Carcinoplax abyssicola ( Miers, 1885 )

Ng, Peter K. L. & Castro, Peter, 2020, A revision of Carcinoplax abyssicola (Miers, 1885) and seven related species of Carcinoplax H. Milne Edwards, 1852, with the description of two new species and an updated key to the genus (Crustacea, Decapoda, Brachyura, Goneplacidae), Zoosystema 42 (17), pp. 239-284 : 243-251

publication ID

https://doi.org/ 10.5252/zoosystema2020v42a17

publication LSID

lsid:zoobank.org:pub:urn:lsid:zoobank.org:pub:52C73176-6867-4415-A6FA-BAD328E9781D

DOI

https://doi.org/10.5281/zenodo.4525489

persistent identifier

https://treatment.plazi.org/id/038B3E2C-FF98-FF88-A6B5-6E20FB9DB2D8

treatment provided by

Felipe

scientific name

Carcinoplax abyssicola ( Miers, 1885 )
status

 

Carcinoplax abyssicola ( Miers, 1885)

( Figs 1 View FIG A-D; 2 View FIG A-H; 3 View FIG A-I; 4 View FIG A-H; 5 View FIG A-H; 23 View FIG A-D, E-H; 26 View FIG A-F)

Pseudorhombila (Pilumnoplax) abyssicola Miers, 1885: 588 [ Fiji].

Pilumnoplax abyssicola Miers, 1886 : xxiv, xl, xlviii, 226, 227 [in list], 228, pl. 19, figs 2, 2a, 2b [ Fiji]. — Tesch 1918: 155 [in list], 156 [in key], 156 [ Indonesia]. — Serène 1968: 90 [in list]. — Guinot 1969: 526; 1971: 1081 [in list]. — Serène & Lohavanijaya 1973: 62 [in list], 65 [in key].

Not Pilumnoplax abyssicola – Whitelegge 1900: 158 (= Pycnoplax meridionalis (Rathbun, 1923)) .

Neopilumnoplax abyssicola – Serène 1968: 90 [in list].

Carcinoplax abyssicola – Guinot 1969: 526; 1989: 305, fig. 38; pl. 9, figs A-C [holotype] [ Fiji]. — Castro 2007: 623 View Cited Treatment [in list]. 627 [in key], 628 [holotype] [ Fiji]. — Ng et al. 2008: 80 [in list].

Carcinoplax specularis [part] – Castro 2007: 640 View Cited Treatment [ Indonesia, New Guinea, Solomon Islands, Vanuatu, New Caledonia, Fiji, Tonga].

TYPE MATERIAL. — Holotype. Fiji. ♂, 8.2 × 10.0 mm ( Castro 2007), Challenger ; stn 173; NHM 84.31 .

TYPE LOCALITY. — Fiji, Challenger; stn 173; 576 m depth.

MATERIAL EXAMINED. — Indonesia • 1 ♀, 11.2 × 15.2 mm; Kai Is.; KARUBAR; stn CP59; 08°20’S, 132°11’E; 399-405 m depth; 31.X.1991; MNHN-IU-2016-100 (= MNHN-B29387 ) GoogleMaps 1 ♀, 19.3 × 24.5 mm; KARUBAR; stn CP63; 08°00’S, 132°58’E; 214-215 m depth; 1.XI.1991; MNHN-IU- 2016-99 (= MNHN-B29380 ) GoogleMaps 1 ♀, 12.4 × 17.6 mm; Java; E. Sunda Strait; SJADES; stn CP7; 05°44.678’S, 104°51.151’E; 379-409 m depth; 25.III.2018; ZRC 2018.1414 View Materials GoogleMaps 4 ♀, 1 ovigerous ♀, 1♂; same data as ZRC 2019.0568 GoogleMaps 1 ♀, 13.9 × 19.9 mm, 1 ♀, 14.8 × 20.0 mm, 1 ♂, 12.8 × 19.1 mm, 1 ♂, 13.6 × 18.4 mm; Java; E. Sunda Strait; SJADES; stn CP8; 05°45.126’S, 104°51.080’E; 425-442 m depth; 25.III.2018; ZRC 2018.1415 View Materials GoogleMaps 5 ♀, 7.6 × 10.1 mm to 14.5 × 21.2 mm; same data as ZRC 2019.0569 GoogleMaps 5 ♀; same data as ZRC 2019.0569 GoogleMaps 1♂, 13.0 × 19.4 mm; SJADES; stn CP10; Java; E. Sunda Strait; 05°45.399’S, 104°56.098’E; 429-446 m depth; 25.III.2018; ZRC 2018.1416 View Materials GoogleMaps 1 ♂, 2♀, 10.0 × 13.8 mm, 11.9 × 16.1 mm, 1 ♂, 13.9 × 20.3 mm; SJADES; stn CP39; E. Indian Ocean; 08°15.885’S, 109°10.163’E; 528-637 m depth; 30.III.2018; ZRC 2018.1418 View Materials GoogleMaps .

