Intesius brevipes, Padate Sherine Sonia Cubelio Masatsune Takeda, 2021

Intesius brevipes View in CoL sp. nov.

( Fig. 5 View Figure 5 )

Zoobank: urn:lsid:zoobank.org:act:8F73C88D-767D-4FFD-92E8-7BA05BD80F39

Material examined. Holotype: female (CL 34.5 mm, CW 42.2 mm) ( IO /SS/BRC/00296), west of Rutland Island , Andamans, Bay of Bengal, FORVSS stn. 334 (leg 1) 11, 11.35°N 92.39°E, 535 m, coll. Dr. S. Venu, HSDT ( CV), 11 January 2015. GoogleMaps

Description of holotype (female). Carapace sub-hexagonal with edges rounded off, 1.22 times wider than long; dorsal surface moderately convex anteriorly, gently convex transversely, microscopically granular, bearing short moderately dense tomentum. Regions demarcated by broad shallow grooves; gastric regions slightly prominent, separated from cardiac region by gastro-cardiac groove, metagastric region with pair of indistinct pits; branchial regions faintly demarcated, subdivided into anterior and posterior parts by broad lateral extension of gastro-cardiac groove; cardiac region as prominent as gastrics, separated from intestinal region by shallow submedian depression ( Fig. 5A View Figure 5 ).

Frontal margin narrow (0.28 times CW), gently deflexed, distinctly projecting, granular, medially notched giving it a bilobed appearance, separated from orbital margin by narrow sulcus ( Fig. 5B, C View Figure 5 ). Supraorbital margin concave, distinctly granular, interrupted by 2 distinct fissures into slightly elevated inner lobe and slightly depressed outer lobe; external orbital tooth short,minutely granular, separated from distinctly granular infraorbital margin by lateral fissure, inner infraorbital angle not extending to level of frontal margin ( Fig. 5B, C View Figure 5 ).

Anterolateral margins distinctly curved, divided into 4 teeth; first tooth shortest, bearing small granules, separated from the external orbital tooth by long granule; remaining teeth spinose — second tooth largest, bearing long granules, separated from first tooth by 2 long granules, and from third tooth by 2 short granules; third tooth subequal to second, bearing smaller granules, separated from fourth tooth by short granules; fourth tooth spinose, bearing 1 posterior granule ( Fig. 5B, C View Figure 5 ). Posterolateral margins gently convex, longer than anterolateral margins, converging posteriorly, anterior halves bearing small scattered granules ( Fig. 5A, B View Figure 5 ).

Antennules folding slightly obliquely. Basal antennal segment elongated rectangular, movable, located in orbital hiatus, f lagellum long, extending to second anterolateral tooth ( Fig. 5C View Figure 5 ).

Epistome small, wide, posterior margin elevated, interrupted by 3 notches ( Fig.5C View Figure 5 ). Endostomial ridges well developed posteriorly. Buccal frame subquadrate. Third maxillipeds sparsely setose, microscopically granular when denuded; ischium sub-rectangular, 1.57 times longer than wide, bearing distinct submedian longitudinal groove, cutting edge thickly setose; merus subquadrate, 0.92 times longer than wide, length 0.60 times ischial length, bearing strong oblique groove, antero-external angle slightly produced, rounded; palp articulating at antero-internally on merus; exopod slender, flagellum well developed ( Fig. 5C View Figure 5 ).

Female chelipeds unequal, heterochelous, sparsely setose.Right cheliped 1.69times CL. Merus triangular in cross-section,anterior,posterior margins and ventral surface microscopically granular, posterior margin with 4 proximal elongate granules and subdistal granular spine; carpus with distinctly granular inner margin, large granular spine at antero-internal angle, dorsal and outer surfaces microscopically granular; palm massive, microscopically granular, dorsal margin distinctly granular proximally; fingers microscopically granular, subequal to upper palm length, pollex bearing one indistinct longitudinal groove each on inner and outer margins, dactylus bearing two indistinct longitudinal grooves each on both margins, occlusal margin of dactylus with large proximal molar tooth fitting into socket on pollex, remaining margins with short dentition, distal tips curved, blunt, crossing in closed position ( Fig.5D View Figure 5 ). Left cheliped 1.32 times CL, ornamentation on merus and carpus similar to that of right cheliped, palm slender, with distinct elongate patch of granules on dorsal margin, outer surface bearing several rows of slightly smaller granules, inner surface with minute granules, ventral margin granular; fingers distinctly granular, longer than upper palm length, grooves similar to those on large cheliped, occlusal margins with short, sharp dentition, dactylus with patch of large granules on proximal one-fourth, distal tip fitting into depression on pollex in closed position ( Fig. 5E View Figure 5 ).

