Ceratothoa carinata (Bianconi, 1869)

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 : 46-47

Taxon classification Animalia Isopoda Cymothoidae

Ceratothoa carinata (Bianconi, 1869) Figure 3

Cymothoa carinata Bianconi, 1869: 210-211, pl. II, figs 2 ( a–b).- Gerstaecker 1901: 258.

Cymothoa (Ceratothoa) carinata .- Hilgendorf 1879: 846.

Ceratothoa carinata .- Schioedte and Meinert 1883: 327-329, pl. XIII (Cym. XX) figs 1-2.- Trilles 1986: 623, tab. 1; 1994: 116-117; 2008: 23.- Kensley 2001: 232.- Bruce 2007: 278.- Trilles 2008: 23.- Martin, Bruce and Nowak 2013: 397-401, figs 1-3.- Nagasawa, Fukuda and Nishiyama 2014: 59-61, fig. 1.- Martin, Bruce and Nowak 2015a: 266-267.

Meinertia carinata .- Lanchester 1902: 378.- Stebbing 1910: 103-104.- Trilles 1972b: 1244-1245, 1256, pl. I, photos 5-7; 1972c: 3-7, photos 1-4.- Avdeev 1979: 48, 50.

Codonophilus carinatus .- Nierstrasz 1931: 132.

Ceratothoa curvicauda Nunomura, 2006: 36-38, figs 12-13.

Ceratothoa sp.- Saito 2009: 7-9, photos 1-2.

Material examined.

Neotype [here designated]. South African Musuem, Cape Town (SAMC-A085795) - female (33 mm TL; 15 mm W), collected from Maputo Bay, Mozambique, from the buccal-cavity of Selar crumenophthalmus , November 2013, coll. Wynand Vlok (HP 221). Paratypes. Three females (27-31 mm TL; 12-14 mm W), same data as holotype (SAMC-A085796).

Description.

Neotype female. Length 33 mm, width 15 mm.

Body rectangular, 1.8 times as long as greatest width, dorsal surface with medial longitudinal ridge present, widest at pereonites 3-5, most narrow at pereonite 1, lateral margins slightly convex. Cephalon 0.6 times longer than wide, visible from dorsal view, subtriangular. Frontal margin rounded to form blunt rostrum. Eyes oval with distinct margins, one eye 0.1 times width of cephalon; 0.2 times length of cephalon. Antennula more stout and same length as antenna, with 7 articles; antennule peduncle articles 1 and 2 distinct and articulated. Antenna with 8 articles.

Pereonite 1 with median projection, anterior border straight, anterolateral angle with small distinct produced point, extend to middle of the eye. Posterior margins of pereonites smooth and straight. Coxae 2-3 narrow; with posteroventral angles rounded; 4-7 with rounded point; not extending past pereonite margin. Pereonites 6 and 7 narrower and becoming more progressively rounded posteriorly. Pleon with pleonite 1 most narrow, visible in dorsal view; pleonites posterior margin with irregular small nodules. Pleonite 2 not overlapped by pereonite 7; posterolateral angles of pleonite 2 narrowly rounded. Pleonite 5 widest, posterior margin produced medially. Pleotelson 0.5 times as long as anterior width, dorsal surface with 2 sub-medial depressions, lateral margins weakly convex, posterior margin subtruncate and shallowly emarginate.

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 1.7 times as long as wide; dactylus moderately slender, 1.2 times as long as propodus, 2.9 times as long as basal width. Pereopod 7 basis as long as greatest width; ischium 1.2 times as long as basis, with a large proximal bulbous protrusion; merus proximal margin with large bulbous protrusion, merus 0.5 times as long as wide, 0.3 times as long as ischium; carpus 0.7 times as long as wide, 0.3 times as long as ischium, without bulbous protrusion; propodus 1.3 times as long as wide, 0.5 times as long as ischium; dactylus moderately slender, as long as propodus, 2.2 times as long as basal width.

Uropod same length as pleotelson, peduncle 0.8 times longer than rami, peduncle lateral margin without setae; rami not extending beyond pleotelson, marginal setae absent, apices narrowly rounded. Endopod apically rounded, 3 times as long as greatest width, lateral margin straight, mesial margin straight, terminating without setae. Exopod extending to end of endopod, 4 times as long as greatest width, apically rounded, lateral margin weakly convex, mesial margin straight, terminating without setae.

