Synalpheus brevrostrus, 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. 355-435 : 364-367

Synalpheus brevrostrus sp. nov.

( Figs 4–6 )

Material examined. Holotype (MBM 283384), ♂, CL 6.5 mm, TL 12.5 mm, Jinqing Island, Xisha Islands (16°27′57″N, 111°44′17″E), 25 April 1958, coll. Zhen-Gang Fan, Jie-Shan Xu. Paratypes: (MBM 283383), 1♀, CL 5.5 mm, TL 15.0 mm, Xisha Islands, 28–29 April 1958, coll. Zhen-Gang Fan, Jie-Shan Xu; (MBM 283384), 1♀, CL 5.6 mm, TL 14.8 mm, Jinqing Island, Xisha Islands (16°27′57″N, 111°44′17″E), 25 April 1958, coll. Zhen-Gang Fan, Jie-Shan Xu.

Description. Carapace smooth, glabrous; rostrum twice as long as wide at base, with lateral margins slightly convex, rounded tip bearing two short setae, hardly reaching 1/2 length of visible part of first segment of antennular peduncle; orbital hoods about 2.7 times as wide at base as rostrum, distinctly longer than rostrum, with rounded tip bearing two short setae; notches between orbital hoods and rostrum deep, narrow, V-shaped; pterygostomial corner produced into blunt acute angle.

Abdominal somites smooth, glabrous, posterolateral margin of sixth pleura with 3–4 small teeth, sex bimorphology, first pleura of male with posterior corner distinctly produced ventrally into anteriorly directed hook; second posterior corner rounded; third-fifth with lower margin produced into acute angle, first pleura of female with posterior corner rounded. Telson about 1.3 times as long as wide at base; lateral margin slightly concave posteriorly; dorsal surface without median groove, with two pairs of large spines, inserted approximately at 1/3 and 2/3 length of telson; posterior margin moderately convex, fringed with long setae, posterolateral angle each with two pairs of spines, lateral 2/3 length of mesial, posterolateral margins each produced into acute tooth, but distinctly shorter than lateral spine.

Eyes concealed in lateral and dorsal view.

Antennular peduncle slender, with distally acute stylocerite, latter overreaching end of first segment of antennular peduncle, about 1/6–1/5 length of second; second segment 1.8 times as long as wide; visible part of first segment slightly longer than second and about twice as long as third. Antenna with basicerite with acute distodorsal tooth, 1/8 length of distolateral tooth, latter hardly reaching end of first segment, distinctly shorter than stylocerite; carpocerite beyond end of antennular peduncle by 1/3 length of third segment; scaphocerite blade narrow, 4/5 length of second segment of antennular peduncle, lateral spine moderately developed, with lateral margin slightly concave posteriorly, almost overreaching end of second segment.

Mouthpart not dissected. Third maxilliped far beyond antennular peduncle and carpocerite when extended; antepenultimate segment longest, about 5.2 times as long as wide; penultimate segment about 1.7 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 four times as long as wide at base, superodistal margin ending in subacute tooth; carpus cup-shaped, with long setae distodorsally; chela cylindrical, not a bit compressed or twisted, with palm about 2.8 times as long as dactylus, distodorsal tooth of palm subacute, straightforward; dactylus longer than pollex.

Minor chela with ventral margin of ischium bearing long setae; merus about 3.3 times as long as wide, longer than that of major cheliped, superodistal margin rounded, without any projecting, ventral margin bearing row of short setae; carpus cup-shaped proportionally longer that of major cheliped; palm about 2.5 times as long as fingers, lateral face near dactylus bearing patch of stiff setae; dactylus tapering, with flexor margin concave, distal single tooth, lateral margin near palm bearing row of long setae; pollex tapering, with flexor surface obliquely convex, distal single tooth.

