Synalpheus carinatus (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 : 368-370

3.2.5 Synalpheus carinatus (de Man, 1888) ( Figs 7–8 )

Alpheus carinatus de Man, 1888 . Arch. Naturgesch., 53(1): 508, pl. 22, fig. 2.

Synalpheus carinatus de Man, 1911 . Siboga Exped. , 39(2): 210, pl. 6, fig. 23; Banner & Banner, 1968. Micronesica, 4 (2): 272.

Svnalpheus carinatus var. binongcensis de Man, 1909 . Tijdschr. ned. dierk. Vereen. II, 11(2): 111; 1911. Siboga Exped. , 39(2): 211, pl. 6, fig. 23a.

Svnalpheus carinatus var. ubianensis de Man, 1909 . Tijdschr. ned. dierk. Vereen. II, 11(2): 111; 1911. Siboga Exped. , 39(2): 212.

nec Synalpheus carinatus Pearson, 1905 . Rep. Pearl Oyst. Fish., Ceylon: 83, pl. 2, figs 9 (= S. trispinosus de Man ).

Material examined. (MBM158008), 1♀, 1♂, CL 7.1 mm, TL 12.5 mm, Yongxing Island, Xisha Islands (16.8°N, 112.3°E), 15 April 1957.

Description. Carapace smooth, glabrous; rostrum depressed, slightly concave in lateral view, acute tip reaching middle of second segment of antennular peduncle; rostrum and carapace bearing strong median carina, extending almost entire length of carapace; orbital hoods half-length of rostrum, with rounded tip bearing two short setae; pterygostomial corner produced into blunt acute angle; cardiac notch well developed.

Telson about 1.5 times as long as wide at base; dorsal surface with two pairs of moderately large spines, inserted approximately at 3/5 and 4/5 length of telson; posterior margin moderately produced, fringed with long setae, posterolateral angle each with two pairs of spines, lateral about 1/2 length of mesial, posterolateral margins not produced.

Eyes concealed in lateral and dorsal view.

Antennular peduncle moderately stout, with distally acute stylocerite, latter reaching 1/3 length of second segment of antennular peduncle; second segment about 1.5 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 2/3 length of visible part of first segment of antennular, distinctly shorter than stylocerite; carpocerite beyond end of antennular peduncle by 1/3 length of third segment; scaphocerite blade narrow, reaching end of third segment of antennular peduncle, lateral spine developed, distally curved inward, overreaching end of antennular peduncle, shorter than carpocerite.

Third maxilliped far beyond antennular peduncle and carpocerite when extended; antepenultimate segment longest, about twice as long as ultimate segment; penultimate segment about 2.5 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 1.8 times as long as dactylus, distodorsal of palm without any projecting; dactylus as long as than pollex, distally slightly curved.

Minor chela with merus about 4.8 times as long as wide at base, superodistal margin with acute triangular tooth, ventral margin bearing short setae; carpus cup-shaped, proportionally longer that of major cheliped; palm about 1.5 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 4: 1: 1: 1: 2, with first segment slightly shorter than sum of last four segment; dorsal margin of palm convex; fingers about 1.25 times as long as palm. Third pereiopod stout; merus shorter 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 six spines along ventral margin plus one distal pair of spines near dactylus; dactylus strongly curved, at right angles 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 four spines. Fifth pereiopod similar to third and fourth pereiopod, propodus with distally two transversal rows of setae and two spines on ventral margin.

Remarks. Synalpheus carinatus was original described by de Man (1888), and redescribed by him (1911) with another two varieties ( S. carinatus var. binongcensis de Man, 1909 ; S. carinatus var. ubianensis de Man, 1909 ). Banner (1958) and Banner & Banner (1968, 1975) have given excellent discussions about the variations in this species.

The present two specimens, collected from Xisha Islands, South China Sea, are obvious S. carinatus . But they are not well agreed with the redescription of Banner & Banner (1975) by following: the stylocerite reaching just 1/3 length rather than middle of second segment of the antennular peduncle; the distolateral tooth of the basicerite distinctly shorter than the stylocerite rather than subequal; the carpus of the major and minor chela normal in form, not bearing acute teeth either in superior or inferior margin; the merus of major and minor margin slender than normal species in this genus, but the inferointernal margin not bearing acute teeth; the ventral margin of the propodus in third pereiopods bearing only 6 spines, less than 12–14 spines.

Distribution. South China Sea; Indonesia; Malaysian Archipelago; Caroline; Marshall; Gilbert Islands.

Figures

Fig. 7. Synalpheus carinatus (de Man, 1888), female (cl 7.1 mm) (MBM 158008). a–b. Frontal region. a. Dorsal. b. Lateral. c–d. Third maxilliped. c. Ventral. d. Tip, dorsal. e–g. Major cheliped (right). e. Mesial. f. Chela, lateral. g. Merus, lateral. h–j. Minor cheliped (left). h. Lateral. i. Chela, mesial. j. Merus, lateral. k. Second pereiopod, lateral. l–m. Third pereiopod. l. Lateral. m. Distal propodus and dactylus, lateral. n. Fourth pereiopod, lateral. Scale bars: a–c, e–k, n=1mm; d, m=0.5mm.

Fig. 8. Synalpheus carinatus (de Man, 1888), female (cl 7.1mm) (MBM 158008). a. Fourth pereiopod, distal propodus and dactylus, lateral. b. Fifth pereiopod, propodus and dactylus, lateral. c. Second pleopod. d. Telson and uropod, dorsal. e. Abdomen, lateral. Scale bars: a–c =0.5mm; d–e =1mm.