Actaea grimaldii Bouchet & Isyeb 2015, sp. nov.
Creators: name: Ng, Peter K. L.
name: Bouchet, Philippe
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Xanthidae
Actaea
Actaea grimaldii

description: Actaea grimaldii sp. nov.
urn:lsid:zoobank.org:act: A736C0FE-D2B4-4256-AB85-4370386B0231
Figs 1–5
Actaea peronii var. squamosa – Calman 1900: 10 (not Actaea squamosa Henderson, 1893).
Actaea spinosissima – Odhner 1925: 59 (part). — Serène 1984: 115, pl. 14F. — Davie 2002: 511 (not Actaea spinosissima Borradaile, 1902).
Diagnosis
Anterior surfaces of carapace regions (1M, 2M, 3M, 2L, 5L) covered with numerous short sharp spines and sharp tubercles of varying sizes, 2M and 2L surface gently convex, not distinctly inflated in frontal view, 2M separated by median longitudinal groove anteriorly, 4M lunate, with sharp granules; 1P flattened, divided into many smaller regions by shallow grooves, with distinct transverse groove on anterior third, confluent with series of flattened granules on 3R, 2R and 1R (Figs 1, 2A, 3A, 4A); frontal margins lined by sharp granules, 1F and 2F with many sharp spines which project anteriorly, hiding frontal margin from dorsal view (Figs 1, 2 A–B, 3A–B, 4A); anterolateral margin with 4 spines (excluding external orbital spine), each with smaller spine or spines basal to it on sub-branchial surface (Figs 1, 2A, 3A, 4A); suborbital and subhepatic regions covered with numerous small, sharp granules (Figs 2B, 3B); third maxilliped with outer surfaces pitted (Fig. 5A); outer surfaces of chelipeds with numerous sharp spines and sharp tubercles, with small, sharp granules interspersed, carpus ovate, inner angle with several short, slightly curved spines, outer surface of chela with strong spines, inner surface of chela with median spine and several smaller sharp tubercles and granules (Figs 1, 2A, C–D, 3A, C–D); ambulatory legs short, outer surfaces of merus, carpus and propodus covered with sharp tubercles or granules, dorsal margins of merus, carpus and dactylus with numerous sharp spines, ventral margin of dactylus with subterminal tubercle, with scattered long, simple setae, some of which extend beyond tip of dactylus (Figs 1, 2A, 3A, 4C); thoracic sternum with surface distinctly pitted (Figs 1B, 5B); male abdomen longitudinally narrow, surfaces of sternites 1–3 pitted (Fig. 5C); G1 elongate, gently sinuous, distal part curves upwards (Fig. 5 D–F).
Etymology
The species name is in honour of His Serene Highness Albert II, Prince of Monaco, patron of the PAPUA NIUGINI Expedition and several other biodiversity expeditions of the “Our Planet Reviewed” programme conducted by MNHN and Pro-Natura International. The red and white colour pattern of the new species also alludes to the colours associated with the House of Grimaldi.
Type material
Holotype
PAPUA NEW GUINEA: Madang District, Expedition PAPUA NIUGINI, stn PB35, outer slope, south of Sek Is., 05°07.0’S 145°49.4’E, 12 m, 4 Dec. 2012, 1 ♂, 6.2 × 4.4 mm (MNHN IU 2013-921).
Paratypes
PAPUA NEW GUINEA: same data as holotype, 1 ♂, 5.1 × 3.8 mm (ZRC, ex MNHN IU 2013-920); Madang District, Expedition PAPUA NIUGINI, stn PR17, west of Kranket Is., 05°11.8’S 145°48.8’E, 15 m, 11 Nov. 2012, 1 ♀, 10.2 × 7.8 mm (ZRC, ex MNHN IU 2013-1245); Expedition PAPUA NIUGINI, stn PR05, Kranket Is., 05°11.3’S 145°49.6’E, 7 Nov. 2012, 1 ♀, 8.5 × 6.2 mm (MNHN IU 2013-222); Expedition PAPUA NIUGINI, stn PB28, east of Kranket Is., 05°11.9’S 145°49.6’E, 10 m, 24 Nov. 2012, 1 young ♀, 6.7 × 4.9 mm (MNHN IU 2013-759).
