Dactylogyrus kikuchii Gussev, 1967

Nitta, Masato & Nagasawa, Kazuya, 2014, 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, Species Diversity 19, pp. 71-79 : 76

Dactylogyrus kikuchii Gussev, 1967

( Fig. 4 )

Dactylogyrus kikuchii Gussev, 1967: 252–254 , fig. 4; Ji et al.

1982: 14; Gussev 1985: 188–189, fig. 282; Wu and Wang

1991: 74–75, fig. 50; Gibson et al. 1996: 18; Wu 2000a:

415–416, fig. 368; Zhang et al. 2001: 77–78, fig. 9–3;

Zhang et al. 2003: 114; Ding and Liao 2004: 628–632;

Šimková et al. 2006: 44; Gerasev et al. 2008: 323, fig. 2.

Lateolabraxogyrus kikuchii: Zhang et al. 1992: 131 ; Xia et al.

1999: 60.

Material examined. Five of the nine specimens deposited (together with 41 specimens of D. gotoi ) (NSMT-Pl 6123), Lake Nakaumi , Shimane Prefecture, Japan, 26 July 2012; ten of the 104 specimens deposited (together with 160 specimens of D. kikuchii ) (NSMT-Pl 6126), Lake Shinji, Shimane Prefecture, Japan, 9 January 2013 .

Description. Body length including haptor 353±70.4 (265–442; n =7), width at mid-body 90±15.5 (65–109; n =7). Internal anatomy shown in Fig. 4A . Three pairs of head organs. Two pairs of eye-spots with some dissociated eyes. Alimentary system consisting of subspherical pharynx (length 25±5.2 [18–35; n =8], width 17±2.2 [14–19; n =8]), 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 expressed as distended part of vas deferens before latter enters base of copulatory organ. Two prostatic reservoirs both saccate. Copulatory organ slender tube, length 46±3.6 (39–50; n =8). Sclerotized accessory piece base length 54±3.5 (48–58; n =8) ( Fig. 4J ). Ovary in mid-body. Vaginal armament unsclerotized; vaginal pore located at midlength on right ventral body surface, vaginal duct arising from left posterior part of seminal receptacle. Oviduct arising from right anterior side of ovary. Uterus extending anteriorly to uterine pore, latter located close to copulatory organ. Mehlis' gland near seminal receptacle. Vitelline system approximately co-extensive with intestinal caeca. Haptor length 69±11.0 (56–89; n =8), width 95±14.1 (76–114; n =8). Single pair of anchors ( Fig. 4B ), total length 53±1.8 (50–56; n =8), length to notch 37±1.9 (33–39; n =8), outer root length 4±1.1 (3–6; n =8), inner root length 18±0.9 (17–20; n =8), point length 21±2.4 (18–24; n =8). Each anchor with two filaments. Dorsal bar ( Fig. 4C ) total length 40±1.3 (38–42; n =8), total width 13±1.4 (10–15; n =8), median width 7±1.3 (5–9; n =8). Hat-shaped ventral bar ( Fig. 4D ) total length 12±1.7 (11–15; n =5), total width 5±1.3 (4–7; n =5), median width 4±1.1 (3–6; n =5). Hooks in 7 pairs ( Fig. 4A ); hook length: pair I ( Fig. 4E ) 38±3.6 (32–42; n =7); pair II ( Fig. 4F ) 24±1.3 (22–25; n =7); pair III 40±2.9 (36–44; n =8); pair IV 32±5.4 (24–39; n =7); pair V 32±2.1 (29–35; n =8), pair VI ( Fig. 4G ) 40±3.6 (36– 46; n =8); pair VII ( Fig. 4H ) 38±2.8 (33–40; n =8). Pair of needles ( Fig. 4I ), length 9±0.6 (8–10; 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 34–72 (55.0) in Lake Shinji; No data for Lake Nakaumi.

Remarks. As with D. gotoi , 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 has been reported since from the same host in China ( Ji et al. 1982; Wu and Wang 1991; Zhang et al. 1992, 2001, 2003; Gibson et al. 1996; Wu 2000a; Ding and Liao 2004; Šimková et al. 2006) and the Russian Far East ( Gussev 1985; Gerasev et al. 2008). The specimens examined in this study are identical in morphology and measurements with D. kikuchii from China examined by Gussev (1967), Wu and Wang (1991), and Wu (2000a). This is the first record of D. kikuchii from Japan. It was reported by Zhang et al. (1992) and Xia et al. (1999) as “ Lateolabraxogyrus kikuchii ” As was noted above, this generic name is an unavailable nomen nudum, and Gibson et al. (1996) and Timofeeva et al. (1997) did not refer to L. kikuchii as such in their catalogues of dactylogyrids. Recently, Zhang et al. (2001, 2003) assigned this species to Dactylogyrus , and in the present study, the generic characteristics of Dactylogyrus , especially the presence of needles, were confirmed.

Figures

Fig. 4. Dactylogyrus kikuchii Gussev, 1967, NSMT-Pl 6126. 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. Scale bars: A, 50µm; B–J, 10µm. 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.