Hexapinus simplex, Rahayu & Ng, 2014
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publication ID |
https://doi.org/ 10.5281/zenodo.5353945 |
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publication LSID |
lsid:zoobank.org:pub:4CF42744-861A-4635-9703-E6639CEBFAA9 |
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persistent identifier |
https://treatment.plazi.org/id/F1D702EA-1AFF-4D0E-BCF4-F205335652F3 |
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taxon LSID |
lsid:zoobank.org:act:F1D702EA-1AFF-4D0E-BCF4-F205335652F3 |
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treatment provided by |
Tatiana |
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scientific name |
Hexapinus simplex |
| status |
sp. nov. |
Hexapinus simplex View in CoL , new species
( Figs. 1A–F View Fig , 18–21 View Fig View Fig View Fig View Fig )
Hexapus (Hexapus) sexpes View in CoL – Sakai, 1976: 554 (part), pl. 196, fig. 2. (not Cancer sexpes Fabricius, 1798 )
Material examined. Holotype: male (7.8 × 5.0 mm) (MZBCru 3790), Ekas, Lombok, 8°52'9"S 116°27' 26.1"E, Indonesia, coll. 15 October 2007. Paratypes: Indonesia: 4 males (8.0 × 5.6 mm, 6.4 × 4.4 mm, 5.6 × 3.8 mm, 5.1 × 3.5 mm), 2 females (6.9 × 4.5 mm, 5.3 × 3.5 mm), 1 ovigerous female (10.9 × 6.7 mm) ( MZB Cru 3791) ; 3 males (6.4 × 4.4 mm, 5.1 × 3.5 mm, 4.5 × 3.1 mm), 2 females (10.0 × 6.0 mm, 6.7 × 4.5 mm)( ZRC 2012.1015 View Materials ), 1 ovigerous female (10.9 × 7.1 mm) ( ZRC 2009.750 View Materials ), Ekas, eastern Lombok , 8°52'9"S 116°27'39"E, 15 October 2007 GoogleMaps ; 1 male (5.4 × 3.4 mm), 2 females (4.5 × 2.8 mm, 6.9 × 4.5 mm) ( ZRC 2013.1689 View Materials ), Ekas, eastern Lombok , 8°52'9"S 116°27' 39"E, coll. 22 July 2009 GoogleMaps ; 5 males (7.3 × 5.0 mm – 8.5 × 5.8 mm), 5 females (4.1 × 2.9 mm – 8.9 × 5.9 mm) ( USNM), Ekas, eastern Lombok , 8°52'9"S 116°27' 39"E, coll. 22 July 2009 GoogleMaps . Others : Indonesia: 28 males (3.3 × 2.0 mm – 8.7 × 5.0 mm), 22 females (3.8 × 2.3 mm – 9.2 × 5.3 mm), 7 ovigerous females (9.5 × 5.3 mm) ( MZB Cru 3919) ; 30 males (4.6 × 3.0 mm – 8.5 × 5.1 mm), 20 females (5.3 × 3.5 mm – 9.1 × 5.7 mm), 6 ovigerous females (8.0 × 4.8 mm – 8.7 × 5.8 mm) ( ZRC 2010.0297 View Materials ), Ekas, eastern Lombok , coll. 22 July 2009 ; 1 male (9.3 × 5.8 mm) ( ZRC), Lembeh Straits , Sulawesi, subtidal, diving, coll. H. H. Tan, 17 July 2003 . Singapore: 1 female (11.9 × 7.3 mm) ( ZRC 2013.1686 View Materials ), St. John Island , north lagoon, 1°13.116'N 103°51.079'E, coll. P. K. L. Ng & A. Anker, yabby pump, 31 May 2013 GoogleMaps ; 1 ovigerous female (8.3 × 6.0 mm) ( ZRC 2013.1687 View Materials ), DR2, Raffles Reserve near Raffles Lighthouse , 1°10'273N 103°45'613E, coll. RV Galaxea , 20 May 2013 ; 1 male (11.2 × 7.0 mm) ( ZRC), station Sen-AA04, Pulau Senang , northern side near jetty, intertidal sand-mud flat with abundant rubble and rocks, 01°10.504'N 103°44.1790.5'E, 0.5 m, from burrow together with chaetopterid worm, coll. A. Anker, yabby pump, 30 March 2014 ; 1 male (6.0 × 3.6 mm) ( ZRC), station grid 0523 DR3 AA19, sandy with broken shell substrate, between Pulau Tekong East and Pengerang , 01°23.914'N 104°05.353'E – 01°24.141'N 104°05.400'E, 10.6-10.7 m, trawl, coll. S. C. Lim et al., 25 March 2014 GoogleMaps . China: 3 females (10.0 × 6.2 mm, 13.7 × 7.7 mm, 11.5 × 6.7 mm) ( MNHN), station 57K29, coastal waters of Guangdong Province, off Longwo, South China Sea , coll. 22 April 1957 ; 1 male (12.7 × 7.5 mm), 1 female (12.5 × 8.2 mm) ( ZRC 2012.1016 View Materials ), station 75C-2368, pearl shell culture ground, Dongshan, Fujian Province, Taiwan Strait, coll. 1 June 1975 ; 1 female (12.5 × 7.5 mm) ( ZRC 2012.1017 View Materials ), station 