Pulcratis amabilis, Mendoza Prema Mani Samuthirapandian Ravichandran, 2020

Pulcratis amabilis View in CoL n. sp.

( Figs. 1 View Figure 1 , 2A–D View Figure 2 , 3 View Figure 3 , 4 View Figure 4 )

Zoobank: urn:lsid:zoobank.org:act:9A6DEFC3–4899–4C3E–9D03–750B6DE7E559

Type material. Holotype, male, 15.3 × 11.3 mm ( CASAU), among bycatch of commercial near-shore trawlers (from depths of 50–100 m), Pazhayar fish port, Nagapattinam District , Tamil Nadu, India, coll. S. Ravichandran and M. Prema, Sep. 2018 . Paratypes: 1 female, 12.5 × 9.1 mm ( CASAU), same data as holotype; 1ovig.female,13.9 × 9.8 mm ( CASAU), from bycatch of commercial near-shore trawlers, Pazhayar fish port, Nagapattinam District , Tamil Nadu, India, coll. S. Ravichandran and M. Prema, 18 Mar. 2018 .

Comparative material. Pulcratis reticulatus Ng and Huang, 1997 : holotype, male, 15.0 × 10.6 mm ( ZRC 1997.0662 View Materials ), from commercial near-shore trawler, 100– 400 m depth, Tungkang fish port, Pingtung, Taiwan, coll. S.-H. Lai, 4 Aug. 1996; paratypes, 1 ovig. female, 14.0 × 10.1 mm ( ZRC 1997.0402 View Materials ), 1 female, 13.7 × 9.9 mm ( NTOU; ZRC 2001.0137 View Materials – long-term loan), from commercial near-shore trawler, 100–400 m depth, Tungkang fish port, Pingtung, Taiwan, coll. P.K.L. Ng, 5 Aug. 1996 .

Etymology. The specific epithet “ amabilis ”, L. lovely (adj.), is used, alluding to the beautiful pattern of the fresh colouration of the new species.

Description. Carapace ( Figs. 1A View Figure 1 , 2A View Figure 2 ) subhexagonal, broader than long, maximum width approximately 1.4 times length at midline; regions poorly defined, cervical groove narrow, gastric grooves indistinct or incomplete; 2M entire with inner margins mostly fused with 3M, only anterior tip of 3M bounded by thin grooves, the rest indiscernible, posterior part fused with 4M, 1P; 1L, 2L, 3L fused, bounded mesially by cervical groove, laterally by thin groove running from notch between second and third lobes of carapace anterolateral margin to cervical groove; dorsal surfaces smooth, slightly punctate, glabrous. Front barely projecting beyond level of orbits, slightly deflexed ventrally, bilobate, lobes separated by narrow fissure which connects with anterior tip of 3M, anterior margin of each lobe broadly convex in dorsal view.Supra-, infraorbital margins finely granular.Anterolateral margin gradually joining junction of supra- and infraorbital margins, widely arcuate, with sharp edge (subcristate) feebly divided into 4 very low lobes (including external orbital angle), each lobe with slightly convex margin, demarcated by short but distinct fissure, except for fissure between second and third lobe which joins with cervical groove; junction of antero-, posterolateral margins rounded; posterolateral margins almost straight, lined with numerous small, rounded granules; posterior margin of carapace distinctly sinuous, lined with small, rounded granules.

Eyes ( Fig. 1B View Figure 1 ) well developed, filling entire orbit, corneas large; distal part of ocular peduncle finely granulated. Basal antennal segment ( Fig. 2B, C View Figure 2 ) subrectangular, completely filling orbital hiatus; antennal flagellum not obstructed from orbital hiatus. Antennular fossa ( Fig. 1B View Figure 1 ) broadly ovate, antennules folding transversely, slightly obliquely. Third maxilliped ( Fig. 1B, C View Figure 1 ) merus subquadrate, slightly broader than long, with shallow submedian depression; ischium subrectangular, twice as long as broad, with submedian oblique sulcus, inner margin minutely crenulated; exopod stout, tapering distally, distal tip reaching anterolateral angle of merus, inner margin with subdistal triangular projection, flagellum present, well–developed. Epistome ( Fig. 1B View Figure 1 ) well developed, with 1 median fissure, 2 lateral fissures, dividing posterior margin into 4 lobes; margins of lateral lobes slightly convex, margins of mesial lobes slightly concave; central portion projecting slightly. Endostomial ridges indiscernible.

