Portunus (Portunus) pelagicus ( Linnaeus, 1758 )

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 : 209-214

Portunus (Portunus) pelagicus ( Linnaeus, 1758)

( Figs. 6A , 7A , 8 , 9 , 10 , 20A , 21A , 22A , 23A, 23E , 24A )

Pagurus Reidjungan Rumphius, 1741: 11, Pl. 7, Fig. R.

Cancer pelagicus Linnaeus, 1758: 626 ; Linnaeus, 1767: 1042.

Cancer pelagicus – Forskål, 1775: 89.

Portunus denticulatus Marion de Procé, 1822: 133 .

Cancer cedonulli Herbst, 1794: 2 (5): 157, Pl. 39.

Lupa pelagica – H. Milne Edwards, 1834: 450; Dana, 1852: 271; Stimpson, 1907: 76.

Neptunus pelagicus – Heller, 1865: 27 (part); Miers, 1884: 229 (part); De Man, 1886–1887: 69; Kemp, 1918: 250.

Neptunus (Neptunus) pelagicus – Miers, 1886: 173 (part); Alcock, 1899: 31 (key), 34, 35 (part); Parisi, 1916: 171 (part); Balss, 1922: 107; Yokoya, 1933: 177; Sakai, 1934: 303; Sakai, 1935: 128, Pl. 38; Sakai, 1939: 387-388, Pl. 49.

Neptunus peiagicus [sic]: Estampador, 1959: 71.

Portunus (Portunus) pelagicus var. sinensis Shen, 1932: 70 , Pl. 3 Fig. 6 , Pl. 4 Fig. 2 .

Portunus (Portunus) pelagicus – Serène, 1968: 68 (list); Utinomi, 1969: 87, Pl. 44; Sakai, 1976: 339, Pl. 118; Ng et al., 2008: 152.

Portunus pelagicus – Fabricius, 1798: 367; Rathbun, 1902: 26; Rathbun, 1910a: 313; Rathbun, 1910b: 360, 361; Stephenson & Rees, 1967b: 34–35 (part), Figs. 12c, d , 17b ; Stephenson, 1967: 17; 1968a: 386 (part), Fig. 2 C, D ; 1972a: 15 key, 41 (checklist); 1972b: 137 (part); Kim, 1973: 355; Takeda, 1982: 148; Miyake, 1983: 84, Pl. 28; Ng, 1998: 1124 (part); Chen, 1989: 353, 355; Dai & Yang, 1991: 212–213, Fig. 112, Pl. 25(7); Gosliner et al., 1996: 237, colour photograph; Poupin, 1996: 32; Naiyanetr, 1998: 14 (photo), 73 (list); Minemizu, 2000: 234; Ng et al., 2001: 17. For other Taiwanese records, see Ng et al., 2001: 17).

