Portunus armatus (A. Milne-Edwards, 1861 )

Lai, Joelle C. Y., Ng, Peter K. L. & Davie, Peter J. F., 2010, A Revision Of The Portunus Pelagicus (Linnaeus, 1758) Species Complex (Crustacea: Brachyura: Portunidae), With The Recognition Of Four Species, Raffles Bulletin of Zoology 58 (2), pp. 199-237 : 219-222

Portunus armatus (A. Milne-Edwards, 1861)

( Figs. 6D , 7D , 17 , 18 , 19 , 20D , 21D , 22D , 23D, 23H , 24D )

Neptunus armatus A. Milne-Edwards, 1861: 322 , Pl. 33, Fig. 2 .

Neptunus pelagicus – A. Milne-Edwards, 1873: 156.

Portunus pelagicus – Hale, 1927: 149-150, Fig. 150; Stephenson & Campbell, 1959: 96–98, Figs. 2A , 3A , Pl. 1 Fig. 1 ; McNeill, 1968: 54; Stephenson & Rees, 1967b: 34, 35 (part); 1968: 21; Stephenson, 1968b: 84, Fig. 1A–D , Pl. 11; Stephenson, 1972a: 15 (key); Stephenson, 1972b: 137 (part); Stephenson, 1976: 18; Healy & Yaldwyn, 1970: 86, Fig. 46; Türkay, 1971: 123 (part); Heath, 1973: 2 (key), 13, Fig. 4b ; Poupin, 1996: 32; Davie, 1998: 100 (col. Fig.); 2002: 467; Davie, 2005: 157; Rice, 1999: 222 (figure); Jones & Morgan, 2002: 157, 158 (top), 159 (top); Laboute & Richer de Forge, 2004: 401(top).

Portunus (Portunus) armatus – Ng et al., 2008: 152.

Type locality. – Shark Bay , Western Australia .

