Hexapinus latus, Rahayu & Ng, 2014

Rahayu, Dwi Listyo & Ng, Peter K. L., 2014, New genera and new species of Hexapodidae (Crustacea, Brachyura) from the Indo-West Pacific and east Atlantic, Raffles Bulletin of Zoology 62, pp. 396-483 : 416-418

publication ID	https://doi.org/ 10.5281/zenodo.5353945
publication LSID	lsid:zoobank.org:pub:4CF42744-861A-4635-9703-E6639CEBFAA9
persistent identifier	https://treatment.plazi.org/id/C0658B02-C8E4-426D-8754-BDF4F09D2F2D
taxon LSID	lsid:zoobank.org:act:C0658B02-C8E4-426D-8754-BDF4F09D2F2D
treatment provided by	Tatiana
scientific name	Hexapinus latus
status	sp. nov.

Treatment

Hexapinus latus View in CoL , new species

( Figs. 16 View Fig , 17 View Fig )

Material examined. Holotype: female (8.1 × 5.0 mm) ( MZB Cru 3918), Kecinan, Lombok, Indonesia, coll. 15 May 2007 . Paratype: Indonesia: 1 female (6.5 × 4.0 mm) ( ZRC 2013.1691 View Materials ), Sira , northern Lombok, Indonesia, coll. 21 July 2009 .

Diagnosis. Carapace subquadrate, about 1.6 times as broad as long, dorsal surface very smooth, region indistinct, median H-shaped depression shallow; some small granules present on dorsolateral margins, only scattered tiny granules on posterior margin ( Fig. 16A View Fig ). Anterolateral margin arcuate, posterolateral margin sinuous with 1 protuberance; posterolateral corner with angled prominence over base of posterior pereopods; lateral margin of carapace wall produced medially. Front deflexed ( Fig. 16C View Fig ). Orbit distinct, eye small, slightly movable, cornea pigmented ( Fig. 16C View Fig ). Pterygostomial region with row of oblique striae. Third maxillipeds relatively broad ( Figs. 16B View Fig , 17B View Fig ); ischium 1.1 times as broad as long, longer than merus, strongly expanded distomesially, with rounded mesial margin; combined length of dactylus, propodus and carpus shorter than that of merus and ischium; exopod narrow, about 0.3 times width of ischium, flagellum well developed. Chelipeds stout, unequal ( Fig. 16C View Fig ); major chela gaping when fingers closed; palm slightly wider than long, outer surface smooth, tubercles on upper margin; minor chela with narrower gap between closed fingers ( Fig. 16C View Fig ). P2–P4 ( Fig. 16A View Fig ) short, stout, P3 longest; merus of P4 about 2 times as long as broad; dactylus longer than propodus; dactylus of P4 slightly upcurved. Female thoracic sternum broad ( Figs. 16B View Fig ), sternites 1 and 2 fused, separated from sternite 3 by distinct ridge; sternite 3 separated from sternite 4 by distinct ridge. Female abdomen broad ( Figs. 16B View Fig , 17C View Fig ) with 6 free somites and subtriangular telson.

Colour. In life, the carapace and appendages are creamishwhite overall.

Etymology. From the Latin latus for broad/wide, alluding to the broad carapace.

Remarks. Although only female specimens were available, this species clearly belongs to Hexapinus as it has a broad and mesially convex ischium of the third maxilliped, and the P2–P4 are short. The broad carapace of H. latus , new species, is similar to H. simplex , new species. However, comparisons of similar-sized females show that H. latus has a proportionately broader abdomen with the telson as long as somite 6 ( Fig. 17C View Fig ) while in H. simplex the abdomen is narrow and the telson is shorter than the sixth abdominal somite ( Fig. 21D View Fig ). In addition, the merus of the third maxilliped of H. latus is shorter than the ischium ( Fig. 17B View Fig ), while in H. simplex , the merus is longer than the ischium ( Fig. 20G View Fig ). The posterolateral margin of the carapace of H. latus has only one protuberance ( Fig. 16A View Fig ) while in H. simplex it always has two protuberances ( Fig. 18B View Fig ). The dorsal carapace surface of H. latus is very smooth ( Fig. 16A View Fig ); specimens of H. simplex the size of H. latus on the other hand, are always distinctively pitted ( Fig. 18 View Fig ).

Although H. latus was collected in the same island as H. simplex , the differences discussed above argue against them being conspecific. The habitats of also appear to be somewhat different. The specimens of H. latus were collected from coarse white sand in shallow depressions in the reef flat. The area had previously been mined for building material by local villagers. The area is always filled with some water, even during low tide. Hexapinus simplex on the other hand seems to prefer finer substrates (see next species).

Hexapinus latus also differs from H. latipes in having broad female abdomen. In a female specimen of H. latipes (10.2 × 7.6 mm, NSMT-Cr 5694), which is slightly larger than the female type specimens of H. latus , the abdomen is still narrow and resembles that of a male ( Fig. 17C View Fig versus Fig. 13G View Fig ). The female abdomens of both H. latus and H. ceres , even though they are relatively small, are already broad. Hexapinus latus and H. ceres are easily distinguished; the carapace surface, chelipeds and P2–P4 of H. latus are smooth ( Fig. 17A View Fig ) but in H. ceres , these are covered with closely spaced granules ( Fig. 14A View Fig ).