Benedenia ishikawae (Goto, 1894) Monticelli 1902

Benedenia ishikawae (Goto, 1894) Monticelli, 1902

(Fig. 7)

Synonyms: Epibdella ishikawae Goto, 1894; Epibdella (Phylline) ishikawae (Goto, 1894) Parona & Perugia, 1895; Epibdella (Benedenia) ishikawae (Goto, 1894) Monticelli, 1902; Benedenia ishikawae (Goto, 1894) Odhner, 1905; Benedenia (Parabenedenia) ishikawae (Goto, 1894) Johnston, 1929; Allobenedenia ishikawae (Goto, 1894) Yamaguti, 1963.

Type host and locality: Lethrinus sp. ‘Kuchibi-dai’ (Perciformes: Lethrinidae), Hagi, Japan (see Goto 1894). Lawler (1981) regards it likely that this host is Lethrinus haematopterus Temminck & Schlegel.

Site on host: Gill (see Goto 1894).

Remarks: It is the opinion of staff at the Meguro Parasitological Museum that the specimen collection of Goto has been either destroyed or lost. We sampled the following species of lethrinids at Heron Island: Gymnocranius audleyi Ogilby (n=20); Lethrinus atkinsoni Seale (n=2); L. miniatus (Forster) (n=12); L. nebulosus (Forsskål) (n=10); L. olivaceus Valenciennes (n=2). We discovered several undescribed species of Benedenia, some of which bear similar novel features to those described by Goto (1894) for B. ishikawae but none that conform to the description in its entirety. Our evaluation of B. ishikawae is, therefore, based on the original description by Goto (1894). Benedenia ishikawae is a medium-sized benedeniine (Whittington et al. 2001, their fig. 3) with strongly ‘hooded’ anterior attachment organs (see Whittington et al. 2001, their fig. 1B and Fig. 7 A here). Other features are typical of Benedenia sensu Whittington et al. (2001). The haptor bears distinctive accessory sclerites with a trident-shaped distal tip (Fig. 7 A, B). The anterior hamuli are long with a broad, bifid, root and shaft in the shape of a ‘wish-bone’ (Fig. 7 A, C). The posterior hamuli are shorter, have a similarly broad root and shaft, also with a ‘wish-bone’-shaped proximal region and a tapering, fine distal hook (Fig, 7A, D). Goto (1894) depicted the penis as broad and muscular, with a tapering distal tip. The common genital pore is submarginal and lies slightly posterior to the left anterior attachment organ at the anterior level of the pharynx. The vagina was depicted as a duct without musculature or adornments and includes several convoluted twists proximally. The vaginal pore is submarginal, posterior to the common genital pore. Goto (1894) described the junctions of the “yolk duct” (= common vitelline duct) and oviduct, and the vaginal canal and vitelline reservoir, notable observations considering the age of his study and the equipment available to him at that time.

Comments and differential diagnosis: Yamaguti (1963) regarded B. ishikawae as belonging in Allobenedenia Yamaguti, 1963, based largely on the ‘hooded’ appearance of the anterior attachment organs. Allobenedenia species possess haptoral septa and are now included in the Trochopodinae, as outlined by Yang et al. (2004), who regarded B. ishikawae a species inquirenda in Allobenedenia because Goto’s description could not be verified as no specimens are available to confirm the description. Unusual features described for Benedenia ovata (Goto, 1894) Johnston, 1929 by Goto (1894) and now confirmed (see Whittington et al. 2001) demonstrate that Goto made insightful observations and convince us that the description of B. ishikawae is likely to be accurate. Goto’s detailed figures and description outline the anatomy of this species in sufficient detail to indicate to us that it fits within the current definition of Benedenia. Despite omitting them from his description, Goto drew several vital features, such as the arrangement of tendons in the haptor, the wall of the accessory gland reservoir and its relationship with the penis canal, the seminal vesicle and the specific morphology of all the large haptoral sclerites. These features are all consistent with the diagnosis for Benedenia amended by Whittington et al. (2001). The accessory sclerites alone are sufficient to differentiate B. ishikawae from all other described species of Benedenia.

Benedenia ishikawae can be differentiated from all other species of Benedenia by a combination of features: a medium-sized benedeniine bearing accessory sclerites with distinctive trident-shaped distal tips, anterior and posterior hamuli with a bifid ‘wish-bone’-shaped root and shaft and strongly hooded anterior attachment organs.