Material examined. – Lectotype of Neptunus armatus A. Milne- Edwards, 1861, male (36.0 × 15.0 mm) ( NHM 1858.172.115) (photograph examined), Shark Bay , Western Australia . Paralectotype – 1 male (34.0 × 16.0 mm) ( NHM 1858.172 .114) (photograph examined), Shark Bay , Western Australia. Others – AUSTRALIA : 1 female (133.3 × 61.4 mm) ( WAM C38994), Rottnest Island , Western Australia, otter trawl at 29 m, 32°02.43'S 115°31.67'E to 32°02.60'S 115°31'E, coll. A. Sampey, 27 Apr.2007 ; 1 female (carapace length 72.5 mm, sides broken) ( WAM C38996), Southwest Cape , Western Australia, trawled at 37 m, 33°33.24'S 115°00.00'E to 33°37.98'S 114°59.99'E, coll. A. Sampey, 30 May 2007 ; 1 male (85.4 × 41.0 mm) ( WAM C38995), Southwest Cape , Western Australia, trawled at 37 m, 33°37.59'S 115°00.13'E to 33°37.72'S 115°00.14’E, coll. A. Sampey, 30 May 2007 ; 1 male (93.5 × 43.8 mm) ( WAM C38997), Southwest Cape , Western Australia, trawled at 37 m, 33°38.24'S 115°00.00'E to 33°37.98'S 114°59.99'E, coll. A. Sampey, 30 May 2007 ; 2 juv. males (larger 34.0 × 14.5 mm) ( WAM C39101), Denham, Shark Bay , Western Australia, coll. B. R. Wilson, 29 Dec.1959 ; 2 juv. males (larger 26.8 × 10.9 mm) ( WAM C39179), Denham, Shark Bay, Western Australia, sand flats at low tide just north of Denham jetty, coll. B. R. Wilson, 29 Dec.1959 ; 1 juv. male (38.6 × 16.4 mm) ( WAM C39180), Monkey Mia, Shark Bay , Western Australia, coll. B. R. Wilson, 2 Jan.1960 ; 1 female (56.9 × 24.0 mm), 1 juv. male, (damaged) ( WAM C20194), Goulet Bluff, south of Denham , Shark Bay, W.A., coll. BTH, 7 Mar.1986 ; 1 juv. male (30.7 × 13.89 mm) ( WAM C20682), Kuri Bay, Kimberleys , Western Australia, UIRB G1 33, intertidal, coll. G. Morgan, 23 Aug.1991 ; 1 juv. female (48.2 × 27.4 mm) ( NHM), Cape Boileau , NW Australia, coll. B. Grey, 13 Mar.1930 ; 1 male (27.7 × 11.1 mm) ( QM-W20210 ), western side of Mermaid Is, Kimberley coast, Western Australia, 16°19'S 123°21'E, muddy reef flat, coll. J. W. Short, 18 Nov.1994 ; 1 male (40.0 × 17.7 mm), 1 female (83.4 × 40.9 mm, one lateral tooth chipped) ( QM-W21064 ), Reveley Island, Cambridge Gulf, Kimberley Coast , Western Australia, 14°22'S 127°50'E, sand flat, in pools, coll. J. W. Short, 21 Nov.1995 ; 1 male (49.8 × 19.9 mm) ( QM-W21203 ), Mackenzie Anchorage, Napier Broome Bay , south of Anjo Peninsula, W. A., 14°20'06"S, 126°30'03"E, rocky cove, pools, muddy sand, backed by Rhizophora mangroves, coll. J. W. Short, 24 Nov.1995 ; 1 male (46.6 × 19.9) ( QM-W21247 ), West Governor Island, NW side, Napier Broome Bay, Kimberley Coast , Western Australia, 13°55'07"S 126°38'00"E, netted, coll. J. W. Short, 26 Nov.1995 ; 1 male moult (75.5 × 31.1 mm) ( QM-W21267 ), Sandy Island, Cape Talbot, Kimberley Coast , Western Australia, 13°45'03"S 126°48'05"E, coll. J. W. Short, 27 Nov.1995 ; Sandy Island, Cape Talbot, Kimberley Coast , Western Australia, 13°45'03"S 126°48'05"E, coll. J. W. Short, 28 Nov.1995 ; 1 male (124.6 × 54.2 mm) ( SAM C15787) , 1 male (136.5 × 65.4 mm) ( SAM C15788) , 1 male (105.6 × 48.1 mm) ( SAM C15789) , 1 male (119.1 × 52.0 mm) ( SAM C15786), Darwin area , Northern Territory ; 1 male (81.1 × 36.6 mm) ( QM-W2205 ), trawled, SE of Wellesby Island, Gulf of Carpentaria , NW Queensland, 16°26'S 139°22'E ; 1 male (54.4 × 25.5 mm) ( QM-W2865 ), trawl, Gulf of Carpentaria, off Karumba , NW Queensland, 17°29'S 140°50'E, coll. B. Campbell, 1966 ; 1 female (138.8 × 66.7 mm, one lateral tooth chipped), 1 male (134.4 × 65.6 mm, one lateral tooth chipped) ( QM-W20688 ), 0.5 m, netted over mud and rubble, Karumba Point , NW Queensland, 17°28'05"S 140°49'04"E, coll. J. W. Short, 23 Jun.1995 ; 1 male (27.7 × 13.3 mm) ( QM-W27092 ), SW coast Sweers Island , Gulf of Carpentaria, Queensland, 17°06'S 139°37'E, coll. P. Davie, 22 Nov.2002 ; 1 female (74.4 × 35.5 mm, one lateral tooth chipped) ( QM-W8903 ), Norman River, Gulf of Carpentaria , Australia, coll. CSIRO ; 1 female (57.7 × 28.8 mm, one lateral tooth broken off) ( QM-W8904 ), Bynoe River , NW Queensland, 17°32'S 140°43'E, coll. CSIRO ; 1 male (90.3 × 38.0 mm) ( QM-W12470 ), Torres Strait , northern Queensland, 10°02'S 142°31'E, coll. Queensland Fisheries Service, 13 m, 21 Apr.1974 ; 1 male (55.4 × 25.6 mm) ( QM-W12434 ), Darnley Island , northern Queensland, 9°35'S 143°46'E, coll. Tosh ; 1 male (55.4 × 25.6 mm) ( QM-W12434 ) , 4 females (66.6 × 28.8 mm, 61.1 × 26.6 mm, 54.4 × 23.3 mm, 57.7 × 25.5 mm), 2 males (58.9 × 25.5 mm, 49.9 × 22.2 mm) ( QM-W12430 ), Cape York ; 1 male (62.2 × 26.6 mm) ( QM-W6428 ), Quintell Beach, Iron Ra. , northern Queensland, 12°50'00"S 143°20'00"E, mangroves, coll. M. J. Bishop, Jul.1976 ; 1 male (51.1 × 23.4 mm) ( QM-W9920 ), 70 km East Coen, northern Queensland, Australia , 13°55'04"S 143°48'06"E, 21.9 m, coll. Queensland Fisheries Service, Sep.1979 ; 1 male (108.8 × 50.0 mm) ( QM-W9915 ), 40 km west Cape Melville , northern Queensland, 14°10'04"S 144°9'04"E, coll. Queensland Fisheries Service, 22 m, Sep.1979 ; 1 female (122.2 × 51.1 mm) ( QM-W18142 ), Starcke R, northern Queensland, 14°47'08"S 144°59'09"E, netted, mid-estuary, sandy mud bottom, salinity 35 ppt, 0.3 m, coll. P. Davie & J. W. Short, 10 Nov.1992 ; 1 male (95.6 × 39.8 mm) ( QM-W18215 ), beach S of Starcke R mouth, northern Queensland, 14°47'09"S 145°01'03"E, netted, 1m, gravel/mud, seagrass salinity 35 ppt, coll. P. Davie & J. W. Short, 13 Nov.1992 ; 1 male (52.2 × 23.3 mm) ( QM-W6085 ), 13 miles due east of Oyster Reef , 17 miles NE Green Island, Queensland, 16°39'S 146°11'E, 73.2 m, coll. L. R. G. Cannon, 21 Feb.1979 ; 2 females (73.3 × 32.2 mm, 45.5 × 21.1 mm, one anterolateral tooth chipped), 1 male (37.8 × 19.8 mm, one anterolateral tooth missing) ( QM-W2675 ), Machan’s Beach , NE Queensland, 16°51'S 145°45'E, 26 Dec.1960 ; 3 males (67.5 × 28.8 mm, 57.7 × 25.5 mm, 63.3 × 27.7 mm) ( QM-W12776 ), SE end of Hinchinbrook Is., NE Queensland, 18°27'5"S 146°22'7"E, trawled, coll. C. Jones, Queensland Fisheries Service, 17 Mar.1985 ; 2 males (68.8 × 29.7 mm, 41.3 × 20.01 mm) ( QM-W15209 ), Gladstone , Queensland, 23°51'S 151°16'E, coll. P. Saenger, Queensland Electricity Commision Survey, 1974–1983 ; 1 male (15.5 × 6.7 mm) ( QM-W2705 ), Burnett R. Heads , SE Queensland, 24°26'S 152°25'E, coll. N. Milward, 20 Apr.1966 ; 1 male (20.0 × 9.9 mm) ( QM-W2674 ), Burnett River Heads , SE Queensland, 24°46'S 152°25'E, coll. N. Milward, 26 Aug.1965 ; 1 female (44.4 × 20.0 mm) ( QM-W5344 ), south of Urangan Boat Harbour, Hervey Bay , SE Queensland, 25°18'S 152°55'E, estuarine, coll. P. Davie & R. Timmins, 23 Jul.1975 ; 1 female (47.6 × 21.1 mm), 3 males (41.1 × 18.8 mm, 40.0 x 18.8 mm, 39.9 × 18.8 mm) ( QM-W5398 ), mud flats S. of Urangan Boat Harbour, Hervey Bay , SE Queensland, 25°18'S 152°55'E, coll. P. Davie, 23 Jul.1975 ; 1 female (71.1 × 20.0 mm) ( QM-W9461 ), Susan River , SE Queensland, 25°26'S 152°56'E, coll. A. Ellis, 31 Oct.1970 ; 2 males (22.2 × 10.0 mm, 21.1 × 10.0 mm), 2 females (36.5 × 15.6 mm, 30.0 × 12.3 mm) ( QM-W9470 ), Susan River , SE Queensland, 25°26'S 152°56'E, coll. A. Ellis, 25 Dec.1970 ; 1 female (108.8 × 43.4 mm), 1 male (63.6 × 41.1 mm, lateral teeth missing, measurement taken from the 8th anterolateral tooth) ( QM-W3393 ), 5–6 miles E. Pt. Cartwright Light , SE Queensland, 26°41'S 153°15'E, 35 m ,, coll. F. Wallace, 6 Mar.1970 ; 1 juv. male (52.2 × 24.4) ( QM-W1060 ), east flat, Green Island , SE Queensland, 27°26'00"S 153°14'00"E ; 2 females (129.9 × 55.5 mm, 117.6 × 53.3 mm), 3 males (117.6 × 53.3 mm, 111.1 × 50.0 mm, 122.1 × 58.8 mm) ( QM-W2492 ), off St. Helena Island , SE Queensland, 27°24'S 153°14'E, coll. L. Wale, University of Queensland, 28 Jul.1966 , trawled; 2 females (82.3 × 37.7 mm, 63.4 × 31.0 mm), 4 males (32.2 × 15.5 mm, 29.9 × 14.5 mm, 35.5 × 17.7 mm, 35.5 × 17.7 mm) ( QM-W26681 ), Scarborough Spit, Moreton