P2–P5 slender, microscopically granular, bearing longer setae (compared to carapace), their lengths 1.55, 1.76, 1.83, and 1.49 times CL, respectively. Length/width ratios for merus,carpus, propodus and dactylus are as follows:P2 = 4.67, 2.64, 3.41, and 7.86; P3 = 5.09, 2.29, 3.86, and 8.78; P4 = 5.02, 2.10, 3.90, and 9.26; P5 = 4.73, 1.96, 2.91, and 6.60. Pereopod meri bearing large granules on anterior margins, those on P5 largest, posterior margins with dense setation, surfaces sparsely setose; carpi with short dense setation on margins, surfaces sparsely setose; propodi with long dense setation on margins, surfaces sparsely setose; dactyli lanceolate, with long dense setation on margins, distal tips corneous ( Fig. 5A View Figure 5 ).

Thoracic sternum wide (width 0.56 times CW), sternites 1–3 and lateral half of sternite 4 microscopically granular, other portions smooth, covered with long silky setae; first 2 sternites completely fused, sternite 2 and 3 separated by sinuous suture, sternites 3–7separated by medially interrupted sutures, sternite 7 and 8 separated by complete suture, midline dividing posterior half of sternite 7 and entire 8 ( Fig. 5F View Figure 5 ).

Female pleon ovate, widest at somite 5 (width 0.35 times CW), with 6 free somites and telson, margins bearing dense long setation; somite 6 three times longer than wide; telson bluntly triangular, 1.45 times wider than long ( Fig. 5G View Figure 5 ). Gonopores large, ovate, extending across much of sternite 6, margins elevated by sternal prominence with oblique suture anteriorly ( Fig. 5H View Figure 5 ).

Color (Coloration preserved in formalin for ca. 5 years; recently transferred to 70 % ethanol). Light brown with slightly darker setae;large cheliped fingers dark brown on distal eight-tenths, small cheliped fingers dark brown on distal three-quarters.

Remarks. Specimens from the genus Intesius Guinot and Richer de Forges, 1981 are extremely rare, with only 18 specimens (including the present study). The genus is characterized by a squarish carapace with less prominent anterolateral teeth, male pleon with strongly ankylosed somites 3–5 and a mobile sixth somite ( Guinot and Richer de Forges, 1981a; Davie, 1998; Crosnier and Ng, 2004). Hitherto known only from the Western Pacific region (eastern Australia, New Caledonia, Norfolk Ridge, Philippines, French Polynesia, and Mariana Islands), the present observation is the first record of this genus from the Indian Ocean region. Intesius brevipes sp. nov. differs from the existing congeners in:

(1) sub-hexagonal carapace, CW/CL ratio 1.22 ( Fig. 5A View Figure 5 ) (vs. quadrangular in I. crosnieri,CW /CL ratio1.17 ( Davie, 1998: figs. 1A, 2A) and I. lucius, CW /CL ratio 1.15–1.17 ( Crosnier and Ng, 2004: figs. 3B, 7); subcircular in I. pilosus, CW /CL ratio 1.07–1.20 ( Davie, 1998: figs. 1B, 2B); rectangular in I. richeri, CW /CL ratio 1.26 ( Crosnier and Ng, 2004: figs. 2, 3A));

(2) relatively less dense short setation on carapace that does not conceal the edges ( Fig. 5A, B View Figure 5 ), similar to I. lucius ( Crosnier and Ng, 2004: figs. 3B, 7) (vs. dense setation in I. crosnieri ( Davie, 1998: figs. 1A, 2A), I. pilosus ( Davie, 1998: figs. 1B, 2B), and I. richeri ( Crosnier and Ng, 2004: figs. 2, 3A));