Size.

Ovigerous female: 28.5-38 mm TL (10-14 mm W); non-ovigerous female: 13-34 mm TL; male: 10-12 mm TL ( Bianconi 1869, Schioedte and Meinert 1883, Stebbing 1910, Trilles 1972b, c).

Distribution.

Western Indian Ocean and southwest Pacific Ocean: Mozambique ( Bianconi 1869, Hilgendorf 1879, Schioedte and Meinert 1883); Great Redangs, Malay Peninsula ( Lanchester 1902); Seychelles ( Stebbing 1910); New Caledonia ( Trilles 1972b, c, Bruce 2007); Red Sea ( Trilles 2008); Japan ( Nunomura 2006, Saito 2009, Nagasawa et al. 2014); and Australia ( Martin et al. 2013).

Hosts.

On Lutjanus adetii (previously Lutjanus amabilis ) ( Trilles 1972b, c); Pseudocaranx dentex (see Nunomura 2006); Decapterus muroadsi (see Nunomura 2006, Saito 2009, Nagasawa et al. 2014); and Selar crumenophthalmus (see Martin et al. 2013, present study).

Remarks.

Ceratothoa carinata can be identified by the characteristic medial ridge extending longitudinally along the dorsal pereon surface. Furthermore, it has a laterally depressed and wider than long pleotelson; pereonite 7 with an enlarged carinate ischium and large bulbous protrusion on the merus; uropods reaching the distal edge of the pleotelson; as well as a concave posterior margin on the pleotelson.

Bianconi (1869) originally described this species from a single ovigerous female from Mozambique and stated that it was most similar to Ceratothoa gaudichaudii and Ceratothoa trigonocephala . Since then, another species, Ceratothoa trillesi ( Avdeev 1979) was also described from the Australia–New Zealand region, and shared many morphological characteristics. There has been some confusion surrounding the synonymy of Ceratothoa trillesi with Ceratothoa carinata (see Avdeev 1979, Trilles 1994), however, these species differ substantially with Ceratothoa trillesi lacking the distinctive medial ridge, enlarged basis and ischium on pereopod 7, and a wide and depressed pleotelson seen in Ceratothoa carinata .

Species and names within Ceratothoa have been moved in and out of synonymy, an indication of both the difficulty of identifying and characterising species. Furthermore, many species are variable ( Hadfield et al. 2014a) and species morphological boundaries are often unclear. In addition, the Cymothoidae also have groups of cryptic species such as has been seen in Mothocya ( Bruce 1986) and Anilocra ( Bunkley Williams and Williams 1981, Bruce 1987) and therefore the designation of a neotype is necessary in the long-term interests of nomenclatural stability.

Schioedte and Meinert (1883) mention a specimen from the type locality (Mozambique) that was originally deposited into Zoologisches Museum, Museum für Naturkunde, Homboldt-Universität, Berlin, Germany. Enquiries to that museum, as well as Muséum National d’Histoire Naturelle, Natural History Museum, London, the Naturalis Biodiversity Center and the Zoological Museum, University of Copenhagen, failed to locate any material that could be identified as the type for Ceratothoa carinata . It is highly probable that this specimen was destroyed in World War II or lost during relocation of the material. As cymothoid isopods are among the most misunderstood and difficult isopods to identify ( Brusca 1981), a complete description (or redescription) of the type material is essential for accurate identifications and research on the species. The current material of Ceratothoa carinata was obtained from the type locality and corresponds with the original drawings of the species ( Bianconi 1869). Both specimens have the noticeable medial ridge or hump running longitudinally down the length of the pereon. The pleotelson is medially concave and is wider than long. Furthermore, the uropods do not extend past the end of the pleotelson and the posterior margin of the pleotelson is indented medially; the eyes are small but clearly visible; and the antennae are stout and extend to the anterior margin of pereonite 1.

As the current specimen is undoubtedly Ceratothoa carinata , it is hereby designated as the neotype for the species, fulfilling all of the requirements necessary in the International Code of Zoological Nomenclature (Anon 1999, ICZN, Article 75).