Upogebia nithyanandan (Sakai, Türkay & Al Aidaroos, 2015)

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 : 484-492

Upogebia nithyanandan (Sakai, Türkay & Al Aidaroos, 2015)

Figs. 5–10

Kuwaitupogebia nithyanandan Sakai, Tu ̈rkay & Al Aidaroos, 2015: 1223–1227, figs 1, 2.

Upogebia balmaorum .— Dworschak & Poore 2018: 72 (in part), fig. 6.

Material examined. DABFUK/AR-AN 109, 1 ovigerous female (cl 4.6 mm), Mandapam, Palk Bay, Tamil Nadu, India, 9°17’40’’N, 79°7’38’’.E, subtidal, associated with unidentified sponge, 2 September 2018, coll. R. Ravinesh and A. Riyas; DABFUK/AR-AN 110–114, 2 males (cl 3.7, 4.3 mm), 3 ovigerous females (cl 5.0, 5.3, 5.6 mm), same data; DABFUK/AR-AN 115–117, 1 male (cl 5.7 mm), 2 ovigerous females (cl 3.4, 7.9 mm), same locality, 2 March 2019, coll. R. Ravinesh and A. Riyas.

Description of specimens from India. Rostrum ( Fig. 5 A–D) very short, broadly triangular to triangular, not reaching distal corneal margins; anterior margin with 3–5 pairs of small, conical spines, terminal pair contiguous; dorsal surface faintly grooved medially, obscured by tuft of dense setae, followed by faint median elevation on gastric region; ventral surface unarmed, but with setal tuft distally. Anterior carapace ( Fig. 5A, D ) with lateral gastric ridges not projecting anteriorly, but each terminating in small spine followed by 9–10 small 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 distinct shoulder along cervical groove ( Fig. 5D ). Linea thalassinica extending from anterolateral notch along cervical groove, but not extending onto posterior carapace.

Pleon fairly flattened dorsoventrally, widest at pleomeres 3 and 4 in females. Pleomere 2 longest. Pleomere 6 ( Fig. 5E ) about 2.1 times as wide as long; lateral margins obtusely angular; posterior margin slightly convex, smooth, laterally with small rounded projection, delimited by short longitudinal suture. Telson ( Fig. 5F ) subrectangular, about 1.2 times as wide as long; dorsal surface with faint longitudinal ridges laterally, proximal part slightly elevated, though not forming distinct carina; lateral margins faintly convex; posterior margin also faintly convex, unarmed.

Ocular peduncle ( Fig. 5A, D ) stout, widened basally, unarmed, not constricted at base of cornea; cornea terminal, pigmented, corneal width less than basal width of ocular peduncle.

Antennular peduncle ( Fig. 5D ) not reaching distal margin of antennal peduncle. Article 1 subequal in length to distal two articles together, unarmed ventrally; statocyst lobe slightly inflated. Article 2 shortest, cup-like, unarmed. Article 3 subcylindrical, unarmed. Dorsal flagellum distinctly longer than peduncle, consisting of about 15 articles; ventral flagellum slightly longer than dorsal flagellum, consisting of about 16 articles, each bearing several short to long setae on distal margin.

Antennal peduncle ( Fig. 5D ) 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 se- tae and conspicuous distal spine. Article 4 with oblique row of setae continuing from ventral margin of article 2/3. Article 5 (ultimate article) longer than article 4. Scaphocerite absent, but membranous area between article 2/3 and article 4 evident.

Epistome anterolateral projection prominent, compressed laterally, laterally curved, unarmed, partially fused with anterolateral carapace ( Fig. 5D ).

Mouthparts not dissected, though external observation made. Mandible with small 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. 8A ) with moderately slender endopod, extending as far as distal end of antennal peduncle; ischium to dactylus with thick long setae on ventral (or flexor) margins, ischium proximally with 2 small curved spines on mesial surface ( Fig. 8B ); dactylus nearly straight, 1.1 times as long as propodus, tapering to blunt tip; exopod falling slightly short of distal margin of merus, flagellum subequal in length to basal article, consisting of about 10 articles; epipod absent.

