Species Diversity 19: 167–171 25 November 2014 DOI: 10.12782/sd.19.2.167 Bivaginogyrus obscurus (Monogenea: Dactylogyridae), a Gill Parasite of Two Cyprinids Pseudorasbora pumila pumila and Pseudorasbora parva, New to Japan Masato Nitta1,2 and Kazuya Nagasawa1 1 Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan E-mail: [email protected] (MN) 2 Corresponding author (Received 29 March 2014; Accepted 28 September 2014) The dactylogyrid monogenean Bivaginogyrus obscurus (Gussev, 1955) is redescribed from the gills of two cyprinids, Pseudorasbora pumila pumila Miyadi, 1930 in Nagano Prefecture and P. parva (Temminck and Schlegel, 1846) in Ibaraki Prefecture. These are the first records of this parasite in Japan. Pseudorasbora p. pumila, which is endemic to central Japan, represents a new host record for B. obscurus. This monogenean is the first helminth and the second parasite discovered from wild P. p. pumila. Key Words: Bivaginogyrus obscurus, Monogenea, Pseudorasbora pumila pumila, Pseudorasbora parva, new country record, new host record, Japan. fecture, central Honshu, Japan, on 23 July and 30 October Introduction 2013, respectively. Pseudorasbora parva was collected in Lake Kasumigaura (36°04′05″N, 140°15′23″E) at Okijuku- Cyprinids of the gobionine genus Pseudorasbora Bleeker, machi, Tsuchiura, Ibaraki Prefecture, central Honshu, Japan 1860 are natively distributed in Far East Asia, and two spe- (eight and two specimens on 13 and 16 June 2014, respec- cies and one unnamed subspecies occur in Japan (Naka- tively). At all sites, trap nets were used for fishing. Fish were mura 1969; Miyadi et al. 1976; Hosoya 2013). Pseudorasbora brought on ice or alive to the laboratory, where they were pumila pumila Miyadi, 1930 is endemic to central Honshu, measured for standard length (SL) in millimeters and exam- Japan, and is on the verge of extinction because of competi- ined for helminth parasites under a dissecting microscope. tion and hybridization with introduced fishes and artificial Monogeneans were picked up from the gills using small alteration of the habitat (Nakamura 1969; Uchiyama 1989; needles and flattened between a slide and a coverslip. Some Konishi et al. 2003, 2009; Konishi and Takada 2004, 2013; of them were fixed in ammonium picrate glycerin (Lim Konishi 2010). It has been designated as an endangered spe- 1991), while others were fixed in 70% ethanol and stained cies by the Ministry of the Environment of Japan (Hosoya in Heidenhain’s iron hematoxylin. All specimens were de- 2003). On the other hand, Pseudorasbora parva (Temminck hydrated through a graded ethanol series, cleared in xylene, and Schlegel, 1846) occurs in Japan, Korea, and China (Hosoya 2013). In Japan, the latter species is popular in rec- reational fishing and has a wider distribution range than P. p. pumila (Nakamura 1969; Anonymous 2010). The dactylogyrid monogenean Bivaginogyrus obscurus (Gussev, 1955) is known to be a gill parasite of P. parva in the Eurasian continent (see the synonymy section for litera- ture citations). In this paper we redescribe B. obscurus from P. p. pumila and P. parva as the first records of this parasite in Japan. The former cyprinid represents a new host record for B. obscurus. Materials and Methods Fig. 1. Measurement axes of hard parts of Bivaginogyrus obscu- rus (Gussev, 1955). A, anchor; B, bar; C, hook; D, copulatory organ. Abbreviations: al, accessory piece length; atl, anchor total length; Pseudorasbora pumila pumila was collected in ponds at bmw, bar median width; btl, bar total length; btw, bar total width; Utabi (36°35′N, 138°06′E; 10 specimens) and Yamabuse cl, copulatory organ length; hl, hook length; pl, point length; rl, (36°36′N, 138°05′E; one specimen), Shinonoi, Nagano Pre- root length; sl, shaft length. © 2014 The Japanese Society of Systematic Zoology 168 M. Nitta and K. Nagasawa and mounted in Canada balsam. Drawings were made with (49–192; n=33). Anchor (Fig. 2B) lacking outer root, total the aid of a drawing tube fitted on an Olympus BX51 light length 25±2.3 (21–29; n=33), shaft length 20±1.7 (18–24; microscope. Axes of measurement of sclerotized parts are n=33), root length 7±1.5 (3–9; n=33), point length 11±1.2 presented in Fig. 1. Measurements, in micrometers, are ex- (9–13; n=34). Dorsal bar (fig. 2C) total length 26±2.4 (21– pressed as the mean±standard deviation followed in paren- 30; n=34), total width 5±1.1 (3–8; n=34), median width theses by the range and the number (n) of specimens exam- 2±0.3 (1–3; n=34). Ventral bar (Fig. 2D) W-shaped, total ined. Fish identification was based on Hosoya (2013). Prev- length 