Heterocotyle chinensis Timofeeva, 1983

Nitta, Masato & Nagasawa, Kazuya, 2015, Heterocotyle chinensis (Monogenea: Monocotylidae) from the Whip Stingray Dasyatis akajei in the Seto Inland Sea, Japan, Species Diversity 20, pp. 89-93 : 89-91

Heterocotyle chinensis Timofeeva, 1983

( Fig. 1 )

Heterocotyle chinensis Timofeeva, 1983: 42–44 , fig. 4; Timofeeva 1985: 54; Chisholm et al. 1995: 177; Chisholm and Whittington 1996: 1175–1176, figs 1B, 2B, 9, 12D; Zhang et al. 1999: 186–187, fig. 8-71; Zhang et al. 2001: 42–43, fig. 2-2; Zhang et al. 2003: 112.

Material examined. Twenty-five specimens (NSMT-Pl 6164) from the mouth of the Kamo River on 28 May 2014, and 6 specimens (NSMT-Pl 6165) from off Ōsaki-kami-jima island on 14 July 2014 .

Description. Body ( Fig. 1A ) including haptor length 865±132.7 (671–1073; n =17), width at mid-body 326±56.1 (194–406; n =17). Two ducts from point of anterolateral glands exiting medial to two ducts from anteromedian gland present in anterior part of head. Trio of other ducts opening on either side of front of head. Eyespots dispersed over dorsal body surface between mouth and pharynx. Mouth muscular, round to elliptical, length 62±11.6 (48–87; n =14), width 71±18.1 (34–108; n =14). Pharynx muscular, spherical to oval, with muscular fibers attached to both sides of its anterior part, length 138±36.2 (65–185; n =17), width 110±31.9 (46–113; n =17). Esophagus not present, bifurcate intestine extending to end of body. Pharyngeal glands present on either side of posterior part of pharynx. Testis single, posterior to ovary. Vas deferens arising from left anterior side of testis, extending along dorsal side of left intestine. Seminal vesicle located beneath branching point of intestine, extending to ejaculatory bulb, and connected to posterior part of ejaculatory bulb. Ejaculatory bulb muscular, oval to pyriform, length 97±9.0 (82–113; n =17), width 75±12.6 (37–98; n =17). Male accessory glands entering posterior part of ejaculatory bulb. Male copulatory organ ( Fig. 1D ) lacking accessory piece, sclerotized slightly curved tube, tip twisted slightly, length 78±4.9 (73–92; n =30) in chord straight line from base to tip. Ovary in mid-body, elongate, wrapping around right intestine. Oviduct arising from anterior part of ovary, continuing on as oötype. Mehlis’ gland connected to middle of oötype. Vagina, without sclerotized structure, connecting between posterior part of oötype and seminal receptacle. Vaginal pore opening on left side of ventral body surface. Vitellaria approximately co-extensive with intestine. Transverse vitelline duct lying at level of oviduct. Pair of posterior glands located near either tip of intestine.

Haptor elliptical, length 232±24.1 (172–269; n =15), width 319±39.3 (223–383; n =15), ventral surface of haptor with 1 central and 8 peripheral loculi. Pair of hamuli ( Fig. 1B ), length 41±2.1 (38–46; n =31). Sinuous ridge single on 3 posterior radial septa, double on 2 lateral septa, triple on 3 anterior septa. Fourteen hooklets ( Fig. 1C ), length 9±0.7 (8–10; n =31), located in marginal valve as illustrated ( Fig. 1A ). Dorsal haptoral accessory structure U-shaped, located on dorsal surface of 4 posterior loculi.

Host. Whip stingray Dasyatis akajei ( Myliobatiformes : Dasyatidae ).

Localities. Mouth of the Kamo River, Takehara city, and off Ōsaki-kami-jima island, Ōsaki-kami-jima town, both in the Seto Inland Sea, Hiroshima Prefecture, Japan.

Site of infection. Gills.