Comparative material
Actaea spinosissima Borradaile, 1902
MALDIVES: Mahlos Atoll, 23 fathoms, J.S. Gardiner coll., holotype, ♂, 5.1 × 3.4 mm (juvenile, no gonopods) (CUMZ I.63106).
BRITISH INDIAN OCEAN TERRITORY: Great Chagos Bank, stn CH 0666, outer reef, among dead branching coral heads, 10 m, Brothers Island, C. Head & H. Koldewey coll., 28 Feb. 2013, 1 ♂, 8.9 × 6.6 mm (ZRC).
Actaea polyacantha (Heller, 1861)
GUAM: southwest of Orote Peninsula, G. Paulay coll., 15–18 Apr. 2000, 1 ♀ (ZRC 2000.731). PAPUA NEW GUINEA: Expedition PAPUA NIUGINI, stn PB17, outer slope, Sek Is., 05°04.9’S 145°49.3’E, 26 m, 14 Nov. 2012, 1 ♀, 6.4 × 4.9 mm (ZRC, ex MNHN IU 2013-1255).
Actaea peronii (H. Milne Edwards, 1834)
AUSTRALIA: New South Wales, M. Ward coll., 2 ♀♀ (ZRC 1969.12.27.3–4).
Description
Regions well demarcated, separated by distinct grooves, anterior surfaces (notably 1M, 2M, 3M, 2L, 5L) covered with numerous spines and sharp tubercles of varying sizes; 2M and 2L surface gently convex, does not appear inflated in frontal view; 2M separated by median longitudinal groove anteriorly; 3M subtriangular, with sharp spines; 4M lunate, with sharp granules; 1P flattened, divided into many smaller regions by shallow grooves, with distinct transverse groove on anterior third, confluent with series of flattened granules on 3R, 2R and 1R; 2O transversely narrow, low; 2P raised, surface rounded (Figs 1, 2A, 3A, 4A). Frontal margin bilobate, lobes separated by broad, U-shaped cleft; margins lined by sharp granules; 1F and 2F with many sharp spines which project anteriorly, hiding frontal margin from dorsal view (Figs 1, 2 A–B, 3A–B, 4A). Supraorbital margin with 3 distinct spines; orbit short, ovate; eye completely filling orbit; peduncle short, stout, with several dorsal granules; cornea large, with granule basally (Figs 2 A–B, 3A–B, 4A–B). Anterolateral margin arcuate, with 4 spines (excluding external orbital spine), each with smaller basal spine or spines on sub-branchial surface; posterolateral margin gently concave, surfaces covered with small, flattened granules; posterior carapace gently sinuous, lined with small, flattened granules (Figs 1, 2A, 3A, 4A).
Suborbital margin with 5 or 6 small spines; suborbital and subhepatic regions covered with numerous small, sharp granules; pterygostomian region almost smooth (Figs 1H, 2B, 3B). Antennules folding laterally (Figs 2B, 3B). Antenna with basal article quadrate, with 1 large and 1 small, sharp granule, mobile; flagellum short, at base of orbital hiatus (Figs 2B, 3B). Epistome transversely rectangular; anterior margin granulated; posterior margin with prominent median triangle, lateral margins sinuous (Figs 2B, 3B).
Third maxilliped relatively short; outer surfaces pitted; ischium subrectangular, with shallow but distinct submedian sulcus, inner margin dentate; merus quadrate, distolateral angle not distinctly auricular; exopod stout, distal end reaching to distolateral edge of merus, flagellum elongate, as wide as merus (Fig. 5A).
Chelipeds slightly asymmetrical; outer surfaces with numerous sharp spines and sharp tubercles, with small, sharp granules interspersed; inner and outer surfaces with scattered short, simple setae (Figs 1, 2A, C–D, 3A, C–D). Basis-ischium lined with small granules. Merus short, rounded; dorso-distal spine largest. Carpus ovate, inner angle with several short, curved spines (Figs 1, 2A, 3A). Chelae short, stout, palm longer than fingers, not pigmented black or dark brown; inner surface with median spine and several smaller sharp tubercles and granules (Figs 2 C–D, 3C–D). Pollex with 2 low, longitudinal ridges, 1 submedian groove; cutting edge with 3 or 4 large, blade-like teeth; tip subspatuliform (Figs 2 C–D, 3C–D). Dactylus with 1 distinct low, longitudinal ridge, 1 submedian groove; upper margin with 2–4 spines on proximal half, cutting edge with 2 larger teeth on proximal half, distal half with 2 or 3 low teeth; tip subspatuliform (Figs 2 C–D, 3C–D).
