Synalpheus stimpsonii (de Man, 1888)

Wang, Yan-Rong & Sha, Zhong-Li, 2015, A review of the genus Synalpheus (Crustacea: Decapoda: Caridea: Alpheidae) from China seas, Zoological Systematics 40 (4), pp. 355-435 : 414-417

3.2.26 Synalpheus stimpsonii (de Man, 1888) ( Figs 39–40 )

Alpheus stimpsonii de Man, 1888 . Arch Naturgesch., 53(1): 513, pl. 22, fig. 3.

Synalpheus stimpsoni Banner & Banner, 1966 . Siam Soe. Mono., 3: 46, fig. 12; 1968. Mieronesica, 4(2): 274; Banner & Banner, 1975. Records of the Australian Museum, 29(12): pl. 286, fig. 2.

Alpheus amhoinae Zehntner, 1894 . Rev. Suisse Zool., 2: 202, pl. 8, fig. 23.

Synalpheus amhoinae de Man, 1911 . Siboga Exped. , 39 (2): 203, fig. 20; 1922. Siboga Exped. , 39(5): 26, fig. 13; Banner, 1958. Pacif. Sci., 12(2): 159, fig. 2.

Synalpheus consobrinus de Man. 1911 . Siboga Exped. , 39(2): 204, fig. 21.

Synalpheus brucei Potts, 1915 . Pap. Dep. Mar. Biol. Carnegie Instn. Wash., 8: 76, pl. I, fig. 2, textfigs 1 a–b, 2a–c, 3; Clark, 1921. Bull. U. S. natn. Mus., 82, 1(2): 625.

Alpheus stimpsoni de Man var? Schenkel, 1902. Verh. naturf. Ges. Basel., 13: 567, pl. 13, fig. 22.

Synalpheus striatus Kubo, 1938 . Annotnes. Zool. Jap., 17(1): 89, figs 1, 2; Miya, 1972. Publ. Amakusa Mar. Biol. Lab. Kyushu, 3(1): 47, pl. 6.

Material examined. ( MBM 157748), 1♀, 1♂, CL 7.3–10.5 mm, TL 17.2–22.3 mm; ( MBM 158719), 1♀, CL 7.9 mm, TL 12.5 mm; ( MBM 157903), 1♂, CL 8.2 mm, 19 April 1975, coll. Xian-Qiu Ren; ( MBM 158503), 1♀, 1♂, CL 11.5–12.1 mm, TL 25.9–28.8 mm; ( MBM 158592), 1♂, CL 8.2 mm, 19 April 1958.

Description. Carapace smooth, glabrous; rostrum slightly depressed, slightly concave in lateral view, acute tip reaching end of second segment of antennular peduncle, with rounded carina, extending to level of eyes; orbital hoods near half-length of rostrum; pterygostomial corner produced into blunt acute angle; cardiac notch well developed.

Telson about 1.3 times as long as wide at base; dorsal surface with two pairs of moderately large spines, inserted approximately at 1/2 and 2/3 length of telson; posterior margin slightly produced, fringed with long setae, posterolateral angle each with two pairs of spines, lateral about 2/3 length of mesial, posterolateral margins not produced.

Eyes concealed in lateral and dorsal view.

Antennular peduncle moderately stout, with distally acute stylocerite, latter reaching about 1/3 length of second segment of antennular peduncle; second segment about 1.3 times as long as wide; visible part of first segment longer than second and about twice as long as third. Basicerite with acute distodorsal tooth, distolateral tooth reaching about 1/2 length of visible part of first segment of antennular, distinctly shorter than stylocerite; carpocerite slightly overreaching end of third segment of antennular peduncle; scaphocerite blade moderately broad, reaching middle of third segment of antennular peduncle, lateral spine developed, distally curved inward, reaching end of antennular peduncle, shorter than carpocerite.

Third maxilliped far beyond antennular peduncle and carpocerite when extended; antepenultimate segment longest; penultimate segment about 1.5 times as long as wide at base; tip of ultimate segment bearing crown of four spine-like setae, with transverse rows of setae along ventral margin.

