Synalpheus lophodactylus Coutière, 1908

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 : 397-399

3.2.16 Synalpheus lophodactylus Coutière, 1908 * ( Fig. 29 )

Synalpheus lophodactylus Coutière, 1908 . Bull. Soc. Philomath, Parish IX, 11(5): 197; 1921. Trans. Linn. Soc. Lond., Zool. Lond. 11, Zool. 14, 17: 417. pl. 61, fig. 11; Banner, 1957. Pacif. Sci., 11(2): 195; Banner & Banner, 1975. Records of the Australian Museum, 29(12): pl. 350, fig. 20.

Material examined. ( MBM 158724), 2♀, 1♂, CL 3.9 mm, TL 8.1 mm, Shalao, South China Sea, depth 2 m, 4 April 1992.

Description. Carapace smooth, glabrous; rostrum about 2.5 as long as wide at base, rounded tip bearing two short setae, reaching end of visible part of first segment of antennular peduncle; orbital hoods about 2.4 times as wide at base as rostrum, shorter than rostrum, with rounded tip bearing two short setae; pterygostomial corner produced into blunt acute angle; cardiac notch well developed.

Telson about 1.2 times as long as wide at base; dorsal surface with two pairs of moderately large spines, inserted approximately at 1/3 and 3/5 length of telson; posterior margin moderately produced, fringed with long setae, posterolateral angle each with two pairs of spines, lateral 1/3 length of mesial, posterolateral margins each produced into acute small tooth, distinctly shorter than lateral spines.

Eyes concealed in lateral and dorsal view.

Antennular peduncle stout, with distally acute stylocerite, latter hardly reaching end of first segment of antennular peduncle; second segment almost as long as wide; visible part of first segment longer than second and about twice as long as third. Basicerite without distodorsal tooth, distolateral tooth reaching middle of second segment of antennular, distinctly longer than stylocerite; carpocerite beyond end of antennular peduncle by total length of third segment; scaphocerite blade narrow, not reaching end of third segment of antennular peduncle, lateral spine developed, 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 three spine-like setae, with transverse rows of setae along ventral margin.

Major cheliped with short, stout ischium; merus about three times as long as wide at base, with dorsal margin convex medially, superodistal margin without triangular tooth; carpus cup-shaped, with setae distodorsally; chela cylindrical, with palm about 1.7 times as long as dactylus, distodorsal of palm with one triangular tubercle, slightly upturned, bearing fine setae; dactylus as long as pollex.

Minor chela with merus about 2.8 as long as wide, longer than that of major cheliped, superodistal margin without any projecting, ventral margin bearing short setae; carpus cup-shaped, proportionally longer that of major cheliped, about 1/2 length of palm; palm about 1.2 times as long as fingers; dactylus tapering, superior surface bearing row of long setae, extending almost full length of dactylus; pollex tapering, distal single tooth.

Second pereiopod with ischium shorter than merus; carpus five-segmented, segment ratio subequal to 5: 1: 1: 1: 3, with first segment shorter than sum of last four segment; dorsal margin of palm convex; fingers about twice as long as palm. Third pereiopod stout; merus longer than propodus, about 4 times as long as wide at base; carpus about 1/2 length of merus, with dorsal margin extended into an obtuse tooth, ventral margin with one distal spine; propodus with eight spines along ventral margin plus one distal pair of spines near dactylus, dorsal margin with fine setae; dactylus around 1/5 propodus length, biunguiculate, extensor tooth as long as flexor tooth, and as wide at base as flexor tooth, notch between extensor and flexor tooth U-shaped. Fourth pereiopod generally similar to third; ventral margin of carpus without distal spine. Fifth pereiopod similar to third and fourth pereiopods, carpus about 4/5 merus length, ventral margin without distal spine; propodus slightly longer than merus, with seven transversal rows of setae and distally pair of spines on ventral margin.

Remarks. S. lophodactylus was originally described by Coutière (1908), based on a male specimen. The description was rather simple and without figures. Coutière (1921) rechecked the holotype and added figures (pl. 61, fig.11). Unfortunately, the major chela was lost. Banner & Banner (1975) rechecked the type at the Muséum d’Histoire Naturelle in Paris, and redescribed this species based on more than 200 specimens. The redescriptions were well agreed with Coutière (1921), except the following characters: the length of the distolateral tooth of basicerite; the length of the brush of setae on the superior margin of dactylus (minor chela), which are taken as variable in this genus. However, the minor chela has lost when Banner rechecked the type.

All present specimens are small in size, collected from South China Sea in a depth 2 meters, agreed with the redescription of Banner & Banner (1975).

Distribution. South China Sea; Chagos Archipelago; Indian Ocean; Marshall Islands; Australian.

Figures

Fig. 29. Synalpheus lophodactylus Coutière, 1908, female (cl 3.9mm) (MBM 158724). a–b. Frontal region. a. Dorsal. b. Lateral. c–d. Third maxilliped. c. Ventral. d. Tip, dorsal. e–h. Major cheliped (left). e. Mesial. f–g. Chela, lateral. h. Merus, lateral. i–j. Minor cheliped (right). i. Lateral. j. Chela, mesial. k. Second pereiopod, lateral. l–m. Third pereiopod. l. Lateral. m. Distal propodus and dactylus, lateral. n–o. Fourth pereiopod. n. Lateral. o. Distal propodus and dactylus, lateral. p. Fifth pereiopod, lateral. q. Second pleopod. r. Telson and uropod, dorsal. Scale bars: a–l, n, p–r=0.5mm; m, o=0.2 mm.