Aniptumnus bijoyi, Hari & Hershey & Mendoza, 2022

Hari, P. Praved, Hershey, N. Regina & Mendoza, Jose Christopher E., 2022, On two species of Aniptumnus Ng, 2002 (Crustacea: Brachyura: Pilumnidae) from India, with a description of a new species from the coast of Kerala, Zootaxa 5214 (2), pp. 261-272 : 263-270

Aniptumnus bijoyi sp. nov.

Figs. 1–4

Type material. Holotype: male, 10.7 by 7.1 mm ( CUSAT / SBN /HRJ/1), Marine Science Boat Jetty, School of Marine Sciences, Cochin University of Science and Technology , Kochi, Kerala, SW India, 9°57′50.8104″N, 76°16′56.7834″E, coll. P.H. Praved & N. R. Hershey, 29 Sep. 2021 (fixed in 5% formalin).

Paratypes: 6 males, 8.1 by 5.9 mm to 10.5 by 7.1 mm, 4 females, 7.6 by 5.6 mm to 8.7 by 5.7 mm ( CUSAT / SBN /HRJ/2–11), same data as holotype ; 1 male, 10.1 by 6.7 mm, 1 female, 8.2 by 5.1 mm ( ZRC 2022.0137 ), same data as holotype ; 1 male, 5.0 by 3.2 mm ( ZRC 2019.1091 ), intertidal rocky area with algae, just outside School of Marine Sciences, Cochin University of Science and Technology , Kochi, Kerala, SW India, coll. N. R. Hershey , Feb. 2019 .

Comparative material. Aniptumnus quadridentatus ( De Man, 1895) . Singapore: 30 males, 5.5 by 3.9 mm to 13.9 by 9.5 mm , 18 females, 5.6 by 4.0 mm to 12.3 by 8.0 mm, 5 ovig. females, 8.2 by 5.8 mm to 10.4 by 7.0 mm ( ZRC 2018.0639 ), off Pulau Ubin , floating fish farm (kelong FC12E), among clumps of Perna viridis attached to submerged ropes, coll. JCE Mendoza, I Iesa & MD Safaruan, 7 Nov. 2017 ; 1 female, 14.0 by 8.9 mm, 1 ovig. female, 10.7 by 7.3 mm ( ZRC 2011 . 0683), Changi Point, on Paku Buoy (fouling), coll. SLM Teo , FS Tan, SC Lee & JL Ong, 2010 ; 6 males, 5.8 by 4.0 mm to 11.1 by 7.4 mm, 3 females, 6.1 by 4.2 mm to 7.7 by 5.1 mm ( ZRC 2021.0421 ), off Pulau Ubin , floating fish farm (kelong E63C), coll. BY Lee, 3 Sep. 2020 . Malaysia: 8 males, 9.5 by 6.5 mm to 11.0 by 7.3 mm , 3 females, 8.9 by 5.6 mm to 9.7 by 6.2 mm, 2 ovig. females, 8.6 by 5.8 mm, 9.3 by 6.0 mm ( ZRC 1992.10966 – 10978 ), Perak, Lumut, coll. H. Singh, 1989 .

Aniptumnus vietnamicus Ng & Clark, 2008 . Vietnam: Holotype, male, 8.3 by 6.1 mm ( ZRC 1970.1.10.1), Nhatrang Bay , coll. R. Serène, 10 Apr. 1966; paratype, female, 9.6 by 6.6 mm ( ZRC 1970.1.10.2), same data as holotype.

Type locality. India: Kochi, Kerala; Kollam-Kottapuram National Waterway No. 3, near Marine Science Boat Jetty, CUSAT-School of Marine Sciences.

Diagnosis. Carapace subhexagonal, broader than long (CW/CL: 1.4–1.5); dorsal surface finely granular with small patches of granules on gastric, branchial regions, sparsely setose with tufts of longer setae on front and on granular patches of gastric, branchial regions. Anterolateral, posterolateral margins subequal in length. First tooth of carapace exorbital margin lobiform, nearly flat, second tooth broadly triangular, denticulate, third and fourth teeth acutely triangular, slightly curved. Orbits without fissures, notch at junction of supra- and infraorbital margins absent. Third maxilliped merus distolateral angle produced, rounded. Chelipeds unequal; major chela external surface sparsely setose, finely granular with scattered larger granules; minor chela more densely setose, with rows of sharp conical granules. P5 basis-ischium with conical tubercles on disto-posterior margin forming comb-like structure; merus posterior margin with sharp conical tubercles proximally. G1 slender, sinuous, distal tip with short, narrow, scoop-shaped apical lobe. G2 small, one-fifth length of G1, terminal, subterminal segments uniformly curving mesially. Penis emerging from anterior tip of coxosternal condyle of P5 coxa.