Bay , SE Queensland, 27°11'05"S 153°7'00"E, 0.5 m, netted over sand and shell substrate, coll. J. Johnson, 21 Jan.2003 ; 2 males (52.3 × 22.2 mm, 42.2 × 19.9 mm) ( QM-W797 ), Moreton Bay , SE Queensland, 27°25'S 153°20'E ; 1 male (17.7 × 8.8 mm) ( QM- W2474 ), beach at Sandgate, Moreton Bay , SE Queensland, 27°20'S 153°04'E, 9 Oct.1962 ; 1 male (42.2 × 18.8 mm) ( QM-W5232 ), Serpentine Creek , SE Queensland, 27°23'S 153°5'E, coll. B. Campbell et al., 12 Oct 1972 ; 5 males (25.6 × 11.1 mm, 12.3 × 6.6 mm, 16.6 × 8.8 mm, 21.2 × 10.0 mm, 28.8 x 12.4 mm) ( QM- W12005), Serpentine Creek, Cribb Island, Nudgee Beach , SE Queensland, 27°21'S 153°7'E, coll. I. Stejskal, 1984 ; 1 male (19.9 × 10.0 mm) ( QM-W8726 ), mouth of Brisbane R., SE Queensland, 27°24'S 153°10'E, 1 m, coll. Zoology Department, University of Queensland, 19 Sep.1975 ; 1 male (18.8 × 9.9 mm) ( QM-W1203 ), mud flat, Myora , SE Queensland, 27°29'S 153°25'E, coll. University Science Students Association ; 1 male (55.4 × 24.4 mm), 1 female (60.0 × 26.7 mm) ( QM-W12432 ), Sandgate , SE Queensland, 27°20'S 153°4'E, coll. R. Hamlyn-Harris ; 1 juv. female (22.2 × 10.0 mm) ( QM-W836 ), Goat I., SE Queensland, 27°31'S 153°23'E, 1 Jan.1938 ; 1 female (107.7 × 48.8) ( QM-W19588 ), Moreton Bay , SE Queensland, 27°17'S 153°15'E, trawled, coll. S. Cook, 3 Jun.1993 ; 2 males (15.6 × 8.7; 15.5 × 7.7), 1 female (17.7 × 8.8) ( QM-W7231 ), Deception Bay, Moreton Bay , SE Queensland, 27°10'S 153°5'E, coll. CSIRO, 6 Nov.1972 ; 3 males (15.5 × 7.7; 21.1 × 9.9; 15.5 × 7.7), 1 female (18.8 × 8.8 mm) ( QM-W7217 ), Deception Bay, Moreton Bay , SE Queensland, 27°10'05"S 153°30'00"E, coll. CSIRO, 6 Nov.1972 ; 1 male (152.1 × 74.4 mm) ( QM-W2515 ), Moreton Bay, near Mud Island , SE Queensland, 27°20'S 153°15'E, trawled, 20 Oct.1966 ; 1 male (22.2 × 10.0 mm) ( QM-W2356 ), South Dunwich , SE Queensland, 27°30'S 153°24'E, coll. F. C. Vohra ; 1 male (144.4 × 68.7 mm) ( QM-W1931 ), Lake Macquarie , New South Wales, 32°59'S 151°38'E, 26 Sep.1953 ; 1 male (143.2 × 65.5 mm) ( QM-W1933 ), Lake Macquarie , New South Wales, 32°59'S 151°38'E, 26 Sep.1953 ; 1 female (136.5 × 62.2 mm) ( QM- W1932 ), Lake Macquarie , New South Wales, 32°59'S 151°38'E, 26 Sep.1953 ; 3 males (largest 150.9 × 73.4 mm), 2 females (larger 135.6 × 67.5 mm) ( ZRC 2007.0232 ), Nelson Bay, Port Stephen , New South Wales ; 6 juv. males (largest 14.6 × 31.4 mm) ( ZRC 2007.0236 ), Sandringham, Botany Bay, on Zostera flats, Sydney , New South Wales, netted at 0.5 m, coll. S. Ahyong, 4 Jul.2003 ; 3 males (largest 134.7 × 65.1 mm), 3 females (largest 132.4 × 65.2 mm) ( ZRC 2007.0212 ), Spencer Gulf , South Australia, coll. S. Ahyong ; 3 male, 1 female (183.7 × 86.4 mm) ( ZRC 2007.0227 ), Brighton Beach, Gulf St. Vincent, South Australia, coll. S. Ahyong & M. Middleton, Dec.2003 ; 1 female (159.1 × 76.2 mm) ( ZRC 2007.0228 ), Whyalla, Spencer Gulf , South Australia, trapped 1-2m, coll. M & L. Middleton, Dec.2003 ; 1 male (133.0 × 66.0 mm) ( ZRC 2007.0229 ), Spencer Gulf vicinity, South Australia, coll. S. Ahyong. NEW CALEDONIA : 2 males (larger 133.0 × 75.6 mm), 1 female (97.1 × 54.6 mm) ( MNHN), Navlie Vauban Croisiere St. Vincent St 4, 14 m (22°05'06"S 166°04'05"E), 24 Apr.1985 ; 1 male (124.0 × 70.7 mm), 1 female (110.5 × 62.7 mm) ( MNHN), ORSTOM Vauban, Chalutage 12, 4– 6 m 21°56'06"S 166°02'02"E, 30 Apr.1985 ; Banc Gail, Prof 30m , 1 female (106.4 × 60.8 mm) ( MNHN), coll. Tivard, 30 Jul.1986 ; 1 female (101.0 × 58.0 mm) ( MNHN), Baie de St Vincent, Chalutage 1, coll. M. Kulbichi, 20 Aug.1985 ; 1 female (132.5 × 88.0 mm) ( MNHN), Lagoon Nord- Ouest St. CP 1060, 12– 14m (20°14'03"S 164°15'04"E), coll. B. Richer de Forges, 5 May 1988 ; 2 juv. males (larger 83.6 × 47.2 mm) ( MNHN), Bourake , St CP 2 from the “Alis”, coll. M. Kulbichi, 30 Jan.1989 ; 2 males (28.8 × 12.3 mm, 25.6 × 11.2 mm) ( QM- W19909), Dumbéa , coll. P. Davie, 7 Dec.1993 , mangroves.

