Benedenia sekii ( Yamaguti, 1937 ) Meserve, 1938

Whittington, I. D., Deveney, M. R. & Wyborn, S. J., 2001, A revision of Benedenia Diesing, 1858 including a redescription of B. sciaenae (van Beneden, 1856) Odhner, 1905 and recognition of Menziesia Gibson, 1976 (Monogenea: Capsalidae), Journal of Natural History 35 (5), pp. 663-777 : 726-728

Benedenia sekii ( Yamaguti, 1937) Meserve, 1938

(®gure 29)

Synonym. Epibdella (Epibdella) sekii Yamaguti, 1937 .

Material studied. MPM: No. 212117 (holotype and 2 paratypes) (1 slide, 3 individuals) ex body surface of Pagrosomus unicolor Bloch and Schneider (5 Pagrus auratus Forster in Bloch and Schneider, see Paulin, 1990) ( Sparidae ) from Inland Sea, Japan; AM: Nos W194651±2 (2 slides, 2 individuals) ex body surface(?) of Chrysophrys auratus (Quoy and Gaimard) (5 Pagrus auratus , see Paulin, 1990) ( Sparidae ) from CoOEs Harbour, NSW, Australia.

Observations. Yamaguti (1937) based his description on`numerous specimens’ from Japan of which only the holotype and two paratypes appear to be registered in a museum. We also examined two specimens of B. sekii collected from Australian waters by Roubal et al. (1983). Some additional information is presented here. Benedenia sekii is 2±6 mm long and is therefore small to medium-sized (e.g. ®gure 3), but has a broad body. Yamaguti (1937) indicated that one contracted paratype is broader than long. Yamaguti (1937) and Roubal et al. (1983) described the anterior attachment organs with a muscular edge, but our examination indicates that folding at the edges of these structures led to this interpretation. Yamaguti described a`liplike ¯ap’ covering the anterior attachment organs dorsally but this appears to be the body margin extending to the anterior edge of the anterior attachment organs. The pharynx of B. sekii is the same size or larger than the anterior attachment organs.

The haptor of B. sekii is large, circular and equipped with relatively small accessory sclerites (up to 360 Mm) lying just posterior to the haptor centre (®gure 29A). Haptoral tendons are shown in ®gure 29A. The anterior hamuli are small and slender with a submarginal, laterally directed spike and overlap the posterior hamuli for half to two-thirds of their length (®gure 29A, C). The posterior hamuli are small with a broad root and recurved tip (®gure 29A, D). Both anterior and posterior hamuli are on the posterior edge of the haptor (®gure 29A). The marginal valve has a single large lobe between each of the hooklets around the haptor but each large lobe comprises several smaller, fused lobes. The details (®gure 29A) are: one lobe of ®ve fused, smaller lobes between hooklets of pair II; one lobe of ®ve fused smaller lobes between hooklets II and the position of the hamuli; one lobe of ®ve fused smaller lobes between the hamuli and hooklet III; one lobe of ®ve fused smaller lobes between hooklets III and IV, and IV and V; one lobe of six fused smaller lobes between hooklets V and VI; one lobe of eight fused smaller lobes between hooklets VI and VII; one lobe of 12 fused smaller lobes between hooklets VII and VIII; one lobe of 12 fused smaller lobes between hooklets of pair VIII.

Much internal anatomical detail for B. sekii cannot be improved upon because of specimen quality. Major characteristics of the reproductive system are the long slender penis, small accessory gland reservoir, relatively small testes and narrow vagina opening close to the common genital pore, each of which is marginal. Glands of Goto were shown but not described by Roubal et al. (1983), but we could not see them in any specimens we examined. A fertilization chamber occurs inside the germarium.

Type-host and locality. Pagrosomus unicolor (now Pagrus auratus ) ( Sparidae ), Otyo, Hiroshima Prefecture, Inland Sea, Japan.

Records. Yamaguti (1937); Roubal et al. (1983, 1996); Sharples and Evans (1995).

Descriptions. Yamaguti (1937); Roubal et al. (1983).

Published host records. Sparidae : Pagrosomus unicolor (now Pagrus auratus ) (see Yamaguti, 1937); Chrysophrys auratus (now Pagrus auratus ) (see Roubal et al., 1983); Pagrus auratus (see Sharples and Evans, 1995; Roubal et al., 1996).

Sites. Body surface ( Yamaguti, 1937); body surface, predominantly on caudal peduncle and beneath the pectoral ®ns ( Sharples and Evans, 1995);`Undetermined but probably body surface. All specimens found in sediment of containers with host ®sh’ ( Roubal et al., 1983); sediment of drums containing ®sh ( Roubal et al., 1996).

Distribution. Inland Sea, Japan ( Yamaguti, 1937); CoOEs Harbour, New South Wales; Gulf of St. Vincent and Wallaroo, South Australia, Australia ( Roubal et al., 1983); Port Hacking, NSW, Australia ( Roubal et al., 1996); Kawau Bay, northern New Zealand ( Roubal et al., 1983); north-eastern New Zealand ( Sharples and Evans, 1995).

Remarks. Roubal et al. (1983) noted that their material from Australia diOEered from material described by Yamaguti (1937) from Japan because the accessory sclerites in the Japanese specimens are larger and there are slight diOEerences in the shape of the anterior hamuli. Most of the Japanese specimens are larger than the Australian material. Sharples and Evans (1995) noted`considerable variability’ in the shape of the anterior hamuli of their New Zealand material. We concur that the species collected by Roubal et al. (1983) and by Sharples and Evans (1995) is B. sekii and is distinguished from other species by a combination of the following characters: broad body; tiny anterior and posterior hamuli relative to accessory sclerites; all median sclerites located posteriorly on haptor; details of marginal valve; long thin penis; and close proximity of common genital pore and vaginal pore.

Paulin (1990) redescribed the species known as`snapper’ in Australasian waters and concluded that Pagrus auratus is the species found widely in the Indo-Paci®c from New Zealand and Australia to China and Japan. It appears, therefore, that the Japanese, Australian and New Zealand material of B. sekii was found on the same host species. Yamaguti (1937) recorded his specimens from the body surface but Roubal et al. (1983, 1996) could not determine the infection site for their specimens because all were found in the sediment of drums containing preserved hosts. Roubal et al. (1983), however, did add that their material was probably from the body surface and Sharples and Evans (1995) noted that their specimens from New Zealand were from the body surface (caudal peduncle and beneath the pectoral ®ns). Benedenia sekii is similar to `B. madai ’ (see p. 735) and both are recorded from Pagrus auratus from Japan, but Ishii and Sawada (1938) described `B. madai ’ as possessing a united common genital pore and vagina.