Etisus sp. A

Etisus sp. A View in CoL ( Fig. 13A–H View Fig )

Material examined: 1 ñ, NMNS 8772-41, 5.2 × 3.6, Jialulan, Taitung County, coll. Y.-W. Tzeng, 23 July 2013.

Description: Carapace ( Fig. 13A–C View Fig ) transversely ovate, width to length ratio about 1.45, dorsal area slightly convex transversely, longitudinally; dorsal surface well covered by microscopic granules, except 3M, 4M, L, P, R regions, stout long setae scattered at anterior regions and lined with grooves of posterior regions; regions well defined, divided by wide, deep grooves; subhepatic, pterygostomial regions granulate, long setae scattered. Front strongly advanced, about 0.33 times as long as carapace width, slightly deflexed ventrally, margin granulate, outer angles well marked and separated by V-shaped notch from orbital rim; divided into 2 lobes by shallow V-shaped notch, continuing posteriorly as deep median groove on dorsal carapace, each lobe with 2 subequal lobules. Anterolateral margin convex, granulate, divided into 4 lobes, separated from each other by wide V-shaped notches; first lobe highest, gradually reducing in height thereafter; third lobe base widest, anterior margin slightly shorter than posterior; fourth lobe smallest, posterior margin continuous with carapace posterolateral margin. Posterolateral margin slightly longer than anterolateral margin, central region slightly concave.

Orbits ( Fig. 13A–C View Fig ) suboval, margins granulate, continuous; inner pre-supraorbital tooth prominent, supraorbital margin with low tooth adjacent to exorbital tooth, separated from pre-supraorbital tooth and from exorbital tooth by V-shaped notch; exorbital tooth sharply triangular. Eyes well developed, eyestalks short, stout, corneas large. Antennular fossae transversely oval; antennules folding transversely. Basal article of antenna short, triangular; flagellum freely entering orbital hiatus, long, tip far exceeding exorbital tooth.

Third maxillipeds ( Fig. 13D View Fig ) subrectangular, length to greatest width ratio about 2.22; palp tapering distally, articles subcylindrical; merus subquadrate, length to greatest width ratio about 0.67, anterolateral angle rounded, slightly projecting, anterior margin straight, cristate, granulate, stout setae scattered, external surface with patched granules, long, thin setae scattered; ischium subrectangular, about 1.83 times longer than merus, sulcate submedially, mesial margin cristate, serrated, lined with submarginal setae, external surface scattered with long setae; exopod stout, margins slightly convex, tapering slightly toward distal end, distal end slightly convex.

Thoracic sternum margins cristate; sternites 1, 2 fused, external surface smooth; sternites 2, 3 and 3, 4 separated by deep and shallow sutures, respectively; sternite 4 with row of long setae at anterior margin, lateral margins clearly convex; sutures 4/5, 5/6 joining toward median longitudinal axis of thoracic sternum; vulvae oval, without operculum, located mesial third of sternite 5.

Left cheliped ( Fig. 13E, F View Fig ) moderately robust. Meri moderate long, distal end clearly extending beyond carapace anterolateral margin in dorsal view. Carpi dorsal margin granulate, subdistal end with large tubercle, internal distal angle with one row of 3 small spines. Palm dorsal margin granulate, with small tubercle proximally, external surface granules compacted, forming perpendicular lines or stripes, proximal end of lower margin with large acetabulum-like structure, distal end of lower margin with shallow groove extending anteriorly to middle of pollex. Finger thick, tips rounded; dactylus brownish in alcohol except distal end, dorsal margin with granulate submargin crests, forming longitudinal groove toward medial region of dorsal margin, distal area moderately recurved, external surface lower submargin with longitudinal shallow groove, extending two-thirds of dactylus from proximal end, three large teeth on proximal end of cutting edge, 2 thin, blade-like low teeth on distal end of cutting edge; pollex beige in alcohol, proximal end of cutting edge with 2 small, low teeth and 3 larger blunt teeth, distal end with 2 medium-sized low teeth.

Ambulatory legs ( Fig. 13G View Fig ) flattened, broad, moderate in length, P2, P3 longest, coxa-to-dactylus length about 0.94 times carapace width, P5 shortest, coxa-to-dactylus length about 0.81 times carapace width; surfaces entirely smooth, anterior margin of meri spinose, anterior margin of carpi, propodi, dactyli granulate, anterior submargin of meri, carpi, propodi, dactyli lined with many short and long setae, posterior margin of meri, carpi smooth, submargin lined with short and long setae, posterior margins of propodi denticulate, submargin lined with short and long setae, posterior margins of dactyli spinose, with single large tubercle posterior to chitinous claw, single-tipped. P5 merus subrectangular, median length about 1.54 times greatest width; carpus curved, distal end distinctly wider than proximal end, median length about 1.60 times greatest width; propodus subrectangular, median length about as long as greatest width; dactylus longer than propodus, stout proximally, tapering distally, terminating in sharp, short chitinous claw with length about 1.86 times greatest width.