Diagnosis. – Carapace width 2.0–2.3 times wider than long, however, on average, carapace width of P. armatus less elongated compared to other species, more quadrate in appearance. Median frontal teeth very sharp, spinous, conspicuous. Carapace regions relatively poorly indicated, branchial regions not markedly swollen, surface with coarser granulations compared with other species. Chelipeds in large males stout, more robust than other species, 3.5 times longer than wide (median ratio of 3.2). Anterior margin of cheliped merus usually with 4 (occassionally 5) spines (including extra enlarged spine proximally near joint). Ambulatory legs relatively stouter compared with P. pelagicus , ratio of 4 th pereiopod propodus length to width ranging from 2.9–3.7 (median 3.6). Natatorial paddle relativey broader, rounder compared with other three species ( Fig. 21D ). Sixth male abdominal somite relatively elongate, tapering ( Fig. 22D ). Base of G1 without round basal spur, or if present blunt, rounded ( Fig. 20D ). Colour pattern with spots tending to remain relatively discrete, though sometimes fusing into thin irregular short bands thinner than those on P. pelagicus . Female patterns similar to males but differs in colour compared with females of other three species ( Fig. 7D ). Maximum size of 200 mm carapace width ( Kailola et al., 1993).

Life colours ( Figs. 6D , 7D , 19 ). – Carapace colouration varies from dark blue and purple to green in males, brown in females. Banding patterns present on carapace present, but thinner and sparse in comparison to the other three species; posterior part of carapace ocellated, markings on carapace resemble thin reticulations, never as thick or as dense as markings on the others. Females with a background colour in varying shades of brown, but similar banding patterns to male. Within P. armatus , there appears to be regional variation in the colour of males around Australia, especially from South Australia in Spencer Gulf and Gulf St. Vincent, where males typically are brighter blue and exhibit less reticulation than those from other localities ( Fig. 19D ) (S. Ahyong, pers. comm.). They are otherwise indistinguishable morphologically and genetically.