Male thoracic sternum ( Figs. 1C View Figure 1 , 2D View Figure 2 ) smooth, glabrous, pitted in some parts. Sternites1, 2 completely fused, triangular; distinct suture present between sternites 2/3; suture between sternites 3/4 medially interrupted with only lateral parts distinct as lateral notches, median part replaced with transversely curved furrow; sutures between sternites 4/5, 5/6, 6/7 interrupted medially in sterno-pleonal cavity; suture between sternites 7/8 complete. Sternite 4 broad, without externally visible median longitudinal line. Lateral margins of sternites 2–4 finely granulated. Exposed portions of sternites 5–7 smooth, broad, relatively short. Very small part of sternite 8 exposed between pleonal somite 2 and P5 coxa when pleon closed over sterno-pleonal cavity. Episternites 5–7 without shallow sulci separating them from main portion of respective sternites; episternite 7 broad, nearly as wide as anterior part. Sternopleonal cavity moderately deep; tubercles of sternopleonal lock placed anteriorly on sternite 5 near suture with sternite 4; within cavity median longitudinal line absent at level of sternites 4–6, present but interrupted on anterior level of sternite 7, complete at level of sternite 8.

Chelipeds (P1) ( Figs. 1A View Figure 1 , 2B View Figure 2 ) robust in both males and females, subequal, surfaces glabrous, smooth to slightly punctate or pitted; outer surface of chela finely punctate, with low row of granules on subventral margin which continues into and throughout length of fixed finger; fingers shorter than palm, dorsal margin of dactylus with distinct crest, cutting edges each with several large, sharp-edged, triangular teeth, fingertips pointed; dorsal margin of palm with well-developed transverse lamellar crest extending inward, lamellar crest broadest proximally near articulation with carpus; inner margin of carpus with well-developed lamelliform tooth which appresses on broadest part of transverse crest on palm; dorsal, ventral margins of merus strongly cristate.

Ambulatory legs(P2–P5)( Figs.1A View Figure 1 , 2C View Figure 2 )moderately long, robust, P3, P4 longest; merus distinctly cristate throughout entire length of dorsal margin, but only on proximal half of ventral margin; carpus with low dorsal crest; propodus with low dorsal, ventral crests; dactylus styliform, ending distally in simple chitinized claw, with well-defined longitudinal row of supple setae on flexor margin, 2 such rows on extensor margin (dorsal and ventral surfaces), but otherwise unarmed. Dactylo-propodal locking mechanism absent.

Male pleon ( Figs. 1C View Figure 1 , 2D View Figure 2 ) relatively broad, short, apex of telson reaching past imaginary transverse line connecting sterno-coxal condyles of P1; lateral margins distinctly concave; somite 1 slightly broader than somite 2; somites 3–5 completely fused without trace of sutures; somite 6 subquadrate, width-to-length ratio = 1.2, lateral margins slightly concave; telson subtriangular, basal width subequal to median length, lateral margins slightly concave, apex widely rounded.

G1 ( Fig. 3A, B, D, E View Figure 3 ) gently curving laterally from base to tip; with distinct papilliform process on inner subdistal margin; sternal surface with numerous short, sharp granules covering most of distal half of G1; tip lamelliform, with seven long, plumose setae. G2 ( Fig. 3C View Figure 3 ) short, sigmoid in shape; terminal segment about one-third length of subterminal segment. Penis emerging from gonopore on P5 coxa positioned anterior to coxo-sternal condyle.

