exopod 3.8 times as long as wide, lateral margin distally concave, distally narrowly rounded with strongly oblique medial margin, mesial margin straight; endopod 4.2 times as long as wide, lateral margin convex, distally narrowly rounded, mesial margin straight.

Uropod same length as pleotelson, peduncle lateral margin without setae; rami not extending beyond pleotelson. Endopod apically slightly pointed, 4.2 times as long as greatest width, lateral margin weakly convex, mesial margin weakly convex. Exopod not extending to end of endopod, 3.8 times as long as greatest width, apically rounded, lateral margin straight, terminating with no setae, mesial margin distally concave.

Male. No male was available as part of this study. Nunomura (2006) noted lateral sides of body nearly parallel, with large lobes on posterolateral angles of pereonite 1.

Colour. Pale brown in ethanol.

Size. Present material: ovigerous female 31 mm. Other records indicate ovigerous female: 28–38 mm, nonovigerous females: 13–34 mm, male: 10–18 mm (Bianconi 1869; Nunomura 2006; Saito 2009; Schioedte & Meinert 1883; Stebbing 1910; Trilles 1972b, 1972c).

Hosts. The Australian specimen is from bigeye scad Selar crumenophthalmus. Other records reported from amberstripe scad Decapterus muroadsi (Temminck & Schlegel, 1844) (see Nunomura 2006; Saito 2009) and Trilles (1972b, 1972c) reported a non-ovigerous female Ceratothoa carinata from yellow-banded snapper Lutjanus adetii (Castelnau, 1873) in New Caledonia.

Distribution. Mozambique (Bianconi 1869; Hilgendorf 1879; Schioedte & Meinert 1883), Great Redangs, Malay Peninsula (Lanchester 1902); Sagami Sea (Nunomura 2006); Toba town, Mie Prefecture (Saito 2009); Seychelles (Stebbing 1910); New Caledonia (Bruce 2007; Trilles 1972b, 1972c); and Red Sea (Trilles 2008).

Remarks. Ceratothoa carinata can be identified by the pleotelson being wider than long with a deeply concave posterior margin, the pereon dorsal surface with a median longitudinal ridge (from which the species takes its name), the adjacent dorsal surfaces on either side being somewhat depressed or concave, and pereopod 7 with a greatly enlarged carinate ischium and basis. The illustration given by Bianconi (1869) clearly shows these characters, and the specimen from the Arafura Sea agrees entirely with the original description and the later figures given by Schioedte and Meinert (1883) and Trilles (1972 b, 1972c).

Similar species to Ceratothoa carinata are Ceratothoa trigonocephala (Leach, 1818) and Ceratothoa trillesi (Avdeev, 1979b), but both have a narrow pleonite 1, shorter pleotelson with a broadly convex posterior margin, a smooth and convex dorsum, and pereopod 7 lacks an enlarged ischium.

The figures and descriptions of Ceratothoa curvicaudata Nunomura, 2006 agree entirely with those of Bianconi (1869), Schioedte and Meinert (1883) and Trilles (1972b, 1972c) and with the present material, showing the characteristic deeply concave posterior margin of the pleotelson, wide pleon (same width as pereon) and pereopod 7 with an enlarged ischium. Nunomura’s (2006) figures of mouthparts agree with the present specimen from Selar crumenophthalmus and we have no hesitation in placing Ceratothoa curvicaudata Nunomura, 2006 into junior synonymy with Ceratothoa carinata Bianconi, 1869.

The holotype deposition is not known. Schioedte and Meinert (1883) mentioned a specimen from the type locality (Mozambique) as deposited at the Zoologisches Museum, Museum für Naturkunde, Homboldt-Universität Berlin, Germany, but it is highly likely that the specimen was destroyed during World War II (Hadfield 2012).