Upogebia singaporensis, Dworschak & Anker, 2022

Dworschak, Peter C. & Anker, Arthur, 2022, Axiidea (Crustacea: Callianassidae, Callichiridae and Ctenochelidae) and Gebiidea (Upogebiidae) collected during the Comprehensive Marine Biodiversity Survey of Singapore, Raffles Bulletin of Zoology 70, pp. 108-133 : 123-126

Upogebia singaporensis , new species

( Figs. 1d , 11, 12)

CMBS material. Holotype: female (16/5.4) ( ZRC 2017.0951 ), sta. IT120, Pulau Hantu, intertidal, coll. KS Koh, TS Ahyong, K Tilbrook et al., 31 May 2013 (SS-3982). Paratypes: 1 female (13/4.8) ( ZRC 2017.0952 ), 1 juvenile (12/3.9) ( ZRC 2017.0950 ), sta. SB055, Kusu Island , coral rubble brushing, ~ 4 m, coll. HH Tan, S De Grave et al., 25 May 2013 (SS-1631); 1 juvenile (11/3.6) ( ZRC 2017.0953 ), sta. TB172, Straits of Singapore near Kusu Island, 1°12.180′N 103°52.125′E, consolidated marine clay, 94.5–100 m, coll. B Richer de Forges et al., 5 June 2013 (SS-4522) .

Comparative material. Upogebia srilankaensis Sakai, 2006 , holotype, male (24/7.4) ( SMF 30213), Sri Lanka, Matara , Weligama Bay (5°59.074′N 80°19.695′E), coll. O. Löw-Beer, 3 December 1912.

Diagnosis. Rostrum elongate, with four strong dorsal spines, without infrarostral spine. Lateral ridges of gastric region weakly developed, with obtuse distal tooth and posterior to that tooth 9–11 tubercles. Postocular spine absent. Pleonal sternites unarmed. First pereopod chelate, merus lacking subdistal dorsal spine and bearing row of obtuse ventral teeth; carpus bearing 1 strong distoventral and 1 strong distodorsal spine. Meri of third to fifth pereopods unarmed.

Description of female holotype. Rostrum (Fig. 11a, b) elongate, twice as long as broad at base, setose on dorsal surface, bearing 1 pair of distal and 1 pair of subdistal dorsal spines, lacking infrarostral spine; lateral ridges of gastric region slightly protruding laterally, bearing row of 8–9 unequal tubercles; mid-dorsal area of gastric region with scattered tubercles. Cervical groove lacking spines. Postocular spine absent. Eyestalk stout, reaching to midlength of rostrum, unarmed. Linea thalassinica reaching to posterior end of carapace.

Antennular peduncle (Figs. 11a, 12a) shorter than antennal peduncle; articles unarmed, second article short, third article elongate; flagella of same length, dorsal thicker than ventral, as long as peduncle.

Antennal peduncle (Figs. 11a, 12b) overreaching rostrum by distal margin of penultimate article; articles unarmed; scaphocerite weakly developed.

Epistome (Fig. 11a) rounded, unarmed. Mandible (Fig. 12c, d) without mesio-anterior tooth. First and second maxilla as illustrated (Fig. 12e, f). First maxilliped (Fig. 12g) without epipod. Second maxilliped (Fig. 12h) with epipod. Third maxilliped (Fig. 12i) without epipod; exopod simple (without flagellum) distally, reaching almost to end of endopodal merus.

First pereopod (Fig. 11c–f) chelate; coxa and basis unarmed. Ischium bearing 1 subterminal spine on ventral margin. Merus bearing row of 13–14 obtuse thick spines on ventral margin, increasing in size to mid-length of merus, distal ones diminishing in size; dorsal margin unarmed. Carpus triangular, lateral surface bearing longitudinal ventral carina; 1 strong, mesially directed dorsal spine, 1 small median spine, and 1 prominent dorsal spine present on distal margin; 6 small spines present on mesial surface. Palm 2.1 times as long as high; upper border unarmed, with several low tubercles on inner dorsal surface; lower border keeled with 7–8 tubercles proximally; 3 tubercles present on lower inner surface proximally. Fixed finger 0.3 times length of palm, with low denticles on cutting edge. Dactylus (Fig. 11d, f) with proximal tooth on cutting edge.

