Bivaginogyrus cingulatus, Nitta & Nagasawa, 2023

Nitta, Masato & Nagasawa, Kazuya, 2023, Gill Monogeneans (Platyhelminthes) Parasitic on Gnathopogon elongatus elongatus and G. caerulescens (Cypriniformes: Gobionidae) from Japan, with Descriptions of One New Species of Dactylogyrus and Three New Species of Bivaginogyrus (Dactylogyridae), Species Diversity 28 (1), pp. 69-97 : 84-86

Bivaginogyrus cingulatus n. sp.

[New Japanese name: Tamoroko-futa-ana-mushi] ( Figs 7 , 8 )

Type materials. Holotype ( MPM Coll.-No. 21924: PG) from the Senō River . Paratypes 25 specimens: three specimens from the Sunaoshi River ( MPM Coll.-No. 21927: PG); 14 specimens from the Senō River ( MPM Coll.-No. 21925: five PG and nine HH); two specimens from an irrigation canal of the Kiso River ( MPM Coll.-No. 21933: PG); two specimens from an irrigation canal of the Ashida River ( MPM Coll.-No. 21930: PG); and one specimen from an irrigation canal of the Midori River ( MPM Coll.-No. 21931: HH) .

Other specimens deposited. Non-type specimens: seven specimens from the Kashiranashi River ( MPM Coll.- No. 21915: PG); two specimens from the Harayachi River ( MPM Coll.-No. 21948); three specimens from an irrigation canal of the Masugata River ( MPM Coll.-No. 21909: PG); three specimens from an irrigation canal of the Mogami River ( MPM Coll.-No. 21912: PG); eight specimens from an irrigation canal of the Nomoto River ( MPM Coll.-No. 21935: PG); two specimens from an irrigation canal of the Sugata River ( MPM Coll.-No. 21937: PG); five specimens from the Chōmeiji River ( MPM Coll.-No. 21938: PG); and 13 specimens from the Ama River ( MPM Coll.-No. 21940: PG) .

Description. Body ( Fig. 7 ) elongate, length including haptor 190–645 (369, n = 24), width at mid-body 42–110 (74, n = 24). Three pairs of head organs. Head gland cells on both sides of body at level of posterior pharynx. One pair of eye-spots with accessory eyes. Pharynx ovate, length 13–34 (23, n = 24), width 11–35 (21, n = 24); esophagus continued bifurcate intestine uniting posterior to germarium.

Haptor with pair of glands, length 55–92 (73; n = 19), width 68–178 (99, n = 19). Dorsal hamulus ( Fig. 8 ), total length 42–55 (49, n = 21), length to notch 32–40 (36, n = 21), outer root poorly developed, length 0–2 (1, n = 21), inner root length 13–19 (17, n = 21), point length 18–23 (20, n = 21). Dorsal bar ( Fig. 8 ) slightly curved, bent at both ends, median length 2–4 (3, n = 20), total width 21–25 (23, n = 20), total length 4–7 (5, n = 20). Rod-shaped ventral bar ( Fig. 8 ) total length 1–3 (2, n = 6), median length 1 (1, n = 6), total width 12–15 (14, n = 6). Marginal hooks ( Fig. 8 ) in 7 pairs; hook length: pair I 16–19 (17, n = 13); pair II 21–23 (22, n = 12); pair III 24–26 (25, n = 12); pair IV longest, 24–28; pair V shortest, 14–17; pair VI 21–24 (22, n = 12); pair VII 18–22 (20, n = 12). Pair of needles ( Fig. 8 ), length 6–8 (7, n = 11) located near tips of marginal hook pair V.

Testis ( Fig. 7 ), dorsal to germarium, length 25–82 (53, n= 9), width 13–47 (28, n = 9). Vas deferens leaving from anterior side of testis, looping around left intestine to ventral side, distending to form seminal vesicle, and entering into base of penis. Two prostatic reservoirs: one pyriform; the other elongate, drained into by prostatic gland located dextrodorsal region of anterior trunk. Male copulatory organ length 16–25 (21, n = 19), consisting penis and accessory piece ( Fig. 8 ), “navicularis” type in Gussev (1985). Penis slightly curved tube, length 22–28 (25, n = 19). Sclerotized accessory piece, length 15–21 (18, n = 19), wrapping copulatory organ from outside, each of two processes touching tip and base of penis.

Germarium ( Fig. 7 ) elongate, in mid-body, length 31–104 (67, n = 9), width 19–52 (35, n = 9). Oviduct leaving from anterior margin of germarium, continuing as oötype. Seminal receptacle located ventral of oviduct, ducting right side of oviduct. Mehlis’ gland connecting lowest part of oötype. Two vaginae arising from each side of seminal receptacle, becoming inflated and thin, opening dorsally at mid-length on each side of body. Vaginal pore unsclerotized. Vitellarium approximately co-extensive with intestine. Egg ovate.