Male pereopod 1 ( Fig. 6 ) moderately stout, chelate. Coxa unarmed. Ischium unarmed. Merus 2.0 times as long as high, with arcuate, unarmed dorsal margin; ventrolateral margin sinuous with shallow concavity in distal third, armed with row of about 8–15 small spines or denticles, increasing in size proximally; ventromesial margin with row of numerous long setae. Carpus cup-shaped, becoming wider distally, less than half length of palm, armed only with 1 tiny spine at flexor distal angle; lateral surface ventrally with some setae along distal margin; mesial surface with oblique row of numerous long setae. Palm about 1.9 times as long as high, moderately compressed laterally, unarmed; dorsal margin in lateral view slightly convex; dactylar condyle on lateral face weakly developed; lateral surface with scattered tufts of short setae in superior half; mesial face also with scattered tufts of short to moderately long setae on superior half (setae increasing in length distally) and longitudinal row of long setae adjacent to ventral margin; ventral margin slightly sinuous; fixed finger subequal in length to dactylus, slightly curved, terminating acutely, occlusal margin smooth, unarmed. Dactylus about 0.5 times as long as palm, slightly curved, terminating in acute 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 on midline); occlusal margin with 1 or 2 small blunt teeth at about midlength.

Female pereopod 1 ( Fig. 7 ) slightly more slender than male pereopod 1. Ischium with 2 small denticles on ventrolateral margin. Merus 2.1 times as long as high, with row of 10–18 small denticles or spines on ventrolateral margin. Palm 2.0 times as long as wide; lateral surface with numerous scattered short to moderately short setae on superior half; mesial surface with scattered tufts of long setae on superior half. Dactylus about 0.5 time as long as palm, setation similar to that of male pereopod 1; occlusal margin with 1 low obtuse tooth slightly proximal to midlength.

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

Pereopod 2 ( Fig. 8C ) 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 subrectangular, distinctly longer than carpus; dorsal (extensor) margin gently convex, flexor proximal margin angular. Dactylus tapering to minute corneous spine, about 0.5 times as long as propodus.

Pereopod 3 ( Fig. 8D, E ) coxa unarmed; gonopore present in females, absent in males. Ischium short, unarmed. Merus spineless, dorsal margin slightly sloping distally. Carpus slightly widened distally, spineless; extensor margin with row of setae. Propodus extensor margin gently convex, with numerous setae; lateral surface with longitudinal row of short setae superior to midline, field of short setae mixed with minute spiniform setae on inferior to midline; flexor margin with numerous setae in distal two-third, in particular distal setae longer, forming prominent cluster. Dactylus 0.6 times as long as propodus, slightly sinuous, tapering to apical corneous spinule; extensor margin with row of small corneous, erect spines over entire length; lateral surface with field of short setae on superior half; flexor margin with comb-like minute spiniform setae in distal 0.4.

Pereopod 4 ( Fig. 8F, 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; unarmed; extensor margin slightly convex, with dense setae; lateral surface with row of short setae superior to midline, field of short setae and minute spiniform setae inferior to midline; flexor margin also slightly 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 small corneous spines over entire length; flexor margin with comb-like, minute, spiniform setae in distal half.

Pereopod 5 ( Fig. 8H, I ) subchelate. Coxa with gonopore on either side in males. Merus 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 thick setae, bearing minute spiniform setae proximomesially. Dactylus about 0.4 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 C (cf. Ngoc-Ho 1981), composed of deeply divided, slender lamellae on either side of rachis.

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

Uropod ( Fig. 5F, G ) with both endopod and exopods reaching posterior margin of telson when posteriorly directed. Protopod with small spine on posterior margin. Endopod trapezoidal with rounded posterior angles, widened distally, 1.1 times as long as wide, distal margin truncate; inner margin slightly sinuous, outer margin faintly convex; dorsal surface with distinct median and lateral carinae. Exopod roundly subtriangular, widened distally, slightly longer than endopod, 1.1 times as long as wide, bearing 1 small spine near base; outer and inner margins slightly convex, distal margin broadly rounded, junction between outer and distal margin rounded; dorsal surface with 2 well delimited carinae.

Eggs relatively large, 1.0 × 1.0 mm.