Remarks. – Alphonse Milne-Edwards described Neptunus armatus in 1861 based on at least one juvenile male collected from Shark Bay, Western Australia, commenting that the shape of its frontal and anterolateral teeth seemed broader at the base than P. pelagicus to which it was otherwise similar. Portunus armatus was accepted as a valid species by both Miers (1884) and Henderson (1893), although Alcock (1899: 34) tentatively regarded it as a junior synonym of P. pelagicus . Following Alcock’s action, the species was essentially forgotten and not mentioned in recent Australian literature. In particular, it was overlooked by Stephenson & Cambell (1959) in their review of the Australian Portunus species , Stephenson (1972a), in his checklist of the Indo-West Pacific Portunidae, Jones (1994) , in her checklist of marine decapod crustaceans from Shark Bay (the type locality), and by Davie (2002), in his synopsis of the Australian fauna.

The confusion over the identity of P. armatus and subsequent lack of records in Australia may be attributed to the fact that the original description was based on a juvenile of only carapace length 15 mm (large adults are typically more than 150 mm), and the length of the last anterolateral spine is much longer than in adult specimens. Secondly, the accompanying illustration (reproduced in Fig. 17B ) differs from the lectotype and paralectotype specimens in at least two key features: 1) the posterolateral corner of the carapace is square in the illustration, but rounded in reality; and 2) the carapace proportions of the drawing are distorted so that it appears wider than the type specimen on which it was based. Henderson (1893) first commented that A. Milne-Edwards gave incorrect carapace dimensions, and that the length of the last anterolateral spine was inaccurately drawn. Photographs of a syntype ( NHM 1858.172 .115) ( Fig. 17A ) kindly provided by P. Clark ( NHM), leave us in no doubt that this is the specimen figured by A. Milne- Edwards (1861), and we here designate it as the lectotype. The general features, positions of the legs and chelipeds all match, although as already mentioned, the last anterolateral spine is exaggerated in the drawing, and the measurements originally given are different .

Stephenson (1968b) had access to a series of specimens collected from across the Indo-West Pacific and Australia, and concluded that perceived differences between samples from different localities may be attributed to regional clines or varieties. Indeed, there does appear to be some regional colour variation between P. armatus specimens collected from localities around Australia. In particular, the colour of specimens collected from Spencer Gulf/Vincent Gulf in South Australia deviate the most from “typical” P. armatus collected in other localities ( Fig. 9D ). However, the fundamental shape and positioning of the underlying patterning is retained, and females are consistently the same as elsewhere. It was also noted by Bryar & Adams (1999) that allozyme data provide no evidence that the marked colour and pattern variations in P. armatus from different regions around Australia are due to the presence of cryptic species or subspecies. Rather, they speculated that variation in pigmentation is probably due to phenotypic plasticity as reported by Meagher (1971) and Bryars (unpublished data) from laboratory held individuals.

Initially, the extreme length of the last anterolateral spine in the lectotype cast some doubt as to whether it was conspecific with the “ P. pelagicus ”-like species occurring in Australia, but a comparison with juvenile specimens collected from both the type locality in Shark Bay , Western Australia, and from New South Wales indicates that spine length is significantly variable, and that longer spined juveniles similar to the lectotype do occur, and seem to be more common in Western Australia ( Fig. 18 ) .

Other specimens identified by Henderson (1893) as P. armatus from outside Australian waters have also been re-examined. Five small specimens (the largest being 30.5 mm wide) from Pamban, Rameswaran, India, are actually juvenile P. reticulatus ; and similarly, specimens identified as P. armatus from Chefoo, China, belong to P. trituberculatus .