Intensity. Two hundred and thirty-two individuals were found infecting the whip stingray (173 mm in disk width) collected at the mouth of the Kamo River, and 50 individuals were collected from the other whip stingray (323 mm in disk width) caught off Ōsaki-kami-jima island.

Remarks. Heterocotyle chinensis was originally described by Timofeeva (1983) and later redescribed by Chisholm and Whittington (1996). The morphology of the specimens collected in this study corresponds to the description by Chisholm and Whittington (1996) and measurements by Timofeeva (1983) and Zhang et al. (2001).

Currently, 19 species of the genus Heterocotyle Scott, 1904 are regarded as valid: H. americana Hargis, 1955 , H. armata Timofeeva, 1983 , H. capapei Neifar, Euzet and Ben Hassine, 2000 ; H. capricornensis Chisholm and Whittington, 1996 ; H. chinensis Timofeeva, 1983 , H. confusa Timofeeva, 1983 ; H. dasyatis ( Yamaguti, 1965) ; H. forcifera Neifar, Euzet and Ben Hassine, 1999 ; H. granulatae Young, 1967 ; H. minima (MacCllum, 1916) , H. mokhtarae Neifar, Euzet and Ben Hassine, 1999 ; H. pastinacae Scott, 1904 , H. pseudominima Hargis, 1955 ; H. scotti Neifar, Euzet and Ben Hassine, 1998 ; H. similis Neifar, Euzet and Ben Hassine, 1998 ; H. striata Neifar, Euzet and Ben Hassine, 1999 ; H. sulamericana Santos, Santos, Cunha and Chisholm, 2012 ; H. taeniuropi Cao, Ding, Zhang and Liu, 2010 ; H. tokoloshei Vaughan and Chisholm, 2010 ( Chisholm and Whittington 1996; Cao et al. 2010; Santos et al. 2012). Heterocotyle armata , H. capricornensis , H. confusa , H. forcifera , H. granulatae , and H. sulamericana all differ from H. chinensis in having a haptor with a single sinuous ridge on all septa ( Young 1967; Timofeeva 1983; Chisholm and Whittington 1996; Neifar et al. 1999; Santos et al. 2012). The accessory piece is absent in H. chinensis , while it is present in H. americana , H. dasyatis , H. minima , and H. tokoloshei ( Hargis 1955; Yamaguti 1965; Chisholm and Whittington 1996; Vaughan and Chisholm 2010). By the male copulatory organ length (79–95 µm: Timofeeva 1983; 83–107 µm: Zhang et al. 2001; 73–92 µm: present study), H. chinensis is differentiated from H. capapei (166–182 µm: Neifar et al. 2000), H. mokhtarae (145–165 µm: Neifar et al. 1999), H. scotti (115–155 µm: Neifar et al. 1998), H. striata (130–155µm: Neifar et al. 1999), H. taeniuropi (193–330 µm: Cao et al. 2010), and H. pseudominima (36–54 µm: Hargis 1955). Although H. pastinacae has sclerotized spines in the proximal part of the vagina ( Chisholm and Whittington 1995, 1996; Neifar et al. 1998) and H. similis possesses a crotchet-shaped male copulatory organ ( Neifar et al. 1998), H. chinensis has no such features.

Figures

Fig. 1. Heterocotyle chinensis Timofeeva, 1983. NMST-Pl 6164. A, whole mount (ventral view); B, hamulus; C, hooklet; D, male copulatory organ. Scale bars: A, 200µm; B–D, 10µm. Abbreviations: alg, anterolateral gland; amg, anteromedian gland; d, duct; dh, dorsal haptoral accessory structure; ej, ejaculatory bulb; ey, eyespots; h, hamulus; ho, hooklet; in, intestine; m, mouth; mag, male accessory gland; mco, male copulatory organ; mg, Mehlis’ gland; o, oötype; od, oviduct; ov, ovary; ph, pharynx; pg, posterior gland; phg, pharyngeal glands; r, sinuous ridge; sr, seminal receptacle; sv, seminal vesicle; t, testis; tv, transverse vitelline duct; u, uterus; vi, vitellaria; v, vagina; vp, vaginal pore; vd, vas deferens.