Palaemon orientis Holthuis, 1950

Ashelby, Christopher W., Lin, Wei-Cheng, Grave, Sammy De & Chan, Tin-Yam, 2018, Notes on the shrimp genus Palaemon Weber, 1795 (Crustacea, Decapoda, Palaemonidae) and related genera from Taiwan, Zootaxa 4446 (4), pp. 575-595 : 584

Palaemon orientis Holthuis, 1950

( Fig. 8 , 13F )

Previous Taiwan records. Balss 1914: 58 [as Leander japonicus Ortmann, 1890 ]; Parisi 1919: 77 [as Leander japonicus ]; Maki & Tsuchiya 1923: 53, pl. 2-fig.4 [as Palaemon japonicus ]; Chan & Yu 1985: 124, text-fig. 5, pl. 1E. [as Palaemon (Exopalaemon) orientis ]; Shy & Yu 1998: 12, unnumbered photo [as Exopalaemon orientis ].

Material examined. Lanyangxi , Yilan County, 1 male (pocl 8.9 mm), 07.III.1992 ( NTOU M01209 ) ; Luodong , Yilan County, 1 ovig. female (pocl 11.7 mm) ( NTOU M01190 ) ; Dongshanhe , Yilan County, 1 male (pocl 8.8 mm), 1 female (pocl 9.0 mm), 03.VII.1992 ( NTOU M01184 ) ; Taitung County, 1 male (pocl 11.3 mm), 01.IV.1985 ( NTOU M01173 ) ; Fengshanxi , Hsinchu County, 1 male (pocl 6.4 mm), 07.X.1997 ( NTOU M01216 ) ; Yangzicuoxi , Changhua County, 1 female (pocl 7.8 mm), 26.XI.1992 ( NTOU M01174 ) ; Dongshi , Chiayi County, 1 female (pocl 6.7 mm), 28.XI.1992 ( NTOU M01175 ) ; Qigu , Tainan City, 1 female (7.8 mm), 29.XI.1992 ( NTOU M01176 ) ; Donggang , Pingtung County, 1 male (pocl 12.4 mm), 2 ovig. females (pocl 10.5–14.3 mm), 07.VI.1984 ( NTOU M01172 ) ; same location, 6 males (pocl 6.8–9.0 mm), 9 ovig. females (pocl 8.8–12.4 mm), 36 females (pocl 7.3– 13.0 mm), 28.VII.2009 ( OUMNH.ZC.2010-02-078); Jiadong , Pingtung County, 5 males (pocl 8.1–9.7 mm), 25 females (pocl 6.8–11.6 mm), 26.VI.2009 ( NTOU M01177 ) ; Penghu County, 3 males (pocl 7.07–9.12 mm), 39 females (pocl 7.06–12.34 mm), 3 juv. (pocl 5.6–6.0 mm), 21.IV.2002 ( NTOUM01383 ); Locality not specified, 1 male (pocl 9.8 mm), III.2005 ( NTOU M01171 ) .

Diagnosis. Rostrum with slender distal portion unarmed dorsally except for subapical tooth and strongly upturned; rostral formula 1+5–7/5–7; third to sixth abdominal somites not carinate in dorsal midline; mandible with 3-segmented palp; first pereiopods chela about 0.75 times length of carpus; second pereiopods with carpus 0.6 times as long as chela; third pereiopods with dactyl about 0.75 times as long as propodus; fifth pereiopods with dactyl no more than half as long as propodus.

Colour pattern. Body largely transparent with scattered red-brown chromatophores across carapace and abdomen, occasionally forming weak lines; antennules and distal end of rostrum are tinged blue; eggs yellow. Ovigerous females with large blue-green patches on abdominal pleura.

Remarks. The Taiwanese material examined agrees with available diagnoses and figures for P. orientis in Li et al. (2004, 2007) although they are very much smaller than the quoted maximum size for the species, despite being sexually mature. Palaemon orientis is considered a pest species in local aquaculture ponds (also see Chan & Yu 1985).

Habitat. Shallow marine waters, occasionally brackish water.

Distribution. Japan and Korea to South China Sea.

Figures

FIGURE 8. Palaemon orientis Holthuis, 1950. Male (pocl. 7.8 mm, OUMNH-ZC 2010-02-078). A) carapace, left lateral view; B) right second pereiopod, mesial view; C) right fifth pereiopod, mesial view; D) right second pereiopod chela, mesial view. Scale bars indicate 1.0 mm.

FIGURE 13. A) Leander tenuicornis (Say, 1818), Lanyu, Taitung County, IV.1993 (specimen not deposited); B) Nematopalaemon tenuipes (Henderson, 1893), female (pocl 10.08 mm), Dongang fishing port, Pingtung County (NTOU M01831); C) Palaemon concinnus Dana, 1852, ovigerous female (pocl. 12.5 mm), Jialeshuei Village, Pingtung County (OUMNH-ZC 2010-02-079); D) Palaemon debilis Dana, 1852, male (pocl 5.51 mm), Ludao, Taidong County (NTOU M02086); E) Palaemon modestus (Heller, 1862), Sun Moon Lake, Nantou County, date unknown (specimen not deposited); F) Palaemon orientis Holthuis, 1950, ovigerous female (pocl 12.2 mm), Donggang, Pingtung County (OUMNH-ZC 2010-02- 078).