Crinitocinus alcocki ( Borradaile, 1902 )

Ng, Peter K. L. & Rahayu, Dwi Listyo, 2014, Revision of the family Acidopsidae Števčić, 2005, and the systematic position of Typhlocarcinodes Alcock, 1900, Caecopilumnus Borradaile, 1902, and Raoulia Ng, 1987, with descriptions of two new genera and five new species (Crustacea: Brachyura: Goneplacoidea), Zootaxa 3773 (1), pp. 1-63 : 16

Crinitocinus alcocki ( Borradaile, 1902)

( Figs. 9–11 , 12A–C , 40E–H )

Pilumnus alcocki Borradaile, 1902: 248 , fig. 48.— Rathbun 1911: 230.— Ng et al. 2008: 141.

Material examined. Holotype: young male (5.6 × 4.8 mm) ( CUMZ I.63692), 20 fathoms, Suvadiva Atoll , Maldives, dredge, coll. J.S. Gardiner. Others: Seychelles: 2 young males (4.5 × 4.3 mm [damaged], 4.3 × 3.9 mm [crushed]) ( CUMZ I.63694), Amirante Is., station E16, 39 fathoms, 13 October 1905; and station E1, 9 October 1905, 29 fathoms, coll. H.M.S. Sealark; Papua New Guinea: 1 female (13.2 × 9.9 mm) ( MNHN IU-2013-865), station PR 95, Tab I., 5°10.2'S 145°50.6'E, coll. Expedition PAPUA NUIGINI, 24 November 2012; 1 female (10.5 × 8.7 mm) ( ZRC 2013.1726 , ex MNHN IU-2013-578), station PR 55, Mizegwadan Reef, northwest of Tab I., 5°09.6'S 145°49.4'E, 20 m, New Guinea, coll. Expedition PAPUA NUIGINI, 18 November 2012; Hawai‘i: 1 dismembered male (carapace 11.1 × 8.8 mm) ( ZRC 2013.1800 ), from stomach of goatfish Parupeneus multifasciatus (Quoy & Gaimard, 1825) (family Mullidae ), off Oahu, coll. B. Schumacher, 8 May 2007.

Diagnosis. As for genus.

Remarks. Borradaile (1902: 248) described the species on the basis of one specimen (sex not stated) measuring 6.2 × 4.8 mm. The type specimen (CUMZ) is a young male, and differs from the data in Borradaile in that it measures 5.6 rather than 6.2 mm in carapace width. Borradaile’s (1902: fig. 48) figure is rather misleading because it depicts a rather broad specimen; the type is actually more quadrate ( Fig. 9A ), and he may have obtained his measurements from the inaccurate figure rather than direct measurements. The holotype male is not mature, although the male abdomen and sternum are well-developed ( Figs. 9B , 11F, G ), we could not find any trace of gonopods, suggesting it is still a juvenile.

The specimens from Amirante Is. in the western Indian Ocean reported by Rathbun (1911) agree very well with the type male except that they are smaller, with the carapace more quadrate and the eyes relatively larger ( Fig. 10A ). Three larger specimens from Papua New Guinea and Hawai‘i are also here referred to C. alcocki as they have all the diagnostic features of the genus. Being larger than the holotype and than Rathbun’s (1911) specimens, their carapaces are proportionately broader and their eyes relatively smaller ( Fig. 10B ), but we cannot discern any major differences with the material from the Indian Ocean. The two intact specimens from Papua New Guinea are both females, and while the specimen from Hawai‘i is an adult male, it was from a fish stomach and badly dismembered. Fortunately, the carapace and male abdomen of this specimen are intact but only one G2 and part of a G1 could be found ( Fig. 11I–K ). It is possible that with the discovery of intact males and a larger series, the populations from the West Pacific and Indian Oceans may be shown to be distinct.

