Nanosesarma andersoni ( De Man, 1888 )

Nanosesarma andersoni ( De Man, 1888) View in CoL

( Figs. 1A View Figure 1 , 2 View Figure 2 , 7A, B View Figure 7 )

Sesarma andersoni De Man, 1888: 172 View in CoL , pl. 12, figs. 1–4. — Alcock, 1900: 418.

Sesarma (Parasesarma) andersoni View in CoL — Tesch, 1917: 129.

Nanosesarma andersoni View in CoL — Tweedie, 1950: 312, fig. 1d, e.

Nanosesarma (Beanium) andersoni View in CoL — Serène and Soh, 1970: 394.

Material examined. 10 males (CL: 4.4–4.8 mm, CW: 5.9–6.5 mm), 7 females (CL: 2.9–4.3 mm, CW: 4.0– 5.8 mm), LFSC.ZRC-185, India, Goa , Chapora Estuary (15°37’21”N 73°44’45”E), coll. Mithila Bhat, 13 April 2016 GoogleMaps .

Diagnosis. Carapace quadrangular, glabrous, 1.34 times wider than long;lateral margins slightly concave, subparallel posteriorly; dorsal surface covered with scattered pits, setal tufts and sparsely placed setae; protogastric and mesogastric regions delimited by inconspicuous grooves. External orbital tooth broadly triangular followed by rudimentary epibranchial tooth.Several oblique, low, setose granulated striations extending across branchial regions ( Figs. 1A View Figure 1 , 2A View Figure 2 ). Frontal margin wide, indistinctly bilobed, frontal lobes separated by shallow depression; 4 inconspicuous postfrontal lobes covered with setose patches, separated by longitudinal grooves ( Fig. 2A View Figure 2 ). Basal antennal article long ( Fig. 2B View Figure 2 ), reaching distal margin of first article.

Third maxillipeds with distinct rhomboidal gap when closed; ischium subrectangular, slightly longer than wide, 1.27 times longer than merus, with oblique setose ridge; merus subovate, 1.01 times as wide as long, with oblique setose ridge. Exopod slender, flattened, with long flagellum ( Fig. 2C View Figure 2 ).

Chelipeds subequal, massive; palm massive ( Fig. 2D View Figure 2 ), surfaces rugose, dorsal surface with two oblique pectinate crests and 4 or 5 oblique granular ridges ( Fig. 2E View Figure 2 ); outer surface pitted, covered with discreet granular striations on posterior half and scattered granules anteriorly, thin granular line on lower half commencing on pollex and extending posteriorly to carpal junction; inner surface sparsely granulated. Fingers (dactylus and pollex) massive, curved, with rounded spatulate tips, gaping when closed. Male cheliped dactylus short, with row of 13 or 14 small smooth transverse tubercles and proximal granules on dorsal surface; inner surface with proximal granular patch. Cutting edge of dactylus with 3 large and 2 small teeth, and large subdistal tooth, pollex with large subdistal tooth, followed by 3 small,1 large median teeth and 4 proximal teeth ( Fig. 2D View Figure 2 ).

P2–5, compressed, shorter than chelipeds. P2 short, P3 and P4 subequal, P5 short. P4 and P5 meri flattened, wider distally. Carpi ventral surfaces with median longitudinal granular ridge. P4 and P5 carpi and propodi without dense setae.Propodi about twice as long as wide, posterior margins with distal spine and few long bristles, ventral surface with inconspicuous oblique groove.Dactyli smooth, tip corneous, slightly curved, dorsal margin with 2 pairs of slender subdistal spines and ventral margin with 1 pair of subdistal spines ( Fig. 2F View Figure 2 ).

Male pleon narrow, bluntly triangular, surface pitted; lateral margins finely granulated, densely setose; telson 1.03 times as long as wide, 1.69 times as long as pleomere 6 ( Fig. 2G View Figure 2 ). Female pleon wide, rounded, pleomere 6 with concave distal margin; telson pentagonal, wider than long, partially sunken into distal margin of pleomere 6 ( Fig. 2H View Figure 2 ).

G1 long, straight, distal part corneous, flattened, slightly curved, medially notched, flanked by thick bristles, groove at base of tip extends along ventral surface to G1 ( Fig. 7A, B View Figure 7 ).

Remarks. The specimens examined in the present study resemble De Man’s (1888) description of his Sesarma andersoni , differing in the presence of a distinct subdistal spine on the anterior margin of P2–P5 meri. Morphological comparison with other Indian congeneric species is provided in Tab. 1.

Distribution. Nanosesarma andersoni was originally described from Mergui Archipelago ( De Man, 1888; Alcock, 1900), and later reported from Malaysia, Singapore ( Tweedie, 1950), Japan ( Komai et al., 2004), and India ( Trivedi et al., 2018). In India, it is known from Goa ( Dev Roy and Bhadra, 2008; present study), Kerala ( Devi et al., 2015), Tamil Nadu ( Ravichandran and Kannupandi, 2007), and Andaman and Nicobar Islands ( Dev Roy and Das, 2000).