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Comprehensive Description

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General Description

The body is moderately robust for the genus. The integument is thin and soft, but not membranous. The surface is smooth. The rostrum is directed downward or forward, and is straight, usually reaching the distal margin of the first segment of the antennular peduncle to the midlength of the second segment in females (0.28–0.50 times as long as the carapace), occasionally reaching or slightly overreaching the distal margin of second segment of the antennular peduncle in males (0.24–0.60 times as long as the carapace). The dorsal margin is armed with 11–19 teeth, including 5–12 teeth on the rostrum proper and 4–7 (usually 5–7) moderately large teeth on the carapace posterior to the level of the orbital margin. The posterior-most tooth arises from 0.21–0.34 of the carapace length. The ventral margin is armed with 3–11 (most frequently 5–7) small, occasionally rudimentary teeth on the anterior 0.30–0.70. The lateral carina is sharp. The carapace is 0.54–0.71 times as wide as it is long. The postrostral median ridge is moderately high, and extends to 0.75–0.80 of the carapace length, sloping anteriorly to the rostrum, with the dorsal angle about 155° at its sharpest. The pterygostomial tooth is strongly produced anteriorly, particularly in large specimens (carapace length > 8.0mm), reaching far beyond the tip of the antennal tooth. The post-antennal groove is relatively deep, and is almost parallel to the horizontal plane of the carapace. The branchial region is somewhat inflated, thus the lateral face is notably convex.

The eighth thoracic sternite has a long median spur that is directed anteroventrally.

The abdomen is rounded dorsally. The pleura of the anterior three somites is broadly rounded. The fourth abdominal pleuron has 1–4 teeth (most frequently 2 or 3) posterolaterally. The fifth pleuron is similarly armed with 1 strong posteroventral tooth and 2–4 additional smaller teeth. The sixth abdominal somite is 1.50–1.70 times longer than high. The telson does not reach the posterior margin of the uropodal endopod, and has a length 2.90–3.20 times its anterior width and 4.90–5.20 times its posterior width. The telson is armed with 6–8 dorsolateral spines on either side, and has a convex posterior margin that is armed with 2 pairs of spines at the lateral angles and 12–14 plumose setae, all of which are longer than the mesial pair of lateral spines.

The eye has a cornea that is imperfectly developed, and unfaceted though diffusely pigmented. The corneal part is ovate in a general outline, but is fused mesially, each with a small upturned tooth or tubercle on the anterodorsal surface.

The antennular peduncle reaches or slightly overreaches the distal margin of the antennal scale. The first segment has a conspicuous proximal tubercle on the dorsal surface laterally and a strong distolateral tooth. The dorsal surface has a distinct longitudinal groove. The stylocerite is sharp, and overreaches the distal margin of the first segment, but does not reach the mid-length of the second segment. The second segment is stout, measuring 1.35–1.89 times as long as wide in females (1.63 on average, n = 24), and 1.52–1.95 times as long in males (1.75 on average, n = 9), with a small distomesial tooth. The lateral flagellum is subequal to the carapace in length. The mesial flagellum is somewhat longer than the lateral flagellum.

The antenna has a stout basicerite that bears strong ventrolateral and weak ventral teeth. The carpocerite is stout, and does not reach the midlength of the antennal scale. The antennal scale is 0.48–0.50 times as long as the carapace, and is 1.70–1.85 times as long as it is wide. The lateral margin is straight or slightly convex, and slightly diverges distally against a dorsal median ridge. There is a moderately broad distolateral tooth that is directed forward, but falls short of the broadly rounded distal margin of the blade.

