Alcomaja irrorata, Ng & Forges, 2015

Ng, Peter K. L. & Forges, Bertrand Richer De, 2015, Revision of the spider crab genus Maja Lamarck, 1801 (Crustacea: Brachyura: Majoidea: Majidae), with descriptions of seven new genera and 17 new species from the Atlantic and Indo-West Pacific, Raffles Bulletin of Zoology 63, pp. 110-225 : 145-147

publication ID	https://doi.org/ 10.5281/zenodo.5384590
publication LSID	lsid:zoobank.org:pub:40BCDD62-D35E-46D1-95A3-2CC0DF219DEE
persistent identifier	https://treatment.plazi.org/id/5B273D47-C7F9-469B-9C1D-B29296A70CC0
taxon LSID	lsid:zoobank.org:act:5B273D47-C7F9-469B-9C1D-B29296A70CC0
treatment provided by	Valdenar
scientific name	Alcomaja irrorata
status	sp. nov.

Treatment

Alcomaja irrorata View in CoL n. sp.

( Figs. 2C View Fig , 16A View Fig , 18E, F View Fig , 19A–C View Fig , 39L View Fig , 41G View Fig , 45A View Fig , 49A View Fig , 52E View Fig , 53M View Fig , 55K, L View Fig )

Material examined. Holotype: male (52.6 × 45.7 mm) ( NMCR), Balicasag, Panglao, Bohol, Philippines , 200–300 m, coll. local fishermen with tangle nets, June 2002 . Paratypes: Philippines – 1 male (45.5 × 39.5 mm, with rhizocephala) , 6 males (47.7 × 43.1 mm, 48.4 × 42.2 mm, 46.7 × 41.5 mm,

44.7 × 39.1 mm, 44.2 × 38.0 mm, 44.7 × 38.4 mm), 2 young males (34.4 × 29.8 mm, 28.7 × 23.9 mm), 2 young females (31.5 × 26.9 mm, 29.7 × 26.1 mm), 10 ovigerous females (43.7 × 38.2 mm, 44.1 × 38.7 mm, 41.1 × 36.9 mm, 44.1 × 36.9 mm, 44.1 × 38.2 mm, 43.7 × 39.2 mm, 45.1 × 40.8 mm, 44.0 × 37.6 mm, 44.1 × 39.2 mm, 41.6 × 36.6 mm), 1 male (28.1 × 23.6 mm, with bopyrid) ( ZRC 2013.1229 View Materials ), Balicasag, Panglao, Bohol , Philippines, 200–300 m, coll. local fishermen with tangle nets, June 2002 . — 2 ovigerous females (42.6 × 37.4 mm, 43.0 × 38.0 mm) ( USNM, ex ZRC 2001.0434 View Materials ), Balicasag, Panglao, Bohol, 200–300 m, coll. local fishermen with tangle nets, Balicasag , Panglao , Bohol, 200–300 m, coll. local fishermen with tangle nets, December 2000 . — 12 males (44.6 × 39.7 mm, 44.4 × 39.7 mm, 45.3 × 39.9 mm, 47.5 × 43.4 mm, 46.4 × 40.2 mm, 40.5 × 35.0 mm, 44.4 × 39.0 mm, 43.9 × 38.3 mm, 44.8 × 39.2 mm, 47.0 × 40.4 mm, 46.5 × 40.1 mm, 44.1 × 39.1 mm); 10 ovigerous females (44.3 × 38.9 mm, 42.5 × 38.1 mm, 39.3 × 34.1 mm, 37.9 × 35.2 mm, 43.7 × 37.7 mm, 45.3 × 39.6 mm, 45.3 × 40.7 mm, 42.9 × 37.9 mm, 40.5 × 35.6 mm, 37.7 × 32.7 mm), 1 young female (32.2 × 26.8 mm) ( ZRC 2001.0616 View Materials ), Balicasag, Panglao, Bohol, 200–300 m, coll. local fishermen with tangle nets, 28 November 2001 . Others: 1 young female (29.7 × 25.4 mm), 1 ovigerous female (26.2 × 22.5 mm) ( ZRC 2013.1222 View Materials , part ex ZRC 2001.0616 View Materials ), Balicasag Island , Panglao, Bohol, coll. fishermen with tangle nets, 28 November 2001 . — 1 male (45.6 × 41.1 mm) ( AM), Balicasag Island, Panglao , Bohol, coll. fishermen with tangle nets, July 2003 . — 1 male with rhizocephalan (38.9 × 33.5 mm) ( ZRC 2013.1221 View Materials ), Balicasag Island, Panglao , Bohol, coll. fishermen with tangle nets, November 2003 . — 4 males, 2 females (NSMT-Cr 15387), Balicasag Island, Panglao , Bohol, coll. local fisherman via M. Takeda & H. Komatsu, February 2003 . — 1 male (43.0 × 37.2 mm) ( ZRC 2013.1223 View Materials ), station CP 2343, off Pamilacan Island, Bohol Sea , 9°27.4’N 123°49.4’E, 273–356 m, coll. PANGLAO 2005, 23 May 2005 GoogleMaps .

