Benedenia haywardi, Deveney, Marty R. & Whittington, Ian D., 2010

Deveney, Marty R. & Whittington, Ian D., 2010, Three new species of Benedenia Diesing, 1858 from the Great Barrier Reef, Australia with a key to species of the genus, Zootaxa 2348, pp. 1-22 : 10-14

Benedenia haywardi n. sp.

(Figs. 5, 6)

Type host and locality: Symphorus nematophorus (Bleeker) ( Perciformes : Lutjanidae ), Heron Island (23°27ˏS, 151°55ˏE), Queensland, Australia.

Site on host: Fins.

Holotype: QM: G 218922 (1 slide, 1 specimen) ex pelvic fin.

Paratypes: QM: G 218923–25 (3 slides, 3 specimens) ex fins (pelvic, anal, soft dorsal).

Etymology: The specific name is in honour of Dr Craig Hayward, who contributed much to the knowledge of taxonomy and is an ongoing source of collaboration and conversation to the authors.

Description and observations: Based on studies of 1 live specimen and 4 wholemounts of preserved, sexually mature specimens. Measurements from all 4 wholemounts unless indicated otherwise. Total length including haptor 1950–2350 (2100); maximum breadth 625–825 (719) at level of testes (Fig. 5A). Haptor elliptical, 346–407 (398) long, 328–373 (353) wide. Accessory sclerite 72–110 (91) long with tapered, recurved distal region, swelling in medial region (Fig. 5A, B, E). Anterior hamulus 92–105 (99) long, slender with knob-shaped, rounded distal tip and subterminal, ventrally-directed spike (Fig. 5A, C). Posterior hamulus 53–71 (58) long, root and shaft with fine, flattened ventral wing-like extension, distal tip hooked (Fig. 5A, D). Fourteen peripheral hooklets each 6–8 (7) long (n=5). Peduncle conspicuous at junction of body with haptor (Fig. 5A, E). Haptor margin indented at positions of hooklets, distal tip of hooklets protrude past haptor edge into indentation (Fig. 5A, E). Marginal valve scalloped with consistent pattern of lobes between hooklets on each side of haptor: 1 lobe comprising 3 small, fused lobes between hooklets of pair II on posterior border of haptor; 1 lobe comprising 3 small, fused lobes between hooklets II and position of posterior hamuli on posterior border of haptor; 1 lobe comprising 2 small, fused lobes between posterior hamuli and hooklets of pair III; 1 lobe comprising 3 small, fused lobes between hooklets III and IV; 2 or 3 lobes between hooklets IV and V; 3 or 4 lobes between hooklets V and VI; 5–7 lobes between hooklets VI and VII; 8–10 lobes between hooklets VII and VIII; 10 lobes between hooklets of pair VIII on anterior border of haptor (Fig. 5E).

FIGURE. 5. Benedenia haywardi n. sp. A. Entire adult animal, ventral view. Drawn from holotype. Abbreviation: pd, peduncle. B. Accessory sclerite. C. Anterior hamulus. D. Posterior hamulus. Drawn from holotype and paratypes. E. Haptor, ventral view, showing details of marginal valve and peduncle. Other abbreviations as in previous Figures. Scale bars: A, 250 Μm; B–D, 60 Μm; E, 175 Μm.

Anterior attachment organs approximately circular, 196–418 (336) in diameter. Three adhesive zones (reported in other Benedenia spp. [see above]) not observed in living or preserved material. Pharynx 117–180 (131) long, 174–202 (182) wide. Two pairs of eyespots, pigment shielded, dorsal, between pharynx and anterior margin of body. Unclear whether gut caeca confluent posteriorly.

Glands of Goto in posterior angle between testes ( Fig. 6A ). Vas deferens swells to form seminal vesicle between testes and germarium ( Fig. 6A ). Vas deferens swells immediately dorsal to penis canal ( Fig. 6 B), joining penis canal dorsally, twisting with duct of male accessory gland reservoir in regular pattern ( Fig. 6A ). Vas deferens and duct of accessory gland reservoir join near distal tip of penis. Penis distinctive, tapering to pointed distal tip ( Fig. 6A ). Penis protrusible via common genital duct and common genital pore. Pair of prominent lobes dorsal to common genital pore ( Fig. 6A ).

Germarium globular, compact with large internal fertilisation chamber. Uterus short (Fig. 5A, 6A). Terminal region of vagina elongate, flask-like, vaginal pore muscular, submarginal, dorsal, at level of posterior margin of pharynx ( Fig. 6A ). Seminal receptacle conspicuous, separate from inflated, more medial proximal region of vagina, communicates with vitelline reservoir via narrow duct ( Fig. 6A ). Vitelline follicles extend from region between anterior attachment organs posteriorly to haptor peduncle (Fig. 5A). Eggs not observed.

Comments and differential diagnosis: Some fish species can be parasitised by>1 species of Benedenia . Benedenia haywardi occurs on the skin of Symphorus nematophorus , the gills of which are parasitised by B. ernsti (see above). A single specimen of S. nematophorus which we examined was infected by B. ernsti and B. haywardi . Both species have similar haptoral morphology, so the ability to distinguish these 2 monogenean species is important. They can be differentiated by a combination of characters: B. haywardi has an unarmed, tapering penis whereas B. ernsti possesses a broader penis armed with a terminal sclerite; the duct of the accessory gland reservoir in B. ernsti bears a muscular swelling which is absent in B. haywardi ; the vaginal pore in B. haywardi lies at the level of the posterior region of the pharynx but in B. ernsti , the vaginal pore opens posterior to the testes. The muscular, gradually tapering penis with a pointed distal tip is unique to B. haywardi , as is the conspicuous, separate, laterally displaced seminal receptacle. Benedenia haywardi possesses a pair of lobes dorsal to the common genital pore like those of B. lutjani . Benedenia lutjani , however, is smaller and has a vaginal pore anterior to the penis canal and a lobe associated with the vaginal pore. The combination of unusual characters outlined above distinguishes B. haywardi from B. ernsti , B. lutjani and all other species of Benedenia .

Figures

FIGURE 6. A. Benedenia haywardi n. sp. Reproductive system of adult, ventral view. Drawn from holotype and living specimen. Abbreviations: em, egg material. Scale bar: 150 Μm. B. Diagrammatic representation of the region immediately dorsal to the penis canal showing the swelling on the vas deferens, not drawn to scale. Abbreviations: pc, penis canal; sw, swelling. Other abbreviations as in previous Figures.