Type host. Gnathopogon e. elongatus ( Cypriniformes : Gobionidae ).

Other host. Gnathopogon caerulescens ( Cypriniformes : Gobionidae ).

Type locality. The Senō River (34°36′16″N, 133°51′52″E), Uchio, Minami District , Okayama City , Okayama Prefecture .

gi Prefecture; an irrigation canal of the Masugata River (38°45′54″N, 140°16′31″E), Tōka-machi, Shinjō City, Yamagata Prefecture; an irrigation canal of the Mogami River (37°58′43″N, 140°09′20″E), Iryūda, Higashi-okitama Takahata-machi, Yamagata Prefecture; the Kashiranashi River (37°29′56″N, 138°55′13″E), Yamazaki-machi, Mitsuke City, Niigata Prefecture; an irrigation canal of the Nomoto River (36°35′20″N, 140°01′28″E), Kami-takane-zawa, Takane-zawa-machi, Shioya County, Tochigi Prefecture; an irrigation canal of the Sugata River (36°25′46″N, 139°50′43″E), Nakadairyō , Shimotsuke City , Tochigi Prefecture; an irrigation canal of the Kiso River (35°17′32″N, 136°42′35″E), Shimo-naka-chō, Hashima City , Gifu Prefecture; the Chōmeiji River (35°09′55"N, 136°04′55"E), Kitatsuda-chō , Ōmi-hachiman City , Shiga Prefecture; the Ama River (34°51′23″N, 134°46′35″E), Yaebata , Shikitō-chō , Himeji City , Hyōgo Prefecture; an irrigation canal of the Ashida River (34°31′51″N, 133°22′04″E), Kawa-minami , Kan-nabe-chō, Fukuyama City , Hiroshima Prefecture; and an irrigation canal of the Midori River (32°45′15″N, 130°46′02″E), Shimo-rokka , Kashima-machi , Kami-mashiki County , Kumamoto Prefecture .

Site of infection. Gill filaments.

Molecular sequence data. DDBJ accession numbers LC731709 (28S rDNA) and LC731719 (18S-ITS1- 5.8S) obtained from specimens collected from G . e. elongatus in Miyagi Prefecture, and LC731710 (28S rDNA) and LC731720 (18S-ITS1- 5.8S) from G . caerulescens from Shiga Prefecture ( MPM Coll. - No. 21938) .

Etymology. The specific name “ cingulatus ” (belted in Latin) refers to vaginae traveling across the mid-body. The new Japanese name, “tamoroko” means the type host in Japanese and “futa-ana-mushi” does the genus Bivaginogyrus .

Remarks. Bivaginogyrus cingulatus n. sp. is the only species of the genus that possesses the “navicularis”- type male copulatory organ. This organ and the rod-shaped ventral bar of B. cingulatus n. sp. resemble those of D. navicularis Gussev, 1955 , D. trullaeformis Gussev, 1955 , and D. imberbis Wu and Wang, 1983 (anatomical details unknown: Gussev 1955; Wu and Wang 1983). However, the outer roots of D. navicularis and D. imberbis are developed ( Gussev 1955; Wu and Wang 1983), while those of B. cingulatus n. sp. are inconspicuous. Two processes of the accessory piece of D. trullaeformis touch the base of the penis ( Gussev 1955), but each of two processes of B. cingulatus n. sp. touch the tip and base of penis. Furthermore, the dorsal hamulus of B. cingulatus n. sp. (42–55 µm) is larger than that of D. trullaeformis [27–30µm ( Gussev 1955)] and D. imberbis [27–33 µm (Wu and Wang 1983)], and the inner root (13–19 µm) and point (18–23µm) of the new species are longer than those of D. navicularis [8–12 µm and 11–13 µm, respectively ( Gussev 1955) and 8–11 µm and 12–15 µm, respectively ( Ma and Zhao 2000a)].

Other localities. The Sunaoshi River (38°18′16″N, 140°58′43″E) and the Harayachi River (38°18′16″N, 140°58′42″E), Nangū-hachiman, Tagajō City, Miya-

Figures

Fig. 7. Whole body of Bivaginogyrus cingulatus n. sp. (paratype, MPM Coll.-No. 21925, dorsal view).

Fig. 8. Sclerotized parts of Bivaginogyrus cingulatus n. sp. (holotype, MPM Coll.-No. 21924, for haptoral parts and left male copulatory organ, dorsal view; paratype, MPM Coll.-No. 21925, for right male copulatory organs, ventral view).