Papua New Guinea • 1 ♂, 14.3 × 19.1 mm; BIOPAPUA; stn CP3570; 1.X.2010; 497-500 m depth; ZRC 2019.1029 View Materials ; ex MNHN- IU-2011-1469 1 ♂, 11.8 × 16.5 mm; BIOPAPUA; stn CP3740; 556-645 m depth; 10.X.2010; MNHN-IU-2011-2471 1 ♂, 13.2 × 16.4 mm; BIOPAPUA; stn CP3742; 448-470 m depth; 10.X.2010; ZRC 2019.1028 View Materials ; ex MNHN-IU-2011-2001 1 ♀, 13.9 × 11.0 mm; PAPUA NIUGNI; stn CP3970; 04°39’S, 145°52’E; 573 m depth; 4.12.2012; MNHN-IU-2013-9399 GoogleMaps 1 ♀, 11.0 × 11.7 mm; PAPUA NIUGNI; stn CP4033; 04°52’S, 145°53’E; 780 m depth; 16.12.2012; MNHN-IU-2013-9402 GoogleMaps 1 ♀, 11.8 × 16.7 mm; PAPUA NIUGNI; stn CP4042; 03°53’S, 144°40’E; 495-693 m depth; 18.XII.2012; MNHN-IU-2013-9391 GoogleMaps 1 ♂, 8.7 × 11.0 mm; PAPUA NIUGNI; stn CP4048; 03°20’S, 143°28’E; 325-345 m depth; 19.XII.2012; MNHN-IU-2013-9405 GoogleMaps 1 ♂, 6.0 × 7.4 mm; same data as MNHN- IU-2013-9405; MNHN-IU-2013-15592 1 ♂, 8.1 × 9.9 mm; same data as MNHN-IU-2013-9405; MNHN-IU-2013-9393 .

Solomon Islands • 1 ♀, 11.7 × 15.9 mm; SALOMON 1; stn CP1747; 09°21.8’S, 159°58.7’E; 364-402 m depth; 25.IX.2001; MNHN- IU-2016-129 (= MNHN-B29394 ) GoogleMaps 1 ♀, 11.1 × 16.1 mm; SALO- MON 1; stn CP1748; 09°20.4’S, 159°58.2’E; 509-522 m depth; 25.IX.2001; MNHN-IU-2016-128 (= MNHN-B29395 ) GoogleMaps 1 ♂, 5.8 × 7.5 mm; SALOMON 1; stn DW1768; 08°21.4’S, 160°41.8’E; 194-286 m depth; 28.IX.2001; MNHN-IU-2016-127 (= MNHN- 29393 ) GoogleMaps 2 ♀, 6.2 × 7.6 mm; 12.9 × 16.5 mm; SALOMON 1; stn DW1808; 09°45.5’S, 160°52.5’E; 611-636 m depth; 2.X.2001; MNHN-IU-2016-130 (= MNHN-B29396 ) GoogleMaps 1 ♀, 12.3 × 18.8 mm; SALOMON 1; stn DW1851; 10°27.6’S, 162°00’E; 297-350 m depth; 6.X.2001; MNHN-IU-2016-131 (= MNHN-B29397 ) GoogleMaps 1 ♀, 10.5 × 13.7 mm; SALOMON 1; stn CP2288; 08°36.3’S, 157°26.5’E; 509-520 m depth; 7.XI.2004; MNHN-IU-2016-133 (= MNHN-B30095 ) GoogleMaps . • 2 ♀, 10.9 × 14.0 mm; 13.8 × 19.2 mm; SALOMON 2; stn CP2195; 08°25.5’S, 159°26.4’E; 543-593 m depth; 24.X.2004; MNHN-IU-2016-136 (= MNHN-B30111 ) GoogleMaps 1 ovigerous ♀, 13.5 × 18.8 mm; SALOMON 2; stn 2212; 07°37.8’S, 157°41.7’E; 400-475 m depth; 26.X.2004; MNHN-IU-2016-134 (= MNHN-B30114 ) GoogleMaps 1 ♂; SALOMON 2; stn CP2213; 07°38.7’S, 157°42.9’E; 495-650 m depth; 26.X.2004; MNHN-IU-2016-138 (= MNHN-B30097 ) GoogleMaps 1 ♀, 2 ♂; SALOMON 2; stn CP2246; 07°42.6’S, 156°24.6’E; 664-682 m depth; 1.X.2004; MNHN-IU-2016-132 (= MNHN-B30109 ) GoogleMaps 1♂, 10.8 × 14.9 mm; SALOMON 2; stn CP2262; 07°56.4’S, 156°51.2’E; 460-487 m depth; 3.X.2004; MNHN-IU-2016-137 (= MNHN-B30112 ) GoogleMaps 1 juvenile, 6.7 × 8.3 mm; SALOMON 2; stn CP2287; 08°40.8’S, 157°24.6’E; 253-255 m depth; 6.XI.2004; MNHN-IU-2016-135 (= MNHN- B30089 View Materials ) GoogleMaps 1 ♀, cl 13.4 mm; carapace damaged; Malaita; SALOMON BOA 3; stn CP2787; 08°31’S, 160°39’E; NW 570-885 m depth; 14.IX.2007; MNHN-IU-2010-5567 GoogleMaps 1 ♂, 8.3 × 9.9 mm; same data as MNHN-IU-2010-5567; MNHN-IU-2010-5568 GoogleMaps .

