Pseudodiaptomus inopinus Burckhardt, 1913

Sakaguchi, Sakiko Orui & Ueda, Hiroshi, 2010, A new species of Pseudodiaptomus (Copepoda: Calanoida) from Japan, with notes on the closely related P. inopinus Burckhardt, 1913 from Kyushu Island, Zootaxa 2623, pp. 52-68 : 62-65

Pseudodiaptomus inopinus Burckhardt, 1913

( Figs. 3 B, 7, 8)

Synonyms. Pseudodiaptomus inopinus Burckhardt (1913) , 379, pl. 11E, figs. 2–5, 7, 8, pl. 11F, figs. 1–4, 9, 10, pl. 11G, figs. 1–4, 6–8, pl. 12H, figs. 1–4, 7, 8, 10, 11; Smirnov (1929), 318, figs. 1–3; Tanaka (1966), 42, fig. 3; Mizuno and Miura (1984), 481, fig. 260; Chang and Kim (1986), 49, pl. 1, figs. 6–9; Cordell et al. (1992), 261; Soh et al. (2001), 203, fig. 3C; Cordell et al. (2007), 214, fig. 4; Eyun et al. (2007), 265; Lee et al. (2007), 140, figs. 6–7; Chang (2009), 110, figs. 24–25.

Pseudodiaptomus japonicus Kikuchi (1928) , 68, pl. 18, fig. 9–12, pl. 19, figs. 13–18.

Schmackeria inopinus, Shen and Tai (1962) , 101; Shen and Lee (1963), 578; Shen et al. (1979), 69, figs. 27, 28.

Material examined. Six females and 20 males from Tsuri-kawa R. (33°50’55”N, 130°30’0 8”E, 18 August 2009; # 10 in Fig. 1 ), 1 female from Imari-gawa R. (33°16’22”N, 129°53’10”E, 19 August 2009; #11), 57 females and 47 males from Yukiura-gawa R. (33°56’34”N, 129°41’0 0”E, 19 August 2009; #12), 4 females and 4 males from Rokkaku-gawa R. (33°11’44”N, 130°12’27”E, 19 August 2009; #13), 39 females and 71 males from Chikugo-gawa R. (33°11’46”N, 130°21’36”E, 20 August 2009; #14), 36 females and 57 males from Manose-gawa R. (31°26’52”N, 130°18’31”E, 20 August 2009; #15), 4 females and 1 male from Hitotsuse-gawa R. (32°0 3’0 8”N, 131°28’18”E, 21 August 2009; #16), 11 females from Shiomi-gawa R. (32°24’57”N, 131°37’0 9”E, 21 August 2009; #17), 2 females and 1 male from Yasaka-gawa R. (33°24’23”N, 131°36’38”E, 21 August 2009; #18), and 2 females and 8 males from Yamakuni-gawa R. (33°36’0 9”N, 131°10’37”E, 21 August 2009; #19). All the specimens were collected by S.O. Sakaguchi and H. Ueda. One female and two male specimens from the Tsuri-kawa River were dissected for close examination of appendages. Ten female and 10 male specimens from the Tsuri-kawa River in alcohol were deposited in each the NSMT (NSMT-Cr 21263, 21264) and the USNM ( USNM 1145709, 114510).

Redescription. FEMALE. Body ( Fig. 7 A, B) length 1.38–1.44 mm (n=5). Second to fourth prosomites laterally with row of fine spinules along posterior margins; fourth and fifth pediger fused with rounded corners, with spiniform process dorsally, small bump terminally (indicated by arrowhead a in Fig. 7 A, C), several long spinules ventral to bump (arrowhead b), and row of spinules on posterolateral corner on each side (arrowhead c). Genital double-somite ( Figs. 7 D, E, 3B) 1.1 times longer than wide, with several spinules on each anterolateral projection, long anterolateral seta and dorsolateral row of spinules at one-third and twothird anteriorly on each side; posterior process of genital flap (indicated by arrowhead in Fig. 7 D) pointed and longer than that of P. nansei sp. nov. Caudal left rami ( Fig. 7 F) slightly larger, lateral and terminal caudal setae thicker and shorter than those of P. nansei , the medial terminal seta especially swollen and as long as ramus, except one specimen from the Yukiura-gawa River with thin, long setae on both rami ( Fig. 7 G). Leg 5 ( Fig. 7 H) coxa with spinules on posterior and anterior surfaces. First exopodal segment with round distomedial process; terminal spine of third segment without notch at base and bearing short anterior spine with teeth medially ( Fig. 7 I). Other morphological characters as in P. nansei .

