Ceratothoa barracuda, Martin, Melissa B., Bruce, Niel L. & Nowak, Barbara F., 2015

Martin, Melissa B., Bruce, Niel L. & Nowak, Barbara F., 2015, Review of the fish-parasitic genus Ceratothoa Dana, 1852 (Crustacea: Isopoda: Cymothoidae) from Australia, with description of two new species, Zootaxa 3963 (3), pp. 251-294 : 261-266

Ceratothoa barracuda sp. nov.

Figures 5–8

Ceratothoa sp. 1.— Trilles, 1979: 269, pl. 2, fig. 13.

Material examined. Holotype: ♀ ovig. (23 mm), Cairns, NEQ, 16º55.0’S; 145º 46.0’E, 25 April 1982, from buccal cavity of Sphyraena forsteri Cuvier, 1829 , Genbank # EF422802 (QM W34274).

Paratype: ♂ (8 mm), same data as holotype (QM W28787).

Non-type: ♀ pre-ovig. (33 mm, dissected), Cruise No JDI Torres Strait Stn. No: 8 9533, 1 March 1985, from buccal cavity of Sphyraena forsteri (269 mm), coll. CSIRO (MTQ W30411).

Ovigerous female. Length 23 mm, width 9 mm.

Body 2.6 times as long as greatest width, dorsal surfaces smooth and polished in appearance, widest at pereonite 5, most narrow at pereonite 1. Cephalon 0.7 times longer than wide, visible from dorsal view, subtriangular, immersed in pereonite 1. Frontal margin simple, not folded. Eyes trapezoid, 0.1 times width of head. Pereonite 1 smooth; anterolateral projections on pereonite 1 subacute; posterior margin of pereonites smooth and straight; pereonites 5–7 progressively narrower in length; pereonite 7 with posterior margins not overlapped by lateral margins of pleonite 2. Coxae 2–7 with posteroventral margins rounded. Pleonites posterior margin concave; posterolateral margins of pleonite 2 forming acute point Pleotelson 0.3 times as long as anterior width, dorsal surface with 2 sub-medial depressions, lateral margins weakly convex, posterior margin almost straight, without median point.

Antennula comprised of 7 articles; peduncle articles 1 and 2 distinct and articulated; article 2 0.6 times as long as article 1; article 3 0.3 times as long as combined lengths of articles 1 and 2, 0.6 times as long as wide, extending to posterior margin of eye. Antenna comprised of 9 articles; article 3 2.0 times as long as article 2, 1.5 times as long as wide; article 4 0.9 times as long as wide, 0.7 times as long as article 3; article 5 0.8 times as long as article 4, 1.0 times as long as wide, extending to posterior margin of head. Oostegites attached to pereopods 2–5.

Pereopod 1 basis 1.2 times as long as greatest width; ischium 0.9 times as long as basis; merus proximal margin without bulbous protrusion; carpus with straight proximal margin; propodus 1.4 times as long as wide; dactylus slender, 1.1 times as long as propodus, 2.1 times as long as basal width. Pereopod 2 propodus 1.5 times as long as wide; dactylus 0.2 times as long as propodus. Pereopod 3 similar to pereopod 2, gradually increasing in size towards posterior. Pereopod 6 basis 0.8 times as long as greatest width, ischium 0.9 times as long as basis, propodus 0.9 times as long as wide, dactylus 2.1 times as long as propodus. Pereopod 7 basis 0.9 times as long as greatest width; ischium times 0.9 as long as basis, with a large proximal protrusion; merus proximal margin with large bulbous protrusion, merus 0.2 as long as ischium, 0.3 times as long as wide; carpus 0.2 times as long as ischium, without bulbous protrusion, 0.4 times as long as wide; propodus 0.4 times as long as ischium, 1.0 times as long as wide; dactylus stout, 2.0 times as long as propodus, 2.5 times as long as basal width.