Vanuatu • 1 ♀, 11.9 × 16.2 mm, 2 ♂, 9.9 × 14.1 mm, 14.5 × 19.8 mm; BOA0; stn CP2304; 16°35’S, 167°59’E, 564-582 m depth; 14.XI.2004; MNHN-IU-2016-118 GoogleMaps 1 ovigerous ♀, 12.8 × 17.5 mm; BOA0 ; stn CP2313; 15°04’S, 166°55’E; 421-482 m depth; 16.XI.2004; MNHN-IU-2016-116) GoogleMaps 1 ♂, 10.7 × 14.0 mm; BOA0; stn CP2330; 295-890 m depth; 18.II.2004; MNHN- IU-2016-117 ) • 1 ♀, 11.9 × 14.8 mm; BOA1 ; stn CP2457, 16°16’S, 167°19’E; 630-690 m depth; 6.XII.2005; MNHN-IU-2016-115 GoogleMaps 2 ♀, 9.7 × 12.9 mm, 10.4 × 14.6 mm; SANTO 2006; stn AT9; W. Malo I.; 15°41.5’S, 167°01.3’E, 481 m depth; 17.IX.2006; ZRC 2008.0970 View Materials GoogleMaps 1 ♂, 8.0 × 10.6 mm; SANTO 2006; stn AT19; W Malo I.; 15°41’S, 167°01’E; 503-600 m depth; 21.IX.2006; ZRC 2018.1419 View Materials GoogleMaps 1 juvenile female; no data; ZRC 2009.0994 View Materials .

New Caledonia. 3 ♂; SMIB 6; stn DW212; 19°05.6’S, 163°30.2’E; 220-225 m depth; 2.III.1990; MNHN-IU-2016-120 (= MNHN- B29818 View Materials ) GoogleMaps 1 ♂, 13.0 × 17.6 mm; BATHUS 4; stn CP910; 18°59.32’S, 163°08.47’E; 560-608 m depth; 5.VIII.1994; MNHN-IU-2016-111 (= MNHN-B29417 ) GoogleMaps 2♂; BATHUS 4; stn CP911; 18°57.80’S, 163°08.47’E; 566- 558 m depth; 5.VIII.1994; MNHN-IU-2016-112 (= MNHN-B29420 ) GoogleMaps 1 ♂, 6.0 × 7.3 mm; EXBODI: stn CP3788; 22°13’S, 167°07’E; 264-273 m depth; 3.IX.2011; MNHN- IU-2011-8816 GoogleMaps .