Description of male holotype. Carapace ( Figs. 1 , 2A ) transversely subhexagonal, broader than long (CW/ CL = 1.5), dorsal regions poorly defined, dorsal surface convex longitudinally and transversely, generally smooth with patches of fine granules on gastric, branchial regions, sparsely setose, most setae aggregated around granular areas. Front moderately projecting, slightly deflexed ventrally, bilobed, lobes divided by median notch, frontal margins uniformly, moderately convex without any distinct lateral lobe or tooth, lined with small granules, with poorly defined row of long setae submarginally. Supraorbital margin concave in dorsal view, granular, without fissures; junction with infraorbital margin without notch. Anterolateral and posterolateral margins similar in length; anterolateral margin granular, sparsely setose, divided into 4 teeth; exorbital angle low, not prominently projecting, separated from first tooth by shallow concavity; first tooth wide, flat or weakly convex lobe, separated from second tooth by small notch; second tooth broadly subtriangular, posterior margin much longer than anterior, apex directed toward anterior; third, fourth teeth similar, acute, apices pointed obliquely; posterolateral margin nearly straight, finely granulate, convergent posteriorly; posterior margin slightly convex, with raised row of fine round granules. Suborbital, sub-branchial and pterygostomial regions finely granular.

Orbits ( Fig. 2C ) transversely ovate; eyes large, filling entire orbital cavity, ocular peduncle stout, unarmed, corneas pigmented. Infraorbital margin granular, without fissures, mesial suborbital tooth absent. Antennular fossae subrectangular, antennules robust, folding transversely and obliquely. Basal antennal article short, subrectangular, filling orbital hiatus; flagellum long, exceeding orbit. Proepistome narrow, smooth. Central region of posterior border of epistome projecting medially, notched laterally. Endostome with prominent oblique ridge on either side. Third maxillipeds (mxp3; Fig. 2B ) finely granular externally, sparsely setose; palps thick, subcylindrical; merus subquadrate, distolateral angle projecting, rounded; ischium subrectangular, about 1.5 times as long as merus, with submedian sulcus, submarginal row of long setae mesially; basis subtriangular, separated from ischium by clear suture; exopod elongate, not tapering, distal tip reaching to three-quarters lateral margin of merus, flagellum long, well developed.

Male thoracic sternum ( Fig. 2D, E ) moderately broad, surface smooth, punctate. Sternites 1, 2 completely fused, forming broad triangle abutting ischia of third maxillipeds. Sternites 2, 3 separated by distinct suture (suture 2/3); sternites 3, 4 almost completely fused, demarcated only laterally by notches that continue mesially as shallow groove. Sutures 4/5, 5/6 interrupted medially. Sutures 6/7, 7/8 complete. Sternopleonal cavity ( Fig. 2E ) deep, anterior tip on sternite 4, just reaching imaginary transverse line formed by coxo-sternal condyles of P1 coxae. Tubercle of sternopleonal lock (press-button) anteriorly positioned on sternite 5, closer to suture with sternite 4. Median line complete at level of sternite 7, 8 only; short portion visible on posterior part of sternite 4 within sternopleonal cavity. Small, median, triangular decalcified area at junction between sternite 6, 7. Sternite 8 ( Fig. 2G ) not visible when pleon folded against thoracic sternum, positioned beneath the posterolateral corner of the pleonal somite 2.

Chelipeds (P1; Figs. 1 , 3A, B ) distinctly heterochelous. Anterior margins of basis-ischium, merus lined with subconical granules. External surface of the carpus granular, inner distal angle projecting as sharp tooth bordered with large tubercles. External surface of major palm ( Fig. 3B ) finely granular, with rows of larger, widely spaced granules near upper margin, also proximally. Fingers thick, noticeably shorter than palm, cutting margins with small teeth; fixed finger with short longitudinal groove on the external surface; dactylus longer, slightly curved, upper margin granular proximally. Minor palm ( Fig. 3A ) smaller, external surface setose, with large, sharp, conical granules, sometimes arranged in rows along long axis of palm; fingers slender, shorter than palm, cutting margins minutely dentate; fixed finger slightly deflexed; dactylus with longitudinal ridge on external surface, upper margin granular proximally.

Ambulatory legs (P2–P5; Figs. 1 , 3C ) moderately long, slender, setose, broad surfaces finely granular; P3 longest, merus-to-dactylus length 1.02 times CW), P5 shortest, merus-to-dactylus length 0.78 times CW. Basisischium unarmed except in P5, where posterodistal margin armed with prominent spines, forming comb-like structure. Merus subrectangular, elongate, anterior margin slightly convex, finely granulate, subdistal tooth present but effaced, posterior margin, slightly convex, finely granulate except in P5, which has several spines and conical tubercles proximally, decreasing in size until mid-length of merus. Carpus subrectangular, widening distally, anterior margin convex, posterior margin straight, dorsal surface without granular ridge. Propodus subrectangular, anterior, posterior margins slightly convex. Dactylus mostly straight, tapering distally, ending in curved chitinous claw; dactylo-propodal lock absent.