Pleon ( Fig. 13H View Fig ) moderate long relative to thoracic sternum, tip of telson reaching anterior margin of sternite 4; somites 1, 2 trapezoidal, much wider than long; somites 3–5 subrectangular, not fused, subequal in width, combined lateral margin gently convex; somite 6 subrectangular, much wider than long, angles rounded, lateral margins convex; telson subtriangular, angles rounded, basal width about 1.5 times median length.

Distribution: Known only from the coast of East Taiwan.

Remarks: Interestingly, Etisus sp. A possesses an acetabulum-like structure on external, lower proximal margin of the propodus of the left chela ( Fig. 13F View Fig ). This feature might be a scar from a previous injury. The morphology of Etisus sp. A is somewhat resembles that of E. anaglyptus (H. Milne Edwards, 1834) , which has subquadrate frontal lobes extending beyond the supraorbital angles and separated by a deep V-shaped notch ( Fig. 13A, B; A View Fig . Milne-Edwards 1873: 80 (4), pl. 12 (1), fig. 3; Serène 1984: 227–228, pl. XXXII A, E). However, Etisus sp. A differs from E. anaglyptus in the following ways: 1) frontal lobes extending well beyond the supraorbital angles (versus slightly beyond); 2) a greater fronto-orbital to carapace width ratio (0.33 versus 0.19); 3) anterolateral tooth N, T and S (2 nd to 4 th) with blunt-tipped (versus acute tips); and 4) outer edge of ambulatory legs covered in granules (versus strong spines) ( Fig. 13A, B, G View Fig ; Serène 1984: 228, pl. XXXII A). More adult male and female specimens are needed to determine the true identity of this distinct Etisus species. The current description is based on a single juvenile female specimen, and it remains uncertain whether there are variations between sexes or ontogenetic morphological changes.

Etisus sp. B ( Figs. 14A–H View Fig , 15A–H View Fig , 16A–F View Fig )

Material Examined: 1 ñ, NMNS 8772-42, 5.3 × 3.8, Shanfu, Liuqiu Township, Pingtung County, 4 May 2007; 1 ò, NMNS 8772-43, 5.7 × 4.1, Shanfu, Liuqiu Township, Pingtung County, 24 October 2008; 1 ñ, NMNS 8772-44, 4.1 × 2.9, Shanfu, Liuqiu Township, Pingtung County, 5 November 2011.

Description: Carapace ( Fig. 14A, C, E View Fig ) transversely ovate, width to length ratio about 1.38, dorsal area slightly convex transversely, longitudinally; dorsal surface well covered by microscopic granules, short setae scattered at anterior regions and level with grooves at posterior regions; regions moderately divided by shallow grooves; subhepatic, pterygostomial regions granulate, glabrous. Front moderately advanced, about 0.41 times as long as carapace width, strongly deflexed ventrally, margin granulate, outer angles well marked, separated by V-shaped notch from orbital rim; divided into two lobes by deep V-shaped notch, continuing posteriorly as shallow median groove on dorsal carapace. Anterolateral margin convex, granulate, divided into 4 or 5 lobes, separated from each other by V-shaped or U-shaped notches with intercalated denticles; right anterolateral margin with 5 lobes, first lobe very low, feebly demarcated from second lobe; second lobe low; third lobe base widest, apex pointing anteriorly, anterior margin much shorter than posterior; fourth lobe similar to third but smaller; fifth lobe triangular, posterior margin continuous with carapace posterolateral margin; left anterolateral margin with 4 lobe, all lobes in equilateral triangle, apex of lobes 1–3 pointed anterolaterally, fourth lobe pointing laterally. Posterolateral margin slightly longer than anterolateral margin, with central region slightly concave.

Orbits ( Fig. 14A, C, E View Fig ) suboval, margins granulate; inner pre-frontal supraorbital and exorbital tooth weakly developed; supraorbital margin with one closed fissure. Eyes well developed, eyestalks short, stout, corneas large. Antennular fossae transversely oval; antennules folding transversely. Basal article of antenna short, subrectangular; flagellum freely entering orbital hiatus, short, tip slightly exceeding exorbital tooth.