Ambulatory legs short, stout; second pair longest; fourth pair shortest (Figs 1, 3A). Basis-ischium lined with small granules. Outer surfaces of merus, carpus and propodus covered with sharp tubercles or granules (Figs 1, 2A, 3A, 4C). Merus with dorsal margin armed with numerous sharp spines which gradually become smaller proximally, distal one largest; ventral margin lined with small, sharp granules (Figs 1, 2A, 3A, 4C). Dorsal margins of carpus and propodus with several sharp spines; ventral margin of carpus with sharp granules; ventral margin of propodus with sharp spines (Figs 1, 2A, 3A, 4C). Dactylus gently curved, surface covered with small, sharp granules; ventral margin with relatively larger subterminal tubercle; tip corneous; surfaces with scattered long, simple setae, those on second to third legs may be very long, extending well beyond tip of dactylus (Figs 1, 2A, 3A, 4C). Dactylo-propodal lock well developed; distal margin of propodus with rounded median projection that overlaps ball-like swelling on proximal margin of dactylus (Fig. 4C).
Thoracic sternum with surface distinctly pitted (Figs 1B, 5B). Thoracic sternites 1 and 2 completely fused; sternites 2 and 3 separated by distinct transverse suture; sternites 3 and 4 completely fused except for lateral cleft (Figs 1B, 5B). Sternoabdominal cavity deep, reaching to median part of sternite 4 (Figs 1B, 5C). Male abdominal locking mechanism a knob-like process, on anterior third of sternite 5.
Male abdomen longitudinally narrow; surfaces of sternites 1–5 pitted (Fig. 5C). Somites 1 and 2 trapezoidal, completely covering surfaces of thoracic sternum between coxae of last pair of ambulatory legs, sternite 8 completely covered; somites 3–5 completely fused, median sutures not discernible; lateral margins concave; somite 6 rectangular, lateral margins gently sinuous, slightly longer than telson; telson triangular, lateral margins gently sinuous, tip rounded (Fig. 5C).
G1 elongate, gently sinuous, distal part curves upwards, subdistal surfaces with numerous long setae and spinules (Fig. 5 D–F). G2 short, c. quarter of length of G1; proximal part sinuous, distal part spatuliform (Fig. 5G).
Females and variation
The females agree with the males in almost all non-sexual characters. A female measuring 6.7 × 4.9 mm (MNHN IU 2013-759) is still immature, with the abdomen triangular in shape. An adult female, 10.2 × 7.8 mm (pleopods fully setose, ZRC, ex MNHN IU 2013-1245), has an ovate abdomen that covers about half the surface of the thoracic sternum. The vulvae are small, positioned on the anterior half of sternite 6 submedially and each has a distinct opercular cover in the form of a narrow plate (Fig. 4B). There is hardly any variation in the diagnostic characters, although some of the specimens (e.g., ZRC, ex MNHN IU 2013-1245) are twice the size of the smaller crabs (e.g., ZRC, ex MNHN IU 2013-920).
The long, simple setae on the ambulatory legs are easily broken, and while obvious in fresh specimens (Fig. 1), they are often lost in preserved material. The holotype male has a developed G1 (Fig. 5 D–F) but does not appear to be fully mature. While the setae on the subdistal part of the G1 are long (Fig. 5 E–F), they are simple and not plumose as is typical for actaeine gonopods (cf. Guinot 1976).
Colour
In life (Fig. 1), the colour is a striking bright orange to red across the median part of the carapace, with the lateral regions white. There may be patches of white on the gastric and adjacent regions in smaller specimens. The legs are banded red and white, and the chelipeds are red and white, with parts yellowishwhite in colour. The fingers of the chela are reddish-orange basally and white at the tips. The ventral surfaces are white, but abdominal somites 1 and 2 may have large patches of red.
Distribution
This species is known for certain from the Moluccas and Papua New Guinea, and is probably also present in Australia.
description: Published as part of Ng, Peter K. L. & Bouchet, Philippe, 2015, Actaea grimaldii, a new species of reef crab from Papua New Guinea (Crustacea, Brachyura, Xanthidae), pp. 1-18 in European Journal of Taxonomy 140 on pages 3-11, DOI: 10.5852/ejt.2015.140, http://zenodo.org/record/3785520