Cymothoa epimerica 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 : 10-18

Cymothoa epimerica Avdeev, 1979

Figures 3–8

Cymothoa epimerica Avdeev, 1979a: 225 , pl. 2–3.— Trilles, 1994: 139; 2008: 23. — Trilles & Bariche, 2006: 228. — Bruce, Lew Ton & Poore, 2002: 175. — Hadfield, Bruce & Smit, 2013: 157 .

Cymothoa pulchra .— Yu & Li, 2003a: 228, fig. 5; 2003b: 267.

Not Cymothoa epimerica . — Trilles, 2008: 23 (part Cymothoa eremita SMF-567; part Cymothoa vicina SMF-572).

Type material. Holotype: 1 ovig. ♀, (17.5 mm), from the Indian Ocean off Australia, on Malabar blood snapper Lutjanus malabaricus (Bloch & Schneider, 1801) (previously Lutianus malabaricus ) ( TINRO АGK 75023).

Paratypes: 4 mature ♂ ( TINRO АPK 75024–75025); same data as holotype.

Types not examined. A request to borrow the holotype and paratypes were unsuccessful as the specimens could not be located.

Material examined. Northern Territory material: 1 ♀ ovig. (27 mm), 2 immature ♂ (8, 9 mm), outer harbour, Darwin, 7 October 2012, from estuary cod Epinephelus coioides (Hamilton, 1822) , coll. Ben Diggles (MTQ W34150). 1 ♀ ovig. (31 mm), 3 immature ♂ (8, 4, 4 mm), inner harbour, Darwin, 8 March 2013, coll. Ben Diggles (MTQ W34170). 1 ♀ ovig. (19 mm), Darwin, 11 October 2012, from estuary cod Epinephelus coioides , coll. Ben Diggles (MTQ W34151). 1 ♀ ovig. (29 mm), north of Melville Island, 10.1189ºS; 129.3192ºE, 2 October 1995, coll. J. Lloyd (AM P89953).

Digital image from the Senckenberg Research Institute: 1 ♀ ovig. (20 mm), 1 immature ♂ (7 mm), Seychelles (SMF-76), without additional information.

Ovigerous female Length 31 mm width 16 mm (non-dissected, MTQ W34170); length 27 mm width 14 mm (dissected, MTQ W34150).

Body ovoid, 1.9 times as long as greatest width, dorsal surface smooth, laterally dome-shaped, widest at pereonites 5 and 6, most narrow at pereonite 1. Cephalon subtriangular, 0.3 times longer than wide, visible from dorsal view, deeply immersed in pereonite 1. Frontal margin rounded to form blunt rostrum, ventrally folded. Eyes partially distinct. Pereonite 1 anterolateral margins curved towards cephalon, reaching anterior margin of cephalon, posterior margins of pereonites 1–6 weakly trisinuate, moderately concave laterally; pereonite 7 extending to pleonite 3, visible in dorsal view. Coxae 2–3 posteroventral margins subtruncate; 4–7 with sharp and acute carinae projecting laterally. Pleon widest at pereonite 5; pleonites posterior margin weakly bisinuate. Pleotelson rounded, 0.5 times as long as anterior width, anterior margin trisinuate, lateral margins convex, posterior margin round, without median point.

Antennula comprised of 8 articles; peduncle articles 1 and 2 distinct and articulated; article 2 0.9 times as long as article 1; article 3 0.5 times as long as combined lengths of articles 1 and 2, 1.0 times as long as wide. Antenna comprised of 9 articles, peduncle article 3 1.2 times as long as article 2, 1.2 times as long as wide; article 4 1.2 times as long as wide; article 5 1.0 times as long as article 4, terminal article without setae, not extending to posterior of pereonite 1. Labrum lateral margins convex, anterior margin narrowly rounded, without small median point.

Pereopod 1 basis 1.3 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 1.8 times as long as wide; dactylus narrow, 1.1 times as long as propodus, 2.8 times as long as basal width. Pereopod 2 propodus 1.1 times as long as wide; dactylus 1.7 times as long as propodus. Pereopod 3 similar to pereopod 2, merus moderately protruding, basis superior proximal margin with sharp carina. Pereopods 4 and 5 similar to pereopod 2, gradually increasing in size, without robust or simple setae. Pereopod 6 basis 1.4 times as long as greatest width, superior proximal margin with sharp and acute carina; ischium 0.5 times as long as basis; propodus 1.7 times as long as wide; dactylus 1.5 times as long as propodus. Pereopod 7 basis 1.2 times as long as greatest width, superior proximal margin with sharp and acute carina; ischium 0.9 times as long as basis, with bulbous protrusion; merus proximal margin with slight bulbous protrusion, 0.3 times as long as ischium, 0.6 times as long as wide; carpus 0.3 times as long as ischium, without bulbous protrusion, 1.3 times as long as wide; propodus 0.5 times as long as ischium, 0.8 times as long as wide; dactylus narrow, 2.5 times as long as propodus, 2.9 times as long as basal width.