The colours of live specimens of Crinitocinus alcocki ( Fig. 40E ) resemble those for Parapilumnus species ( Fig. 40C, D ), with the carapace and pereopods white and covered with patches of orange or red.

Distribution. Maldives, Amirante I. and Papua New Guinea; 20– 71 m.

Figures

FIGURE 9. Crinitocinus alcocki (Borradaile, 1902). A–C, holotype male (5.6 × 4.8 mm) (CUMZ I.63692), Suvadiva Atoll, Maldives; D, male (4.5 × 4.3 mm) (CUMZ I.63694), Amirante Is.. A, dorsal view; B, anterior thoracic sternum and male abdomen; C, left chela; D, right chela.

FIGURE 10. Crinitocinus alcocki (Borradaile, 1902). A, male (4.5 × 4.3 mm) (CUMZ I.63694), Amirante Is.; B–D, female (13.2 × 9.9 mm) (MNHN IU-2013-865), Madang, New Guinea. A, B, dorsal views; C, left third maxilliped; D, female thoracic sternum and vulva.

FIGURE 11. A–C, Acidops cessacii (A. Milne-Edwards, 1878), male (10.0 × 7.7 mm) (MNHN), Cape Verde; D–G, Crinitocinus alcocki (Borradaile, 1902), holotype male (5.6 × 4.8 mm) (CUMZ I.63692), Suvadiva Atoll, Maldives; H, Crinitocinus alcocki (Borradaile, 1902), male (4.5 × 4.3 mm) (CUMZ I.63694), Amirante Islands; I–K, Crinitocinus alcocki (Borradaile, 1902), male (carapace 11.1 × 8.8 mm) (ZRC 2013.1800), Hawai‘i. A, B, G1; C, G2; D, left antenna and antennule; E, right third maxilliped; F, male anterior thoracic sternum; G, H, male abdomens; I, damaged left G1 (proximal parts broken off); J, distal part of left G1; K, left G2. Scales: D–H, I, K = 0.5 mm; J = 0.05 mm. A–C after Guinot & Ribeiro (1962: figs. 27a, b, 28).

FIGURE 12. A–C, Crinitocinus alcocki (Borradaile, 1902), female (13.2 × 9.9 mm) (MNHN IU-2013-865), Madang, New Guinea; D–F, Acidops cessacii (A. Milne-Edwards, 1878), female (12.6 × 9.9 mm) (ZRC 1998.58), Ascension. A, D, right orbits and eyes (partially denuded); B, E, female anterior thoracic sterna and abdomens; C, F, right third and fourth ambulatory legs.

FIGURE 40. Colours in life. A, Acidops fimbriatus (Stimpson, 1871), female (19.7 × 14.9 mm) (MNHN-IU-2013-9470), Clipperton I. [photograph L. Albenga, courtesy of J. Poupin]; B, Acidops cessacii (A. Milne-Edwards, 1878), ovigerous female (9.7 × 7.3 mm) (ZRC 2013.1459), São Tomé [photograph A. Anker]; C, Parapilumnus cristimanus (A. Milne-Edwards, 1873), female (23.2 × 17.7 mm) (ZRC 2013.1905), Paeowa I., Papua New Guinea [photograph T.-Y. Chan]; D, Parapilumnus cristimanus (A. Milne-Edwards, 1873), female (10.1 × 8.0 mm) (MNHN 2013-513), Sek I., Papua New Guinea [photograph T.- Y. Chan]; E, G, Crinitocinus alcocki (Borradaile, 1902), female (13.2 × 9.9 mm) (MNHN IU-2013-865), New Guinea [photographs A. Anker]; F, Crinitocinus alcocki (Borradaile, 1902), female (10.5 × 8.7 mm) (ZRC 2013.1726), New Guinea [photograph A. Anker]; G, Crinitocinus alcocki (Borradaile, 1902), Kona coast, Hawai‘i, in situ, specimen not preserved [photograph Tina Owens, courtesy of J. Hoover].