Upogebia hexaceras ( Ortmann, 1894 )

Komai, Tomoyuki, Ravinesh, Raveendhiran, Riyas, Abdul & Kumar, Appukuttannair Biju, 2020, New records of two sponge-associated species of Upogebia Leach, 1814 from southern India (Decapoda: Gebiidea: Upogebiidae): U. hexaceras (Ortmann, 1894) and U. nithyanandan (Sakai, Tu ̈ rkay & Al Aidaroos, 2015) resurrected from the synonymy of U. balmaorum Ngoc-Ho, 1990, Zootaxa 4747 (3), pp. 477-494 : 478-484

Upogebia hexaceras ( Ortmann, 1894)

Figs 1–4

Gebia (Gebiopsis) hexaceras Ortmann, 1894: 23 , pl. 3 fig. 1.

Upogebia (Calliadne) hexaceras .—de Man 1928: 81, pl. 8 fig. 11–11(f).

Upogebia (Upogebia) hexaceras .— Sakai 1982: 23, pls A4, C4.

Upogebia hexaceras .— Ngoc-Ho 1990: 979, fig. 8.— Dworschak 2019: 28.

Upogebia darwinii .—Sakai 2006: 101 (part), fig. 16.— Naderloo & Türkay 2012: 19 (part).

Not Upogebia (Calliadne) hexaceras . — Poore & Griffin, 1979: 299, fig. 50 [= Upogebia darwinii ( Miers, 1884) ].

Material examined. DABFUK/AR-AN 107, 1 ovigerous female (cl 4.9 mm), Vellapatti fish landing beach, Tamil Nadu, India, 08°51.21’N, 78°09.59’E, subtidal, associated with unidentified sponge, 2 March 2019, coll. R. Ravinesh and A. Riyas; DABFUK/AR-AN 108, 1 ovigerous female (cl 7.3 mm), same data.

Description of specimens from India. Rostrum ( Fig. 1A, B ) short, rounded in dorsal view, not reaching distal corneal margins; anterior margin with 3 pairs of small, conical spines, terminal pair narrowly spaced; dorsal surface nearly flat, without median groove, partially obscured by numerous short setae; ventral surface unarmed, but with numerous setae laterally. Anterior carapace ( Fig. 1A, B ) with lateral gastric ridges not projecting anteriorly, but each terminating in small, obliquely erect spine followed by 8 small, obliquely erect spines or tubercles decreasing in size posteriorly; median part of anterior carapace flanked by very shallow longitudinal grooves running along gastric lateral ridges and having scattered small tubercles or spines extending onto rostrum and tufts of short setae on either side of midline, unarmed median area broadened posteriorly; anterolateral margin unarmed; postorbital region unarmed; pterygostomial margin rounded. Posterior carapace with slightly developed shoulder along cervical groove ( Fig. 1A ). Linea thalassinica interrupted, anterior part extending from anterolateral notch of carapace along cervical groove, convex against cervical groove, posterior part extending from posterior to cervical groove to posterodorsal margin of carapace.

Pleon fairly flattened dorsoventrally (artificially deformed because of preservation). Pleomere 6 ( Fig. 1C, D ) 1.6 times as wide as long; ventrolateral margin with 2 spine-like projections; posterior margin broadly rounded, minutely denticulate, laterally with small rounded projections, delimited by short obliquely longitudinal suture. Telson ( Fig. 1C, E ) subrectangular, narrowing posteriorly, about 1.2 times as wide as long; dorsal surface with faint longitudinal ridges laterally (bearing few minute denticles), proximal part elevated, forming distinct carina, bearing row of spinules or granules; lateral margins nearly straight, bearing obtuse lobe proximally; posterior margin gently convex, unarmed.

Ocular peduncle ( Fig. 1A, B ) stout, slightly widened basally, unarmed, slightly constricted at base of cornea; cornea terminal, pigmented, corneal width less than basal width of ocular peduncle.