The mouthparts typical of genus. The second maxilliped is moderately slender. The epipod has a simple podobranch. The third maxilliped is comprised of 4 segments, and overreaches the antennal scale by 0.30–0.50 times the length of the ultimate segment. The ultimate segment is distinctly longer than the penultimate segment (= carpus), and is trigonal in cross section, with a

truncate terminal margin that has 2 or 3 spines. The mesial face has several sets of obliquely transverse tracts of stiff setae. The carpus also has grooming apparatus that is comprised of transverse rows of stiff setae on the mesial face. The antepenultimate segment is comprised of a completely fused merus, ischium and basis, and is flattened dorsoventrally, appearing sinuously curved in a dorsal view. There are long marginal setae and 1 slender spine at the ventrolateral distal angle. The dorsal surface of the antepenultimate segment has a prominent tuft of short to long setae proximomesially. The coxa is stout, and has a small projection dorsal to the base of the epipod. The epipod is directed laterally, and is slightly bi-lobed.

The first pereopod reaches about as far as the third maxilliped, and is robust. The fingers are curved downward and inward. The outer surface of both fingers is convex. The inner concavity has opposed edges that are uniformly offset, closing without a gape, each armed with a fine row of closely set setae. The tip of each finger is slightly spooned. The palm is stout, with a greatest height at 0.65 times the length of the chela. The carpus is cupped distally to receive the palm. The dorsodistal margin has a blunt to subacute projection mesially. The ventral surface flares into a strong lateral ridge that terminates in a small to large tooth and a smaller mesial ridge that ends in a smaller blunt tooth. The surface between the ridges has dense grooming setae and 1–3 small movable spines. The mesial face has a shallow depression. The merus and ischium are strongly obliquely articulated in a lateral view. The merus is sometimes inflated ventrally, and occasionally has a small subdistal tooth on the ventrolateral margin. The ischium is always unarmed.

The second pereopod is shorter and more slender than the first pereopod, and does not reach the distal margin of the antennal scale. The fingers are subequal to the palm in length, each terminating in a small corneous unguis that cross each other when closed. The cutting edges close without a gape, each being pectinate with a single row of minute corneous teeth. The carpus is slightly longer than the chela. The merus and ischium are obliquely articulated in a lateral view. The ischium has 1 ventrolateral spine.

The third to fifth pereopods are moderately stout, and are generally similar in length and structure. They are usually setose, with the third pereopod reaching beyond the distal margin of the antennal scale by 0.40–0.50 the length of the propodus. The propodus-carpus combined is shorter than the merus-ischium combined in the third pereopod, subequal in the fourth, and longer in the fifth. The dactyli are short (0.08–0.15 of the propodi length), and are armed with 3–5 corneous spines on the flexor margin. The propodi of the third and fourth pereopods have slender spinules arranged in two rows on the ventral surface, whilst the propodus of the fifth pereopod has numerous spiniform setulose setae arranged in three or four rows on the distal half of the ventral surface. The carpi are 0.50–0.65 of the propodi length. The meri each have 1–3 movable spines ventrolaterally in the third and fourth pereopod, but is unarmed or with 1 spine in fifth. The ischia has 1 or 2 ventrolateral spines in third and fourth pereopods, and is unarmed or with 1 spine in the fifth.

The male first pleopod has an endopod about 0.60 the length of the exopod, and a faintly bilobed distal part. The distomesial lobe has 4 long spiniform setae directed mesially or distomesially on the mesial margin. The distolateral lobe is obsolete. The endopod of the female is bluntly pointed distally, and has a fringe of plumose setae similar to those fringing the remaining margins. The appendices internae on second to fourth pleopods are not greatly reduced in size, but are slender. The appendix interna on the second pleopod is simple, and is without a terminal cluster of cincinnuli, but those on third and fourth pleopods have a few cincinnuli, whilst the appendix interna on the fifth pleopod is better developed than others, having a terminal cluster of cincinnuli. The appendix masculina is moderately robust, and is slightly shorter than the appendix interna, with about 10 long, terminal or subterminal bristles.

The uropod has rami subequal in length, an exopod with a small movable spine mesial to a smaller distolateral tooth, and a sinuous diaeresis.

(Komai et al., 2005)


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