Pleopods with slight depression present on central dorsal surface of each pleopod ramus, exopod larger than endopod; exopod lateral margins weakly convex, distally rounded with strongly oblique medial margin, mesial margin straight; endopod weakly concave, distally rounded, mesial margin straight. Pleopods 3–5 endopods proximal borders do not extend below exopod to peduncle.

Uropod same length as pleotelson, peduncle 1.2 times longer than rami, peduncle lateral margin without setae; rami not extending beyond pleotelson, apices narrowly rounded. Endopod 5.3 times as long as greatest width, lateral margin weakly convex. Exopod more stout and short than endopod, 5.3 times as long as greatest width, apically not bifid, lateral margin weakly convex, terminating without setae, mesial margin straight.

Male. Male similar to females except for the body size approximately 2.8 times smaller than females, margins subparallel, pleonites of subequal width, pleotelson 0.4 times as long as anterior width, posterior margin semicircular.

Colour. Ivory white to pale brown in alcohol.

Variation. Cephalon with frontal margin obtuse, eyes are either narrow (QM W34274) or faintly visible (QM W28287), pereonite 1 anterior margin with median point. The non-type female has a more acute rostral point and a more convex pleotelson posterior margin than the holotype.

Size. Present material: Ovigerous female: 23 and 33 mm, male: 8 mm. Trilles (1979) noted one ovigerous female as 27 mm and a pre-ovigerous female as 28 mm.

Etymology. Named after the bigeye barracuda , the only known host.

Remarks. Ceratothoa barracuda sp. nov. can be identified by the elongate body; subtriangular cephalon not immersed in pereonite 1, subacute anterolateral projections on pereonite 1, pleonites 2–5 wider than pereonite 7, pleotelson 0.3 times as long as anterior width with a convex posterior margin, and pereopods 5–7 basis each with a strong carinae and enlarged ischium.

Ceratothoa barracuda is most similar to Ceratothoa carinata , the differentiating characters are C. carinata has a pleotelson with a strongly concave posterior margin, an enlarged ischium and basis only present on pereopod 7, and the articles distal to article 4 of the antennula are narrower than those of C. barracuda .

Trilles (1979) mentioned two specimens of Ceratothoa sp. from Papua and West Papua. The figured specimens were recognisable as C. barracuda , as Trilles (1979) had mentioned “characters of the large width of pleotelson and the last four pleonites is more accentuated.”

Distribution. Cairns and Torres Strait, northern Queensland. Trilles (1979) reported this species from Serui (formerly Seroei), the principal town of Yapen island (= île Japen) from Cenderawasih Bay (formerly Geelvink Bay), Papua Province.

Hosts. Present material from the mouth of the bigeye barracuda Sphyraena forsteri ( Cuvier, 1829) , the only known host for this cymothoid species.

Figures

FIGURE 5. Ceratothoa barracuda sp. nov., ovigerous female holotype (23 mm) (MTQ W 34274). A, dorsal view; B, antennula; C, dorsal view of cephalon; D, antenna; E, ventral view of mouthparts; F, uropod; G, ventral view of pleotelson; H, dorsal view of pleotelson; I, lateral view.

FIGURE 6. Ceratothoa barracuda sp. nov., ovigerous female (33 mm, dissected) (MTQ W 30411). A, dorsal view; B, ventral view of mouthparts; C, antennula; D, antenna; E, uropod; F, dorsal view of pleotelson; G, lateral view.

FIGURE 7. Ceratothoa barracuda sp. nov., male paratype (8 mm; MTQ W 28287 A, B) and ovigerous female mouthparts and pleopods (33 mm; MTQ W 30411 C – K). A, dorsal view; B, lateral view; C, maxilla; D, maxilliped; E, mandible; F, maxillula tip; G – K, pleopods 1 – 5 respectively.

FIGURE 8. Ceratothoa barracuda sp. nov., ovigerous female holotype (23 mm) (MTQ W 34274). A – G, pereopods 1 – 7 respectively.