Cymothoa carangi Avdeev, 1979

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 : 7-10

Cymothoa carangi Avdeev, 1979

Figures 1–2

Cymothoa carangi Avdeev, 1979b: 53 , pl. 3. — Trilles, 1994: 138. — Bruce, Lew Ton & Poore, 2002: 174. — Trilles & Bariche, 2006: 228.

Cymothoa carangii .— Kensley, 2001: 232.

Material examined. Holotype: 1 ovig. ♀ (31 mm), northern Australia (precise locality not given), from Caranx sp. ( TINRO АGK 75022).

Ovigerous female. Length 31 mm, width 13 mm (holotype).

Body subrectangular, 2.1 times as long as greatest width, dorsal surface smooth, laterally sub-parallel, widest at pereonite 6, most narrow at pereonite 1. Cephalon subtriangular, 0.5 times as long as wide, visible from dorsal view, immersed in pereonite 1. Frontal margin rounded to form blunt rostrum, ventrally folded. Eyes absent. Pereonite 1 anterolateral margins broad, reaching anterior margin of cephalon; pereonites 1–4 subequal in length; pereonites 5–7 progressively narrower in length, posterior margin linear. Coxae 2–3 posteroventral margins subtruncate; 4–7 with progressively acute carinae. Pleonites not subequal in width; posterolateral margins of pleonite 2 acute; pleonites 3–5 progressively increasing in width, posterior margins slightly irregular. Pleotelson subtruncate, 0.6 times as long as anterior width, anterior margin not linear, lateral margins weakly convex, posterior margin straight, without median point.

Antennula comprised of 8 articles; peduncle articles 1 and 2 distinct and articulated; article 2 1.4 times as long as article 1; article 3 0.6 times as long as combined lengths of articles 1 and 2, 1.2 times as long as wide. Antenna comprised of 8 articles, peduncle article 3 1.5 times as long as article 2, 1.1 times as long as wide; article 4 1.0 times as long as wide; article 5 1.0 times as long as article 4, terminal article without setae, extending to anterior margin of pereonite 1. Labrum lateral margins convex, anterior margin narrowly rounded.

Pereopod 1 basis 1.4 times as long as greatest width; ischium 0.7 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 narrow, 1.5 times as long as propodus, 1.2 times as long as basal width. Pereopod 2 propodus 1.0 times as long as wide; dactylus 1.1 times as long as propodus. Pereopods 3–5 similar to pereopod 2, gradually increasing in size, without robust or simple setae. Pereopod 6 basis 1.3 times as long as greatest width, superior proximal margin with acute carina; ischium 0.6 times as long as basis; propodus 0.9 times as long as wide; dactylus 2.1 times as long as propodus. Pereopod 7 basis 1.3 times as long as greatest width, superior proximal margin with acute carina; ischium 0.6 times as long as basis, inferior distal margin with bulbous protrusion; merus proximal margin with slight bulbous protrusion, 0.4 times as long as ischium, 0.5 times as long as wide; carpus 0.2 times as long as ischium, without bulbous protrusion, 0.4 times as long as wide; propodus 0.5 times as long as ischium, 0.9 times as long as wide; dactylus stout, 2.5 times as long as propodus, 2.5 times as long as basal width.

Uropod not extending beyond posterior margin of pleotelson; peduncle lateral margin without setae, marginal setae absent. Exopod not extending past endopod, 4.7 times as long as greatest width, apically rounded, lateral margin convex, terminating without setae, mesial margin concave. Endopod 5.0 times as long as greatest width, apically blunt, lateral margin weakly convex, terminating without setae, mesial margin weakly concave.

Colour. Yellowish–tan.

Remarks. Cymothoa carangi can be identified by the body being subparallel, 2.1 times as long as wide and widest at pereonite 6; subtriangular cephalon immersed in pereonite 1; broad anterolateral margins of pereonite 1 anteriorly reaching rostrum; pereonites 1–4 subequal in length; pereonite 7 posterolateral margins extending to pleonite 4; pleotelson subtruncate and 1.8 times wider than long; uropods not extending beyond posterior margin of pleotelson, pereopods 4–7 basis with sharp carinae (see lateral view in fig. 1F) and pereopod 7 with a projection on the proximal superior region of the ischium. Avdeev (1979b) illustrated the maxillula with three terminal setae; maxilla lateral lobe partly fused to the mesial lobe, with one recurved robust seta on each lobe; maxilliped weakly segmented with three recurved robust setae on terminal article 3; and pleopod 1 exopod 1.1 times longer than wide, weakly concave lateral margin, rounded distal margin and a strongly convex mesial margin. To date, no males have been reported for the species.

This species resembles C. parupenei in the dorsally visible coxae, pereonite 1 anterolateral margins reaching rostrum, pleotelson subtruncate and the subparallel body shape. Cymothoa carangi can be distinguished from C. parupenei by the subtriangular cephalon (compared to the subtruncate cephalon of C. parupenei ), pereopods 6 and 7 basis with sharp carinae (compared to the rounded and smooth basis on C. parupenei holotype) and the pleopod 1 endopod is smaller than the exopod (compared to the subequal endopod and exopod of C. parupenei pleopod 1).

Other Cymothoa species known to occur on the Carangidae are Cymothoa eremita ( Brünnich, 1783) ; Cymothoa indica Schioedte & Meinert, 1884 ; Cymothoa propria Avdeev, 1979 and Cymothoa pulchrum Lanchester, 1902 . These four species differ from C. carangi in the following characteristics: C. eremita has a subtruncate cephalon, broad anterolateral margins of pereonite 1 which taper to a small produced point and rounded posteroventral margins of coxae 4–7; C. indica has anterolateral margins of pereonite 1 not reaching medial region of cephalon and pereopod 7 basis without sharp carina; C. propria has the cephalon frontal margin ventrally folded, anterolateral margins of pereonite 1 with minute projection, posterior margin of pleonites irregular and uropod reaching posterior margin of pleotelson; C. pulchrum has pereopods 6 and 7 basis without the distinctly “blade-like” carinae, pereopods 6 and 7 dactyli more slender, and body lateral margins subparallel (especially pereonites 1–5, which are progressively wider in C. carangi ).

Distribution. Known only from northwestern Australia without specific locality ( Avdeev 1979b).

Hosts. Only known from the family Carangidae : Caranx sp. ( Avdeev 1979b).

Figures

FIGURE 1. Cymothoa carangi, ovigerous female holotype (31 mm; AGK 75022). A, dorsal view; B, dorsal view of pereonite 1 and cephalon; C, ventral view of mouthpart; D, antennula; E, antenna; F, lateral view.

FIGURE 2. Cymothoa carangi, ovigerous female holotype (31 mm; AGK 75022). A – D, pereopods 1, 2, 6, 7 respectively; E, uropod; F, dorsal view of pleotelson.