6160, southeast Hainan Island, 18°30'N 110°30'E, South China Sea GoogleMaps . Japan: 1 female (9.2 × 7.4 mm) (RUMF-ZC-2107), river mouth of Nakara River, Iriomote Island , coll. J. Nawa, 22 July 2005 ; 1 ovigerous female (16.1 × 11.1 mm) (RUMF-ZC-2108), Oura Bay, Okinawa Island, in front of Camp Schwab , coll. 21 Jul. 2010 ; 1 female (13.6 × 8.1 mm), 1 male (12.6 × 8.4 mm) (RUMF- ZC-2110), Tekebu, Amami Island , coll. T. Maenosono, 25 April 2012 ; 2 males (10.7 × 7.1 mm, 10.9 × 7.2 mm), 1 female (12.4 × 7.4 mm) (RUMF-ZC-2109), Funaura Bay, Iriomote Island , coll. T. Naruse, 12 and 17 Jun. 2007 ; 1 male (12.6 × 8.4 mm) ( ZRC 2013.1688 View Materials ), Funaura Bay, Iriomote Island , coll. T. Naruse, 1 July 2011 ; 2 females (13.0 × 8.2 mm, 12.5 × 8.1 mm), 1ovigerous female (12.9 × 7.9 mm) ( ZRC 2012.1018 View Materials ), Tekebu, Amami Island , coll. T. Maenosono, 27 Apr. 2012 ; 1 male (13.1 × 8.0 mm), 10 females (12.2 × 7.3 mm – 15.3 × 8.7 mm), 3 ovigerous females (13.3 × 7.8 mm – 13.8 × 8.0 mm) (RUMF-ZC-2111) Tekebu, Amami Island , coll. T. Maenosono, 27 April 2012 .
Diagnosis. Carapace subquadrate, about 1.5–1.6 times as broad as long, dorsal surface finely pitted to smooth, regions indistinct, median H-shaped depression shallow; some granules present on dorsolateral margins, only scattered granules on posterior margin ( Figs. 18 View Fig , 20A View Fig ). Anterolateral margin arcuate, posterolateral margin sinuous with 2 protuberances; posterolateral corner with angled prominence over base of posterior pereopods. Front deflexed, fringed medially with setae ( Fig. 19A View Fig ). Eye small, slightly movable, cornea pigmented ( Figs. 19A View Fig , 20A View Fig ). Pterygostomial region with row of oblique, broken and entire, striae ( Fig. 20D View Fig ). Third maxillipeds relatively broad, densely setose ( Figs. 19B View Fig , 20G View Fig ); ischium 1.1 times as broad as long, slightly shorter than merus, strongly expanded distomesially, with rounded mesial margin; combined length of dactylus, propodus and carpus shorter than that of merus and ischium; exopod broad, about 0.5 times width of ischium, flagellum well developed. Chelipeds stout, unequal ( Fig. 19A, D View Fig ), dactylus with tufts of setae on upper margin proximally; major chela ( Fig. 20E View Fig ) slightly gaping when fingers closed; palm slightly wider than long, surface covered with tubercles on upper half; minor chela ( Fig. 20F View Fig ) with wider gap between closed fingers. P2–P4 ( Fig. 18A, C View Fig ) short, stout, P3 longest; merus of P4 1.9 times as long as broad; dactylus of P2–P4 straight. Male thoracic sternum broad ( Figs. 19B, C View Fig , 20B, C View Fig ), sternites 1 and 2 fused, separated from sternite 3 by distinct ridge; sternite 3 separated from sternite 4 laterally, medially appear fused, short thoracic sternal groove, extends obliquely from sternoabdominal cavity to middle of sternite 3 to below base of third maxilliped ( Fig. 20B, C View Fig ); sternite 8 exposed, triangular, half length of abdominal somite 1; sternoabdominal cavity reaches base of sternite 2 ( Fig. 20C View Fig ). Male abdomen relatively narrow ( Figs. 19B, C View Fig , 21E–G View Fig ), somites 1 and 2 free; somites 3–5 fused, lateral margin sinuous; somite 6 sligthly shorter than length of somites 3–5, lateral margin sinuous; telson subpentagonal with setose margin. G1 ( Fig. 21A, B View Fig ) bent submedially, directed anterolaterally, distal part tapered, glabrous or with sparse short setae, apices not concealed under abdomen, exposed on thoracic sternal groove, obscured by setae of telson. Female abdomen ( Fig. 21C, D View Fig ) with 6 free somites and rounded telson.