Female morphology. Female morphology similar to that of male except for sexual characters. Female sternopleonal cavity setose at level of sternite 4; sternopleonal lock not well developed, tubercles absent in adult; vulvae moderately large, placed anteriorly on sternite 6, abutting against suture with sternite 5. Pleon subovate in outline, lateral margins distinctly convex; somites freely articulated, somites 3–6 progressively longer, somite 6 largest, lateral margins convex; telson semi-circular, lateral margins slightly convex, apex broadly rounded.

Color in life. Base color off-white, interspersed with orange, both forming reticulated patterns on carapace and chelipeds; fingers of chela off-white. Orange splotches on off-white ambulatory legs, forming banded pattern on ambulatory meri, carpi, and propodi. Ventral and internal surfaces off-white ( Fig. 4 View Figure 4 ). Live coloration very similar to that of P. reticulatus (cf. Ng and Huang 1997: fig. 8D, E).

Remarks. Pulcratis amabilis n. sp. is superficially similar to P. reticulatus Ng and Huang, 1997 , in the general form of the carapace and pereopods, as well as the live coloration. Several consistent morphological differences, however, distinguish P. amabilis n. sp. from P. reticulatus : (1) the carapace outline is much rounder, with the front less produced, the posterolateral margins straight, and the lateral angle marking the juncture of the antero- and posterolateral margins more rounded ( Figs. 1A View Figure 1 , 2A View Figure 2 ) [vs. carapace outline more fan-shaped, with the front more produced, the posterolateral margins slightly concave, and the lateral angle more acute in P. reticulatus ; Fig. 2E View Figure 2 (cf. Ng and Huang, 1997: figs. 8D, E, 10A, B)]; (2) the P1 carpus and the palm of the chela are relatively more inflated, and the proximo-internal angle (superior margin) of the palm is more rounded in P. amabilis ( Figs. 1A View Figure 1 , 2B View Figure 2 ) [vs. P1 carpus and palm less inflated, proximo-internal angle of palm more angular in P. reticulatus ; Fig. 2F View Figure 2 (cf. Ng and Huang, 1997: fig. 10E)]; (3) the ambulatory legs, particularly the meri and propodi, are shorter and stouter, sometimes slightly, as between the male holotypes of both species, or more distinctly, as between the female paratypes ( Figs. 1A View Figure 1 , 2C View Figure 2 ) [vs. ambulatory legs longer and more slender; Fig. 2G View Figure 2 (cf. Ng and Huang, 1997: figs. 8D, E, 11E)]; (4) the male telson is relatively broader, median length/basal width ratio = 1.04 ( Fig. 1C View Figure 1 , 2D View Figure 2 ) [vs. the male telson is relatively narrower in P. reticulatus , median length/ basal width ratio = 1.27; Fig. 2H View Figure 2 (cf. Ng and Huang, 1997: fig. 11C)]; (5) the G1 is relatively stouter, and more bent at the subdistal region, the subterminal papilliform branch is also stouter ( Figs. 3A, B, D, E View Figure 3 ) [vs. G1 more slender, relatively straighter or less curved at subdistal region, and the subterminal branch smaller in P. reticulatus (cf. Ng and Huang, 1997: fig.11F–H)]; and (6) the G2 terminal segment is slightly longer ( Fig. 3C View Figure 3 ) [vs. G2 terminal segment slightly shorter in P. reticulatus (cf. Ng and Huang, 1997: fig. 11I)].

Pulcratis amabilis n. sp. is the first representative of the genus to be recorded from the Indian Ocean, the only other species of the genus, P. reticulatus , being found in the South China Sea. Currently, the new species is only known from the waters off the coast of southeastern India (Tamil Nadu) in the Bay of Bengal, eastern Indian Ocean, and occurring at depths of 50– 100 m on muddy to silty bottoms.