While we are sufficiently certain that the specimen here designated as lectotype ( NHM 1858.172.115) is the same as that described and illustrated by A. Milne-Edwards (1861), a second specimen of P. armatus with the same register number ( NHM 1858.172 ) but a different specimen number (114) was uncovered by P. Clark. As these two specimens were listed together as a single lot in the accession book, it is likely that A. Milne-Edwards examined both specimens. However, he did not indicate how many specimens he had seen. As no holotype was selected, we here recognise both specimens as syntypes and designate a lectotype and paralectotype as earlier indicated .

Portunus armatus appears to be the largest of the four species in the P. pelagicus -complex, with the biggest specimen recorded attaining 200 mm in carapace width ( Kailola et al., 1993). It is of significant economic importance in Australian fisheries and subject to stringent catch quotas and size restrictions. As such, its population dynamics and biology in Australian waters are relatively well studied (see Shields, 1992; Sumpton et al., 1994; Weng, 1987, 1992; Xiao & Kumar, 2004).

Habitat. – Lives in a variety of inshore and continental shelf waters from low intertidal to 50 m depth; prefers flatter sandy to muddy bottoms with algal and seagrass communities ( Edgar, 1990; Williams, 1982). Juveniles are common near low water mark on intertidal flats; adults can also sometimes be found in shallow water near low tide mark, but mostly crabs move into deeper water as they age in response to changes in water temperature and inshore salinity ( Potter et al., 1983). At least in Moreton Bay, ovigerous crabs move into deeper more oceanic water for spawning ( Potter et al., 1987).

Distribution. – In Australia from Cape Naturaliste, Western Australia, around northern Australia south to about the southern border of New South Wales; also found in the warmer waters of the South Australian Gulfs, as far south as Barker Inlet in Gulf St Vincent ( Kailola et al., 1993). Lord Howe Island; Arafura Sea off southern Papua; occasional records from the North Island of New Zealand, but apparently not able to form a sustainable population ( Dell, 1964). In New Caledonia, they are present but rare within the shallow lagoon fringing the island. P. armatus has no commercial value in New Caledonia, and is more often regarded as a pest as they tend to congregate around floating fish holding pens within the lagoon and damage nets as well as fish stocks kept within. With the decline in fish holding aquaculture in New Caledonia, P. armatus density within the lagoon has also diminished (B. Richer de Forges, pers. comm.).

Figures

Fig. 6. Live colours of males. A, Portunus pelagicus (Linnaeus, 1758) (142.7 × 67.1mm) (ZRC 2007.0235), Pulau Tekong, Singapore; B, Portunus segnis (Forskål, 1775) (140.1 × 62.3mm) (ZRC 2007.0220), Tulear, Madagascar (photograph: H. H. Tan); C, Portunus reticulatus (Herbst, 1799) (132.2 × 59.8mm) (ZRC 2007.0223), Chennai, India (photograph: Z. Jaafar); D, Portunus armatus (A. Milne-Edwards, 1861) (no specimen, photograph only) Brisbane, Queensland (photograph: P. J. F. Davie).

Fig. 7. Live colours of females. A, Portunus pelagicus (Linnaeus, 1758) (142.7 × 67.1mm) (ZRC 2007.0235), Pulau Tekong, Singapore; B, Portunus segnis (Forskål, 1775) (124.3 × 53.4mm) (ZRC 2007.0220), Madagascar, Tulear (photograph: H. H. Tan); C, Portunus reticulatus (Herbst, 1794) (132.2 × 59.8mm) (ZRC 2007.0223), Chennai, India (photograph: Z. Jaafar); D, Portunus armatus (A. Milne-Edwards 1861) (133.2 × 64.2 mm) (ZRC 2007.0232), Nelson Bay, New South Wales, Australia (photograph: S. Ahyong).

Fig. 17. Portunus armatus (A. Milne-Edwards, 1861). A, Lectotype male (36.0 × 15.0 mm) (NHM 1858.172.115) (photograph: P. Crabb, NHM photo unit); B, original figure in A. Milne-Edwards (1861).

Fig. 18. Lateral spine length variation in juvenile Portunus armatus (A. Milne-Edwards, 1861). A, B, Botany Bay, New South Wales; C–F, Shark Bay, Western Australia. A, male (27.14 × 12.4 mm) (ZRC 2007.236); B, male (28.5 × 13.9mm) (ZRC 2007.236); C, male (30.7 × 13.9 mm) (WAM C20682); D, male (29.5 × 12.3 mm) (WAM C39181); E, male (34.0 × 14.5 mm) (WAM C39181) F, male (26.8 × 10.9 mm) (WAM C39179).

