Palaemon debilis Dana, 1852

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 : 583

Palaemon debilis Dana, 1852

( Figs. 6 , 13D )

Previous Taiwan records. (?) Maki & Tsuchiya 1923: 54, pl. 3-fig. 5.

Material examined. Ludao , Taitung County, 9.VIII.2017, 3 males (pocl 5.1–6.0 mm) ( NTOU M02071 ) , 1 male (pocl 5.5 mm) (NTOU M02086 ), 1 male (pocl 5.5 mm) (NTOU M02087 ), 1 male (pocl 4.4 mm) (NTOU M02088 ).

Diagnosis. Rostrum strongly ascendant distally, tapering gradually; rostral formula 1+5–8/3–10; basal antennular segment with disto-lateral spine falling short of adjacent convex distal margin of segment; free portion of shorter ramus of dorsal antennular flagellum approximately equal in length to fused part; mandible with or without palp, when present 1, 2 or 3 segmented; first pereiopod with carpus more than twice times as long as chela; second pereiopod with carpus more than twice as long as chela; fifth abdominal pleuron acute distoventrally; first pleopod of male without marginal appendix on endopod.

Colour pattern. Body semi-transparent with few brown dots. Rostrum largely brownish. Carapace with some brown stripes. Sixth abdominal somite at bases of uropods with a large brown spot.

Remarks. Palaemon debilis was reported from Taiwan by Maki & Tsuchiya (1923) with this record further cited in Holthuis (1950). The photo in Maki & Tsuchiya (1923) bears a superficial resemblance to P. debilis , but is rather unclear. Nevertheless, the present newly collected material confirms the presence of this species in Taiwan.

Ecology. Fresh, brackish and salt waters.

Distribution. Red Sea to South Africa to Ryukyu Islands, Philippines and Indonesia, Great Barrier Reef of Australia, and eastward to Hawaii and the Tuamotu Archipelago.

Figures

FIGURE 6. Palaemon debilis Dana, 1852: A–D, male (pocl. 5.5 mm, NTOU M02087); E–F, male (pocl. 4.4 mm, NTOU M02088). A) carapace, right lateral view; B) left second pereiopod, chela, mesial view; C) left fifth pereiopod, mesial view; D) left second pereiopod, lateral view; E) left endopod of first pleopod of male, posterior view; F) right antennule dorsal view. Scale bars: A, B, D, E = 1.0 mm; C, F = 0.5mm.

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).