Cymothoa vicina Hale, 1926

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 : 46-57

Cymothoa vicina Hale, 1926

Figures 29–38

Cymothoa vicina Hale, 1926: 214 , fig. 9 (a–g). — Nierstrasz, 1931: 136. — Avdeev, 1978b: 282. — Springthorpe & Lowry, 1994: 64. — Trilles, 1994: 149. — Bruce, Lew Ton & Poore, 2002: 174. — Trilles & Bariche, 2006: 228. Cymothoa epimerica . — Trilles, 2008: 23 (SMF-572).

Material examined. Holotype: 1 ovig. ♀ (15 mm), Tweed River, NSW, 28°21.0’S, 153°17.0’E, from a mullet, coll. Franks (AM P8590).

Australian material: 1 mature ♂ (15 mm), Mandurah, WA, 1984, from gills of cobbler Cnidoglanis macrocephalus (Valenciennes, 1840) , coll. C. M. A. Williams (MTQ W30410). 2 ovig. ♀ (23, 25 mm), 4 immature ♂ (4, 4, 9, 10 mm), Moreton Bay, QLD, 3 May 1977, from mullet Mugil sp. (MTQ W7302).

Digital images from the Senckenberg Research Institute: 3 ♀ ovig. (19,22, 23 mm), 1 immature ♂ (11 mm), Red Sea (SMF-572).

Ovigerous female Length 15 mm, width 7 mm (holotype).

Body oblong, 2.1 times as long as greatest width, dorsal surface smooth, laterally subparallel, widest at pereonite 4 and pereonite 5, most narrow at pereonite 1, Cephalon subtruncate, 0.4 times longer than wide, visible from dorsal view. Frontal margin without median point. Eyes oval with distinct margin, 0.4 times width of head. Pereonite 1 anterior margin moderately produced medially, anterolateral margins broad, reaching past eyes; pereonites 1–4 posterior margin smooth, progressively wider; pereonites 5–7 subequal in length, posterior margin moderately arched. Coxae 2–3 posteroventral margins rounded; 4–7 with acute carinae. Pleonites 1–4 subequal in length and width, visible in dorsal view; pleonites posterior margin smooth; pleonite 5 posterior margin straight. Pleotelson 0.4 times as long as anterior width, anterior margin linear, lateral margins weakly concave, posterior subtruncate, without median point.

Antennula comprised of 8 articles; peduncle articles 1 and 2 distinct; article 2 0.9 times as long as article 1; article 3 0.7 times as long as combined lengths of articles 1 and 2, 1.1 times as long as wide; extending to middle of eye. Antenna comprised of 9 articles, peduncle article 3 0.9 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. Labrum lateral margins convex, anterior margin rounded, without small median point. Mandibular process present, ending with an acute incisor; articles of mandibular palp distinct. Maxilliped comprised of 3 articles, well segmented, article 3 with 1 apical spine and 4 setae.

Pereopod 1 basis 1.7 times as long as greatest width, superior proximal margin smooth, without raised carina; ischium 1.2 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, 1.7 times as long as propodus, 2.4 times as long as basal width. Pereopod 2 basis 1.4 times as long as greatest width, superior proximal margin smooth, without raised carina; propodus 1.6 times as long as wide; dactylus 1.3 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 smooth, without raised carina; ischium 1.0 times as long as basis, propodus 1.2 times as long as wide, dactylus 1.7 times as long as propodus. Pereopod 7 basis 1.4 times as long as greatest width, superior proximal margin smooth, with moderately raised carina; ischium 0.6 times as long as basis, with slight bulbous protrusion; merus proximal margin without slight bulbous protrusion, merus 0.5 times as long as ischium; carpus 0.3 times as long as ischium, without bulbous protrusion, 0.5 times as long as wide; propodus 0.7 times as long as ischium, 1.7 times as long as wide; dactylus stout, 1.5 times as long as propodus, 2.8 times as long as basal width.

Pleopods without depression on central dorsal surface of each pleopod rami; basal projections present; exopod proximal mesial margins extending past peduncle; exopod larger than endopod. Pleopod 1 exopod 1.1 times as long as wide, lateral margin weakly concave, distally narrowly rounded, medial margin weakly oblique, mesial margin strongly convex; peduncle 0.3 times as wide as long, without retinaculae; pleopod 2 appendix masculina with straight margins, 0.6 times as long as endopod, distally broadly rounded.

Uropod not extending beyond posterior margin of pleotelson; peduncle 1.3 times as long as greatest width, 0.8 times as long as exopod, lateral margin without setae, marginal setae absent, apices broadly acute, lateral margin straight, mesial margin strongly convex. Exopod extending past endopod, 3.3 times as long as greatest width, apically rounded, lateral margin convex, terminating without setae, mesial margin concave. Endopod 3.2 times as long as greatest width, apically rounded, lateral margin weakly straight, terminating without setae, mesial margin straight.

Males. Body 2.2 times as long as greatest width. Cephalon subtriangular, 0.4 times longer than wide. Pereonite 1 anterolateral minute, reaching posterior margin of eyes; pereonites 1–6 posterior margins straight and smooth. Coxae 2–7 dorsally visible, posteroventral margins rounded. Pleonites subequal in width, similar to female. Pleotelson semi-rounded. Antennula similar size to antenna. Antenna comprised of 8 articles.

