Neogebicula johorensis, 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 : 128-130

Neogebicula johorensis , new species

( Figs. 1e–h , 14, 15)

CMBS material. Holotype: male (18/5.6) ( ZRC 2017.0956 ), sta. DR001, eastern Straits of Johor, W of Pulau Pengerang, MPA grid 0422, rectangular dredge, 6.7–7.6 m, coll. SC Lim, A Anker, H Wong, CK Chim et al., 25 March 2014 (0326DR1-AA01). Paratypes: 1 ov. female (21/6.3) ( ZRC 2017.0955 ), sta. DR108, eastern Straits of Johor, beside E Pulau Tekong and Pulau Pengarang, MPA grid 0422, rectangular dredge, 11.9–12.0 m, coll. SC Lim, A Anker, H Wong, CK Chim et al., 25 March 2014 (0422DR2-A108); 1 ov. female (21/6.6) ( ZRC 2017.0959 ), sta. DR235, east of Pulau Tekong , MPA grid 0524, rectangular dredge 13.1–14.7 m, coll . TMSI team, 5 November 2013 (SEA-1944); 1 male (14/3.9) ( ZRC 2017.0958 ), sta. DR264, Straits of Johor off Punggol, near Punggol jetty, MPA grid 5425, sandmud, rectangular dredge, 11.2–11.3 m, coll . TMSI team, 16 January 2014 (SEA-3482); 1 female (19/5.3 left first pereopod missing) ( ZRC 2017.0954 ), sta. DR333, W Straits of Johor, between Tuas and Pulau Merambong , MPA grid 3718, rectangular dredge, 7.2–7.5 m, coll . TMSI team, 11 February 2014 (SEA-4248) .

Diagnosis. Rostrum long. Lateral ridges of gastric region strongly projecting forward. Linea thalassinica extending to end of carapace. Ocular spine present, with or without hepatic spines. Proximal antennular peduncle article with ventral spine. Antennal peduncle with articles 3 and 4 each with ventral spine. Upper border of first pereopod propodus with several spines. Sixth pleomere as long as wide. Telson with small median spine.

Description. Rostrum long, triangular, 1.7 times as long as wide at base, twice as long as eyestalks, reaching to end of fourth article of antennular peduncle, narrowing anteriorly, rounded distally (Figs. 14a, b, i, k, 15a, b); dorsal surface of rostrum and gastric region with shallow median groove and low tubercles, extending onto gastric region of carapace, covered with short serrulate setae. Ventral surface of rostrum unarmed. Carapace with lateral ridges of gastric region strongly projecting forward, almost reaching end of eyestalks, anteriorly acute, separated from median gastric region by distinct longitudinal grooves; median gastric region setose, with low tubercles, diverging posteriorly; linea thalassinica extending well beyond cervical groove, reaching posterior border of carapace; anterolateral border of carapace with prominent ocular spine (may be absent in juveniles); cervical groove with (Fig. 14a, b, i, k) or without (Fig. 15a, b) hepatic spine.

Antennule (Fig. 15c) with first article of peduncle armed with distoventral spine; second article short; third article as long as first. Dorsal flagellum longer and thicker than ventral flagellum, as long as length of second and third article combined.

Antenna (Fig. 15d) with acute scaphocerite; second article of peduncle with ventral spine; third article fused with second one; fourth article with median ventral spine.

Epistome (Figs. 14a, j, 15a) with 2–3 spines.

Mandible (Fig. 15e, f) with large mesio-anterior tooth. First and second maxilla as illustrated (Fig. 15g, h). First maxilliped (Fig. 15i) with small epipod. Second maxilliped (Fig. 15j) with small epipod; exopod simple.

Third maxilliped (Fig. 15k) without epipod; exopod without flagellum, reaching mid-length of endopod merus; ischium with single spine proximally on mesial face (not shown).