Fig. 19. Regional colour variation in Portunus armatus (A. Milne-Edwards, 1861). A, figure by F. Bauer from voyage of H.M.S Investigator to Australia (after Rice, 1999), exact locality unknown; B, adult male (photograph only), Hacking River, Sydney C, male (132.4 × 65.2 mm) (ZRC 2007.0212) (Nelson Bay, Port Stephen, New South Wales), incomplete specimen; D, male (133.0 × 66.0 mm) (ZRC 2007.0229) (Spencer Gulf vicinity, South Australia). (Photographs B, C and D taken by S. Ahyong).

Fig. 20. G1 and distal part of G1 structures. A, Portunus pelagicus (110.7 × 48.8 mm) (RMNH D384); B, P. segnis (147.2 × 66.8 mm) (ZRC 2007.225); C, P. reticulatus (138.5 × 60.7 mm) (ZRC 2007.222); D, P. armatus (150.8 × 73.6 mm) (ZRC 2007.232). Scale = 1 mm.

Fig. 21. Fourth and fifth pereiopod merus, carpus, dactylus. A, Portunus pelagicus (152.9 × 68.0 mm) (ZRC 2007.233); B, P. segnis (134.5 × 62.6 mm) (ZRC 2007.226); C, P. reticulatus (138.5 × 60.7 mm) (ZRC 2007.222); D, P. armatus (133.0 × 66.0 mm) (ZRC 2007.229).

Fig. 22. Male abdominal somites. A, Portunus pelagicus (152.9 × 68.0 mm) (ZRC 2007.233); B, P. segnis (134.5 × 62.6 mm) (ZRC 2007.226); C, P. reticulatus (138.5 × 60.7 mm) (ZRC 2007.222); D, P. armatus (133.0 × 66.0 mm) (ZRC 2007.229).

Fig. 23. Frontal margin and merus of left cheliped A, E, Portunus pelagicus (152.9 × 68.0 mm) (ZRC 2007.233); B, F, P. segnis (134.5 × 62.6 mm) (ZRC 2007.226); C, G, P. reticulatus (138.5 × 60.7.0 mm) (ZRC 2007.222); D, H, P. armatus (133.0 × 66.0 mm) (ZRC 2007.229).

Fig.24.Frontal view showing differences in branchial swelling.A, Portunus pelagicus (152.9 × 68.0 mm) (ZRC 2007.233); B, P.segnis (134.5 × 62.6 mm) (ZRC 2007.226); C, P. reticulatus (141.7 × 63.0 mm) (ZRC 2007.222); D, P. armatus (150.8 × 73.6 mm) (ZRC 2007.232).

Fig. 2. Scatter plot of canonical scores from forward stepwise discriminant function analysis. Group 1, Portunus armatus; 2, P. reticulatus; 3, P. segnis; 4, P. pelagicus.

Fig. 3. Minimum Evolution bootstrap tree incorporating all unique COI haplotypes. Haplotypes of specimens obtained from Portunus pelagicus, P. segnis, P. reticulatus and P. armatus with P. trituberculatus, P. sanguinolentus and Charydis lucifera as outgroups. ‘*’ Indicates the dominant haplotype found in P. pelagicus shared with eight P. reticulatus individuals. ‘**’ Denotes two individuals collected from Japan that may constitute a possible cryptic species.

Fig. 1. Schematic drawings of a generalized Portunus pelagicus illustrating morphological terms and measurements used in the study. A, dorsal surface and appendages; B, cheliped; C, pereiopods; D, abdomen.

Fig. 4. Frequency histogram of intra and inter-specific divergence for COI locus for the four species excluding outlier haplotypes for clarity.A, Divergence between Portunus armatus and P.reticulatus; B, divergence between P. pelagicus and P. segnis; C, divergence between P. armatus/P. reticulatus and P. segnis/P. pelagicus.

Fig. 9. Portunus denticulatus de Procé 1822, junior synonym of P. pelagicus (Linnaeus, 1758), neotype male (119.7 × 54.0 mm) (ZRC 2002.302), Tagbilaran Market, Bohol, Philippines.