Three Species of Dactylogyrus (Monogenea: Dactylogyridae) Parasitic on Japanese Seabass Lateolabrax japonicus (Perciformes: Lateolabracidae) in Japan, with New Country Records for Dactylogyrus gotoi and Dactylogyrus kikuchii Author Nitta, Masato Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1 - 4 - 4, Higashi-Hiroshima, Hiroshima 739 - 8528, Japan E-mail: licht. bsn. mono @ gmail. com (MN) & Corresponding author bsn.mono@gmail.com Author Nagasawa, Kazuya Graduate School of Biosphere Science, Hiroshima University, Kagamiyama 1 - 4 - 4, Higashi-Hiroshima, Hiroshima 739 - 8528, Japan E-mail: licht. bsn. mono @ gmail. com (MN) bsn.mono@gmail.com text Species Diversity 2014 2014-05-25 19 71 79 journal article 10.12782/sd.19.1.071 2189-7301 5737343 Dactylogyrus gotoi Gussev, 1967 ( Fig. 3 ) Dactylogyrus gotoi Gussev, 1967: 251–252 , fig. 3; Ji et al . 1982: 12 ; Chen 1984: 54 ; Gussev 1985: 188–189 , fig. 282; Wu and Wang 1991: 75 , fig. 51; Gibson et al . 1996: 16 ; Wu 2000a: 414–415 , fig. 367; Zhang et al . 2001: 75–76 , fig. 9–1; 2003: 114; Gerasev et al . 2008: 323 ; Gussev et al . 2010: 24 . Lateolabraxogyrus gotoi : Zhang et al . 1992: 131 ; Xia et al . 1999: 60. Material examined. Five of the 41 specimens deposit- ed (together with nine specimens of D. kikuchii ) (NSMT-Pl 6123) and 10 specimens (NSMT-Pl 6124), Lake Nakaumi , Shimane Prefecture , Japan , 26 July 2012 ; five of the 15 specimens deposited (together with 11 specimens of D. kikuchii ) (NSMT-Pl 6125), Lake Shinji , Shimane Prefecture , Japan , 9 January 2013 . Description. Body length including haptor 380±76.7 (254–509; n =20), width at mid-body 88±12.2 (58–109; n =20). Internal anatomy shown in Fig. 3A . Three pairs of head organs. Two pairs of eye-spots with some dissociated eyes. Alimentary system consisting of subspherical pharynx (length 23±2.8 [18–28; n =20], width 19±2.3 [15–23; n =20]), short oesophagus, and bifurcate intestine with branches confluent just posterior to testis. Testis ovoid, postovarian. Vas deferens arising from anterior region of testis, looping around left intestinal caeca towards ventral side of body. Seminal vesicle represented by distended part of vas deferens before latter enters base of copulatory organ. Two prostatic reservoirs both saccate. Copulatory organ a slen- der tube, length 33±3.0 (28–39; n =20). Sclerotized accessory piece, length 32±2.1 (28–36; n =20), with bifurcate base cradling posterior-most part of copulatory organ and hood-like apical part with hole for anterior point of copulatory organ ( Fig. 3J ). Ovary in mid-body. Vaginal armament unsclerotized; vaginal pore located at midlength on right dorsal body surface, vaginal duct arising from right side of seminal receptacle. Oviduct arising from anterior side of ovary. Uterus extending anteriorly to uterine pore, latter located close to copulatory organ. Mehlis’ gland near anterior part of seminal receptacle. Vitelline system approximately co-extensive with intestinal caeca. Haptor length 73±12.4 (50–99; n =20), width 108±15.4 (83–137; n =20). Single pair of anchors ( Fig 3B ), total length 44±2.0 (41–48; n =20), length to notch 30±1.7 (28–34; n =19), outer root length 4±0.6 (3–5; n =19), inner root length 16±1.5 (13–18; n =19), point length 21±1.4 (18–23; n =20). Each anchor with two filaments. Dorsal bar ( Fig. 3C ) total length 35± 1.5 (33–37; n =19), total width 9±1.1 (8–12; n =19), medi- an width 6±0.8 (5–7; n =19). Hat-shaped ventral bar ( Fig. 3D ) total length 12±0.8 (11–13; n =16), total width 4±0.9 (3–6; n =16), median width 4±1.0 (2–6; n =16). Hooks in 7 pairs ( Fig. 3A ); hook length: pair I ( Fig. 3E ) 41±3.3 (35–48; n =19); pair II ( Fig. 3F ) 27±2.2 (22–31; n =20); pair III 41± 2.4 (36–44; n =20); pair IV 33±2.7 (28–38; n =20); pair V 40±3.2 (33–45; n =20), pair VI ( Fig. 3G ) 45±4.0 (37–52; n =20); pair VII ( Fig. 3H ) 38±6.4 (33–45; n =20). Pair of needles ( Fig. 3I ), length 9±0.5 (8–9; n =10) located near tips of second hooks. Host. Japanese seabass Lateolabrax japonicus ( Perciformes : Lateolabracidae ). Site of infection. Gills. Prevalence and intensity range (mean). 100% (10/10) and 40–82 (55.8) in Lake Shinji; no data for Lake Nakaumi. Remarks. The present species was originally described by Gussev (1967) from the gills of “ Lateolabrax japonicus ” in the Liaohe River and the Yellow Sea, China . It was subsequently reported from the same host in China ( Ji et al . 1982 ; Chen 1984 ; Wu and Wang 1991 ; Zhang et al . 1992 , 2001 , 2003 ; Gibson et al . 1996 ; Wu 2000a ) and the Russian Far East ( Gussev 1985 ; Gerasev et al . 2008 ). The morphology of the specimens examined in this study is in general agreement to that of D. gotoi from China described by Gussev (1967) , Wu and Wang (1991) , and Wu (2000a) . This is the first record of D . gotoi in Japan . Although Zhang et al . (1992) and Xia et al . (1999) reported the species as “ Lateolabraxogyrus gotoi ,” this generic name has never been formally proposed, so it is a nomen nudum . In comprehensive catalogues of genera and species of the Dactylogyridae , neither Gibson et al . (1996) nor Timofeeva et al . (1997) referred to L. gotoi as such. Zhang et al . (2001 , 2003 ) recently assigned this species to Dactylogyrus , and the present study confirms that the species has the needles that are the generically diagnostic of Dactylogyrus . Fig. 3. Dactylogyrus gotoi Gussev, 1967 , NSMT-Pl 6124. A, whole mount (ventral view); B, dorsal anchors; C, dorsal bar; D, ventral bar; E, hook of pair I; F, hook of pair II; G, hook of pair VI; H, hook of pair VII; I, needle; J, male copulatory organ (from three specimens). Scale bars: A, 50 µ m; B – J, 10 µ m. Abbreviations: an, anchor; ap, accessory piece; co, copulatory organ; es; eye-spots; hk, hook; ho, head organ; in, intestine; mg, Mehlis’ gland; od, oviduct; oe, oesophagus; ov, ovary; ph, pharynx; pr, prostatic reservoir; sv, seminal vesicle; te, testis; ut, uterus; va, vaginal duct; vd, vas deferens; vp, vaginal pore; vs, vitelline system. The correct scientific name of the type host of D. gotoi , reported as “ Lateolabrax japonicus ” in China , is discussed later in this paper.