Third maxillipeds ( Fig. 16B, D View Fig ) subrectangular, length to greatest width ratio about 2.05; palp tapering distally, articles subcylindrical; merus subquadrate, length to greatest width ratio about 0.83, anterolateral angle rounded, slightly projecting, anterior margin slightly sinuous, cristate and granulate, stout and thin setae scattered, external surface well covered with granules; ischium subrectangular, about 1.85 times longer than merus, sulcate submedially, mesial margin cristate, serrated, lined with submarginal setae; exopod stout, margins slightly convex, inner margin cristate, tapering slightly toward distal end, distal end slightly concave.

Thoracic sternum ( Fig. 14G View Fig ) margins cristate; sternites 1, 2 fused, external surface smooth; sternites 2, 3 and 3, 4 separated by deep and shallow sutures, respectively; sternite 4 with prominent median longitudinal line extending through half of exposed length, lateral margins slightly convex; median longitudinal line interrupted on sternite 4 within anterior region of sternopleonal cavity, continued at posterior limit of sternite 4, absent in sternites 5, 6, continued in sternites 7, 8 without interruption; sutures 4/5, 5/6 joining toward median longitudinal axis of thoracic sternum; vulvae oval, without operculum, located mesial third of sternite 5; small, central, triangular, non-calcified area present between sternites 6, 7 within sternopleonal cavity; press-button on anterior half of sternite 5.

Chelipeds ( Figs. 14A View Fig , 15A–D View Fig ) subequal, moderately robust, external surface almost fully granulate, except distal areas of fingers. Meri moderate long, distal end extending slightly beyond carapace anterolateral margin in dorsal view, dorsal margin granulates, with triangular projection distally. Carpi dorsal margin granulate, with 2 large, triangular tubercles subdistally. Palm dorsal margin granulate, granules raised forming as crest, with two triangular tubercles sub-proximally and 1 rounded tubercle distally, external surface granules compacted, forming reticulated pattern, or arranged in longitudinal rows. Fingers thick, tips hemi-cupuliform; dactylus dorsal margin with 2 parallel crests, forming groove extending toward subdistal end, proximal end with triangular tubercle, distal area strongly deflexed, meeting only at tip with pollex, leaving large gap between fingers, 3 large teeth on proximal end of cutting edge; pollex distal area slightly deflexed, 1 small, 2 large teeth on proximal end of outer cutting edge, 1 small tooth on proximal end of inner cutting edge.

Ambulatory legs ( Figs. 14A View Fig , 16A View Fig ) flattened, broad, moderate in length, P3, P4 longest, coxa-to-dactylus length about 0.91 times carapace width, P5 shortest, coxa-to-dactylus length about 0.71 times carapace width; surfaces entirely smooth; anterior margin of meri spinose, submargin lined with short and long setae, carpi, propodi, dactyli denticulate, submargin lined with short and long setae; posterior margin of meri, submargin lined with long setae, carpi, propodi smooth, without setae, dactyli spinose, with single medium-sized spine posterior to chitinous claw, single-tipped. P5 merus subrectangular, median length about 1.72 times greatest width; carpus curved, distal end distinctly wider than proximal end, median length about 1.25 times greatest width; propodus subrectangular, median length about 1.19 times greatest width; dactylus longer than propodus, stout proximally, tapering distally, terminating in sharp, short, slender chitinous claw with length about 2.0 times greatest width.

Pleon ( Fig. 14G View Fig ) moderate long relative to thoracic sternum, tip of telson reaching level to anterior sternal condyles of P2 coxae; somites 1, 2 trapezoidal, much wider than long; somites 3–5 fused, base subequal in width, combined lateral margin straight; somite 6 subquadrate, slightly longer than wide, lateral margins straight; telson subtriangular, angles rounded, basal width about as long as median length.

Female morphology: The female ( Figs. 14B, D, F, H View Fig , 15E–H View Fig , 16C View Fig ) is morphologically similar to the male in most body parts, with differences in the carapace, sexual characters, and chelipeds. The female’s carapace is less concave compared to that of the male. The front of the female shows only traces of submedian lobules and is slightly retreated laterally, whereas the male has broader submedian lobules that are moderately retreated. The female's pleon is generally wider and more triangular than the male’s. Additionally, the sternopleonal cavity of the female is wider but shallower. The vulvae are oval and located on the mesial third of sternite 5. The female’s chelipeds are less robust and nearly equal in size, in contrast to the male’s, which are robust and subequal. The dactylus of both chelae in the female is slightly recurved distally, leaving a smaller gap when close, whereas in the male, it is strongly recurved and leaves a larger gap.

Distribution: Known only from the Liuqiu Island, offshore from southwestern Taiwan.