MALE. Body ( Fig. 8 A, B) length 1.10–1.15 mm (n=5). Second to fourth prosomites each with group of minute spinules near anteroventral corner, fifth pediger with spiniform process dorsally, and posterolateral spinules on each corner. Second urosomite with patch of minute spinules anterolaterally and ventral transverse rows of spinules ( Fig. 8 C). Right antennule ( Fig. 8 D) segmentation pattern and setal formula as in P. nansei ; serration of 18th with longer teeth than those of P. nansei ; length ratios of 18–20th segments to 17th segment 1.5, 1.4, 2.6, respectively. Left leg 5 ( Fig. 8 E) without spinules at base of distal smaller process of basoendopod; second exopodal segment of 5 specimens paddle-shaped among 20 specimens examined ( Fig. 8 F). Right leg 5 first exopodal segment with proximomedial spinule and distolateral spine extending more than mid length of second segment with small lateral spine; third segment not swollen proximally. Other morphological characters as in P. nansei .

Remarks. Diagnostic characters of our specimens closely agree with Burckhardt’s (1913) original description from Taifu Lake of the Yangtze River delta. However notable differences were observed in the following two respects. First, the female leg 1 is much shorter than that illustrated by Burckhardt (1913, plate 11G, fig. 6); e.g. the second exopodal segment is as long as wide in our specimens as in the new species, but two times longer than wide in the original description. The proportions of the leg 1 segments illustrated by Lee et al. (2007) and Chang (2009), who provided illustrations of P. inopinus from Korea, are similar to those of our specimens. Second, a clear row of spinules is present medially to the conspicuous dorsal spinule of the female fifth pediger in Burckhardt’s illustration (plate 11E, fig. 5), whereas in our specimens a spinule row is present ventrally to the bump. Lee et al. (2007) and Chang (2009) described another type of ornamentation in which no spinule rows were present except for those on the distolateral corner of the somite.

Considering these morphological differences among specimens from different localities, they may be a species complex. However, we call them P. inopinus for convenience in this study. Revising this potential complex worldwide is clearly beyond the scope this paper. This species occurred in most river estuaries in Kyushu but was never found in collections from the Nansei Islands .

Figures

FIGURE 1. Map of the Nansei Islands and Kyushu Island. Locations of the rivers (R.) where sampling occurred are indicated by black spots, among which those with the numbers represent the rivers from which specimens of the new species or P. inopinus Burckhardt, 1913 were collected in the Nansei Islands (1, Hirakubo-gawa R.; 2, Miyara-gawa R.; 3, Yakashimoguchi-gawa R.; 4, Tokuhina-gawa R.; 5, Ginozafukuchi-gawa R.; 6, Chinaze-gawa R.; 7, Kawauchi-gawa R.; 8, Yakugachi-gawa R.; 9, Ura-gawa R.) and Kyushu Island (10, Tsuri-kawa R.; 11, Imari-gawa R.; 12, Yukiura-gawa R.; 13, Rokkaku-gawa R.; 14, Chikugo-gawa R.; 15, Manose-gawa R.; 16, Hitotsuse-gawa R.; 17, Shiomi-gawa R.; 18, Yasaka-gawa R.; 19, Yamakuni-gawa R.).

FIGURE 3. Pseudodiaptomus nansei sp. nov. and P. inopinus Burckhardt, 1913. SEM photographs of genital flaps: A, P. nansei sp. nov. from the Hirakubo-gawa River, ventral view; B, P. inopinus from the Tsuri-kawa River, with lateral hyline frill somewhat turned up, ventrolateral view.

FIGURE 7. Pseudodiaptomus inopinus Burckhardt, 1913. Female (A – F, H, I, the same specimen from the Tsuri-kawa River; G, from Yukiura-gawa River): A, habitus, dorsal; B, habitus, right lateral; C, fifth pediger, right lateral; D, genital double somite, ventral; E, genital double somite, right lateral; F, caudal rami, dorsal; G, caudal rami with thin setae, dorsal; H, leg 5, posterior; I, base of third exopodal segment of leg 5, anterior.

FIGURE 8. Pseudodiaptomus inopinus Burckhardt, 1913. Male (A – E, the same specimen from Tsuri-kawa River; F, from Tsuri-kawa River) A, habitus, dorsal; B, habitus, right lateral; C, second urosomite, ventral; D, 16 – 17 th segments of right antennule; E, leg 5, posterior; F, paddle-shaped second exopod of left leg 5, posterior.