Antennular peduncle ( Fig. 1B ) not reaching distal margin of antennal peduncle. Article 1 slightly longer than distal two articles together, unarmed ventrally; statocyst lobe slightly inflated. Article 2 shortest, about half-length of article 3, unarmed.Article 3 slender than article 2. Dorsal flagellum distinctly longer than peduncle, consisting of about 18 articles; ventral flagellum slightly longer than dorsal flagellum, consisting of about 14 articles, each bearing several short to long setae on distal margin.

Antennal peduncle ( Fig. 1B ) consisting of 4 articles (article 2 and 3 fused). Article 1 stout, unarmed; excretory pore surrounded by short setae. Article 2/3 fused unarmed dorsally; ventral margin with row of numerous long setae, but spineless. Article 4 with oblique row of setae continuing from ventral margin of article 2/3. Article 5 (ultimate article) shorter than article 4. Scaphocerite small, rounded. Flagellum subequal in length to carapace; each article with some setae on distal margin, decreasing in number and length distally.

Epistome anterolateral projection ( Fig. 1B ) prominent, compressed laterally, laterally curved, unarmed, partially fused with anterolateral carapace.

Mouthparts not dissected, though external observation made. Mandible with conspicuous tooth on distolateral end of incisor process. Maxillule and maxilla without distinctive features. No epipods on maxilliped 1. Maxilliped 2 with small epipod. Maxilliped 3 ( Fig. 4A ) with endopod moderately slender, extending as far as distal end of antennal peduncle; ischium to dactylus with thick long setae on ventral (or flexor) margins, ischium with 1 small hooked-spine on mesial surface proximally ( Fig. 4B ), other articles spineless; dactylus nearly straight, 1.1 times as long as propodus, tapering to rounded tip; exopod falling slightly short of merus distal margin, flagellum subequal in length to basal article, consisting of 2 articles; epipod absent.

Female pereopod 1 ( Figs. 2A, C ; 3A, C ) chelate. Coxa unarmed. Ischium with row of 4 small tubercles on ventral margin. Merus 2.3–2.9 times as long as high, dorsal margin gently arcuate, unarmed; ventrolateral margin nearly straight, having row of 8 or 9 tiny spines or tubercles, increasing in size proximally ( Figs. 2B ; 3B ); ventromesial margin with row of numerous long setae. Carpus cup-shaped, becoming wider distally, less than half length of palm, spineless; lateral surface almost glabrous; mesial surface with short oblique row of numerous long setae proximodorsally. Palm 1.7–2.1 times as long as high, moderately compressed laterally, unarmed; dorsal margin in lateral view slightly convex; dactylar condyle on lateral face poorly developed; lateral surface with median row of short setae connecting with vertical row of setae near base of fixed finger, otherwise nearly glabrous with few individual or tufts of shorter setae; mesial face with numerous short to long setae on superior half and adjacent to base of fingers and longitudinal row of long setae arising on ridge adjacent to ventral margin; ventral margin slightly sinuous; fixed finger slightly shorter or subequal in length to dactylus, slightly curved, terminating acutely, occlusal margin with row of tiny, rounded teeth ( Figs. 2D ; 3A, D ). Dactylus about 0.5 times as long as palm, slightly curved, terminating in subacute tip, crossing fixed finger distally when closed; extensor margin with row of stiff setae; lateral surface with 2 rows of short stiff setae on either side of midline; mesial surface also with 2 rows of short to moderately short setae (1 row adjacent to extensor margin and 1 row adjacent to occlusal margin) and median row of blunt tubercles ( Fig. 3D ); occlusal margin with 1 obsolescent tooth proximal to midlength.

Pereopods 2–5 moderately slender, decreasing in length toward posterior.