Fiji • 3 ♀, largest 11.2 × 15.6 mm; MUSORSTOM 10; stn DW1330; 17°09.5’S, 177°56.3’E; 567-699 m depth; 8.VIII.1998; MNHN- IU-2014-11513 (= MNHN-B29504 ) GoogleMaps 3 ♀, 1 ♂, 10.5 × 15.3 mm; BORDAU 1; stn DW1393; 16°45’S, 179°59’E; 426-487 m depth; 23.II.1999; MNHN-IU-2014-11531 (= MNHN-B29505 ) GoogleMaps 1 juve- nile ♀, 7 ♀, largest 11.7 × 16.0 mm, 2 ♂, larger one 11.0 × 15.5 mm; BORDAU 1; stn DW1395; 16°45’S, 179°59’E; 423-500 m depth; 23.II.1999; MNHN-IU-2014-11529 (= MNHN-B29505 ) GoogleMaps 1 ♀, 2 ♂; ZRC 2019.1030 View Materials ; same data as MNHN-IU-2014-11529 GoogleMaps 1 ♂, cl 13.4 mm, carapace damaged; BORDAU 1; stn CP1401; 16°35’S, 179°41’E; 600-648 m depth; 25.II.1999; MNHN-IU-2014-11532 (= MNHN-B29506 ) GoogleMaps 1 ♂, 13.3 × 17.8 mm; BORDAU 1; stn CP1407; 16°40’S, 179°39’E, 499-527 m depth; 25.II.1999; MNHN- IU-2014-11533 (= MNHN-B29507 ) GoogleMaps 9 ♀, largest 11.1 × 15.0 mm, 4 ♂, largest 12.4 × 17.6 mm; BORDAU 1; stn DW1447; 16°45’S, 179°59’E; 420-513 m depth; 4.III.1999; MNHN-IU-2014-11530 (= MNHN-B29503 ) GoogleMaps 2 ♀, 2 ♂; ZRC 2019.1027 View Materials ; same data as MNHN-IU-2014-11530 GoogleMaps 1 ♀; BORDAU 1; stn CP1448; 16°45’S, 179°59’E; 410-500 m depth; 4.III.1999; MNHN-IU-2014-11534 (= MNHN-B29508 ) GoogleMaps 2 ♀, 1 ♂; BORDAU 1; stn DW1451; 16°45’S, 179°59’E; 400-460 m depth; 4.III.1999; MNHN-IU-2014-11535 (= MNHN-B29509 ) GoogleMaps 1 juvenile ♀, 1 ♀, cl 9.4 mm, carapace damaged; BORDAU 1; stn DW1453; 16°45’S, 179°59’E; 414- 510 m depth; 4.III.1999; MNHN-IU-2014-11536 (= MNHN- B29510 View Materials ) GoogleMaps 1 ♀, 7.2 × 9.9 mm; BORDAU 1; stn DW1463; 18°10’S, 178°44’W; 300-400 m depth; 6.III.1999; MNHN-IU-2014-7671 (= MNHN-B29511 ) GoogleMaps 1 ♂; BORDAU 1; stn DW1491; 18°50’S, 178°52’W; 777-787 m depth; 11.III.1999; MNHN-IU-2014-7697 (= MNHN-B29511 ) GoogleMaps .

Tonga • 1 juvenile ♀; BORDAU 2; stn CP1530; 21°12’S, 174°58’W; 802-803 m depth; 3.VI.2000; MNHN-IU-2014-11538 (= MNHN- B29555 View Materials ) GoogleMaps 3 ♀; BORDAU 2; stn CP1539; 21°37’S, 175°19’W; 558-586 m depth; 4.VI.2000; MNHN-IU-2014-11539 (= MNHN- B29558 View Materials ) GoogleMaps 1 ♀, 1 ♂; BORDAU 2; stn DW1553; 20°42’S, 174°54’W; 650-676 m depth; 6.VI.2000; MNHN-IU-2014-11544 (= MNHN- B29566 View Materials ) GoogleMaps 1 ♀; BORDAU 2; stn CP1556; 20°11’S, 174°45’W; 589-591 m depth; 7.VI.2000; MNHN-IU-2014-11541 (= MNHN- B29560 View Materials ) GoogleMaps 1 juvenile ♀; BORDAU 2; stn CP1557; 20°10’S, 174°42’W; 578 m depth; 7.VI.2000; MNHN-IU-2014-11543 (= MNHN-B29563 ) GoogleMaps 8 ovigerous ♀, 4 ♀, 1 ♂; BORDAU 2; stn CP1568; 21°02’S, 175°19’W; 431 m depth; 10.VI.2000; MNHN- 2014-11537 (= MNHN-B29309 ) GoogleMaps 1 ♀, 1 ♂; ZRC 2019.1031 View Materials ; same data as MNHN-2014-11537; 2 ovigerous ♀, largest 13.3 × 18.0 mm, 8 ovigerous ♀, 5 ♀, 2 ♂; same data as MNHN- 2014- 11537; MNHN-2014-11537 (= MNHN-B29309 ) GoogleMaps 2 ovigerous ♀; BORDAU 2; stn CP1620; 24°18’S, 176°20’W; 572 m depth; 18.VI.2000; MNHN-IU-2014-11540 (= MNHN-B29559 ) GoogleMaps 1 ju- venile ♀; BORDAU 2; stn CP1641; 21°09’S, 175°22’W; 395 m depth; 21.VI.2000; MNHN-IU-2014-11542 (= MNHN-B29561 ) GoogleMaps .

