Ancyrocephalus pseudorasborae Achmerow, 1952

Nitta, Masato & Nagasawa, Kazuya, 2016, New Geographical Records of Three Gill Monogeneans (Platyhelminthes) Parasitic on Pseudorasbora parva (Cypriniformes: Cyprinidae) in Japan, Species Diversity 21 (1), pp. 1-7 : 5-6

Ancyrocephalus pseudorasborae Achmerow, 1952

[New Japanese name: Motsugo-yotsume-ikari]

( Fig. 3 )

Ancyrocephalus pseudorasborae Achmerow, 1952: 189 , 194, fig. 4z; Gussev 1955: 299–300, fig. 48; Bykhovskaya-Pavlovskaya et al. 1962: 390, 391, fig. 742; Yamaguti 1963: 51, fig. 715; Anonymous 1973: 149, 266, figs 209–210; Ji et al. 1982: 5; Chen 1984: 54; Gussev 1985: 203, fig. 306; Wu 1991: 143–144, fig. 150; Wu 2000: 457–458, fig. 404; Gerasev 2008: 408, 411, 423, 424; Gussev et al. 2010: 286, 288, fig. 362. Davydov et al. 2012: 73, 74.

Material examined. Twenty specimens were used for the description. Soft anatomy was observed in 10 specimens (NSMT-Pl 6180) from Ibaraki Prefecture stained in Heidenhain’s iron hematoxylin . Sclerotized structures were measured in eight and two specimens (NSMT-Pl 6180 and 6182) fixed in APG, from Ibaraki and Okayama prefectures, respectively.

Description. Body ( Fig. 3A ) elongate, length 400±43.6 (335–483, n =10) including haptor, width at mid-body 71±11.7 (55–94, n =10). Three pairs of head organs. Two pairs of eye-spots. Pharynx subspherical, length 26±2.0 (23–30, n =10), width 23±2.1 (19–26, n =10); esophagus present; intestine bifurcate with branches confluent just posterior to testis. Testis pyriform, dorsal to ovary. Vas deferens leaving from anterior region of testis, passing along dorsal to loop of sinistral intestine to ventral side, ascending to anterior part of copulatory organ, looping downwards and becoming distended to form seminal vesicle, narrowing to enter initial part of copulatory organ. Single prostatic reservoir elongate; prostatic gland occupying dorsal region of anterior trunk, with its duct leading into the anterior part of prostatic reservoir. Copulatory organ ( Fig. 3G ) a slender curved tube, organ length 28±1.6 (25–30, n =10), tube length 50±4.0 (41–55, n =10); accessory piece curved in same direction as copulatory organ, trifurcate at tip, length 20±1.4 (18–22, n =10). Ovary ovate, in mid-body. Oviduct arising from anterior side of ovary, continuing as oötype surrounded by Mehlis’ gland and uterus. Seminal receptacle dorsal to oviduct. Vagina ( Fig. 3H ) sclerotized, a slightly curved tube, length 17±3.1 (13–21, n =10), arising from anterior part of seminal receptacle and opening at midlength on right ventral body surface. Vitellaria approximately coextensive with intestine.

Haptor length 55±5.7 (44–61, n =10), width 74±11.2 (59–99, n =10). Dorsal anchor ( Fig 3B ) more slender than ventral anchor, of total length 24±0.6 (23–25, n =10), length to notch 20±0.8 (19–21, n =10), outer root length 1±0.7 (0–2, n =10), inner root length 7±0.7 (6–8, n =10), point length 4±0.5 (4–5, n =10). Ventral anchor ( Fig. 3C ) of total length 20±1.2 (19–22, n =10), length to notch 18±0.8 (16–19, n =10), outer root length 1±0.5 (1–2, n =10), inner root length 8±1.1 (7–10, n =10), point length 4±0.7 (3–5, n =10). Dorsal bar ( Fig. 3D ) rod-shaped, of total length 18±0.7 (17–19, n =10), total width 4±0.4 (3–4, n =10), median width 3±0.4 (2–3, n =10). Ventral bar ( Fig. 3E ) Vshaped with posteriorly directed enlargement at each end, of total length 25±0.8 (23–26, n =10), total width 5±0.6 (4–6, n =10), median width 3±0.5 (2–4, n =10). Seven pairs of marginal hooks ( Fig. 3F ), all of approximately same length, 12±0.5 (11–12, n =10).