Remarks: Of the known congeners, Etisus sp. B shares morphological similarities with E. demani Odhner, 1925 and E. odhneri Takeda, 1971 , notably in the following features: 1) a bi-lobed front separated by a median V-shaped notch with frontal lobes being slightly sinuous and fringes with pearly granules; 2) intercalated denticles between the anterolateral lobes of the carapace; and 3) strongly recurved distal fingers of chelipeds ( Figs. 14A–D View Fig , 15A–D View Fig ; Gordon 1941: 135–136, fig. 9c; Guinot 1964b: 51, 53, figs. 19, pl. VI, fig. 1; Takeda 1971: 193– 195, pl. 3, figs. 1–2; Serène 1984: 219, 223). However, Etisus sp. B can be distinguished from E. demani by the following: 1) a smaller carapace width/length ratio (1.38 versus 1.46–1.48) ( Fig. 14A–D View Fig ; Guinot 1964b: 51, fig. 19, pl. VI, fig. 1); 2) a single-rimmed front fringed with one row of pearly granules (versus double-rimmed with two rows of pearly granules) ( Fig. 14A–D View Fig ; Gordon 1941: 134, fig. 9d); 3) a granulate supraorbital margin with one fissure (versus smooth and with two fissures) ( Fig. 14C–D View Fig ; Gordon 1941: 134, fig. 9d; Guinot 1964b: 51, figs. 19, pl. VI, fig. 1); 4) a shallow, longitudinal groove dividing the middle of the 3M region in males (versus undivided) ( Fig. 14A, C View Fig ; Guinot 1964b: 51, figs. 19, pl. VI, fig. 1); 5) three uneven-sized teeth on the proximal half of the major chela’s dactylus cutting edge (versus two) ( Fig. 15A–H View Fig ; Gordon 1941: 134, fig. 9c); 6) two rows of teeth on the proximal cutting edge of the major chela’s pollex, with the outer and inner rows featuring three uneven conical teeth and one small teeth, respectively (versus with one row of one large and several minute teeth) ( Fig. 15B, D, F, H View Fig ; Gordon 1941: 134, fig. 9c); 7) a mosaic of granules on upper region and two rows of small conical granules on lower region of the minor chela’s palm (versus smooth) ( Fig. 15C View Fig ; Gordon 1941: 134, fig. 9c); 8) conical granules on the outer margins of the fourth ambulatory leg (versus strong spines) and a smooth inner margin on the fourth leg’s merus (versus spines) ( Fig. 16A View Fig ; Gordon 1941: 134, fig. 9a); 9) a smaller dactylus width/length ratio of the fourth ambulatory leg (0.33 versus 0.43) ( Fig. 16A View Fig ; Gordon 1941: 134, fig. 9a); 10) a smaller ischium width/length ratio of the third maxilliped (1.13 versus 1.48) ( Fig. 16B–D View Fig ; Guinot 1964b: 53, fig. 24, pl. VI, fig. 1); 11) a fully granulated outer surface of the third maxilliped’s merus and palp (versus smooth) ( Fig. 16B– D View Fig ; Guinot 1964b: 53, fig. 24, pl. VI, fig. 1); and 12) a strongly curved posteroventrally G1 distal part and subapex with eight short, stout setae (versus moderately curved with five long and two short setae) ( Fig. 16E, F View Fig ; Gordon 1941: 135, fig. 10d; Takeda 1971: 192, fig. 3C, D; Serène 1984: 222, fig. 140).

Etisus sp. B differs from E. odhneri View in CoL by: 1) broader submedian lobules on the front, single-rimmed with one row of pearly granules (versus feeble submedian lobules and double-rimmed with two rows) ( Fig. 14A–D View Fig ; Takeda 1971: 193, 209, pl. 3); 2) a divided middle 3M region by a shallow, longitudinal groove (versus undivided) ( Fig. 14C View Fig ; Takeda 1971: 193, 209, pl. 3, fig. 1); 3) a granulate supraorbital margin with one fissure (versus with two notches) ( Fig. 15A–H View Fig ; Takeda 1971: 193, 209, pl. 3, fig. 1); 4) three uneven teeth on the proximal cutting edge of the major chela’s dactylus (versus two) ( Fig. 15A–H View Fig ; Takeda 1971: 194, 209, pl. 3, fig. 2); 5) two rows of teeth on the major chela’s pollex, with the outer and inner rows having three uneven sized conical teeth and one small teeth

(versus one row and four uneven teeth) ( Fig. 15B, D, F, H View Fig ; Takeda 1971: 194, 209, pl. 3, fig. 2); and 6) a strongly curved posteroventrally G1 distal area and a spatulate apex (versus moderately curved) ( Fig. 16E, F View Fig ; Takeda 1971: 192, fig. 3E–F; Serène 1984: 222, fig. 141). The described characteristics of Etisus sp. B are based on juvenile specimens, leaving the possibility of ontogenetic morphological changes as the species matures.