Carcinoplax adelphia, Ng & Castro, 2020

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 : 268-272

publication ID 10.5252/zoosystema2020v42a17

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Carcinoplax adelphia

sp. nov.

Carcinoplax adelphia View in CoL n. sp.

( Figs 19 View FIG A-H; 20 View FIG A-I; 25 View FIG F-I; 27 View FIG E, F)

TYPE MATERIAL. — Holotype. Vanuatu • ♂, 19.4 × 25.4 mm; Vanuatu ; MNHN-IU-2016-8002.

Paratypes. Vanuatu • 2 ♀, largest 16.9 × 22.4 mm; SANTO 2006, stn AT19, S. Urelapa I.; 15°41’S, 167°01’E; 503-600 m depth; 21.IX.2006, ZRC 2009.0997 View Materials GoogleMaps 1 ovigerous ♀, 14.4 × 19.0 mm; SANTO 2006, stn AT96, Big Bay , Santo; 15°06.9’S, 166°52.8’E; 328-354 m depth; 14.X.2006; ZRC 2018.1412 View Materials GoogleMaps 1 ♀, 16.9 × 22.4 mm, 1 ♂, 15.7 × 21.2 mm; SANTO 2006, stn AT98, Big Bay ; 15°06.6’S, 166°50.6’E; 347-394 m depth; 14.X.2006; ZRC 2009.0922 View Materials GoogleMaps 5 ♀, 16.5 × 22.5 mm, 2 ♂, larger one cl 12.3 mm, damaged; same data as ZRC 2009.0922; ZRC 2009.0998 View Materials GoogleMaps 1 ♂, 18.8 × 29.9 mm; SANTO 2006, stn AT99, Big Bay ; 15°05.5’S, 166°50.9’E; 351-395 m depth; 14.X.2006; ZRC 2008.0907 View Materials GoogleMaps 10 ♀, largest 13.6 × 18.3 mm, 15.9 × 20.8 mm, 1 ♂, 16.0 × 22.9 mm; same data as ZRC 2008.0907; ZRC 2009.0996 View Materials GoogleMaps 1 ovigerous ♀, 17.7 × 24.2 mm; same data as ZRC 2008.0907; ZRC 2018.1413 View Materials GoogleMaps 3 ♀, largest 15.1 × 19.3 mm, 14 ♂; SANTO 2006, stn AT100, Big Bay ; 15°06.0’S, 166°51.4’E; 399-416 m depth; 14.X.2006; MNHN-IU-2016-8002 GoogleMaps 1 ovi- gerous ♀, 8.5 × 11.2 mm, 1 ♂, 7.6 × 11.2 mm; SANTO 2006, stn AT121, W Malo I.; 15°38.7’S, 167°01.2’E; 275-290 m depth; 19.X.2006, ZRC 2009.0989 View Materials GoogleMaps • 1 ♂, trap 3, no other data, MNHN-IU-2010-5546.

TYPE LOCALITY. — Vanuatu, SANTO 2006; stn AT100, Big Bay; 15°06.0’S, 166°51.4’E; 399-416 m depth.

DIAGNOSIS. — Carapace ( Figs 19A, B View FIG ; 20A, B View FIG ; 27E, F View FIG ) quadrate, slightly wider than long (1.4 × wider than long in holotype); slightly convex, smooth. Front ( Figs 19C, D View FIG ; 20C, D View FIG ) straight, slight notch between front, inner edge of supraorbital border. Rounded, short tooth on outer orbital angle; two slender, acutetipped anterolateral teeth on each side of carapace. Conspicuous granules on subhepatic, pterygostomial regions ( Figs 19C, D View FIG ; 20C, D View FIG ), becoming more pronounced in pterygostomial crest, ridge; short granules on anterior, dorsal surface of carapace. Posterior margin of epistome ( Figs 19D View FIG ; 20D View FIG ) straight, slight notch on each lateral margin. Distal 2/3 to half of fingers dark brown in females ( Fig. 20A, F, I View FIG ), males ( Fig. 19A, F, H View FIG ). Smooth, oblong “window” on inner, dorsal surface of cheliped propodi of some males ( Fig. 19F View FIG ). Inner (ventral), distal margin of cheliped carpus ( Figs 19F View FIG ; 20F View FIG ) with triangular tooth. P2-P5 ( Figs 19A View FIG ; 20A View FIG ; 27E, F View FIG ) moderately stout in appearance, P5 not reaching second anterolateral tooth. Male pleon ( Fig. 19G View FIG ) proportionally narrow. G1 ( Fig. 25 View FIG F-H) slender; pointed tip with scattered spinules; G2 ( Fig. 25I View FIG ) slender, nearly equal or slightly longer than G1, slightly curved flagellum, tip with two lateral spinules.

ETYMOLOGY. — The name is derived from the Greek adelphos for ‘brother’ or ‘sister,’ alluding to the close affinities of the new species with C. specularis . The name is treated as a noun.

COLOUR IN LIFE. — Orange with a semi-circular row of small white spots on each side of the carapace ( Fig. 27E, F View FIG ).


DEPTH. — Present in samples collected at depths of 275- 600 m.


Carcinoplax adelphia n. sp. and C. specularis are superficially very similar, including the spots on the dorsal surface of the carapace shown in life ( Fig. 27E, F View FIG for C. adelphia n. sp.; Fig. 27D View FIG for C. specularis ). They are, however, easily separated by the structure of their G1s. The G1 is relatively shorter and stouter in C. specularis ( Fig. 25A, B View FIG ,) than in C. adelphia n. sp., which is more elongated, particularly the distinctly more slender distal half ( Fig. 25F View FIG ).

Carcinoplax specularis can be also separated from allied species by the obtusely triangular median part of the posterior margin of its epistome, which extends beyond the lateral margins, with the lateral margins gently concave ( Figs 10D View FIG ; 11D View FIG ; 12D View FIG ) (median part very low and almost at the same level as the lateral margins, which are almost straight in C. adelphia n. sp.; Figs 19D View FIG ; 20D View FIG ). Both share a similar colour pattern, with two unique semi-circular rows of white spots on the dorsal surface of the carapace of live individuals ( Fig. 27D View FIG for C. specularis ; Fig. 27E, F View FIG for C. adelphia n. sp.).

Like in C. specularis , a “window” on the chela was found in a few large males of C. adelphia n. sp.: 15.7 × 21.2 mm (ZRC 2009.0922), 18.8 × 29.9 mm (ZRC 2008.0907) and the holotype 19.4 × 25.4 mm (MNHN-IU-2016-8002). These are not obvious in females or juveniles.

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