Material examined. – Neotype of Cancer pelagicus Linnaeus, 1758 (designated here), 1 male (142.0 × 67.1 mm) ( ZRC 2007.0235), Pulau Tekong, Singapore, coll. H. H. Tan, Nov.2004 (simultaneous neotype of Cancer cedonulli Herbst, 1794 ). Others – AUSTRALIA: 1 male ( SAM C15784), 1 male ( SAM C15779), 1 male ( SAM C15781), 1 male (122.1 × 53.9 mm) ( SAM C15780), 1 male ( SAM C15783), 1 male ( SAM C 15785), Darwin, Northern Territory, coll. R. Buckworth, 22 Aug.1993; 1 male (120.6 × 52.7 mm) ( SAM C15782), Darwin, Northern Territitory, coll. Northern Territories Fisheries Department, 2 Dec.1993. CHINA: 1 male (113.5 × 64.0 mm) ( NHM 62.95), Shanghai, coll. Jamiachi; 10 male (largest 152.8 × 70.8 mm), 10 females (largest 144.3 × 65.3 mm) ( ZRC), Ying Ping Market, Xiamen, Fujian Province, coll. Z. Jaafar & N. K. Ng, 12 Nov.2005. INDONESIA: 4 males (largest 125.5 × 72.0 mm), 2 females (larger 124.7 × 70.3 mm), 1 ovi. female (115.0 × 64.8 mm) ( ZRC 2007.0216), fish market, Padang, West Sumatra, coll. J. C. Y. Lai & N. K. Ng, 6–8 Jul.2003; 1 female (129.3 × 58.2 mm) ( ZRC 2003.0583), 3 males (largest 118.0 × 53.7 mm), 11 females (largest 125.5 × 56.7 mm) ( ZRC 2007.0221) (Geropok, Lombok) coll. J. C. Y. Lai, 11–12 Feb.2003; 1 male (135.1 × 63.0 mm), 1 female ( RMNH LOLNR 16221), Ambon, Molukken, coll. D. J. Hoedt, 1864; 1 male (110.7 × 48.8 mm) ( RMNH D384), Ambon, Moluccas, Indonesia, coll. Schorel, 1879; 1 male (115.6 × 53.8mm), 4 females (largest 137.3 × 61.8 mm) ( ZRC), Manado fish market, Sulawesi, coll. T. H. T. Tan & H. H. Tan, Jun.2003; JAPAN: 12 males (largest 157.1 × 70.4 mm), 3 females (largest 146.4 × 65.0 mm) ( ZRC 2007.0233) Naha Fish Port, Okinawa Island, Ryukyus, coll. T. Naruse, Nov.2003. MALAYSIA: 1 female ( ZRC 2001.0999), Parit Jawa, Muar Johore, coll. B. Jayne et al. 11 Apr.2001; 1 male (damaged), 3 females ( ZRC 1987.646–649), Pulau Tiga, Sabah, coll. Lee Nyanti no.110, 27 Apr.1987. PHILIPPINES: 1 male (119.7 × 54.0mm) ( ZRC 2002.302) (neotype of Portunus denticulatus Marion de Procé, 1822 ), Philippines: Bohol, Tagbilaran market, coll. J. C. Y. Lai et al., Nov.2001; 1 male (119.7 × 54.0 mm) ( ZRC 2002.302), Tagbilaran market, Bohol, coll. J. C. Y. Lai et al., Nov.2001; 1 female (117.9 × 49.9 mm) ( ZRC), fish market, Cebu City, coll. P. K. L. Ng, 21 Nov.2001. SINGAPORE: 5 males (largest 97.3 × 43.4 mm), 4 females ( ZRC 2002.380), Changi Beach, coll. J. C. Y. Lai, 26 Jun.2003; 5 males (largest 155.7 × 73.4 mm), 2 females (larger 160.7 × 74.6 mm) ( ZRC 2007.0235), Pulau Tekong South, coll. H. H. Tan, Nov.2004; 1 male (150.5 × 72.4 mm) ZRC 1981.8.14.102), Jurong Fish Market, coll. H. K. Voris, 11 Mar.1981; 5 males (largest 145.0 × 69.4mm) ( ZRC 1990.615-619), Tuas, no other details; 2 males (larger 125.0 × 70.5 mm), 1 female (87.5 × 49.9 mm) ( ZRC 1981.7.24.18), Tuas, coll. Mr Lee, 19 Feb.1981; 1 male (151.6 × 70.5 mm), 1 female (107.3 × 49.9 mm) ( ZRC 2000.1334) Bedok Market, no other details; 2 males (larger 118.4 × 67.0 mm) ( ZRC 2007.217), Beting Bronok, coll. P. K. L Ng, 27 Oct.2003; 1 male (130.4 × 57.9 mm), 1 female (127.5 × 56.8 mm) ( ZRC 2007.215), Pulau Hantu lagoon, coll. P. K. L. Ng, 13 Jul.2003. TAIWAN: 1 male (144.2 × 64.8 mm), 1 female (78.9 × 37.3 mm) ( ZRC 2007.214), Hsin-Chu Fish Market, coll. J. C. Y. Lai, Dec.2003; 2 male (larger 143.3 × 66.2 mm), 3 females (152.0 × 66.2 mm) ( ZRC 2007.218), exact locality unknown, coll. H. C. Liu, Jun.2004. VIETNAM: 1 male (145.4 × 66.2 mm), 1 female (133.8 × 62.0 mm) ( ZRC 2007.211), fish market, Cat Ba Island, Hai Phong, coll. A. D. Tran, 22 Jun.2003; 1 male (127.2 × 60.5 mm), 1 female (135.6 × 60.7 mm) ( ZRC 2007.0219), fish market, Nha Trang, coll. A. D. Tran, May/ Jun.2003. “HAWAII”: 1 male (43.0 × 24.5 mm) ( NHM 80.35), from the “Challenger” collection, off Honolulu coral reefs, dredged from 40 to 10 fathoms or less, coll. H. M. S Challenger, 31 Jul.1875. “TAHITI”: 2 males (photographs examined) ( NHMW 2860), coll. “Novara” Expedition (1857–1859), reported by Heller (1865).

