Bivaginogyrus obscurus ( Gussev, 1955 )

Nitta, Masato & Nagasawa, Kazuya, 2014, Bivaginogyrus obscurus (Monogenea: Dactylogyridae), a Gill Parasite of Two Cyprinids Pseudorasbora pumila pumila and Pseudorasbora parva, New to Japan, Species Diversity 19, pp. 167-171 : 168-170

Bivaginogyrus obscurus ( Gussev, 1955)

( Fig. 2 )

Dactylogyrus obscurus Gussev, 1955: 206–207 , figs 10.1, 10.2; Bykhovskaya-Pavlovskaya et al. 1964: 307, fig. 613; Strelkov 1971: 53; Anonymous 1973: 140, figs 163–164; Gvozdev and Agapova 1988: 109, 112; Davydov et al. 2012: 74.

Neodactylogyrus obscurus: Yamaguti 1963: 41 , fig. 623.

Bivaginogyrus obscurus: Gussev and Gerasev 1985: 192–194 , figs 289, 291; Gussev and Gerasev 1986: 373–375, fig. 1; Wu and Wang 1991: 133–135, figs 139–140; Matsaberidze 1993: 9; Xia et al. 1999: 59; Zhang et al. 1999: 130–131, fig. 8-13; Wu 2000: 426–428, fig. 378; Karabekova 2008: 331; Gerasev 2008: 407, 411, 419; Gussev et al. 2010: 274– 275, figs 345–346; Anonymous 2012: 51–52; Davydov et al. 2012: 73; Teo et al. 2013: 3–8, figs 1A, 2, 3, 4, 8A, 8B.

Material examined. 15 specimens (NSMT-Pl 6131) and 1 specimen (NSMT-Pl 6132) from P. p. pumila collected on 23 July and 30 October 2013, respectively; and 14 specimens (NSMT-Pl 6133) and 5 specimens (NSMT-Pl 6134) from P. parva collected on 13 and 16 June 2014, respectively.

Description. Body ( Fig. 2A ) including haptor length 301±55.3 (128–411; n=34), width at mid-body 43±9.3 (24–68; n=34). Surface of body corrugated. Three pairs of head organs. Two pairs of eye-spots with some accessory eyes. Pharynx spherical, diameter 16±3.7 (11–28; n=33); short esophagus followed by bifurcate intestine with branches confluent posterior to testis. Testis ovate to pyriform, postero-dorsal to ovary. Vas deferens leaves from anterior margin of testis, loops dorsoventrally around left intestine, and distends small seminal vesicle before entering into copulatory organ. Two prostatic reservoirs both saccate. Copulatory organ (CO) ( Fig. 2M, N ) a curved tube, length 18±1.7 (16– 21; n=30). Sclerotized accessory piece ( Fig. 2M, N ) touches base of CO, extends along CO, and covers point of CO in spatulate distal expansion, latter with process attached to inner tip; length of accessory piece 14±1.5 (10–16; n=34). Ovary in mid-body. Two vaginal pores ( Fig. 2O ) open individually on both sides of mid-body surface, two vaginae each connect oötype. Oötype surrounded by Mehlis’ gland. Oviduct arises from anterior margin of ovary, continues as oötype and uterus. Vitellaria approximately co-extensive with intestine.

Haptor length 42±9.3 (28–70; n=34), width 118±32.1 (49–192; n=33). Anchor ( Fig. 2B ) lacking outer root, total length 25±2.3 (21–29; n=33), shaft length 20±1.7 (18–24; n=33), root length 7±1.5 (3–9; n=33), point length 11±1.2 (9–13; n=34). Dorsal bar (fig. 2C) total length 26±2.4 (21– 30; n=34), total width 5±1.1 (3–8; n=34), median width 2±0.3 (1–3; n=34). Ventral bar ( Fig. 2D ) W-shaped, total length 45±3.5 (37–52; n=32), total width 6±1.8 (3–11; n=30), median width 1±0.3 (1–2; n=32). Hooks 7 pairs; hook length: pair I ( Fig. 2E ) 14±0.7 (13–15; n=34); pair II ( Fig. 2F ) 16±1.0 (14–18; n=34); pair III ( Fig. 2G ) 17±1.0 (15–18; n=34); pair IV ( Fig. 2H ) 16±0.9 (14–18; n=32); pair V ( Fig. 2I ) 23±1.0 (21–25; n=34), pair VI ( Fig. 2J ) 24±1.4 (21–27; n=34); pair VII ( Fig. 2K ) 17±0.8 (15–18; n=34). Pair of needles present ( Fig. 2L ), length 7±0.6 (6–8; n=25), located near second hooks.