45±3.5 (37–52; n=32), total width 6±1.8 (3–11; alence and intensity of infection are as defined by Bush et n=30), median width 1±0.3 (1–2; n=32). Hooks 7 pairs; al. (1997). Specimens are deposited in the Platyhelminthes hook length: pair I (Fig. 2E) 14±0.7 (13–15; n=34); pair II collection of the National Museum of Nature and Science, (Fig. 2F) 16±1.0 (14–18; n=34); pair III (Fig. 2G) 17±1.0 Tsukuba, Ibaraki Prefecture, Japan (NSMT-Pl 6131–6134). (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) Bivaginogyrus obscurus (Gussev, 1955) 24±1.4 (21–27; n=34); pair VII (Fig. 2K) 17±0.8 (15–18; (Fig. 2) n=34). Pair of needles present (Fig. 2L), length 7±0.6 (6–8; n=25), located near second hooks. Dactylogyrus obscurus Gussev, 1955: 206–207, figs 10.1, Host and Locality. Pseudorasbora pumila pumila 10.2; Bykhovskaya-Pavlovskaya et al. 1964: 307, fig. 613; (Cypriniformes: Cyprinidae: Gobioninae) from ponds at Strelkov 1971: 53; Anonymous 1973: 140, figs 163–164; Utabi and Yamabuse, Shinonoi, Nagano Prefecture, Japan; Gvozdev and Agapova 1988: 109, 112; Davydov et al. and Pseudorasbora parva (Cypriniformes: Cyprinidae: 2012: 74. Gobioninae) from Lake Kasumigaura at Okijuku-machi, Neodactylogyrus obscurus: Yamaguti 1963: 41, fig. 623. Tsuchiura, Ibaraki Prefecture, Japan. Bivaginogyrus obscurus: Gussev and Gerasev 1985: 192–194, Site of infection. Gills. figs 289, 291; Gussev and Gerasev 1986: 373–375, fig. 1; Prevalence and intensity. All 11 P. p. pumila (39–70 Wu and Wang 1991: 133–135, figs 139–140; Matsaberidze [mean: 44] mm SL) were infected, and no count was made 1993: 9; Xia et al. 1999: 59; Zhang et al. 1999: 130–131, of worms on each fish. Eight (80%) of the 10 P. parva (26–51 fig. 8-13; Wu 2000: 426–428, fig. 378; Karabekova 2008: [40] mm SL) had 1–8 (mean: 5.4) worms each. 331; Gerasev 2008: 407, 411, 419; Gussev et al. 2010: 274– Remarks. Bivaginogyrus obscurus was originally de- 275, figs 345–346; Anonymous 2012: 51–52; Davydov et scribed by Gussev (1955) as a species of the genus Dac- al. 2012: 73; Teo et al. 2013: 3–8, figs 1A, 2, 3, 4, 8A, 8B. tylogyrus Diesing, 1850 from P. parva in the Amur River Basin. Yamaguti (1963) transferred the species to the genus Material examined. 15 specimens (NSMT-Pl 6131) and Neodactylogyrus Price, 1938, although the latter genus had 1 specimen (NSMT-Pl 6132) from P. p. pumila collected on been synonymized with Dactylogyrus by Mizelle and Do- 23 July and 30 October 2013, respectively; and 14 specimens nahue (1944). Subsequently, Gussev and Gerasev (1985) es- (NSMT-Pl 6133) and 5 specimens (NSMT-Pl 6134) from P. tablished a monotypic genus for the species, Bivaginogyrus parva collected on 13 and 16 June 2014, respectively. Gussev and Gerasev, 1985, because it has a distinctive fea- Description. Body (Fig. 2A) including haptor length ture, two vaginae. The morphology and measurements of 301±55.3 (128–411; n=34), width at mid-body 43±9.3 the species reported herein are approximately compatible (24–68; n=34). Surface of body corrugated. Three pairs of with the past descriptions from Russia by Gussev (1955), head organs. Two pairs of eye-spots with some accessory Bykhovskaya-Pavlovskaya et al. (1964), Gussev and Gerasev eyes. Pharynx spherical, diameter 16±3.7 (11–28; n=33); (1985, 1986), and Gussev et al. (2010), and from China by short esophagus followed by bifurcate intestine with branch- Anonymous (1973), Wu and Wang (1991), and Wu (2000). es confluent posterior to testis. Testis ovate to pyriform, pos- There is no marked difference in morphology and measure- tero-dorsal to ovary. Vas deferens leaves from anterior mar- ments of B. obscurus from P. parva and P. p. pumila in Japan gin of testis, loops dorsoventrally around left intestine, and (Fig 2M, N; Table 1). distends small seminal vesicle before entering into copulato- The present finds include a new country record (Japan) ry organ. Two prostatic reservoirs both saccate. Copulatory for B. obscurus, and a new host record for P. p. pumila. The organ (CO) (Fig. 2M, N) a curved tube, length 18±1.7 (16– parasite fauna of this fish is very poorly known. Only one 21; n=30). Sclerotized accessory piece (Fig. 2M, N) touches parasite, Lernaea cyprinacea Linnaeus, 1758 (Crustacea: Co- base of CO, extends along CO, and covers point of CO in pepoda) has been reported until now from a wild popula- spatulate distal expansion, latter with process attached to tion of P. p. pumila (Nakamura 1963), and plerocercoids of inner tip; length of accessory piece 14±1.5 (10–16; n=34). Gangesia parasiluri Yamaguti, 1934 (Cestoda: Proteocephal- Ovary in mid-body.