Colour. Fresh specimens from Lombok, Indonesia, are brownish grey in colour ( Fig. 1A View Fig ). One specimen collected by diving from Sulawesi is a striking bright orange ( Fig. 1B View Fig ). Those from Amami Island, Ryukyus, Japan, are brown, with the chelipeds, and P2–P4 light brown ( Fig. 1C View Fig ). The specimen from Iriomote Island, Ryukyus, has a reddish brown carapace and light brown chelipeds and P2–P4 ( Fig. 1D View Fig ). Specimens from Singapore are light to greyish-brown on the dorsal surfaces ( Fig. 1E, F View Fig ).
Etymology. The species name is derived from the relatively simple appearance of the carapace and G1.
Remarks. Hexapinus simplex , new species, is easily distinguished from other species in the genus by having the lateral margin of the carapace arcuate anterolaterally and the posterolateral margin sinuous with two distinct protuberances ( Figs. 18B View Fig , 20A View Fig ). In H. latipes and H. latus , there is only one protuberance on posterolateral margin ( Figs. 10A View Fig , 11A View Fig , 12A View Fig , 13A View Fig , 16A View Fig , 17A View Fig ), while in H. ceres the protuberance is on the median part of lateral margin of the carapace ( Figs. 14A View Fig , 15A View Fig ).
Hexapinus simplex is also different from H. latipes by the relatively shorter ischium of the third maxilliped with more strongly convex mesial margin, with merus as broad as long ( Fig. 20G View Fig versus Fig. 13C View Fig ). Furthermore the carapace of H. simplex is broader (1.5–1.6 times as broad as long), the surface smooth with some granules on dorsolateral surface and posterolateral margin. In H. latipes the carapace is more squarish (1.2–1.3 times as broad as long) and the carapace surface is more heavily pitted with only a few granules on dorsolateral surface.
Hexapinus simplex is the only species in the genus in which males were available for study. In all adult specimens, the male abdomen is slender with a long somite 6 that is almost as long as the entire length of fused somites 3–5 ( Fig. 21G View Fig ). In adults, the length of somite 6 does not vary with the size although the shape of male telson varies slightly ( Fig. 21E–G View Fig ). In one small male (5.4 × 3.4 mm, ZRC 2013.1689), the telson is only very slightly subpentagonal with the distal margin rounded ( Fig. 21E View Fig ); in the holotype male (7.8 × 5.0 mm, MZB Cru 3790), it is subpentagonal with a rounded distal magin ( Fig. 21F View Fig ), while in larger specimens (e.g., male 12.7 × 7.5 mm, ZRC 2012.1016) is more rounded ( Fig. 21G View Fig ). The abdomen of a small paratype female from Lombok (4.5 × 2.8 mm, ZRC 2013.1689) is interesting as it is narrow and resembles that of a male except it is relatively shorter and less narrow ( Fig. 21D View Fig ). In this specimen, which is clearly a juvenile female, the sutures between somites 3–5 are shallow but are complete although all the somites do not appear to articulate very freely. This is the same condition observed in juvenile female of Hexapinus latipes (see discussion for that species). Male specimens of Hexapinus simplex , even when juvenile, on the other hand, always have elongate and slender abdomens with somites 3–5 completely fused. With regards to the male thoracic sternal groove, the condition does not vary in Hexapinus simplex , even when the specimens are small. All the male specimens, however, have distinct G1 structures suggestinng none of them are immature.
Biological notes. In Lombok, specimens were collected by sieving substrates consisting of mud, fine and coarse sand in intertidal areas, among frames established for seaweed culture. In Singapore, the specimens were collected by yabby pumping and dredging on sandy mud substrates. The specimens from the Ryukyus were collected from burrows in intertidal seagrass beds by using yabbie pumps. The specimens from Amami-Ohshima were collected from tubes of chaetopterid worms. Zehntner (1984) and Sakai (1976) observed the association of their specimens of “ Hexapus sexpes ” with annelid tubes.
Type locality. Ekas , Lombok, Indonesia .
Distribution. South coast of Lombok Island, Indonesia; Singapore; Ryukyu Islands, Japan; South China Sea; and Taiwan Strait. Intertidal and subtidal.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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Hexapinus simplex
| Rahayu, Dwi Listyo & Ng, Peter K. L. 2014 |
Hexapus (Hexapus) sexpes
| Sakai T 1976: 554 |