Plesionika izumiae Omori, 1971

Li, Xinzheng & Komai, Tomoyuki, 2003, Pandaloid Shrimps From The Northern South China Sea, With Description Of A New Species Of Plesionika (Crustacea: Decapoda: Caridea), Raffles Bulletin of Zoology 51 (2), pp. 257-275 : 261

Plesionika izumiae Omori, 1971

Plesionika izumiae Omori, 1971: 242 , figs. 1, 2. [type locality: Suruga Bay, Japan]; Hayashi & Koike, 1976: 46, figs. 1, 2; Hayashi, 1986: 132, 133, 271, fig. 84; Jiang et. al., 1985: 91 (Palesionika izumae), Wang, 1987: 49; Liu & Zhong, 1994: 560.

Plesionika izumiae ? – Chace, 1985: 75, fig. 34.

Material examined. – 2 males (cl 7.3, 7.5 mm), 1 female (cl 7.3 mm), 1 ovig. female. (cl 7.3 mm) ( IOCAS), CN 17-8 , Beibu Bay , 17 30’N, 108 30’E, 97 m depth, muddy sand, BT, coll. Z. Fan, 28 Jan.1959 ; 1 ovig. female. (cl 6.7 mm) ( IOCAS), CN S40 B-2, 23 15’N, 117 00’E, 24m, AT, coll. W. Zhang, 2 Apr.1959 ; 2 ovig. females (cl 6.6-7.2 mm) ( IOCAS), 1 ovig. female ( ZRC), CN S62 B-28, 22 30’N, 115 00’E, 22 m, AT, coll. S. Wu, 7 Apr.1959 ; 1 female (cl 6.3 mm) ( IOCAS), CN 144 B-12, 17 30’N, 109 00’E, 92 m, mud, AT, coll. Z. Fan, 11 Apr.1959 ; 2 males (cl 5.9, 6.5 mm), 1 ovig. female (cl 7.5 mm) ( IOCAS), CN Q55 B-36, 17 30’N, 108 00’E, 85 m, sandy mud, BT, coll. F. Xu, 16 Apr.1959 ; 1 female (cl 7.8 mm) ( IOCAS), CN SIII2 B-25, 22 00’N, 114 00’E, 34 m, mud, AT, coll. Weiquan Zhang, 9 Jul.1959 ; 1 female (cl 5.2 mm) ( IOCAS), CN N93 B-50B, 19 00’N, 111 00’E, 90 m, muddy sand, AT, coll. Z. Tang ,, 28 Oct.1959 ; 1 female (cl 6.3 mm), 1 ovig. female (cl 7.6 mm) ( IOCAS), CN Q78 B-22, 17 30’N, 109 00’E, 101 m, sandy mud, AT, coll. H. Li, 2 Nov.1959 ; 2 males (cl 6.0, 6.1 mm), CN Q87 B-11, 17 30’N, 110 00’E, 125 m, muddy sand, AT, coll. Z. Tang, 23 Nov.1959 ; 1 male (cl 7.0 mm) ( IOCAS), CN X40 B-18, Beibu Bay , 18 00’N, 108 00’E, 93 m, muddy sand, AT, coll. X. Ma, 11 Dec.1959 ; 1 male (cl 6.3 mm), 3 females (cl 4.3- 6.1 mm), 1 ovig. female (cl 6.1 mm) ( IOCAS), CN S175 B-25, 23 30’N, 117 30’E, 34 m, sand, AT, coll. S. Wu, 4 Jan.1960 ; 1 male (cl 7.4 mm) ( IOCAS), CN N152 B-30A, 17 00’N 109 00’E, 128 m, sandy mud, BT, coll. J. Liu, 11 Mar.1960 ; 1 male (cl 4.0 mm), 2 ovig. females (cl 4.3, 5.7 mm) ( IOCAS), CN S227 B-33, 22 00’N, 116 00’E, 84 m, mud, AT, coll. J. Qu, 22 Apr.1960 ; 3 males (cl 5.4-6.6 mm), 1 ovig. female (cl 5.1 mm) ( IOCAS) , 1 male ( ZRC), CN S238 B-5, 23 30’N, 117 30’E, 39 m, muddy sand, AT, coll. J. Chen and S. Lu, 24 Apr.1960 .

Supplemental material. – 10 males (cl 4.7-7.5 mm), 2 females (cl 4.8, 5.3 mm), 8 ovig. females (cl 4.8-8.4 mm), used by Omori (1971) ( CBM-ZC 6588 ), RV Tansei-maru , stn 392-1, Suruga Bay, Japan, 34 54.0’N, 138 27.0’E, 72 m, beam trawl, 13 May.1969 ; 3 males (cl 6.0- 6.8 mm), 7 ovig. females (cl 5.3-8.3 mm) ( CBM-ZC 3370 ), RV Toyohata-maru , Tosa Bay, Shikoku, Japan, 33 21.02’N, 133 36.98’E, 90-92 m, beam trawl, 3 Oct.1994 ; 4 ovig. females (cl 10.9-11.6 mm) ( CBM-ZC 3776 ), Tokyo Bay off Yokohama, Japan, 30 m, commercial trawler, 28 Nov.1996 .

Distribution. – Japan, northern part of South China Sea, and Philippines, at depths of 22- 209 m.

Remarks. – The specific identity of the specimens from the South China Sea was confirmed by a comparison with 20 topotypic specimens of Plesionika izumiae from Suruga Bay used in Omori (1971) (CBM-ZC 6588).

After comparing with six specimens of P. izumiae kindly deposited by the original author in the USNM collection, Chace (1985) provisionally identified six Albatross specimens from the Philippines, including two males and four ovigerous females, with P. izumiae , as the Philippine specimens were apparently different from the original series in being somewhat larger size, in having the rostrum nearly twice as long as the carapace, rather than little more than 1.3 times as long, and in having the dactylus of the three posterior pairs of pereopods slightly shorter in proportion to the other segments (according to Chace’s figure (Fig. 34c), the dactylus is 0.48 times as long as the propodus). Examination of other Japanese specimens in the collection of CBM has shown that the size of ovigerous specimens is considerably variable from 4.8 mm to 11.6 mm in carapace length. As Omori (1971) noted, the rostrum tends to be proportionally longer in males than in females, though in males it appears become longer with the increase of body size. In the 20 topotypic specimens (CBM-ZC 6588), the rostrum is 0.93-1.84 times as long as the carapace in males, and 0.98-1.45 times as long in females. The dactylus of the third pereopod is 0.40-0.55 times as long as the propodus in 10 specimens with complete pereopods from the topotypic series. Thus, the supposed difference cited by Chace (1985) could all be within the range of variation of a single species.