Synalpheus modestus de Man, 1909

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 : 399-401

3.2.17 Synalpheus modestus de Man, 1909 * ( Fig. 30 )

Synalpheus modestus de Man, 1909 . Tijdschr. ned. dierk. Vereen, 11(2): 115, fig. 31; Banner & Banner, 1985. Marine Research in Indonesia: pl. 46.

Material examined. (MBM 158475), 1 ovigerous ♀, CL 4.1 mm, TL 10.2 mm, Xincun, depth 1–3 m, 26 March 1992; (MBM 159310), 1♂, CL 3.5 mm, TL 8.9 mm; (MBM 159278), 2 ovigerous ♀, 3♂, CL 3.1–3.9 mm, TL 8.1–10.2 mm; (MBM 159244), 1♂; (MBM 107778), 2♂, CL 3.4 mm, TL 8.9 mm, Shalao, South China Sea, depth 6 m, coll. Xin-Zheng Li; (MBM 158542), Xincun, depth 1–3 m, 26 March 1992.

Description. Carapace smooth, glabrous; rostrum about 4.2 times as long as wide at base, acute tip reaching middle of second segment of antennular peduncle; orbital hoods distinctly shorter than rostrum, not reaching end of first segment of antennular peduncle; pterygostomial corner produced into acute angle; cardiac notch well developed.

Telson about 1.3 times as long as wide at base; dorsal surface with two pairs of moderately small spines, inserted approximately at 2/5 and 3/5 length of telson; posterior margin strongly produced, fringed with long setae, posterolateral angle each with two pairs of spines, lateral about 1/4 length of mesial, posterolateral margins each produced into acute small tooth, but distinctly shorter than lateral spines.

Eyes concealed in lateral and dorsal view.

Antennular peduncle slender, with distally acute stylocerite, latter overreaching middle of second segment of antennular peduncle; second segment about 1.25 times as long as wide at base; visible part of first segment longer than second and about twice as long as third. Basicerite with acute distodorsal tooth, distolateral tooth distinctly shorter than stylocerite, reaching end of first segment of antennular peduncle; carpocerite overreaching end of third segment of antennular peduncle; scaphocerite blade moderately narrow, reaching about 3/4 length of third segment of antennular peduncle, lateral spine developed, far overreaching end of antennular peduncle, distinctly longer than carpocerite.

Third maxilliped far beyond antennular peduncle and carpocerite when extended; antepenultimate segment longest; penultimate segment about 1.4 times as long as wide at base; tip of ultimate segment bearing crown of moderately long five spine-like setae, with transverse rows of long setae along ventral margin.

Major cheliped with short, stout ischium; merus about three times as long as wide at base, superodistal margin with one acute triangular tooth; carpus cup-shaped, with setae distodorsally; palm about 2.9 times as long as dactylus, distodorsal of palm with one strong subacute projecting; dactylus slightly longer than pollex.

Minor chela with merus about 3.5 times as long as wide at base, superodistal margin with one acute triangular tooth; carpus cup-shaped, proportionally longer that of major cheliped; palm about 1.7 times as long as fingers; dactylus and pollex tapering, distal single tooth.

Second pereiopod with ischium shorter than merus; carpus five-segmented, segment ratio subequal to 5: 1: 1: 1: 2.2, with first segment slightly shorter than sum of last four segment; dorsal margin of palm convex; fingers about 1.2 times as long as palm. Third pereiopod moderately slender; merus near as long as propodus, about 4 times as long as wide at base, ventral margin with 2 spines; carpus about 2/5 length of merus, with dorsal margin extended into an obtuse tooth, ventral margin with one distal spine; propodus with seven spines along ventral margin plus one distal pair of spines near dactylus; dactylus about 3/11 length of propodus, slightly curved to propodus, biunguiculate, extensor tooth near as long as flexor tooth, notch between extensor and flexor tooth V-shaped, flexor tooth wider at base than extensor tooth. Fourth pereiopod generally similar to third; merus shorter than propodus, ventral margin of propodus with six spines. Fifth pereiopod similar to third and fourth pereiopod, ventral margin of carpus without one distal spine; ventral margin of propodus with five transversal rows of spine-like setae and two spines.

Remarks. De Man (1909) described this species based on single specimen. It was morphologically “closely related to S. streptodactylus ”. Banner & Banner (1985) had ever discussed the validity of the species, and considered the slender rostrum of this species to be unique in this genus. The slender rostrum is most similar to another the Indo-Pacific species, S. gracilirostris de Man, 1910 , which can be easily distinguished by the spines on the merus of the third pereiopod.

The species is also different from S. streptodactylus Coutière, 1905 by the slender rostrum, the projecting situated on the distal-superior margin of the palm in the major chela subacute.

Distribution. Xincun, South China Sea; Banda Reef.

Figures

Fig. 30. Synalpheus modestus de Man, 1909, female (cl 4.1 mm) (MBM 158475). a–b. Frontal region. a. Dorsal. b. Lateral. c–d. Third maxilliped. c. Ventral. d. Tip, dorsal. e–f. Major cheliped (left). e. Mesial. f. Chela, lateral. g–h. Minor cheliped (right). g. Lateral. h. Chela, mesial. i. Second pereiopod, lateral. j–k. Third pereiopod. j. Lateral. k. Distal propodus and dactylus, lateral. l–m. Fourth pereiopod. l. Lateral. m. Distal propodus and dactylus, lateral. n. Fifth pereiopod, propodus and dactylus, lateral. o. Second pleopod. p. Telson and uropod, dorsal. Scale bars: a–c, e–g, i–j, l, o–p=1 mm; d, h, k, m–n=0.5mm.