Male pleon ( Fig. 2D, F, G ) smooth, with all somites and telson freely articulating, lateral margin concave. Somite 1 much wider than long, anterior margin deeply concave, posterior margin slightly sinuous, lateral margins straight. Somite 2 much wider than long, anterior margin slightly concave, posterior margin strongly convex, lateral margins rounded. Somite 3 widest, transversely subhexagonal, lateral margins strongly convex. Somites 4–6 trapezoidal, gradually decreasing in width, with somite 6 narrowest, lateral margins straight to slightly concave. Telson triangular with rounded apex, lateral margins convex, median length 0.83 times basal width.

G1 ( Fig. 3D, E, G, H ) moderately long, slender, sinuous; margins lined with simple or plumose setae; distal part curved, ending in small scoop-shaped apical lobe, with stiff, simple spiniform subdistal setae; G2 ( Fig. 3F ) short, about one-fifth length of G1,terminal, subterminal segments uniformly curving mesially. Penis ( Fig. 2E ) emerging from anterior portion of coxosternal condyle of P5 coxa.

Female. The female morphology is similar to the male in all non-sexual aspects. Thoracic sternum relatively wider than that of male. Pleon ( Fig. 4A ) much wider, lateral margin convex, setose, external surfaces smooth; somites and pleon freely articulating; somite 3 widest. Telson large, subtriangular, apex rounded, lateral margins convex, median length subequal to basal width. Vulvae ( Fig. 4B ) mesially on thoracic sternite 6, abutting suture with sternite 5; semicircular in outline.

Live colouration. Fresh specimens are usually covered with a copious amount of sediment and debris when collected such that they need to be gently brushed clean to expose the natural coloration ( Fig. 1 ). The dorsal carapace and pereopods are generally tan or pale brown with patches and scattered spots of dark purple that are sometimes surrounded by lighter areas of purple. The setae covering them are similarly tan. The thoracic sternum, pleon, and ventral and internal surfaces are creamy white. The fingers of the chelae are brown with pale tips.

Etymology. The species is named in honor of Prof. S. Bijoy Nandan, Dean, Faculty of Marine Sciences, Cochin University of Science and Technology, for his significant contributions in the field of marine biology and wetland ecology in India.

Habitat and ecology. Aniptumnus bijoyi sp. nov. was found in larger numbers on encrusting communities such as clumps of mussels ( Mytella strigata and Perna virdis ), submerged structures, and roots of decaying aquatic weeds ( Eichornia crasipes ) in the School of Marine Science Jetty. Their occurrence was also noticed in the other parts of the Cochin Estuary. The species is usually abundant during the pre-monsoon period (January–May) in sites with a salinity range of 10–28 ppt and depth range of 1– 6 m. The habitat is muddy to clayey-silty, the pH of the sediment generally ranged from 7.5–8, and the average redox potential from -135 to -275mV. The total carbon of the sediment ranged from 30–35 g /kg and the total organic carbon ranged from 1.9–2.5 %. Aniptumnus bijoyi sp. nov. was observed to occur together with the brachyuran crabs Thranita crenata (Rüppell, 1830) , Neorhynchoplax alcocki (Kemp, 1917) , and N. demeloi (Kemp, 1917) .

Remarks. Aniptumnus bijoyi sp. nov. is morphologically most similar to A. quadridentatus ( De Man, 1895) and A. neolaevis (Deb, 1985) comb. nov. in the general form of the carapace, thoracic sternum, male pleon, and pereopods (cf. Ng 2002; Trivedi et al. 2021; Widyastuti & Rahayu 2022). The new species is easily distinguished from A. nefissurus and A. vietnamicus by the general form of the carapace, by its less granular major chela and by the G1 morphology (cf. Garth & Kim 1983: fig. 11; Ng & Clark 2008: figs. 19–21).

Aniptumnus bijoyi sp. nov. can most easily be distinguished from A. neolaevis in the following features: the tuberculation on the posteroproximal margin of the P5 merus is much more prominent, with the conical tubercles being larger ( Fig. 3C ) (vs. tuberculation, while present, is much reduced, tubercles are smaller in A. neolaevis , cf. Trivedi et al. 2021: fig. 8A); pleonal somite 2 of the male is considerably wider, and consequently, thoracic sternite 8 is completely concealed when the pleon is folded and locked onto the thoracic sternum ( Fig. 2E ) (vs. pleonal somite 2 much narrower, thoracic sternite 8 exposed in A. neolaevis ; cf. Trivedi et al. 2021: fig. 8D); and the distal tip of the G1 has a short, projecting, scoop-shaped apical lobe ( Fig. 3D, E, G, H ) (vs. apical lobe absent in H. neolaevis ; cf. Deb 1999: fig. 4; Trivedi et al. 2021: fig. 10G, H).