RE- DESCRIPTION

Carapace ( Figs 1A, D View FIG ; 2A, B, I View FIG ; 3A, B View FIG ; 4A, B View FIG ; 5A, B View FIG ; 26 View FIG A-F) Quadrate, slightly wider than long (1.2 × as wide as long in holotype; Castro 2007), anterolateral borders arched; slightly convex, mostly smooth, rarely granular in large specimens, marked by slight transverse elevations in branchial regions. Front ( Figs 3C, D View FIG ; 4C, D View FIG ; 5C View FIG ) lamellar, straight, margin not marked by median notch; notch between front, inner edge of supraorbital border. Supraorbital borders sinuous, margins smooth; suborbital borders with short, rounded inner tooth, reduced in some specimens. Outer orbital angles truncated when seen dorsally; first anterolateral teeth rounded but sometimes acute, second curved, acute-tipped. Posterolateral borders arched. Subhepatic, pterygostomial regions, pterygostomial crest, pterygostomial lobe, merus, ischium of third maxilliped endopod with short, small granules. Posterior margin of epistome ( Figs 2C View FIG ; 3C, D View FIG ; 4C, D View FIG ; 5C View FIG ) straight, slight median projection in some specimens; u- or v-shaped notch on each lateral margin.

Chelipeds ( Figs 1A, C View FIG ; 2A, F, H View FIG ; 3A, F, I View FIG ; 4A, F, H View FIG ; 5A, H View FIG ; 26 View FIG A-F) and ambulatory legs ( Figs 1A, D View FIG ; 2A View FIG ; 3A View FIG ; 4A View FIG ; 5A View FIG ; 26 View FIG A-F)

Chelipeds (P1) nearly equal in females and males; fingers slender, about as long or slightly shorter as propodus, with cutting edges, broadly blunt teeth; nearly all distal portion of fingers dark brown in males, half to 3/ 4 in females ( Figs 1A, C View FIG ; 2A, F, H View FIG ; 3A, F, I View FIG ; 4A, H View FIG ; 5A, H View FIG ; 26 View FIG A-F). “Window” (see discussion of C. specularis below) observed on outer surface of cheliped propodi in several males (e.g. MNHN- IU-2014-11529, 11.0 × 15.5 mm [ Fig. 3I View FIG ] and MNHN- IU-2016-127, 5.8 × 7.5 mm). Inner, outer (dorsal), distal margin of cheliped carpus with short, triangular to acute tooth ( Figs 1A, C View FIG ; 2F View FIG ; 3F View FIG ; 4F View FIG ; 5E View FIG ). P2-P5 ( Figs 1A, D View FIG ; 2A View FIG ; 3A View FIG ; 4A View FIG ; 5A View FIG ; 26 View FIG A-F) slender, proportionally long, smooth; many short, simple setae along inner, outer margins of P5 propodus, dactylus, outer margin of P5 carpus; P5 dactylus long, slender, smooth.

Sternum, male pleon ( Figs 2D View FIG ; 3H View FIG ; 4G View FIG ), and male gonopods ( Fig. 23 View FIG A-C, E-G)

Tomentum on sternum and pleon of large individuals of both sexes. Male pleon ( Figs 2D View FIG ; 3H View FIG ; 4G View FIG ) proportionally wide, with 6 freely-movable somites plus telson; telson slightly wider than long, somite 3 covering space between P5 coxae. Somites 1, 2 slightly narrower than somite 3, thoracic sternite 8 not visible. G1 ( Fig. 23 View FIG A-C, E-G) straight, short, obtuse to slightly laterally pointed tip; dorsal surface with numerous minute spinules that nearly reach tip. G2 ( Fig. 23D, H View FIG ) slender, slightly longer than G1, slightly curved flagellum, tip with spinule at each side.