Pereopod 2 ( Fig. 4C ) reaching base of pereopod 1 dactylus, with setation typical for genus. Coxa unarmed. Ischium to dactylus all spineless. Merus straight, dorsal margin slightly sloping distally. Carpus slightly widened distally. Propodus narrowing distally, distinctly longer than carpus; dorsal (extensor) margin slightly convex, flexor proximal margin angular. Dactylus tapering to corneous tip, about 0.4 times as long as propodus.

Pereopod 3 ( Fig. 4D, E ) coxa unarmed; gonopore present in females. Ischium short, unarmed. Merus spineless, dorsal margin faintly sinuous. Carpus slightly widened distally, spineless; extensor margin with row of sparse setae. Propodus extensor margin slightly convex, with numerous setae; lateral surface with longitudinal row of short setae superior to midline, field of short setae on inferior to midline; flexor margin with numerous setae in distal one-third, in particular distal setae longer, forming prominent cluster. Dactylus 0.6 times as long as propodus, lance-shaped, tapering to apical corneous spinule; extensor margin with row of 7 small corneous, blunt spines over entire length; lateral surface with field of short setae on superior half; flexor margin with comb-like minute spiniform setae in distal half.

Pereopod 4 ( Fig. 4F, G ) coxa unarmed. Ischium short, unarmed. Merus spineless; lateral surface with sparse setae adjacent to ventral margin. Carpus slightly widened distally, unarmed. Propodus subequal in length to carpus; extensor margin slightly convex, with numerous setae; lateral surface with row of short setae superior to midline, field of short setae inferior to midline; flexor margin faintly convex, with row of mixture of long flexible setae and bristle-like setae. Dactylus slightly sinuous, shorter than propodus, tapering to apical corneous spinule; extensor margin with row of blunt corneous spines; flexor margin with comb-like minute, spiniform setae in distal half.

Pereopod 5 (Fig. H, I) subchelate. Merus not constricted near base. Carpus slightly widened distally, with short setae on distal half of extensor margin. Propodus slightly longer than carpus, slightly arcuate, with short, distally rounded fixed finger; extensor surface naked along midline, flanked by field of setae, bearing minute spiniform setae proximomesially. Dactylus about 0.3 times as long as propodus, strongly curved, rounded terminally, slightly twisted; extensor surface with numerous long setae; terminal margin with row of minute spiniform setae.

Arthrobranchs of type B (cf. Ngoc-Ho 1981), composed of slender lamella on either side of rachis.

Pleopods 1 uniramous in females. Pleopods 2–5 generally similar, moderately broad.

Uropod ( Fig. 1F ) with both endopod and exopods reaching posterior margin of telson when posteriorly directed. Protopod with small spine on posterior margin, directed mesially. Endopod trapezoidal with rounded posterior angles, widened distally, almost as long as wide, distal margin truncate; inner margin slightly sinuous, outer margin nearly straight; dorsal surface with distinct submedian and lateral carinae. Exopod roundly subtriangular, widened distally, slightly longer than endopod, nearly as long as wide, bearing 1 small spine near base; outer margin gently convex, inner margin nearly straight, distal margin broadly rounded, bearing minute denticles, junction between outer and distal margin rounded; dorsal surface with 2 well delimited longitudinal carinae.

Eggs about 0.6 × 0.7 mm.

Variation. Notable variation is seen in the shape of the pereopod 1, although the two specimens examined are both female. The entire pereopod 1 is more slender in the larger specimen than in the smaller specimen. Spines or denticles on the ventral margin of the pereopod 1 merus are more conspicuous in the smaller specimen. The ventral margin of the palm is more strongly sinuous in the larger specimen.

Colour in life. Not available.

Distribution and habitat. Previously known from Thursday Island, Torres Strait, Australia (type locality), Indonesia, Philippines, and Persian Gulf; 0.75–32 m ( Ortmann 1894; Sakai 1982; Ngoc-Ho 1990; Dworschak 2019). The occurrence in India is now confirmed. The two specimens lived in burrows constructed in an unidentified sponge.

