Ceratothoa verrucosa (Schioedte & Meinert, 1883)

Hadfield, Kerry A., Bruce, Niel L. & Smit, Nico J., 2016, Redescription of poorly known species of Ceratothoa Dana, 1852 (Crustacea, Isopoda, Cymothoidae), based on original type material, ZooKeys 592, pp. 39-91 : 63-65

Taxon classification Animalia Isopoda Cymothoidae

Ceratothoa verrucosa (Schioedte & Meinert, 1883) Figure 10

Oniscus Ceti Spengler, 1775: 312 [nomen nudum].

Rhexana verrucosa Schioedte & Meinert, 1883: 291-296, tab. XI (Cym. XVIII) figs 5-10.- Thielemann 1910: 34-35, tab. 3.- Sanada 1941: 209-217.- Bruce and Bowman 1989: 2.- Trilles 1994: 134-135.

Rhexanella verrucosa .- Stebbing 1911: 179.- Nierstrasz 1915: 87.- Shiino 1951: 83, figs 1 a–b.- Trilles 1972b: 1255-1256, pl. II, figs 17-18.- Nunomura 1981: 52.- Avdeev 1982b: 69-77.- Bruce and Bowman 1989: 2.- Yamaguchi 1993: 193-194, fig. 21.

Ceratothoa verrucosa .- Yamauchi and Nunomura 2010: 73, figs 7-8.

Ceratothoa verrucosa Identity uncertain: Rhexanella verrucosa .- Nierstrasz 1931: 131.

Material examined.

Lectotype. National Museum of Natural History (Naturalis), Leiden, Netherlands (RMNH.CRUS.I.7706) - ovigerous female (40 mm TL; 21 mm W), collected from Japan, unknown host, 1823-1829, coll: Siebold, Ph.F.v (designated by Yamaguchi 1993). Paralectotypes. Immature female (26 mm TL; 10.5 mm W), two males (16-19 mm TL; 7-8 mm W), same data as holotype (RMNH.CRUS.I.39). Female slightly twisted, non-ovigerous, damaged pereopods and pleopods with uropods missing.

Description.

Lectotype female. Length 40 mm, width 21 mm.

Body oval, 1.9 times as long as greatest width, dorsal surfaces slightly bumpy, widest at pereonite 4, most narrow at pereonite 1, lateral margins slightly convex. Cephalon 0.7 times longer than wide, visible from dorsal view, subtriangular. Frontal margin rounded to form blunt rostrum. Eyes irregular in outline. Pereonite 1 with unique bulbous orientation, anterior border slightly indented, anterolateral angle with large wide projections, extend to anterior margin of eyes. Posterior margins of pereonites slightly damaged and bumpy. Coxae 2-3 wide; 4-7 large and produced on pereonite margins, not extending past pereonite margin. Pereonites subequal. Pleon with pleonite 1 most narrow, visible in dorsal view; pleonites posterior margin not smooth, mostly concave. Pleonite 2 not overlapped by pereonite 7; posterolateral angles of pleonite 2 narrowly rounded. Pleonites 3-5 similar in form to pleonite 2; pleonite 5 free, not overlapped by lateral margins of pleonite 4, posterior margin produced medially. Pleotelson 0.5 times as long as anterior width, dorsal surface with lateral indent, lateral margins weakly convex, posterior margin evenly rounded. Antennula more stout than antenna, same length as antenna, consisting of 7 articles. Antenna consisting of 9 articles.

Pereopod 1 basis 1.4 times as long as greatest width; ischium 0.7 times as long as basis; merus proximal margin with large bulbous protrusion; carpus with rounded proximal margin; propodus 1.2 times as long as wide; dactylus slender, 0.9 times as long as propodus, 1.9 times as long as basal width. Pereopod 7 basis 0.8 times as long as greatest width; ischium as long as basis, with slight bulbous protrusion; merus proximal margin with large bulbous protrusion, merus 0.4 times as long as wide, 0.3 times as long as ischium; carpus 0.6 times as long as wide, 0.9 times as long as ischium, without bulbous protrusion; propodus 0.7 times as long as wide, 0.4 times as long as ischium; dactylus slender, 1.8 times as long as propodus, twice as long as basal width.

Uropod half the length of pleotelson, peduncle as long as rami, peduncle lateral margin without setae; rami not extending beyond pleotelson, marginal setae absent, apices narrowly rounded.

Size.

Ovigerous females: 27-50 mm TL (15.5-25.5 mm W); non-ovigerous females 20.5-40 mm TL; males 15-35 mm TL (11 mm W); larvae 3.5 mm TL ( Schioedte and Meinert 1883, Thielemann 1910, Nierstrasz 1931, Trilles 1972b, Nunomura 1981, Yamauchi and Nunomura 2010).

Distribution.

Known from Japan and surrounding islands ( Schioedte and Meinert 1883, Thielemann 1910, Sanada 1941, Trilles 1972b, Nunomura 1981, Yamauchi and Nunomura 2010).

Hosts.

In the mouth of Pagrus major (previously Pagrosomus major ) ( “Tai” in Japanese) ( Sanada 1941, Shiino 1951, Nunomura 1981, Yamauchi and Nunomura 2010).

Remarks.

Ceratothoa verrucosa is distinguished by the large, oval body; wide anterolateral projections on pereonite 1; pleon as wide as pereon; and short uropods not extending to the posterior margin of the pleotelson.

This species was originally thought to infect a Greenland whale ( Spengler 1775) but Spengler (1775) may have tried to relate this isopod to the whale lice Cyamus ceti . Cymothoid isopods had not been mentioned often before this time and researchers had some confusion with their identification. Schioedte and Meinert (1883), however, stated that this species (referred as "Oniscus Ceti") was undoubtedly the same as their " Rhexana " species. There is no detailed description and no type material for Spengler’s (1775) species, so the original description is a nomen nudum; the correct authority for the species is Schioedte and Meinert (1883) who first made the name available. The name Rhexana was preoccupied, and the genus was then changed to Rhexanella Stebbing, 1911, this name being later synonymised with Ceratothoa (see Hadfield et al. 2014b).

Nierstrasz (1931) listed this species from the East Indian Archipelago, specifically from Nangamessi Bay, Sumba (Indonesia) after being collected during the H.M. Siboga expeditions. If confirmed, this distribution range would increase the distribution of Ceratothoa verrucosa (previously only found from Japan and only from one host, Pagrus major ).