Palaemon ortmanni Rathbun, 1902

(Fig. 9, 14A)

Previous Taiwan records. Chan & Yu 1985: 120, text-fig. 2, pl. 1B.

Material examined. Bachimen, Keelung City, 1 male (pocl 8.8 mm) , 6 females (pocl 16.7–17.6 mm), 12.V.1984 (NTOU M01219); same location, 3 males (pocl 9.8-–11.0 mm), 5 ovig. females (pocl 15.6–16.5 mm), 15.V.1984 (NTOU M01163); same location, 3 ovig. females (pocl 15.3-– 15.7 mm), 26.V.1984 (NTOU M01164);

same location, 1 male (pocl 11.7 mm), XI.1984 (NTOUM01167); same location, 1 male (pocl 8.8 mm), 06.IX.1986 (NTOU M01168); same location, 1 male (pocl 9.8 mm), 10.IX.1986 (NTOU M01169); same location, 1 female (pocl 10.4 mm), 14.VIII.1988 (NTOU M01210); Badouzih, Keelung City , 1 male (pocl 10.2 mm), 31.V.1984 (NTOU M01165); same location, 2 males (pocl 9.9–10.2 mm), 2 ovig. females (pocl 15.0– 15.4 mm), 2 juv. (pocl 4.4–6.0 mm), 04.VI.1984 (NTOU M01166); same location, 1 ovig. female (pocl 12.0 mm), IV.2010 (NTOU M01185); No data specified , 1 female (pocl 5.2 mm), (NTOU M01241).

Diagnosis. Rostrum strongly ascendant in anterior half, tapering gradually; rostral formula 1–3+7–9/5–9; basal antennular segment with disto-lateral spine distinctly overreaching adjacent convex distal margin of segment; free portion of shorter ramus of dorsal antennular flagellum 2.3–3.5 times as long as fused part; mandible with 3 segmented palp; first pereiopod with carpus twice as long as chela; second pereiopod with chela 1.5–1.8 times length of carpus; fifth abdominal pleuron with distoventral tooth; first pleopod of male without marginal appendix on endopod.

Colour pattern. Body semi-transparent; carapace with strong horizontal and diagonal red pigment lines; first to fourth abdominal pleurae with strong vertical pigment bands, fifth and sixth with strong horizontal pigment bands; distal end of uropods tinged orange, sometimes entire tailfan reddish brown; third to fifth pereiopods with orange pigment at joints between segments; fingers of chela of second pereiopod with red, yellow and orange bands, palm with light purple band, distal end of carpus with light purple and yellow band, distal end of other segments with light purple and orange bands; eggs brownish.

Remarks. Holthuis (1950) suggested that, given examination of more material, P. ortmanni and P. gravieri (Yu, 1930) may prove to represent two extremes of variation of a single species. In fact, a number of important morphological differences may be found between the two species. The rostra are clearly different shapes being nearly straight in P. gravieri and greatly upturned in P. ortmanni, there are fewer teeth on the upper margin of the rostrum in P. ortmanni than P. gravieri, and the dactyli of the ambulatory pereiopods are more slender and curved in P. gravieri than P. ortmanni . Palaemon ortmanni also has a much stronger, more defined colour pattern in life than P. gravieri . These morphological differences support the recognition of two discrete species and recent genetic evidence presented by Carvalho et al. (2017) also demonstrated that they are distinct.

Ecology. Rocky shores, over sand or muddy bottoms, under or around rocks.

Distribution. Japan to China and Taiwan.