Second pereopod (Fig. 11h) unarmed; merus 5.3 times as long as wide; propodus 2.8 times as long as wide. Third and fourth pereopods (Fig. 11i, k) simple; dactylus with comb on lower border and 5 spaced corneous spines on upper border (Fig. 11j, l). Fifth pereopod (Fig. 11m) subchelate; dactylus curved, with corneous tip (Fig. 11n).

Telson (Fig. 11p) slightly longer than maximal width; dorsal surface with U-shaped concavity, latter with denticulate transverse carina. Uropodal endopod broadened, about as long as telson, with somewhat truncate, slightly convex distal margin; uropodal exopod broadened, about as long as endopod, with prominent spine proximally (Fig. 11o).

Arthrobranchs of type A, one pair each on third maxilliped, and first to fourth pereopods.

Variations. The number of spines on the lower border of the first pereopod merus ranges from 9 (juvenile 11/3.6) to 15 (female 13/4.8) on the right side and between 9 and 14 on the left side. The teeth on the lower border of first pereopod propodus differ between sides and range from 3 to 8.

Etymology. Named after the type locality, the Straits of Singapore.

Distribution. Only known from the Straits of Singapore.

Habitat. Upogebia singaporensis , new species, has a wide bathymetric distribution: one female (16.1/5.42) was collected in the intertidal zone at Pulau Hantu (together with U. ancylodactyla ); two specimens came from coral brushings at 4 m depth at Kusu Island, and one from consolidated clay at a depth of 94.5– 100 m.

Remarks. The new species is similar to Upogebia srilankaensis Sakai, 2006 in possessing a long rostrum with two pairs of prominent dorsal spines (1 distal and 1 subdistal pair); in the shape of the spines on the lower border of the first pereopod merus; in having upper and lower spines on the first pereopod carpus; and in the general shape of telson and uropods. However, U. singaporensis , new species, differs from U. srilankaensis (characters in parentheses) by 1) the absence of a ventral spine on the first article of the antennal peduncle (present); 2) the slightly produced lateral ridges of the gastric carapace region (not protruding); 3) the dorsal spine on the mesial surface of the first pereopod carpus prominent (much smaller); 4) the ventral margin of the first pereopod propodus with several tubercles proximally (without tubercles); and 5) the fixed finger of the first pereopod entire (with a deep concavity on the occlusal margin).

A re-examination of the holotype of U. srilankaensis (Fig. 13) revealed some inconsistencies and omissions in the original description by Sakai (2006): 1) the antennal peduncle has a distinct, acute scaphocerite; 2) the first pereopod palm has a row of three tubercles proximally on the lower mesial surface (only one visible in lateral view in Sakai, 2006: fig. 23D); 3) there are two spines on the upper mesial face of the first pereopod carpus; 4) the left first pereopod has two spines ventrally on the ischium; and 5) the third and fourth pereopod dactyli have a comb on the lower border and a row of corneous spines on the upper border, as in the present new species (not illustrated nor mentioned by Sakai, 2006).

Figures

Fig. 1. Specimens, habitus (dorsal and/or ventral views), showing colouration in life: a, Gourretia sinica Liu & Liu, 2010, female (23/5.3) (ZRC 2017.0947); b, Karumballichirus karumba (Poore & Griffin, 1979), female (32/7.6) (ZRC 2018.0526); c, Aqaballianassa brevirostris Sakai, 2002, ovigerous female (28/5.6) (ZRC 2017.0948); d, Upogebia singaporensis, new species, female holotype (16/5.4) (ZRC 2017.0951); e, f, Neogebicula johorensis, new species, male holotype (18/5.6) (ZRC 2017.0956); g, h, same, ovigerous female paratype (21/6.3) (ZRC 2017.0955); i, j, Wolffogebia phuketensis Sakai, 1982, male (37/10.3) (NHMW 26036). Not to scale. [Photographs by AA].