Female pleon ( Fig. 5F View FIG ) and vulva ( Fig. 5G View FIG )

Female pleon ( Fig. 5F View FIG ) wide; telson slightly wider than long. Somites 1, 2 covering space between P5 coxae, thoracic sternite 8 not visible.Vulva of mature females ( Fig.5G View FIG ) extending from edge of suture 5/6 to suture 6/7; membrane covering aperture leaving space open along pointed anterior margin.

COLOUR IN LIFE. — Carapace and chelipeds light to bright orange; legs white with broad orange band across middle ( Fig. 26 View FIG A-F).

GEOGRAPHICAL DISTRIBUTION. — Indonesia (Kai Is and southern Java), Papua New Guinea, Solomon Islands, Vanuatu, New Caledonia, Fiji, and Tonga.

DEPTH. — Present in samples collected at depths of 194- 890 m.

REMARKS

The taxonomy of C. abyssicola , C. longipes , and C. verdensis has been confused mainly because of a shortage of specimens, as well as having type specimens that are small or females. It has been made more difficult because these species sometimes overlap in distribution, with C. abyssicola and C. longipes now known to co-occur in southern Java.

Carcinoplax abyssicola has been a problematic species because it was described from only one small male (8.2 × 10.0 mm, NHM 84.31), and its affinities with allied taxa have been far from clear. Guinot (1989) and Castro (2007) examined the holotype male and the present study confirms the specimens from Fiji, Papua New Guinea, Solomon Islands, Vanuatu, New Caledonia, Tonga and Indonesia (Kai Is and southern Java) are conspecific with the type. The anterolateral armature varies to some degree; the holotype has a small first tooth on the right side while that on the left side is missing ( Fig. 1B View FIG ). A male (10.5 × 15.3 mm, MNHN-IU-2014-11531) also has an acute right tooth but an obtuse left tooth ( Fig. 2I View FIG ). The holotype specimen no longer has the male pleon and the gonopods are not in the bottle. The G1 and G2 of the holotype, however, were sketched by the second author in 2004. Their morphology agrees with the gonopods drawn here ( Fig. 23 View FIG A-C, E-G), except that the tip of the G1 appears slightly longer. It, however, falls within the variation observed in the species.

The description by Miers (1886: 228) agrees with the material at hand but the diagnostic details in the description are scant. We are therefore re-describing the species in order to include a good number of diagnostic characters not included in the original description. No mention was made of the notch at the lateral borders of the front as well as details on the morphology of the epistome and the gonopods. Miers’ figures clearly show the small granules along the anterior portion of the ventral surface of the carapace, which are diagnostic for the species ( Miers 1886: pl. 19, fig. 2a; Fig. 1B, C View FIG ), and the fingers of the male holotype were black along their distal twothirds ( Miers 1886: pl. 19, fig. 2b; Fig. 1A, C View FIG ) (now faded in the type specimen; Fig. 1G, H View FIG ).

With only one specimen at that time, Guinot (1989) accepted the validity of C. abyssicola and indicated that it was close to C. longipes . Castro (2007) commented on the similarities between the holotype of C. abyssicola and specimens of C. specularis s.l., a species in which he included two species now being resurrected. He found that the main difference between the two species was the truncated and posteriorly inclined outer orbital angles of the holotype of C. abyssicola , a condition that is visible in the illustrations of the holotype by Guinot (1989: fig. 38; pl. 9, figs A, B).

Although we are now able to separate C. specularis s. str. (and the allied C. adelphia n. sp.) from the other species previously included under it (see Remarks for this species), the taxonomic history of C. abyssicola , C. longipes , and C. verdensis is confusing and is best discussed together here.

The presence of a good series of fresh specimens of C. abyssicola and C. longipes in the deep waters of southern Java is significant as it allows us to compare them directly. They are most easily distinguished by the proportions of their legs, which in C. longipes are distinctly longer ( Figs 6A View FIG ; 7A View FIG ; 8A View FIG ; 9A View FIG ; 27 View FIG A-C), especially the meri. The ambulatory meri of C. abyssicola are relatively shorter and stouter ( Figs 1A, E View FIG ; 2A View FIG ; 3A View FIG ; 4A View FIG ; 5A View FIG ; 26 View FIG A-F). Another obvious difference, which can vary occasionally, is the armature of the anterolateral margin (not including the external orbital tooth). The anterolateral teeth of C. abyssicola , especially the first one, are more obtusely triangular in adults ( Figs 1E View FIG ; 2B, I View FIG ; 3B View FIG ; 4B View FIG ; 5B View FIG ). In C. longipes , the teeth are acutely triangular, appearing almost spiniform, and are spaced further apart as a result ( Figs 6B View FIG ; 7B View FIG ; 8B View FIG ; 9B View FIG ). The structure of the posterior margin of the epistome is also useful to separate the two species in most cases; in C. abyssicola , the median truncated lobe is separated from the lateral margins by a relatively shallower and narrower cleft ( Figs 2C View FIG ; 3D View FIG ; 4F View FIG ; 5C View FIG ) but this cleft is deeper and wider in C. longipes ( Figs 5C View FIG ; 6C View FIG ; 7D View FIG ; 8D View FIG ). The structures of their G1 are superficially similar but the general structure is proportionately shorter and more slender, especially on the basal part ( Fig. 23A, E View FIG ) in C. abyssicola , whereas the G1 is more elongated and the basal part is relatively broader and more truncated in C. longipes ( Fig. 23I View FIG ).