Variation. Intraspecific variation is seen in the shape of the rostrum and the spination of the ventral margin of the pereopod 1 merus. Of the seven specimens examined, the rostrum falls far short of the distal corneal margins (cf. Fig. 5A, B ), but in one male specimen (cl 4.3 mm, DABFUK/AR-AN 111; cf. Fig. 5C ), it nearly reaches this margin. Spines or tubercles on the ventral margin of the pereopod 1 merus are eight to 18 in the number, and often differ between left and right. The pereopod 1 is slightly sexually dimorphic, differing in the setation of the dorsolateral surface of the palm (more strongly setose in females than in males; the shape and armature are generally similar between sexes) (cf. Figs. 6 , 7 ).

Colour in life. Body and appendages entirely whitish; corneas darkly pigmented, reflective; eggs yellowish ( Figs. 9 , 10A, B ).

Distribution and habitat. The type material was collected at Al Khiran, Kuwait, at sublittoral depths of 3–4 m ( Sakai et al. 2015). The present material extends the geographical range of the species to southern India. No precise information on habitat was given in the original description ( Sakai et al. 2015), but Dr. Peter C. Dworschak kindly informed us that some of original labels attached to the type specimens contain information that the specimens were associated with sponges. The present specimens were all found in burrows in colonies of an unidentified sponge ( Fig. 10A ) as well.

Remarks. Sakai et al. (2015) established a new family Kuwaitupogebiidae Sakai, Türkay & Al Aidaroos, 2015 for their new taxon Kuwaitupogebia nithyanandan Sakai, Türkay & Al Aidaroos, 2015 , but after reexamination of the type material, Dworschak & Poore (2018) concluded that the taxon described by Sakai et al. (2015) was identical with Upogebia balmaorum Ngoc-Ho, 1990, originally described from the Seychelles. Dworschak & Poore (2018) demonstrated that characters used by Sakai et al. (2015) to diagnose the new family and new genus were not real at all. They synonymized Kuwaitupogebiidae and Kuwaitupogebia Sakai, Türkay & Al Aidaroos, 2015 with Upogebiidae Leach, 1814 and Upogebia Leach, 1814 , respectively. We concur with their family and genus synonymy.

The present specimens from southern India were initially identified as Upogebia balmaorum following the view by Dworschak & Poore (2018). However, detailed examination revealed that our specimens differ from the original description of U. balmaorum (cf. Ngoc-Ho 1990) in the following particulars: (1) the rostrum falls short of the distal corneal margins in all of the Indian specimens (cf. Fig. 5 A–D), while reaching the distal corneal margins in U. balmaorum ( Ngoc-Ho 1990: fig. 1a, b); (2) the antennal scaphocerite is absent in the Indian specimens ( Fig. 5D ), whereas it is present in U. balmaorum ( Ngoc-Ho 1990: fig. 1b); (3) the pereopod 1 merus is relatively stouter in the Indian specimens ( Figs 6A , 7A ) than in U. balmaorum ( Ngoc-Ho 1990: fig. 1c); (4) the occlusal margins of both fingers of the pereopod 1 are quite smooth except for one or two small teeth on the dactylus in the Indian specimens ( Figs 6A, C , 7C ), whereas those margins each bears a row of small teeth or denticles in U. balmaorum ( Ngoc-Ho 1990: fig. 1c, d, f); (5) the extensor margin of the pereopod 1 dactylus is smooth in the Indian specimens ( Figs 6A, C , 7C ), but denticulate to whole extent and provided with a fine longitudinal groove in U. balmaorum ( Ngoc-Ho 1990: fig. 1c, f).

