Synalpheus tonkinensis, Wang & Sha, 2015

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. 357-435 : 421-424

Synalpheus tonkinensis sp. nov.

( Figs 44–45 )

Material examined. Holotype (MBM 270602), ♀, CL 5.3 mm, TL 16.5 mm, Tonkin Gulf (Beibu Gulf), Sta. 7305, depth 62 m, 21 January 1962, coll. Fu-Zeng Sun. Paratype (MBM 270602), 1♂, CL 4.8 mm, TL 12.0mm, same data as holotype.

Description. Carapace smooth, glabrous; rostrum flattened dorsally, with lateral margins slightly convex, rounded tip overreaching 1/2 length of visible part of first segment of antennular peduncle, tip of rostrum bearing two short setae; orbital hoods about twice as wide at base as rostrum, length almost equal to rostrum, rounded tip bearing two short setae; notch between orbital hoods and rostrum deep, between V- and U- shaped; pterygostomial corner produced into blunt acute angle.

Abdominal somites smooth, glabrous, sex bimorphology, female with posterior corner of first pleura broadly rounded, ventral and posterior margins of second pleura longer and wider; male with posterior corner of first pleura acutely produced ventrally. Telson about 1.4 as long as wide at base; lateral margins concave posteriorly; dorsal surface with two pairs of spines, inserted approximately at 1/4 and 1/2 length of telson; posterior margin strongly producing, fringed with long setae, posterolateral angle each with two pairs of spines, lateral about 1/2 length of mesial, posterolateral margins forming right angles.

Eyes concealed in lateral and dorsal view.

Antennular peduncle with distally acute stylocerite, latter hardly reaching distal margin of first segment of antennular peduncle; second segment distinctly longer than wide; visible part of first segment longer than second and about twice as long as third segment. Antenna with basicerite without distodorsal tooth, distolateral tooth distinctly longer than stylocerite, overreaching middle of second antennular segment; carpocerite beyond end of antennular peduncle by the length of third segment; scaphocerite blade narrow, hardly reaching end of second segment of antennular peduncle, lateral spine robust, with lateral margin slightly concave, subequal to antennular peduncle.

Mouthparts not dissected. Third maxilliped far beyond antennular peduncle and carpocerite when extended; antepenultimate segment longest, about 5.5 times as long as wide; penultimate segment about 1.8 times as long as wide at base; tip of ultimate segment bearing crown of 5–6 spine-like long setae, with several brush consisting of 6–8 transverse rows of setae along ventral margin.

Major cheliped with short, stout ischium; merus three times as long as wide at base, superodistal margin rounded without any projecting, inferointernal margin with rounded tooth; carpus cup-shaped, with long setae distodorsally; chela cylindrical, not a bit compressed or twisted, with palm about 3.2 times as long as dactylus, distodorsal tooth on palm subacute, slightly curved downward to dactylus; dactylus far longer than pollex.

Minor chela with merus about two times as long as wide, longer than that of major cheliped, superodistal margin same with that of major cheliped, without any projecting; carpus cup-shaped, proportionally longer than that of major cheliped; palm 1.3 times as long as fingers, lateral margin near dactylus bearing patch of stiff setae; both dactylus and pollex dorsal surface convex, broadened from base to 8/9 length of fingers, terminating in slender, acute, curved teeth, crossing distally, lateral margins of fingers bearing 6–8 long stiff setae that cross in regular fashion.

Second pereiopod with ischium distinctly shorter than merus; carpus five-segmented, segment ratio subequal to 4: 1: 1: 1: 2, with first segment shorter than sum of last four segments; fingers 1.3 times as long as palm. Third pereiopod stout; merus longer than propodus, about four times as long as wide, without spines on ventral margin; carpus about 3/8 merus length, with dorsal margin extended into an obtuse tooth, ventral margin with one short distal spine; propodus with usual seven spines along ventral margin plus one distal pair of spines near dactylus; dactylus around 2/11 propodus length, biunguiculate, moderately slender, extensor tooth slightly longer, thicker at base than flexor tooth, notch between extensor tooth and flexor tooth V-shaped. Fourth pereiopod generally similar to third; but ventral margin of carpus without distal spine. Fifth pereiopod with merus about 3.7 times as long as wide, without spines on ventral margin; carpus about 9/11 merus length, ventral margin without distal spine; propodus as long as merus, with seven brush consisting of 5–6 transverse rows of short setae along on posterior face, and two mobile spines on ventral margin plus one distal pair of spines near dactylus.

Etymology. “ Tonkin ” means the Tonkin Gulf (Beibu Gulf), the type locality of this new species.

Type locality. Tonkin Gulf (Beibu Gulf), South China Sea.

Distribution. Tonkin Gulf (Beibu Gulf), presently known only from the type locality in South China Sea.

Remarks. Synalpheus tonkinensis sp. nov. is mainly identified by the configuration of the frontal region of the carapace; the shape of the major and minor cheliped and the telson. This new species can be distinguished from its morphologically similar species by the combination of characters summarized in Table 3.

Figures

Fig. 44. Synalpheus tonkinensis sp. nov., female (cl 5.3mm) (MBM 270602). a–b. Frontal region. a. Dorsal. b. Lateral. c–d. Third maxilliped. c. Ventral. d. Tip, dorsal. e. Major cheliped, lateral. f–g. Minor cheliped. f. Lateral. g. Merus, lateral. h. Second pereiopod, lateral. i–j. Third pereiopod. i. Lateral. j. Distal propodus and dactylus, lateral. k. First pleopod. l. Third pleopod. Scale bars: a–i, k, l=1 mm; j =0.25 mm.

Fig. 45. Synalpheus tonkinensis sp. nov., female (cl 5.3 mm) (MBM 270602). a. Fourth pereiopod, lateral. b. Fifth pereiopod, propodus and dactylus. c. Telson and uropod, dorsal. Scale bars=1mm.