The two species differ in their colour in life. Carcinoplax abyssicola is a distinct orange ( Fig. 26 View FIG A-F), with larger specimens dull or dark orange. The legs are white with a broad orange band across middle portions. In contrast, the overall colour in C. longipes is a faded yellowish-orange with the legs more uniformly coloured ( Fig. 27 View FIG A-C).

Carcinoplax abyssicola and C. longipes are both superficially similar to C. verdensis in the shape of their carapaces and the relatively more elongated legs, but C. verdensis can usually be distinguished by several clear features. The inner distal tooth of the carpus of the cheliped in C. verdensis is usually elongated, with the distal half sharply tapering to an acute spine in both sexes and usually even in subadults ( Figs 14F View FIG ; 15E View FIG ). The inner distal tooth of the carpal spine is always more obtuse and the distal part is never spiniform in C. abyssicola ( Figs 2E View FIG ; 3G View FIG ; 4F View FIG , 5E View FIG ) and C. longipes ( Figs 6E View FIG ; 7F View FIG ; 8F View FIG ; 9E View FIG ). The carpal spine of Miers’ drawing of the holotype of C. abyssicola is nevertheless spiniform ( Fig. 1C View FIG ), but obtuse in Guinot’s photograph of the holotype ( Fig. 1E View FIG ). Some specimens of C. verdensis from the Philippine and South China seas, however, have relatively less elongated carpal spines ( Fig. 13F View FIG ); so this character is not always reliable. The ambulatory meri of C. verdensis is usually elongated and slender ( Figs 13A View FIG ; 14A View FIG ; 15A View FIG ) like in C. longipes ( Figs 6A View FIG ; 7A View FIG ; 8A View FIG ), but the ambulatory merus appears relatively shorter in a few specimens ( Fig. 9A View FIG ), although it is still longer than those of adult C. abyssicola ( Figs 1A, E View FIG ; 2A View FIG ; 3A View FIG ; 4A View FIG ; 5A View FIG ). The structure of the posterior margin of the epistome of C. verdensis resembles that of C. abyssicola , with the truncated median lobe separated from the lateral margins by a relatively deep cleft ( Figs 2C, D View FIG ; 4D View FIG ; 5C View FIG for C. abyssicola ; Figs 6C View FIG ; 7D View FIG ; 8D View FIG ; 9C View FIG for C. longipes ). Carcinoplax verdensis more closely resembles C. longipes in the shape of their anterolateral teeth, with the spines typically more acute and spiniform ( Figs 6B View FIG ; 7B View FIG ; 8B View FIG ; 9B View FIG for C. longipes ; Figs 13B View FIG ; 14B View FIG ; 15B View FIG for C. verdensis ). There are, however, several specimens that have more obtuse teeth ( Fig. 13B View FIG ), demonstrating that the shape of anterolateral teeth is not always a reliable character among these and other species of Carcinoplax .

Two characters, however, seem constant for C. verdensis and support our view that this is a distinct species. The fingers of the chelipeds in adult C. verdensis of both sexes are dark brown or almost black only along the distal two-thirds to half of the fingers ( Figs 13I, J View FIG ; 14H View FIG ; 15A View FIG ); whereas in C. abyssicola and C. longipes , almost the entire length of the fingers in adults is pigmented ( Figs 1C View FIG ; 2F, H View FIG ; 3F, I View FIG ; 4H View FIG ; 5H View FIG for C. abyssicola ; Figs 6A View FIG ; 7A View FIG ; 8H View FIG ; 9H View FIG for C. longipes ). While the G1 of C. verdensis is similar to that of C. abyssicola , being relatively shorter and less broad basally, the distal part in C. verdensis is always directed obliquely outwards ( Fig. 24 View FIG A-C), whereas the distal part is more truncated and the tip is directed laterally in C. abyssicola ( Fig. 23 View FIG A-C, E-G).