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

First pereopods (Figs. 14c, d, k–m, 15l, m) subchelate, equal in size and shape, sexually dimorphic. Ischium with distoventral spine. Merus about 4.4 times as long as wide, with 5 spines on lower border in proximal 0.6 of meral length, and 1 dorsodistal spine. Carpus triangular, with 3 strong distal spines, 1 dorsal, 1 mesial, and 1 ventral, 1 small spine present dorsal to strong ventral spine; mesial face with 1 small spine. Propodus 2.6 (male) or 4.6 (females) times as long as wide; ventral border unarmed; dorsal border with 2 (male) or 4 (females) spines; fixed finger small in females (Figs. 14l, m, 15l, m), distinctly larger in males (Fig. 14c, d); dactylus 0.6–0.7 times as long as propodus, with 1 low proximal tubercle on ventral border and 2 tubercles on mesial face in males only, with dorsolateral plate in males and females.

Second pereopod (Figs. 14e, 15n) with median spine on coxa; ischium unarmed; merus 4.4 times as long as wide, with 1 proximal and 1 median spine on ventral border, as well as 1 distal spine on dorsal border; carpus with 1 distal spine on ventral border, and 1 median and 1 distal spine on dorsal border; propodus unarmed, 2.3 as long as wide; dactylus 0.7 length of propodus, narrowing distally.

Third pereopod (Figs. 14f, 15o) with ischium armed with distal spine ventrally; merus 3 times as long as wide, with 3 strong spines on ventral border; carpus with 1 strong distal spine ventrally and 1 small spine dorsally; propodus twice as long as wide, unarmed; dactylus as long as propodus, slender.

Fourth pereopod (Fig. 15p) simple, unarmed. Fifth pereopod (Fig. 15q) subchelate, unarmed.

Sixth pleomere (Fig. 14g) slightly longer than wide; telson broader than long, lateral margin broadest at proximal third; distal margin broadly truncate, with median spine; dorsal surface with longitudinal median groove in distal 0.6 of segment length.

Pleopod 1 absent in males, uniramous in females.

Uropodal protopod (Figs. 14g, h, 15r, s) with stout spine; exopod 1.8 times as long as broad, bearing sharp proximal spine, with truncate distal margin; endopod about twice as long as broad, shorter than exopod.

Embryos 570–640 µm in diameter.

Variations. The number of spines on the upper border of the first pereopod propodus ranges from 2 to 4, one male ( ZRC 2017.0958 ) lacks postocular spines, whereas two specimens ( ZRC 2017.0954 and ZRC 2017.0958 ) lack the hepatic spines. One ovigerous female ( ZRC 2017.0955 ) shows a male gonopore on the coxa of the left fifth pereopod, whilst another female ( ZRC 2017.0954 ) has a male gonopore on the right side .

Etymology. The new species is named after the type locality, the Straits of Johor between Singapore and Johor, Malaysia.

Distribution. Presently only known from the type locality.

Habitat. Sand-mud bottoms at depths of 6.7–14.7 m.

Remarks. Neogebicula johorensis , new species, is most similar to N. leptomorpha ( Sakai, 2006) from the Persian Gulf, with respect to the general shape of the rostrum and lateral ridges of the gastric region. The new species differs from N. leptomorpha (characters in parentheses) by 1) the presence of only one postocular spine (two postocular spines); 2) the proximal article of the antennular peduncle having a ventral spine (without spine); 3) the third and fourth articles of the antennal peduncle each armed with a ventral spine (unarmed); and 4) the posterior margin of the telson with a small median spine (without spine). The new species also shows some similarities with the eastern Atlantic N. contigua (Božić & de Saint Laurent, 1972) , differing from it (characters in parentheses) in 1) the presence of a large mesio-anterior tooth on the mandible (absent); 2) the antennular acicle being simple distally (with bifid tip); 3) the presence of several spines on the upper border of the first pereopod propodus (only one distal spine); and 4) the sixth pleomere being as long as wide (1.2 times longer than wide). In addition, both N. leptomorpha and N. contigua lack hepatic spines, whereas in N. johorensis , new species, they are present in three out of five specimens of the type series.

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].