Pleopods margins irregular, lobes increasing in size from 1–5, exopods 1–5 gradually decreasing in size, exopod size almost similar to endopod. Pleopod 1 exopod 0.8 times as long as wide, lateral margin deeply convex, distally round and irregular, mesial margin strongly convex; peduncle 1.9 times as wide as long, without retinaculae. Pleopod 2 similar to pleopod 1, mesial margin becoming more strongly produced, endopod with deep depressions. Pleopods 3–5 endopods proximal margins extending below exopod to peduncle, with large fleshy folds and medial lobes present, increasing in size from pleopods 1–5.

Uropod not extending beyond posterior margin of pleotelson; peduncle 1.4 times as long as greatest width, 0.4 times as long as exopod, lateral margin without setae, marginal setae absent, apices narrowly acute, lateral margin straight, mesial margin strongly convex. Exopod extending past endopod, 8.3 times as long as greatest width, apically rounded, lateral margin straight, terminating without setae, mesial margin weakly straight. Endopod 7.0 times as long as greatest width, apically rounded, lateral margin weakly convex, terminating without setae, mesial margin straight.

Males. Length 4 mm width 2 mm (non-dissected, MTQ W34170); length 8 mm width 3 mm (dissected, MTQ W34150).

Body 2.0 times as long as greatest width. Cephalon rounded, 0.3 times longer than wide, visible from dorsal view, not deeply immersed in pereonite 1. Eyes distinct, 0.4 times width of cephalon (combined eyes width). Pereonite 1 anterolateral margin minute; posterior margins of pereonites 1–6 straight and smooth. Coxae 2–7 posteroventral margins rounded. Pleonite 3 subequal in width to pleonites 4 and 5, visible in dorsal view; pleonites posterior margin not trisinuate. Pleotelson subtruncate. Antennula comprised of 6 articles; shorter than antenna. Antenna comprised of 10 articles.

Pereopod 1 basis 2.0 times as long as greatest width; ischium 0.3 times as long as basis; merus proximal margin without bulbous protrusion; carpus with straight proximal margin; propodus 2.4 times as long as wide; dactylus 1.5 times as long as propodus. Pereopods 2–7 similar to pereopod 1, moderately bigger in size, pereopods 6 and 7 basis superior proximal margin without raised carinae. Pleopods margins smooth, exopods greater than endopods from 1–5; pleopod 2 appendix masculina with parallel margins, 0.6 times as long as endopod, distally acute. Uropod exopod similar length to endopod, apices broadly rounded.

Manca. Length 2.2 mm width 1 mm.

Body 2.2 times as long as greatest width. Cephalon anterior margin rounded, 0.6 times longer than wide, visible from dorsal view, not deeply immersed in pereonite 1. Eyes distinct, 0.4 times width of cephalon (combined eyes width). Pereonite 1 anterolateral margin minute; posterior margins of pereonites 1–6 straight and smooth. Pleonite 1 subequal in width to pleonites 3–5, visible in dorsal view; pleonites posterior margin smooth and straight. Pleotelson 1.1 times as long as anterior width; lateral margins smooth and concaved; posterior margin converging to caudomedial point, with setae. Antennula as long as antenna. Uropod endopod 4.9 times as long as exopod length, apices narrowly rounded; exopod with setae.

Pre-manca. Length 2.2 mm width 1 mm.

Pre-manca similar to manca in body size ratio, eye shape, pereon and pleon morphology. Eyes 0.4 times width of cephalon (combined eyes width). Cephalon anterior margin weakly subtriangular, 0.5 times longer than wide. Pleotelson without setae. Uropod endopod 2.2 times as long as exopod length, apices narrowly rounded; exopod without setae.

Colour. Ivory white.

Size. Present material: ovigerous females: 19–31 mm; immature males: 4–9 mm.