(3) distinctly projecting, bilobed frontal margin separated from the supraorbital margin by a distinct notch ( Fig. 5A–C View Figure 5 ) (vs. very distinctly projecting, strongly bilobed frontal margin separated from the supraorbital margin by a wider notch in I. pilosus ( Guinot and Richer de Forges, 1981a:pl.7, fig.1,1a; Davie, 1998: figs.1B, 2B); less distinctly projecting, weakly bilobed frontal margin separated from the supraorbital margin by a narrow notch in I. crosnieri ( Davie, 1998: figs. 1A, 2A), I. lucius ( Crosnier and Ng, 2004: figs. 3B), and I. richeri ( Crosnier and Ng, 2004: fig. 3A));

(4) slightly elevated inner supraorbital lobe ( Fig. 5A–C View Figure 5 ) similar to I. pilosus ( Davie, 1998: fig. 2B) (vs. indiscernible inner supraorbital lobe in the remaining species ( Davie, 1998: fig. 2A; Crosnier and Ng, 2004: fig. 3A–B));

(5) distinctly curved anterolateral margins ( Fig. 5A–C View Figure 5 ) (vs. moderately curved in its first part and then runs sub-parallel to longitudinal axis in I. pilosus ( Guinot and Richer de Forges, 1981a: pl. 7, fig. 1, 1a; Davie, 1998: figs. 1B, 2B); gently convex in I. lucius ( Crosnier and Ng, 2004: figs. 3B, 7); gently convex in its first part and then runs sub-parallel to longitudinal axis in I. crosnieri ( Davie, 1998: figs. 1A, 2A) and I. richeri ( Crosnier and Ng, 2004: figs. 2, 3A));

(6) more salient anterolateral teeth of carapace, particularly second and third teeth, bearing distinct granules ( Fig. 5A–C View Figure 5 ), similar to I. pilosus ( Davie, 1998: figs. 1B, 2B) (vs. moderately salient teeth bearing moderately large granules in I. crosnieri ( Davie, 1998: figs. 1A, 2A) and I. richeri ( Crosnier and Ng, 2004: figs. 2, 3A); less developed teeth bearing short granules in I. lucius ( Crosnier and Ng, 2004: figs. 2, 3A));

(7) palm of large chela distinctly granular proximally on dorsal margin ( Fig. 5D View Figure 5 ), similar to I. pilosus ( Davie, 1998: fig. 1B) (vs. finely granular dorsal margin and outer surface in I. richeri ( Crosnier and Ng, 2004: fig. 2); sharply granular dorsal and proximal portions of outer surface in I. crosnieri ( Davie, 1998: fig. 1A); granular dorsal and ventral margins in I. lucius ( Crosnier and Ng, 2004: fig. 7));

(8) pereopods 2–5 bearing relatively short setae ( Fig. 5A View Figure 5 ), similar to I. lucius ( Crosnier and Ng, 2004: fig. 7) and I. richeri ( Crosnier and Ng, 2004: fig. 2) (vs. long dense setae in I. crosnieri ( Davie, 1998: fig. 1A) and I. pilosus ( Davie, 1998: fig. 1B));

(9) relatively shorter P4–5 (pereopod length/ CL ratio 1.83 for P4, 1.49 for P5) with much more slender pereopod meri and carpi (length/width ratio 5.02 and 2.10 for P4, 4.73 and 1.96 for P5) (vs. longer P4–5 (pereopod length/ CL ratio 1.99–2.20 for P4, 1.78–1.97 for P5) with less slender meri (length/width ratio 3.88–4.48 for P4, 3.55–4.35 for P5) and carpi (length/width ratio 1.87–2.06 for P4, 1.48–1.83 for P5) in the remaining congeners).

Etymology. The species name is derived from the combination of Latin terms “brevis” and “pede” alluding to the relatively shorter P4–P5. Gender is masculine.

Distribution. Known only from the type locality in the southeastern Bay of Bengal, India at 535 m depth (present study).