Diagnosis. Carapace pyriform; dorsal surface of carapace and ambulatory legs covered with short, hooked setae; with small and large rounded granules, some of which merge basally ( Fig. 16A View Fig ). Pseudorostral spines dorsoventrally flattened in adults ( Fig. 18E, F View Fig ). Intercalated spine subtruncate basally; antorbital spine gently curved. Lateral and branchial spines strong in juveniles, weak in adults ( Fig. 18E, F View Fig ). Subhepatic region with rugose and unevenly granulated surface ( Fig. 39L View Fig ). Basal antennal article weakly granulated, with 6 small granules, 2 stout spines distally ( Figs. 39L View Fig , 41G View Fig ). Ischium of third maxilliped smooth or rugose, without distinct granules ( Fig. 45A View Fig ). Adult male ambulatory legs long, especially merus and propodus first leg which can be twice length of carapace; surfaces almost smooth or with setae when young ( Figs. 16A View Fig , 55K, L View Fig ). G1 strongly curved, distal part curved upwards ( Fig. 19A–C View Fig ).

Etymology. The name is derived from the Latin “ irroratus ” which means covered with granules, alluding to the appearance of the species.

Remarks. In general appearance, A. irrorata n. sp. is closest to A. gracilipes ( Chen & Ng, 1999) , described from the South China but is now also recorded from the Philippines. However, there are several key differences between the two species. Most significantly, while the G1 structures are superficially similar, it is more strongly curved in A. irrorata ( Fig. 19A–C View Fig ) with that of A. gracilipes relatively straighter along the median part ( Fig. 19D–F View Fig ). This difference is consistent even for smaller specimens. In addition, the outer surface of the ischium of the third maxilliped is smooth or almost so in A. irrorata ( Fig. 45A View Fig ) (distinctly granulous in A. gracilipes , Fig. 45B, C View Fig ); the pseudorostral spines in A. irrorata is relatively stouter with the cross-section more dorso-ventrally flattened ( Fig. 18E, F View Fig ) (relatively more slender with a rounded cross-section in A. gracilipes , Fig. 18C, D View Fig ); the postorbital spine is usually relatively wider in A. irrorata ( Fig. 8E, F View Fig ) (more slender in A. gracilipes , Fig. 18C, D View Fig ); and the ambulatory legs are relatively longer in adult A. irrorata than in A. gracilipes ( Fig. 16A View Fig versus Fig. 16B, C View Fig ).

Alcomaja irrorata is also similar to A. confragosa ( Griffin & Tranter, 1986) . However, the intercalated spine is more acutely triangular in A. confragosa ( Fig. 18A, B View Fig ) (relatively stouter in A. irrorata , Fig. 18E, F View Fig ); the postorbital spine is relatively more narrow in A. confragosa ( Fig. 18A, B View Fig ) (relatively stouter in A. irrorata , Fig. 18E, F View Fig ); the basal antennal article is lined with granules on the outer margin in A. confragosa (see Griffin & Tranter, 1986: fig. 72d) (with only several granules on the inner margin in A. irrorata , Fig. 39L View Fig ); the ischium of the third maxilliped is relatively shorter with the outer surface is weakly granular in A. confragosa (see Griffin & Tranter, 1986: fig. 72c) (ischium relatively longer with the outer surface smooth or almost so in A. irrorata , Fig. 45A View Fig ); and the G1 is relatively shorter with the distal half more prominently curved and the distal part after the subdistal flap proportionately shorter in A. confragosa ( Fig. 19G View Fig , Griffin & Tranter, 1986: 215, fig. 73a, b) (G1 relatively longer with the distal half gently curved and the distal part after the subdistal flap proportionately longer in A. irrorata , Fig. 19A–C View Fig ).

For A. irrorata , we observed that male specimens under 35 mm length are still juveniles, with adults possessing inflated chelae only at lengths of 44 mm or longer. In small specimens, the armature is relatively sharper, in particular the three lateral and two branchial spines and the series of large granules along the median row. The smallest ovigerous female, however, is only 26.2 by 22.5 mm (ZRC 2013.1222a). Another slightly larger female specimen from the same site (29.7 × 25.4 mm, ZRC 2013.1222b), however, was still immature.

The spines on the posterior carapace margin and on the lateral margins are always present but get relatively smaller and blunter as the specimens get larger. The ambulatory legs are relatively longer in adult males, with the surfaces generally smooth ( Fig. 55K View Fig ). Smaller male and female specimens, however, have the articles distinctly more setose, particularly the dactylus ( Fig. 55L View Fig ).

Although juveniles of A. irrorata (cf. 1 juvenile female 29.7 × 26.1 mm, 1 male 28.7 × 23.9 mm, ZRC 2013.1229) are superficially similar in general form to young Paramaja (of P. gibba and P. turgida ), the pseudorostral spines are invariably relatively longer in A. irrorata , the carapace is far more granulous but less swollen, the spines are relatively stronger, and the ambulatory legs are proportionately longer.