Entobdella stenolepis, Kearn & Whittington & Evans-Gowing, 2007

Kearn, Graham C., Whittington, Ian D. & Evans-Gowing, Richard, 2007, A revision of Entobdella Blainville in Lamarck, 1818, with special emphasis on the nominal (type) species “ Entobdella hippoglossi (Müller, 1776) Blainville, 1818 ” (Monogenea: Capsalidae: Entobdellinae) from teleost flatfishes, with descriptions of three new species and a new genus, Zootaxa 1659, pp. 1-54 : 47-48

Entobdella stenolepis n. sp.

( Figs. 2, 4, 5, 6, 14, 15C, 18, 39)

Type host and locality: Pacific halibut, Hippoglossus stenolepis Schmidt, 1904 ( Pleuronectiformes : Pleuronectidae ); captive host held at the Pacific Biological Station, Nanaimo, British Columbia, Canada.

Other records: Lawler (1981) lists references in his tables 68 and 77 as “ E. hippoglossi ” and “ E. squamula ” respectively. Hoskins et al. (1976) report “ E. hippoglossi ” on Pacific halibut caught in Hecate Strait, Brit- ish Columbia, Canada.

Other hosts: Petrale sole, Eopsetta jordani (Lockington, 1879) ( Pleuronectiformes : Pleuronectidae ), north-east Pacific Ocean ( Klassen et al. 1989). Parasites were also found on the lower surface of E. jordani from Sydney Inlet on the west coast of Vancouver Island by Margolis (1952) but these were identified as Entobdella squamula . But see Comments below.

Site on host: Skin. A report by Mamaev (1965) of “ E. hippoglossi ” on the gills of H. stenolepis caught in the Bering Sea needs confirmation.

Holotype: Adult specimen donated to us by Dr S. Jones. ( BMNH No.2007.4.26.23, 1 slide), from captive host held at the Pacific Biological Station , Nanaimo, British Columbia, Canada.

Paratypes: 2 adult specimens from a captive host held at the Pacific Biological Station , British Columbia, Canada, donated to us by Dr. S. Jones ( BMNH Nos. 2007.4.26.24-25, 2 slides). Three adult specimens from a captive host held at the Pacific Biological Station, British Columbia, Canada, donated to us by Dr S. Jones ( SAMA AHC Nos. 29199, 3 slides) .

Voucher specimens: 4 adult specimens from Hecate Strait , British Columbia, Canada, donated to 1 of us ( GCK) by Dr L. Margolis ( BMNH Nos. 2007.4.26. 26-29, 4 slides). Three immature specimens from a captive host held at the Pacific Biological Station, British Columbia, Canada, donated to us by Dr. S. Jones ( BMNH Nos. 2007.4.26.30-32, 3 slides) .

Etymology: The parasite species is named after the type host, Hippoglossus stenolepis .

Specimens studied: Holotypes, paratypes and voucher specimens as listed above.

Description ( Fig. 39): Dimensions of adults: total length 1.015 (0.719 – 1.32) cm (n = 10); body width 5.628 (3.89 – 7.865) mm (n = 10); haptor length and breadth 2952 (2166 – 3790) and 3163 (2121 – 4091) respectively (n = 10); accessory sclerite ( Fig. 39C) 401 (306 – 500) (n = 19) long; anterior hamulus length 676 (537 – 875) (n = 20); posterior hamulus length 137 (100 – 155) (n = 5); pharynx length and breadth 601 (431 – 875) and 741 (553 – 1163) respectively (n = 10); testis length and breadth 1269 (675 – 1684) (n = 19) and 1050 (663 – 1444) (n = 19) respectively. Anatomically similar to Entobdella hippoglossi . Vaginal opening small and inconspicuous ( Figs. 5, 6), leading to narrow entrance tube about 60 long, diameter 4 – 6. Entrance tube leads to another short tube (50 long) following a winding path with relatively thick, possibly glandular wall with affinity for toluidine blue ( Figs. 5, 6). Glandular (?) tube communicates with main vagina via restricted opening. Main vagina follows convoluted path (not as regularly coiled as illustrated by Klassen et al., 1989, figs. 1, 5); opens into vitelline reservoir ( Figs. 4, 39A) (not into a seminal receptacle as claimed by Klassen et al.). Sub-tegumental fibres arranged in circular pattern around vaginal opening observed in 1 specimen ( Fig. 39A) and a partial ring of fibres in a second specimen. As many as 7 seminal receptacles arranged in cluster around the ovo-vitelline duct (in whole mounts as few as 4 may be visible). Papillae present on ventral surface of haptor, lateral to and between median sclerites but not extending anterior to junction of peduncle. Papillae density 75 (59 – 97) (n = 5) per mm 2. Papillae 30 – 70 wide. Papillae roughly circular, lacking circular ridges ( Fig. 39B). Fleshy apical protuberances uncommon and weakly developed; no papillae with more than 1 apical lobe. Mean ratio of lengths of anterior hamuli and accessory sclerites 1.71 ( Table 3).

Dimensions of immature parasites: total body lengths: 5100, 5600 and 5800; lengths of anterior hamuli: 419/404, 449/444, 431/439 respectively. Mean ratio of lengths of anterior hamuli and accessory sclerites 1.7 ( Table 3).

Differential diagnosis: Most closely resembles Entobdella hippoglossi from Atlantic halibut, Hippoglossus hippoglossus , but distinguished from it by higher density of ventral haptor papillae [75 (59 – 97) per mm 2 compared with 45 (33 – 59) per mm 2] and smaller size of individual papillae (<70 in diameter compared with diameters regularly>100). Fleshy apical protuberances on papillae uncommon. No lobed protuberances. On skin of Pacific halibut ( H. stenolepis ).

Comments. Petrale sole, Eopsetta jordani , and Pacific halibut, Hippoglossus stenolepis , occur in the Pacific Ocean. It is important to determine the identity of parasites from E. jordani , identified as “ E. hippoglo- ssi ” by Klassen et al. (1989) and E. squamula by Margolis (1952). Eopsetta jordani may be an additional host for Entobdella stenolepis n. sp. or the entobdelline on Eopsetta jordani may be a distinct species. Our efforts to obtain parasite specimens from E. jordani were not successful (see Materials and methods).