In these regards, the Indian specimens better agree with the original description of Kuwaitupogebia nithyanandan by Sakai et al.’s (2015) and the account of the type material of this taxon by Dworschak & Poore (2018) (as Upogebia balumaorum ). Dworschak & Poore (2018) disclosed that the development of the rostrum is variable in the type material of Kuwaitupogebia nithyanandan , illustrating the female paratype that has a triangular rostrum just reaching the distal corneal margins (fig. 6E). In spite of the variation, however, the weak development of the rostrum is still useful as a diagnostic marker. With regard to the antennal scaphocerite, Sakai et al. (2015) did not specifically mention on the presence of absence of it in the type material of Kuwaitupogebia nithyanandan , although the given illustration ( Sakai et al. 2015: 1 B) does not depict the antennal scaphocerite. The absence of the antennal scaphocerite in the holotype of Kuwaitupogebia nithyanandan has been confirmed by examination of photographs kindly provided by Dr. Dworschak. Sakai et al. (2015: 1226) stated that the dactylus of the pereopod 1 was unarmed on the occlusal margin (as “prehensile margin”), but Dr. Dworschak kindly informed us that there are one or two teeth on that margin in the type specimens. Furthermore, in addition to the characters discussed above, it is remarkable that in our Indian specimens and the type material there is no linea thalassinica on the posterior carapace, whereas in U. balmaorum , the posterior carapace bears a posterior extension of the linea thalassinica reaching nearly to the posterodorsal margin (Dr. P.C. Dworschak, personal communication). Consequently, we propose to reinstate Sakai et al ’s (2015) taxon as a valid species of Upogebia , i.e., U. nithyanandan , and refer our specimens to this species.

Ngoc-Ho (2008) identified provisionally specimens from the Dampier Archipelago, Western Australia, and Madagascar as U. balmaorum , pointing out some minor differences in the pereopod 1 fingers armature from the type material. Ngoc-Ho’s (2008) specimens differ from our Indian specimens in the rostrum reaching the distal corneal margins ( Ngoc-Ho 2008: fig. 5A, B), fewer ventral spinules or denticles on the pereopod 1 merus (fig. 5D), the presence of a short row of small denticles on the occlusal margin of the pereopod 1 dactylus (fig. 5D, E), and more slender pereopod 1 merus (fig. 5D). These differences would seem to suggest that our Indian specimens are not conspecific with the specimens from Western Australia and Madagascar, but the status of the latter specimens remains to be reassessed.

Figures

FIGURE 5. Upogebia nithyanandan (Sakai, Türkay & Al Aidaroos, 2015), A, B, D–G, ovigerous female (cl 7.9 mm), DAB- FUK/AR-AN 117; C, male (cl 4.3 mm), DABFUK/AR-AN 111. A, anterior carapace and ocular peduncles, dorsal view (setae partially omitted); B, rostrum, dorsal view (setae omitted); C, rostrum and ocular peduncles, dorsal view (setae omitted); D, anterior carapace and cephalic appendages, right lateral view; E, pleomere 6, dorsal view; F, telson, dorsal (perpendicular) view; G, left uropod, dorsal (perpendicular) view

FIGURE 6. Upogebia nithyanandan (Sakai, Türkay & Al Aidaroos, 2015), male (cl 5.7 mm), DABFUK/AR-AN 115. A, left pereopod 1, lateral view; B, same, detail of ventral armature of merus, lateral view; C, same, carpus and chela, mesial view.

FIGURE 7. Upogebia nithyanandan (Sakai, Türkay & Al Aidaroos, 2015), ovigerous female (cl 7.9 mm), DABFUK/AR-AN 117. A, right pereopod 1, lateral view; B, same, carpus and chela, mesial view; C, fingers, mesial view (setae omitted).

FIGURE 8. Upogebia nithyanandan (Sakai, Türkay & Al Aidaroos, 2015), ovigerous female (cl 7.9 mm), DABFUK/AR-AN 117. A, left maxilliped 3, lateral view; B, same, proximal part of ischium, ventral view (setae omitted); C, right pereopod 2, lateral view (setae omitted); D, right pereopod 3, lateral view; E, same, distal part of propodus and dactylus, mesial view (setae partially omitted); F, right pereopod 4, lateral view; G, same, distal part of propodus and dactylus, mesial view (setae partially omitted); H, right pereopod 5, lateral view; I, same, propodus and dactylus, extensor view.

FIGURE 9. Upogebia nithyanandan (Sakai, Türkay & Al Aidaroos, 2015), ovigerous female (cl 7.9 mm), DABFUK/AR-AN 117, habitus in lateral view. Photo taken by Tin-Yam Chan.

FIGURE 10. Upogebia nithyanandan (Sakai, Türkay & Al Aidaroos, 2015). A, living specimen (male cl 4.3 mm; DABFUK/ AR-AN 111) inhabiting burrow in an unidentified sponge; B, living specimen (ovigerous female cl 5.6 mm; DABFUK/AR-AN 114) removed from sponge.