Major cheliped with short, stout ischium; merus about 3.5 times as long as wide at base, superodistal margin with acute triangular tooth; carpus cup-shaped, with setae distodorsally; chela slightly compressed, with palm about 2.2 times as long as dactylus, distodorsal of palm with one obtuse projecting; dactylus as long as than pollex, distally slightly curved..

Minor chela with merus about 5.2 times as long as wide at base, superodistal margin with acute triangular tooth, ventral and dorsal margin bearing fine long setae; carpus cup-shaped, proportionally longer that of major cheliped; palm about 1.6 times as long as fingers, dorsal and ventral margin with fine setae; dactylus and pollex tapering, distal single tooth, margin with fine setae.

Second pereiopod with ischium shorter than merus; carpus five-segmented, segment ratio subequal to 5.5: 1: 1: 1: 2.1, with first segment slightly longer than sum of last four segment; dorsal margin of palm convex; fingers near as long as palm. Third pereiopod slender; merus slightly longer than propodus, about 6.6 times as long as wide at base; carpus about 1/3 length of merus, with dorsal margin extended into an obtuse tooth, ventral margin with two distal spines; propodus with ten small spines along ventral margin plus one distal pair of spines near dactylus; dactylus slightly curved to propodus, biunguiculate, extensor tooth about twice as long as flexor tooth, notch between extensor and flexor tooth V-shaped. Fourth pereiopod generally similar to third; ventral margin of propodus with six small spines. Fifth pereiopod similar to third and fourth pereiopods, propodus with distally 13 transversal rows of spine-like setae and three spines on ventral margin.

Remarks. This species was original described by de Man (1888). It is so variable in some characters ( Banner & Banner, 1966) that some varieties ( S. amboiae de Man, 1911 , S. consobrinus de Man, 1911 , Alpheus stimpsoni de Man var?, S. striatus Kubo, 1938 ) were described as new forms at first, and then synonymized with S. stimpsonii (de Man, 1888) ( Banner & Banner, 1966, 1968, 1975). The variable characters mainly are: the length of the rostrum; the length of the orbital hoods compared to the rostrum; the length of first segment of the antennular peduncle compared to the sum of two following segments; the relative length of the distodorsal and distolateral tooth; the proportions of the pereiopods; the dorsal spines and posterolateral margins of telson ( Banner & Banner, 1975). Those characters were taken variable in Synalpheus .

The present seven specimens are also varied in the length of the rostrum. Other than the length or relative length of characters mentioned above, the specimens also differ from Kubo (1938: 84–85, pl. 6, fig. D) and Banner & Banner (1966: 79, fig. 12B) by the small and obtuse tooth on the superodistal margin of the palm of major chela.

Distribution. South China Sea; Eastern Africa and Madagascar to Singapore; Thailand; Japan; Philippines; Indonesia; Australia; Marshall; Gilbert; Loyalty Islands.

Figures

Fig. 39. Synalpheus stimpsonii (de Man, 1888), male (cl 8.2 mm) (MBM 157903). a–b. Frontal region. a. Dorsal. b. Lateral. c–d. Third maxilliped. c. Ventral. d. Tip, dorsal. e–g. Major cheliped (left). e. Mesial. f. Chela, lateral. g. Merus, lateral. h–j. Minor cheliped (right). h. Lateral. i. Chela, lateral. j. Merus, lateral. k. Second pereiopod, lateral. l–m. Third pereiopod. l. Lateral. m. Distal propodus and dactylus, lateral. Scale bars: a–c, e–l=1mm; d, m=0.5mm.

Fig. 40. Synalpheus stimpsonii (de Man, 1888), male (cl 8.2 mm) (MBM 157903). a–b. Fourth pereiopod. a. Lateral. b. Distal propodus and dactylus, lateral. c. Fifth pereiopod, propodus and dactylus, lateral. d. Second pleopod. e. Abdomen, lateral. f. Telson and uropod, dorsal. g. Female (cl 7.9mm) frontal region, dorsal. Scale bars: b=0.5mm; a, c–g=1mm.