Aniptumnus bijoyi sp. nov. differs from A. quadridentatus in the following morphological features: the carapace outline is generally wider and shorter, with anterolateral and posterolateral margins nearly identical in length, and the posterolateral margins slightly convex ( Fig. 2A ) (vs. carapace outline narrower and longer, with posterolateral margins longer than anterolateral margins, and posterolateral margins straight in A. quadridentatus ; Fig. 5A ; cf. De Man 1897: pl. 13 fig. 6; Takeda 2001: figs. 2, 3A; Widyastuti & Rahayu 2022: fig. 3A); on the carapace anterolateral margin, the first tooth after the exorbital angle is much reduced, more like a flat lobe ( Fig. 2A ) (vs. first tooth lobiform and low but with distinct, denticulate convex protuberance in A. quadridentatus ; Fig. 5A ; cf. Takeda 2001: fig. 3B; Ng 2002: fig. 1A); the dorsal surface of the carapace is widely convex transversely in the frontal view ( Fig. 2C ) (vs. dorsal surface more acutely convex transversely in frontal view in A. quadridentatus ; Fig. 5C ; cf. Widyastuti & Rahayu 2022: fig. 3B); there is no notch on the orbit at the junction of the supraorbital and infraorbital margins ( Fig. 2C ) (vs. present in A. quadridentatus ; Fig. 5C ); the distolateral angle of mxp3 merus is more rounded and projecting ( Fig. 2B ) (vs. less projecting in A. quadridentatus ; Fig. 5B ; cf. Ng 2002: fig. 1B; Widyastuti & Rahayu 2022: fig. 3C); in the male, thoracic sternite 8 not visible when the pleon is folded and locked onto the thoracic sternum ( Fig. 2G ) (vs. sternite 8, sometimes exposed, small but distinct, positioned in between the lateral margin of the pleonal somite 2 and the mesial margin of the coxo-sternal condyle of the P5 coxa in A. quadridentatus ; Fig. 5E ); and the distal tip of the G1 has a narrower apical lobe ( Fig. 3D, E, G, H ) (vs. apical lobe wider in A. quadridentatus ; Fig. 5F–I ; cf. Takeda 2001: fig. 3H, I; Ng 2002: fig. 1F, G).

Figures

FIGURE 1. Aniptumnus bijoyi sp. nov., paratype, male, 10.1 by 6.7 mm (ZRC 2022.0137), Kochi, Kerala, SW India. Dorsal habitus and live coloration.

FIGURE 2. Aniptumnus bijoyi sp. nov., holotype, male, 10.7 by 7.1 mm (CUSAT/SBN/HRJ/1), Kochi, Kerala, SW India. A, carapace, dorsal view; B, left third maxilliped, external view; cephalothorax and chelipeds, frontal view; D, anterior thoracic sternum and telson, ventral view; E, thoracic sternum and sternopleonal cavity, ventral view; F, pleon, ventral view; G, pleonal somites 1–3, posteroventral view. Scale bars: 2.0 mm (A, C); 1.0 mm (B, D–G).

FIGURE 3. Aniptumnus bijoyi sp. nov., holotype, male, 10.7 by 7.1 mm (CUSAT/SBN/HRJ/1), Kochi, Kerala, SW India. A, minor cheliped, external view; B, major cheliped, external view; C, right P5, dorsal view; D, E, left G1 (D, pleonal/ventral view; E, mesiosternal/mesiodorsal view); F, left G2, sternal/dorsal view; G, H, distal tip of left G1 (G, pleonal/ventral view; H, mesiosternal/mesiodorsal view). Scale bars: 1.0 mm (A–C); 0.5 mm (D–F); 0.25 mm (G, H).

FIGURE 4. Aniptumnus bijoyi sp. nov., paratype, female, 8.2 by 5.1 mm (ZRC 2022.0137), Kochi, Kerala, SW India. A, detached pleon, external view; B, thoracic sternum and vulvae, ventral view. Scale bars: 1.0 mm (A, B).

FIGURE 5. Aniptumnus quadridentatus (De Man, 1895), male, 11.1 by 7.4 mm (ZRC 2021.0421), off Pulau Ubin, Singapore. A, carapace, dorsal view; B, third maxillipeds, external view; C, cephalothorax, frontal view; D, anterior thoracic sternum and pleon, ventral view; E, pleonal somites 1–3 and thoracic sternite 8, posteroventral view; F–I, left G1 (F, pleonal/ventral view; G, mesiosternal/mesiodorsal view; H, lateral view; I, sternal/dorsal view). Scale bars: 2.0 mm (A, C); 1.0 mm (B, D, E); 0.5 mm (F–I).