Second pereiopod with ischium shorter than merus; carpus five-segmented, segment ratio subequal to 4.3: 1: 1: 1: 2, with first segment shorter than sum of last four segment, segments 2–4 wider than long; dorsal margin of palm convex; fingers subequal to palm. Third pereiopod stout; merus longer than propodus, about 3.8 times as long as wide at base, without spines on ventral margin; carpus about 1/3 merus length, with dorsal margin extended into an obtuse tooth, ventral margin with one distal spine; propodus with usual seven spines along ventral margin plus one distal pair of spines near dactylus; dactylus around 3/14 propodus length, biunguiculate, moderately slender, ventral margin near to flexor tooth concave, extensor tooth slightly thicker than flexor tooth at base, subequal; notch between extensor and flexor tooth V-shaped. Fourth pereiopod generally similar to third; but ventral margin of carpus without distal spine. Fifth pereiopod with merus about three times as long as wide; carpus about 5/7 merus length, ventral margin without distal spine; propodus as long as merus, with six transversal rows of setae along ventral margin plus one pair of spines near dactylus.

Etymology. “ brev ” means short, “ rostrus ” means the rostrum. The specific name is referring to the rostrum distinctly shorter than the orbital hoods.

Type locality. Jinqing Island, Xisha Islands, South China Sea.

Distribution. Xisha Islands, presently known only from the type locality in South China Sea.

Remarks. Synalpheus brevrostrus sp. nov. can be easily distinguished from other species by the following: the deep, narrow notches between rostrum and orbital hoods; the rostrum distinctly shorter than the orbital hoods and distinctly lower than the orbital hoods in lateral view; the reduced scaphocerite blade and lateral spine. It is morphologically similar to S. readi and S. quadrispinosus , but can be distinguished by the characters summarized in Table 1.

In addition, one paratype has slight differences with another two types by following characters: notches between rostrum and orbital hoods U-shaped rather than V-shaped ( Fig. 6a ); distolateral tooth of basicerite distinctly longer than stylocerite and overreaching middle of second segment of antennular peduncle rather shorter than latter; scaphocerite blade overreaching middle of third segment rather than 4/5 length of second; lateral spine of scaphocerite far beyond antennular peduncle by the length of third segment rather than almost overreaching second; superodistal margin on palm of large cheliped rounded, without distinctly projecting rather than with an subacute, straightforward tooth ( Figs 6b–d ); propodus of third pereiopod with ten spines along ventral margin rather than usual seven spines ( Fig. 6e ); extensor tooth of third pereiopod distinctly longer than the flexor tooth rather than subequal to latter ( Fig. 6f ). However, as only one specimen is present such characters, and those characters are always variable in this genus, it is tentatively put into the new species.

Figures

Fig. 4. Synalpheus brevrostrus sp. nov., male (tl 12.5mm) (MBM 284484). a–b. Frontal region. a. Dorsal. b. Lateral. c–d. Third maxilliped. c. Lateral. d. Tip, lateral. e–f. Major cheliped. e. Mesial. f. Lateral. g–h. Minor cheliped. g. Lateral. h. Chela, mesial. i. Second pereiopod, lateral. j–k. Third pereiopod. j. Lateral. k. Distal propodus and dactylus, lateral. l. Fourth pereiopod, lateral. Scale bars: a–c, e–j, l=1 mm; d, k=0.5mm.

Fig. 5. Synalpheus brevrostrus sp. nov., male (tl 12.5mm) (MBM 284484). a. Fifth pereiopod, distal propodus and dactylus, lateral. b. Abdomen, lateral. c. Second pleopod. d. Telson, dorsal. e. Right uropod, distolateral margin of exopod, dorsal. Scale bars=1mm.

Fig. 6. Synalpheus brevrostrus sp. nov., female (tl 14.8 mm) (MBM 284484). a. Frontal region, dorsal. b–d. Major cheliped. b. Mesial. c. Chela, lateral. d. Chela, mesial. e–f. Third pereiopod. e. Lateral. f. Distal propodus and dactylus. Scale bars: a–e = 1 mm; f=0.5mm.