Orientomysis robusta ( Murano, 1984 ) Fukuoka & Murano, 2005

Fukuoka, Kouki & Murano, Masaaki, 2005, A revision of East Asian Acanthomysis (Crustacea: Mysida: Mysidae) and redefinition of Orientomysis, with description of a new species, Journal of Natural History 39 (9), pp. 657-708 : 683-684

Orientomysis robusta ( Murano, 1984) comb. nov.

Acanthomysis sp. Ii 1964: 507–509 (part), Figure 131A.

Acanthomysis robusta Murano 1984: 107–110 , Figures 1 , 2 , 3a ; Müller 1993: 197 (list).

Type locality

Off Tsuchisaki, Akita, northern Japan.

Material examined

Holotype: female (13.3 mm), off Tsuchisaki , Akita, northern Japan, 4.5–5 m, sandy bottom, 23 April 1975, NSMT-Cr 8606 . Allotype: male (13.3 mm), same data as

N, number of individuals examined; +, a dorsal transverse fold present; 2, fold absent.

holotype, NSMT-Cr 8607. Paratype: eight males (12.4–14.4 mm) and 10 females (13.4– 16.2 mm), same data as holotype, NSMT-Cr 8608 .

Others. Eighty-nine males (7.0– 16.4 mm) and 171 females (7.7–14.2 mm), same data as holotype, NSMT-Cr 15589. Two females (7.2 mm and damaged), Okushiri Island, southwestern Hokkaido, northern Japan, 2 September 1986, on loan from Y. Hanamura .

Remarks

It was observed for the first time that the carpopropodus of the endopod of the third to eighth thoracic limbs is divided into five or six subsegments.

Orientomysis robusta is similar to O. fujinagai and O. koreana in the abdominal somites with a spine row, the lateral margin of the telson with several subequal small spines between larger ones, and the apex of the telson with two pairs of strong spines. Morphological differences among these three species are shown in Table III.

Distribution

This species has been recorded from Japan Sea coastal waters of Japan, from Hokkaido to Niigata ( Ii 1964; Murano 1984; Hirota et al. 1989; present study).

This species inhabits waters shallower than 10 m deep ( Ii 1964; Murano 1984; Hirota et al. 1988). In Igarashi-hama beach, Niigata, this is a dominant species in mysid assemblages in depths of 2–10 m ( Hirota et al. 1988).

Figures

Figure 1. Orientomysis aspera (Ii, 1964) comb. nov. Telson, dorsal. (A) Male (8.0 mm), Ise Bay (34°55.109N, 136°46.609E), NSMT-Cr 15553; (B) female (8.6 mm), Ise Bay (34°55.109N, 136°46.609E), NSMT-Cr 15553.

Figure 2. Orientomysis hwanhaiensis (Ii, 1964) comb. nov. (A, B) Telson, dorsal; (C–F) distal end of telson, dorsal. (A) Male (12.2 mm), syntype; (B) female (13.6 mm), syntype; (C) male (9.8 mm), East China Sea, NSMT-Cr 15559; (D) male (7.5 mm), East China Sea, NSMT-Cr 15559; (E) female (10.7 mm), East China Sea, NSMT- Cr 15559; (F) female (10.6 mm), East China Sea, NSMT-Cr 15559.

Figure 3. Orientomysis japonica Marukawa, 1928. (A) First to sixth abdominal somites, lateral; (B–E) telson, dorsal. (A) Male (11.0 mm), Tateyama Bay, Pacific, NSMT-Cr 15562; (B) male (11.0 mm), Tateyama Bay, NSMT-Cr 15562; (C) male (14.2 mm), Uchiura Bay, Pacific, NSMT-Cr 15560; (D) female (17.0 mm), Kashima, Pacific, NSMT-Cr 15570; (E) male (10.6 mm), Japan Sea side of Aomori, NSMT-Cr 15571.