Remarks. Cymothoa epimerica has an ovoid body (1.9 times longer than wide); subtriangular cephalon deeply immersed in pereonite 1; pereonite 1 anterolateral margins deeply curved towards cephalon; narrow uropodal rami (exopod 8.3 times longer than wide); pereopods 5–7 superior proximal margin with acute carinae and dorsally visible; coxae 6 and 7 posteroventral margins acute and dorsally visible; pleotelson posterior margin smooth and rounded; pleopod morphology appearing damaged and irregular, and increased fleshy folds on endopods from pleopods 3–5. The mouthparts of specimen MTQ W34150 is similar to Avdeev’s (1979a) illustrations, which showed a maxillula with 3 terminal robust setae; lateral lobe of maxilla partly fused to mesial lobe, with 4 and 5 recurved setae on the mesial lobe and lateral lobe respectively; and a weakly segmented maxilliped. The male specimens have a broader, subquadrate body; eyes distinct; straight pleonite posterior margins; coxae with broad posteroventral margins, visible in dorsal view; pereopods slender without bulbous protrusions, and pleopods 1–5 margins smooth.

Cymothoa epimerica pre-mancae (fig. 5B) and mancae (fig. 5C) have unique uropod morphology, with the endopod twice the length of the exopod long in pre-mancae (four times the exopod length in mancae). The pleotelson and uropods of pre-mancae are without setae (setae present in mancae). Both stages of pre-mancae and mancae were found within the same brood pouch of the ovigerous female specimen from MTQ W34170. The premancae develops into free-swimming mancae which is released from the female marsupium in search of a suitable host (Smit et al. 2014).

Trilles (2008) recorded C. epimerica from Seychelles (SMF-76) and the Red Sea (SMF-567 and SMF-572) without host association or illustrations, and briefly mentioned the similarities of C. epimerica and C. curta . After examining the digital images from the Senckenberg Research Institute, specimen SMF-76 from the Seychelles agrees with C. epimerica , whereas SMF-567 from the Red Sea is here re-identified as C. eremita and SMF-572 reidentified as Cymothoa vicina Hale, 1926 . Cymothoa epimerica and C. curta have a similar ovoid body, pleotelson posterior margin rounded and cephalon immersed in pereonite 1. Cymothoa curta differs from C. epimerica in the small and acute anterolateral margins of pereonite 1; posterolateral margins of coxae rounded and not dorsally visible; pereopod 6 basis superior proximal margin rounded; pereopod 7 basis highly raised and broad; uropodal rami broader than C. epimerica , uropod apices rounded; and the smooth mesial and lateral margins of pleopods 1– 5.

Yu & Li’s (2003a, b) illustrations of their specimens identified as C. pulchra agree with C. epimerica in having a wide and oval-shaped body; dorsally visible and posteriorly acute coxae; rounded posterior margin of pleotelson and in dorsal view, the uropods not extending beyond pleotelson posterior margin. Cymothoa pulchrum has a more subrectangular and subparallel body shape, rostrum dorsally appearing more subtruncate compared to the rounded rostrum of C. epimerica , subequal and stout uropodal rami and pereopod 7 basis superior proximal margin not dorsally visible.

Distribution. Northern Territory, Australia.

Hosts. Known from the family Serranidae : Epinephelus coioides (present study) and family Lutjanidae : Lutjanus malabaricus ( Avdeev 1979a) .

Figures

FIGURE 3. Cymothoa epimerica ovigerous female (31 mm; MTQ W 34170). A, dorsal view; B, dorsal view of pereonite 1 and cephalon; C, ventral view of mouthpart; D, antennula; E, antenna; F, dorsal view of pleotelson; G, lateral view.

FIGURE 4. Cymothoa epimerica ovigerous female (27 mm; MTQ W 34150). A – E, pereopods 1, 2, 5, 6, 7 respectively; F, uropod; G – K, pleopods 1 – 5 respectively.

FIGURE 5. Cymothoa epimerica male (4 mm), pre-manca (2.2 mm) and manca (2.2 mm) (MTQ W 34170). A, dorsal view of male; B, dorsal view of pre-manca; C, dorsal view of pre-manca; D, male uropod; E, male antennula; F, male antenna; G, lateral view male.

FIGURE 6. Cymothoa epimerica male (8 mm) (MTQ W 34150). A – D, pereopods 1, 2, 6, 7 respectively; E – I, pleopods 1 – 5 respectively.

FIGURE 7. Cymothoa epimerica, female (20 mm; SMF- 76) A, dorsal view; B, lateral view; C, ventral view. (picture credit Sven Tränkner, Senckenberg Research Institute).

FIGURE 8. Cymothoa epimerica, male (7 mm; SMF- 76) A, dorsal view; B, ventral view; C, lateral view. (picture credit Sven Tränkner, Senckenberg Research Institute).