Host and Locality. Pseudorasbora pumila pumila ( Cypriniformes : Cyprinidae : Gobioninae ) from ponds at Utabi and Yamabuse, Shinonoi, Nagano Prefecture, Japan; and Pseudorasbora parva ( Cypriniformes : Cyprinidae : Gobioninae ) from Lake Kasumigaura at Okijuku-machi, Tsuchiura, Ibaraki Prefecture, Japan.

Site of infection. Gills.

Prevalence and intensity. All 11 P. p. pumila (39–70 [mean: 44] mm SL) were infected, and no count was made of worms on each fish. Eight (80%) of the 10 P. parva (26–51 [40] mm SL) had 1–8 (mean: 5.4) worms each.

Remarks. Bivaginogyrus obscurus was originally described by Gussev (1955) as a species of the genus Dactylogyrus Diesing, 1850 from P. parva in the Amur River Basin. Yamaguti (1963) transferred the species to the genus Neodactylogyrus Price, 1938 , although the latter genus had been synonymized with Dactylogyrus by Mizelle and Donahue (1944). Subsequently, Gussev and Gerasev (1985) established a monotypic genus for the species, Bivaginogyrus Gussev and Gerasev, 1985 , because it has a distinctive feature, two vaginae. The morphology and measurements of the species reported herein are approximately compatible with the past descriptions from Russia by Gussev (1955), Bykhovskaya-Pavlovskaya et al. (1964), Gussev and Gerasev (1985, 1986), and Gussev et al. (2010), and from China by Anonymous (1973), Wu and Wang (1991), and Wu (2000). There is no marked difference in morphology and measurements of B. obscurus from P. parva and P. p. pumila in Japan ( Fig 2M, N ; Table 1).

The present finds include a new country record ( Japan) for B. obscurus , and a new host record for P. p. pumila . The parasite fauna of this fish is very poorly known. Only one parasite, Lernaea cyprinacea Linnaeus, 1758 (Crustacea: Copepoda) has been reported until now from a wild population of P. p. pumila ( Nakamura 1963) , and plerocercoids of Gangesia parasiluri Yamaguti, 1934 ( Cestoda: Proteocephalidae ) are known to experimentally infect it ( Shimazu 1999). Bivaginogyrus obscurus is thus the first helminth and the second parasite discovered from wild P. p. pumila .

This monogenean is native to Far Eastern Russia, China, and Japan (e.g., Gussev et al. 2010; Wu et al. 2000; this paper), but it has recently been spread into the following four countries along with introduced of P. parva from Far East Asia: Georgia ( Matsaberidze 1993), Kyrgyzstan ( Karabekova 2008), Kazakhstan ( Gvozdev and Agapova 1988), and Italy ( Anonymous 2012).

The year in which Bivaginogyrus Gussev and Gerasev, 1985 was erected has been reported erroneously as 1986 by Gibson et al. (1996), Timofeeva et al. (1997), Gerasev (2008, 2009), and Gussev et al. (2010). It was, in fact, established in 1985 ( Gussev and Gerasev 1985).

Figures

Fig. 2. Bivaginogyrus obscurus (Gussev, 1955). NMST-Pl 6132 for A and NMST-Pl 6131 for B–M and O (from Pseudorasbora pumila pumila Miyadi, 1930); NMST-Pl 6134 for N [from Pseudorasbora parva (Temminck and Schlegel, 1846)]. A, whole mount (ventral view); B, anchors; C, dorsal bar; D, ventral bar; E, hook of pair I; F, hook of pair II; G, hook of pair III; H, hook of pair IV; I, hook of pair V; J, hook of pair VI; K, hook of pair VII; L, needle; M, copulatory organs of B. obscurus from P. p. pumila (from two specimens); N, copulatory organ of B. obscurus from P.parva; O, vaginal pore (left, front view; right, lateral view). Scale bars: A, 20µm; B–O, 10µm. Abbreviations: ap, accessory piece; co, copulatory organ; es, eye-spot; ho, head organ; i, intestine; mg, Mehlis’ gland; o; oötype; od, oviduct; ov, ovary; ph, pharynx; pr, prostatic reservoir; sv, seminal vesicle; t, testis; u, uterus; v, vitellaria; va, vagina; vp, vaginal pore; vd, vas deferens.