Pereopod 1 basis 1.7 times as long as greatest width; ischium 0.5 times as long as basis; merus proximal margin without bulbous protrusion; carpus with straight proximal margin; propodus 2.0 times as long as wide; dactylus 1.2 times as long as propodus. Pereopods 2–6 similar to pereopod 1, moderately bigger in size. Pereopod 7 basis superior proximal margin without raised carina, inferior margin of ischium, merus and carpus straight. Pleopods margins smooth, exopods greater than endopods from 1–5. Pleopod 2 appendix masculina with parallel margins, 0.7 times as long as endopod, distally broad. Pleopods 3 and 5 endopods proximal margins extending below peduncle. Uropod exopod similar length to endopod, apices broadly rounded.

Colour. Holotype dark brown, non-type material whitish to yellowish tan.

Size. Ovigerous females: 15–25 mm; males: 4–10 mm.

Remarks. The female holotype has shrivelled since Hale’s (1926) illustration of the specimen. Cymothoa vicina has a suboval body [appearing wider in Hale’s (1926) illustration]; eyes distinct (0.3 times length of cephalon for combined eyes width); subtruncate cephalon [rostrum appearing acute in Hale’s (1926) illustration]; anterolateral margins of pereonite 1 almost reaching anterior margin of the cephalon; subequal in length and width of pereonites 1–4; pleonites of subequal width; smooth and raised carina on pereopod 7 basis; and 2.5 times wider than long pleotelson. Hale (1926) also noted that the appendix masculina was retained on pleopod 2 of the female.

Two ovigerous females from Moreton Bay (MTQ W7302) occurred on the host Mugil sp., a host-association similar to that of the holotype. Both the Moreton Bay specimens and the holotype have a subtriangular cephalon; subtruncate pleotelson; uropods not extending beyond pleotelson; pleonites subequal in width; smooth and raised carina on pereopod 7 basis. The Moreton Bay specimens differ from the holotype in having a more ovate rather than suboval body (1.7 times longer than wide); eyes partially visible; pereonites 1–4 anterolateral margins broad and more pronounced; inferior distal margin of pereopod 7 ischium more produced (compared to holotype); and pleopods 1 and 2 margins irregular (compared to the simpler endopod and pleopod margins in the female holotype) The males differ from the females (both males and females from Moreton Bay) by having a subparallel body, rounded pleotelson posterior margin; and the minute anterolateral margins of pereonite 1.

Trilles (2008) recorded C. epimerica from the Seychelles (SMF-76) and the Red Sea (SMF-567 and SMF-572) without host association or illustrations. Digital images obtained from the Senckenberg Research Institute shows all the female Red Sea specimens (19, 22 and 23 mm) from SMF-572 to be Cymothoa vicina Hale, 1926 . These specimens are the same as the specimens from Moreton Bay, particularly the female’s ovate body; eyes partially visible; pereonites 1–4 anterolateral margins broad and more pronounced and the inferior distal margin of pereopod 7 ischium more produced.

Cymothoa vicina resembles C. oestrum in the pereonite 1 anterolateral margins broad and reaching past eyes, cephalon anterior margin subtruncate, pleotelson posterior margin subtruncate, and pereopod 7 basis with raised carina. The differences noted in C. oestrum are the dorsally visible coxae and the rhomboidal body morphology (compared to the oval-shaped body in female specimens from MTQ W7302). Thatcher’s et al. (2003) illustration of C. oestrum showed antennula articles 1–3 has small spinules, which are not present in C. vicina .

Distribution. Reported from western and eastern Australia and the Red Sea ( Trilles 2008, specimens SMF- 572).

Hosts. Known from hosts of families Plotosidae and Mugilidae .

Figures

FIGURE 29. Cymothoa vicina ovigerous female holotype (15 mm; AM P 8590). A, dorsal view; B, front view of female pereonite 1 and cephalon; C, antennula; D, antenna; E, uropod; F, dorsal view of pleotelson; G, lateral view.

FIGURE 30. Cymothoa vicina ovigerous female holotype (15 mm; AM P 8590). A, maxilliped; B, mandible; C – F, pereopods 1, 2, 6, 7 respectively; G – H, pleopods 1 and 2 respectively.

FIGURE 31. Cymothoa vicina ovigerous female (23 mm; MTQ W 7302). A, dorsal view; B, ventral view of mouthpart; C, antennula; D, antenna; E, view pereonite 1 and cephalon; F, uropod; G, lateral view.

FIGURE 32. Cymothoa vicina ovigerous female (23 mm; MTQ W 7302). A – D, pereopods 1, 2, 6, 7 respectively; E – H, pleopods 1, 2, 4, 5 respectively; I, dorsal view of pleotelson.

FIGURE 33. Cymothoa vicina male (9 mm; MTQ W 7302). A, dorsal view; B, ventral view of mouthpart; C, antennula; D, antenna; E, uropod; F, lateral view.

FIGURE 34. Cymothoa vicina male (9 mm; MTQ W 7302). A – C, pereopods 1, 2, 7 respectively; D – F, pleopods 2, 3, 5 respectively.

FIGURE 35. Cymothoa vicina, female (22 mm; SMF- 572) A, dorsal view; B, ventral view; C, lateral view. (picture credit Sven Tränkner, Senckenberg Research Institute).

FIGURE 36. Cymothoa vicina, male (11 mm; SMF- 572) A, dorsal view; B, ventral view; C, lateral view. (picture credit Sven Tränkner, Senckenberg Research Institute).

FIGURE 37. Cymothoa vicina, female (23 mm; SMF- 572) A, dorsal view; B, ventral view; C, lateral view. (picture credit Sven Tränkner, Senckenberg Research Institute).

FIGURE 38. Cymothoa vicina, female (19 mm; SMF- 572) A, dorsal view; B, ventral view; C, lateral view. (picture credit Sven Tränkner, Senckenberg Research Institute).