Additional support on the distinct nature of C. abyssicola has been provided by preliminary data based on the barcode region of the cytochrome oxidase I ( COI) gene (L. Corbari, unpublished data) as well as C. abyssicola and the remaining species treated here (L. M. Tsang, unpublished data).

On the basis of the figures of the specimens, and in particular the structures of the G1, it is clear that the material referred to as ‘ Carcinoplax aff. longipes ’ by Guinot (1989) ( Fig. 24E, G View FIG ) belongs to C. verdensis as presently defined.

The known geographical distributions of the four species being discussed are relatively distinct. Carcinoplax abyssicola so far is known from the western Pacific, from southeastern Moluccas and southern Java in Indonesia to Tonga (see above) as well as in the easternmost part of the Indian Ocean. Carcinoplax longipes is known only from the Indian Ocean, although it occurs in the same area as C. abyssicola in southern Java. The two species, however, seem to have different habitats and were only collected together from one station (out of 10 stations) in Java. Carcinoplax verdensis is known for certain only from Japan, Taiwan, Philippines, and South China Sea (see below). Carcinoplax fasciata is so far known from the Arabian Sea off the coast of Kerala, India. Carcinoplax abyssicola and the species treated here so far extend east as far as Tonga. The only species of Carcinoplax east of Tonga are two small-size species, C. velutina Castro, 2007 and C. uncinata Castro, 2009 both known from French Polynesia. Carcinoplax velutina is also found in Vanuatu, New Caledonia, and Fiji ( Castro 2007); C. uncinata in New Caledonia and Solomon Islands ( Castro 2009). Carcinoplax uncinata is herein recorded from French Polynesia for the first time (male 8.8 × 11.4 mm, TARASOC; stn CP3376, Tuamotu Archipelago, 15°41’S, 146°54’W, 646- 737 m depth; 10.V.2009, MNHN-IU-2011-5233).

The depth distribution is similar in all three species. Specimens of C. abyssicola and C. longipes were taken at maximum depths of 890 m and 870 m, respectively, but one specimen of C. verdensis was recorded at 2149 m, which is likely to be in error.

Individuals of C. abyssicola and C. verdensis appear to be larger in size (largest specimens measured reaching 19.3 mm CL and 19.2 mm CL, respectively) than those of C. longipes (largest specimen measured 10.8 mm CL). Of the six species being treated here, C. polita is characterised by having the largest measured individuals, with one specimen 25.9 mm CL.

Specimens collected by the Siboga Expedition from Indonesia and identified as C. abyssicola by Tesch (1918) could not be found in the ZMA, where all other Siboga goneplacids were originally deposited. This record is provisionally recognised as correct as the species is known from that area.

Guinot (1989: 307) commented that in the form of the carapace and anterolateral teeth, C. abyssicola was closest to C. verdensis , but differed in having the teeth more spiniform and the chelae being short and globose. While this difference is usually valid for the structure of the anterolateral teeth, the form of the chela varies with size and sex and it is not a reliable character. As discussed earlier, the two species, however, differ in other characters.

COI

University of Coimbra Botany Department

ZMA

Universiteit van Amsterdam, Zoologisch Museum

Kingdom

Animalia

Phylum

Arthropoda

Class

Malacostraca

Order

Decapoda

Family

Goneplacidae

Genus

Carcinoplax

Loc

Carcinoplax abyssicola ( Miers, 1885 )

Ng, Peter K. L. & Castro, Peter 2020
2020
Loc

Carcinoplax specularis

CASTRO P. 2007: 640
2007
Loc

Carcinoplax abyssicola

NG P. K. L. & GUINOT D. & DAVIE P. J. F. 2008: 80
CASTRO P. 2007: 623
GUINOT D. 1989: 305
GUINOT D. 1969: 526
1969
Loc

Neopilumnoplax abyssicola

SERENE R. 1968: 90
1968
Loc

Pilumnoplax abyssicola

SERENE R. & LOHAVANIJAYA P. 1973: 62
GUINOT D. 1969: 526
SERENE R. 1968: 90
TESCH J. J. 1918: 155
1918
Loc

Pilumnoplax abyssicola

WHITELEGGE T. 1900: 158
1900
Loc

Pseudorhombila (Pilumnoplax) abyssicola

MIERS E. J. 1885: 588
1885