Host. Pseudorasbora parva ( Cypriniformes : Cyprinidae ).

Site of infection. Gills.

Prevalence and intensity range (mean). 90% (9/10) with no data for intensity in Lake Kasumigaura , Ibaraki Prefecture; seven worms infected one P . parva in the Senō River , Okayama Prefecture .

Remarks. Ancyrocephalus pseudorasborae was originally described by Achmerow (1952) from the gills of Pseudorasbora parva in Lake Bolon, Far-East Russia. It was subsequently reported from the same host in Heilongjiang, Liaoning, Shandong, Shanghai, Jiangxi, Hubei, Zhejiang and Yunnan, China ( Anonymous 1973; Ji et al. 1982; Chen 1984; Wu 1991, 2000) and the Amur River, Russia ( Gussev 1955, 1985; Bykhovskaya-Pavlovskaya et al. 1962; Gussev et al. 2010). The measurements of sclerotized structures examined in this study are slightly smaller than those reported by Gussev (1955, 1985), Bykhovskaya-Pavlovskaya et al. (1962), Anonymous (1973), Wu (1991, 2000), and Gussev et al. (2010), but the ranges of the measurements overlap, and all the descriptions of the male copulatory organ are in general agreement. The present collection represents the first record of Ancyrocephalus pseudorasborae in Japan.

Japanese names. The new Japanese generic name, “yotsume-ikari” (“zoku” means a genus), refers to the opisthohaptor with four anchors possessed by Ancyrocephalus spp. and means a grapnel anchor in Japanese. Part of the new Japanese name of the species is “motsugo”, which is the Japanese name of the host.

Genus Bivaginogyrus Gussev and Gerasev, 1985

[New Japanese name: Futa-ana-mushi-zoku]

Bivaginogyrus obscurus ( Gussev, 1955)

[New Japanese name: Motsugo-futa-ana-mushi]

Host. Pseudorasbora parva ( Cypriniformes : Cyprinidae ).

Site of infection. Gills.

Material examined. Two and three specimens collected from the Tomio River, Nara Prefecture (NSMT-Pl 6179), and the Senō River , Okayama Prefecture (NSMT-Pl 6182), respectively .

Prevalence and intensity. 50% (1/2) and 2 in the Tomio River , Nara Prefecture; four worms infected one P . parva in the Senō River , Okayama Prefecture .

Remarks. In Japan this monogenean was first described from Pseudorasbora parva and P. pumila Miyadi, 1930 in Lake Kasumigaura, Ibaraki Prefecture and in ponds of Shinonoi, Nagano Prefecture, respectively by Nitta and Nagasawa (2014). The specimens from Nara and Okayama prefectures correspond well with those from Lake Kasumigaura and ponds of Shinonoi. The present collections constitute new prefectural records and extend the geographical distribution of the species from Ibaraki and Nagano prefectures westward to Nara and Okayama prefectures.

Japanese names. The new Japanese generic name is a combination of “Futa-ana” and “mushi” which mean two holes (i.e., vaginae) and worms, respectively (“zoku” means a genus). Part of the new Japanese name of the species is “motsugo”, which is the Japanese name of the host.

Figures

Fig. 3. Ancyrocephalus pseudorasborae Achmerow, 1952, NSMT-Pl 6180. A, whole mount (dorsal view); B, dorsal anchors; C, ventral anchors; D, dorsal bar; C, ventral bar; F, marginal hook; G, male copulatory organ; H, vagina. Scale bars: A, 50µm; B–H, 10µm. Abbreviations: ap, accessory piece; co, copulatory organ; dan, dorsal anchor; e, eye-spots; h, haptor; ho, head organ; in, intestine; mg, Mehlis’ gland; mh, marginal hook; o; oötype; ov, ovary; pg, prostatic gland; ph, pharynx; pr, prostatic reservoir; sr, seminal reservoir; sv, seminal vesicle; t, testis; va, vagina; van, ventral anchor; vd, vas deferens; vl, vitellaria; vo, vaginal opening.