Sinergasilus lieni Yin, 1949

Nitta, Masato & Nagasawa, Kazuya, 2020, Alien Gill Parasites of the Silver Carp Hypophthalmichthys molitrix (Cypriniformes: Cyprinidae) in Tochigi Prefecture, Central Japan, Species Diversity 25 (1), pp. 61-73 : 66-68

Sinergasilus lieni Yin, 1949

[New Japanese name: Chūka-era-jirami]

( Fig. 6 )

Pseudergasilus polycolpus (not of Markewitsch, 1940): Markewitsch, 1946: 233. (in part, incorrect subsequent spelling for Pseudergasilus undulatus Markewitsch, 1940 )

Sinergasilus lieni Yin, 1949: 36–39 , figs 10–19; Bykhovskaya-Pavlovskaya et al. 1962: 760–761, fig. 1567; Musselius 1969: 238; Yukhimenko 1972: 155–156; Mirzoeva 1972: 253–258, fig. S. lieni ; Mirzoeva 1973: 143–158, figs 1–11; Musselius 1973: 33–36, fig. 10a; Gussev 1987: 404–406, fig. 487; Molnár and Székely 2004: 53–59, figs 1–8; Zhokhov and Molodozhnikova 2006: 478; Ký and T ề 2007: 282, 284, fig. 2981; Davydov et al. 2012: 139.

Sinergasilus polycolpus (not of Markewitsch, 1940): Yin, 1956: 257–258, pl. XVII, figs 1–9; Wang 1959: 25; Yamaguti 1963b: 40, 478–479, pl. 44, fig. 1; Anonymous 1973b: 235–236, 432, figs 108–116; Song and Kuang 1980: 15, figs 1–5; Kuang 1991: 344; Kuang and Qian 1991: 97–98, fig. 62; Kuang and Liu 1992: 353, figs 16–17; Jin et al. 1993: 382–383: fig. 254; Nie and Yao 2000: 241–244; Wang et al. 2002: 237–239; Cakic et al. 2004: 265–266; Song et al. 2008: 302–305; Peng et al. 2010: 178–181; Zhu et al. 2010: 1192, pl. 1; Delibaier et al. 2014: 93; Wang et al. 2014: 180; Dimovska and Stojanovski 2015: 33–37, figs 1–7.

Pseudergasilus undulatus (not of Markewitsch, 1940): Markewitsch 1956: 64–66 (in part); Markewitsch 1976: 98–100 (in part).

Material examined. Six whole and three dissected females (NSMT-Cr 26718).

Description of adult female. Body ( Fig. 6A ) elongate, cylindrical, length 1760–2066. Prosome length 1334–1775, width, 394–494, depth 181–340, 2.5–3.2 times as long as urosome, pseudosegments present. Cephalothorax triangular in dorsal view, length 437–549, width 412–518. First to fourth pedigers approximately equal in length. Urosome ( Fig. 6J ) consisting of fifth pedigerous and genital doublesomite, length 513–630, width, 130–184 and indistinctly three segmented abdominal somites. Anal somite deeply incised posteromedially. Caudal ramus length 115–135, width 30–40 (ratio 3.0–4.2: 1), with 4 caudal setae.

Antennule ( Fig. 6B ) distinctly six-segmented, length 218– 250, with armature formula: 3, 9, 5, 4, 2, 7. All setae naked. Antenna ( Fig. 6C ) 4-segmented; first segment shorter than long, length 121–181, width 175–220, with prominent outer expansion wider than segment itself; second segment length 220–295, width 111–126; third segment tapering, length 145–155; terminal claw short, slightly curved, length 122– 130, ratio of length of second segment and claw 1.7–2.4: 1.

Mandible (fig. 6D) with 2 blades; posterior and anterior margin of anterior blade spinulated; posterior blade bearing spinules on posterior margin. Maxillule ( Fig. 6D ) with 2 long terminal setae. Maxilla ( Fig. 6D ) two-segmented; first segment unarmed; second segment spinulated in distal half.

Egg sac ( Fig. 6A ) length 1372–2292, width 168–309, usually slightly curved; each egg 65–82 in diameter.

Legs 1–3 with three segmented rami ( Fig. 6 E–G). Leg 4 ( Fig. 6H ) with two segmented exopod and three-segmented endopod. Armature formula of leg 1–4 shown in Table 1 . Leg 5 ( Fig. 6I ) consisting of conical exopod with 1 seta on apex and conical endopod with 2 setae on apex and lateral side. Leg 6 absent. All setae naked.

Male. Undiscovered.

Host. Silver carp Hypophthalmichthys molitrix ( Cypriniformes : Cyprinidae )

Site of infection. Gill filaments.

Remarks. The specimens examined in this study conform to the descriptions of S. lieni by Yin (1949, 1956) from the bighead carp Hypophthalmichthys nobilis (Richardson, 1845) and H. molitrix in China. This species is differentiated from two congeners, Sinergasilus major (Markewitsch, 1940) and S. undulatus , based on the ratio of the length of the second segment and claw of the antenna ( Bykhovskaya-Pavlovskaya et al. 1962). The antennule armature of S. lieni is obscure in the past descriptions (e.g., Yin 1949, 1956; Mirzoeva 1973), but the present description almost agrees with the figure of the redescription by Yin (1956: pl. 16, fig. 2) and redefined herein the armature formula.

The present collection represents the first record of S. lieni from Japan. This copepod is natively distributed in China and Far-East Russia with H. molitrix and H. nobilis ( Markewitsch 1946; Yin 1956; Wang et al. 2014). It also infects H. harmandi Sauvage, 1884 (Cyprinidae) in Vietnam (Ký and Tề 2007). Sinergasilus lieni has been reported as an alien species from the European region of Russia ( Musselius 1969; Mirzoeva 1972, 1973; Zhokhov and Molodozhnikova 2006), Hungary ( Molnár and Székely 2004), and Macedonia ( Dimovska and Stojanovski 2015) from H. molitrix and H. nobilis ; and Serbia and Montenegro from H. nobilis ( Cakic et al. 2004) .

Japanese name. The new Japanese generic and specific name is a combination of “chūka” and “era-jirami”, which mean China and a gill louse in Japanese, respectively (“zoku” means a genus).

Figures

Fig. 6. Sinergasilus lieni Yin, 1949. NSMT-Cr 26718. A, whole mount (dorsal view); B, antennule; C, antenna; D, mandible, maxillule and maxilla; E, leg 1; F, leg 2; G, legs 3; H, leg 4; I, leg 5; J, urosome (ventral view). Scale bars: A, 500µm; B–J, 50µm.