Remarks. In his revision of the Indo-West Pacific Upogebiidae, Sakai (1982) treated U. hexaceras as a valid species, although he suggested that it was not significantly different from U. darwinii ( Miers, 1884) . Ngoc-Ho (1990) considered U. hexaceras as a valid species and outlined the diagnostic features differentiating U. darwinii , U. hexaceras and U. octoceras Nobili, 1904 . On the other hand, U. hexaceras was considered as a junior synonym of U. darwinii by Sakai (1993, 2006) and Sakai & Türkay (2014), which has been rebutted by Ngoc-Ho (2008). Dworschak (2019) also recognized U. hexaceras as a valid species. Considering the characteristic armature of pleomere 6, consisting of two lateral projections and minutely denticulate posterior margin, combined with the minutely spinulose dorsal transverse carina on the telson and the unarmed carpus and palm of pereopod 1, it seems reasonable to recognize U. hexaceras as a valid species.

The two specimens from southern India are referred to Upogebia hexaceras because of the following features ( Ngoc-Ho 1990): rostrum with three pairs of marginal spines; pleomere 6 with two conspicuous lateral projections and minutely denticulated posterior margin; telson subtrapezoidal, with conspicuous, minutely denticulated proximal transverse carina; pereopod 1 merus bearing row of small spines or tubercles on ventral margin; pereopod 1 carpus unarmed on distomesial margin; pereopod 1 palm unarmed on mesial side of dactylar base; pereopod 1 fixed finger with row of small blunt teeth on occlusal margin.

The rostra of the present specimens are rather short, not reaching the distal corneal margins. The illustration by De Man (1928: pl. 8 fig. 11) shows the rostrum just reaching the distal corneal margins. In the specimen illustrated by Ngoc-Ho (1990: fig. 8g), the rostrum distinctly overreaches the distal corneal margins. Thus it is suggested that the rostrum length somewhat varies in U. hexaceras .

Henderson (1893) recorded Upogebia darwini (as Gebiopsis) from Rameswaram, Tuticorin and Cheval Par. Tuticorin is very close to the locality where the present specimens were collected. Considering the previous taxonomic confusion regarding U. darwini and allied taxa (see above), it is likely that the material studied by Henderson (1893) might actually be U. hexaceras .

Figures

FIGURE 1. Upogebia hexaceras (Ortmann, 1894), ovigerous female (cl 7.3 mm), DABFUK/AR-AN 108.A, anterior carapace, dorsal view (setae omitted); B, anterior carapace and cephalic appendages, left lateral view; C, pleomere 6, dorsal view; D, telson, dorsal view; E, pleomere 6 and telson, lateral view; F, left uropod, dorsal (perpendicular) view.

FIGURE 2. Upogebia hexaceras (Ortmann, 1894), ovigerous female (cl 7.3 mm), DABFUK/AR-AN 108. A, right pereopod 1, lateral view; B, same, detail of ventral armature of merus; C, same, carpus and chela, mesial view; D, same, fixed finger, lateral view (setae omitted); E, same, dactylus, mesial view (setae omitted).

FIGURE 3. Upogebia hexaceras (Ortmann, 1894), ovigerous female (cl 4.9 mm), DABFUK/AR-AN 107. A, left pereopod 1, lateral view; B, same, detail of ventral armature of merus; C, same, carpus and chela, mesial view; D, same, fingers, mesial view (setae omitted).

FIGURE 4. Upogebia hexaceras (Ortmann, 1894), ovigerous female (cl 7.3 mm), DABFUK/AR-AN 108. A, left maxilliped 3, lateral view; B, same, proximal part of ischium, ventral view (setae omitted); C, left pereopod 2, lateral view; D, left pereopod 3, lateral view; E, same, distal part of propodus and dactylus, mesial view (setae partially omitted); F, left pereopod 4, lateral view; G, same, distal part of propodus and dactylus, mesial view (setae partially omitted); H, left pereopod 5, lateral view; I, same, propodus and dactylus, extensor view.