Type material. – The lectotype specimen of Cancer pelagicus Linnaeus, 1758 , designated by Holthuis (2004: 1268) is no longer extant (see Remarks). Owing to the strong potential for confusion, and the commercial importance of the species, it is necessary to designate a neotype to ensure nomenclatural stability. We here designate a male (142.0 × 67.1 mm) ( ZRC 2007.0235) collected from Singapore as the neotype for the species. This specimen was freshly collected for the present study, has been photographed in colour, and both fixed and preserved in 100% ethanol for DNA extraction.

Diagnosis. – Carapace width 2.2–2.3 times wider than long; median teeth of frontal margin spinous, small but conspicuous; in larger adults, especially males, carapace regions relatively well indicated, branchial regions markedly swollen. Chelipeds with anterior margin of merus usually with 3 spines; normally without enlarged spine proximally near joint; in large males chelipeds narrow, elongated, merus up to 4.6 times longer than wide. Ambulatory legs elongated, slender, with ratio of 4 th pereiopod propodus length to width ranging from 3.7– 4.5 (median 4.1). Natatorial paddle elongate oval, obtusely angled distally, about 1.7 times longer than wide ( Fig. 21A ); relatively narrowest of species in complex. Sixth male abdominal somite relatively elongate, tapering ( Fig. 22A ). Base of G1 with round basal spur ( Fig. 20A ). In males, carapace patterning consists of spots and a broad recticulate network of bands, no obvious pattern of spotting on females but with a black mark on posterobranchial region. Largest known size is a male 155.7 × 73.4 mm (ZRC 2007.0235) from Singapore.

Live colours ( Figs. 6A , 7A , 10 ). – Males, dark blue green carapace with purple blue chelipeds, tips rusty red; females, a uniformly brownish green carapace with red tipped chelipeds. Merus, carpus and manus of chelipeds speckled with pale white spots. Pale white broad bands and large blotches on carapace on background of blue green in males. Some females may also possess spots and bands on the posterior and branchial regions of carapace.

Remarks. – Linnaeus (1758: 626) described Cancer pelagicus as follows: “C. brachyurus, thorace laevi utrinque unispinoso, fronte octo-dentata, manibus multangulo-prismaticis. Osb. iter. 307. C. manuum articulis omnibus dentatis: extimoheptagono. Rumph. mus. t. 7. f. R. Brown jam. 421. t. 41. f. 2. Habitat in Pelagi universi orbis. Fuco natante.”

This description is brief and uninformative, and as noted by Holthuis (2004), it mentions three sources, viz., Osbeck (1757), Browne (1756) and Rumphius (1705). No type was designated and thus, any specimens Linnaeus may have had at the time of his description, as well as the material listed in the works he refers to, must all be regarded as syntypes. The extant Linnaean crustacean material is deposited in the Uppsala Museum in Sweden ( Holm, 1957: 56). In this collection is a dried “type” specimen of Cancer pelagicus Linnaeus, 1758 (UUZM 243), however, it is also labelled as “from the collection of Gustav IV Adolf”, and was first reported by Linnaeus six years later in his 1764 work ( Holm, 1957: 56; see also Wallin, 1997: 16). Consequently, this specimen cannot be a syntype of Cancer pelagicus .

Of the other authors referenced by Linnaeus (1758) in his description, Osbeck (1757: 307) described a swimming crab collected in 1752 from the Sargasso Sea in the mid- Atlantic; Browne (1756: 421, Pl. 47 Fig. 1 ) described and figured a crab collected from St. Mary’s in Jamaica; and Rumphius (1705: 11, Pl. 7 Fig. R) recorded his material from Ambon, Indonesia. It is now clear that Osbeck’s and Brownes’ descriptions refer to Portunus sayi (Gibbes, 1850) and Lupella forceps (Fabricius, 1793) , respectively ( Holthuis, 2004). Only the specimen figured by Rumphius (1705) (reproduced in Fig. 8 ) clearly belongs to P. pelagicus sensu lato. To ensure there was no future confusion over the identity of all three names, Holthuis (2004: 1268) selected the “specimen figured by Rumphius, 1705, Pl. 7 Fig. R” as the lectotype of Cancer pelagicus Linnaeus, 1758 . Although Holthuis knew that the specimen of Rumphius was no longer extant, he considered there was no need for a neotype because the identity of Portunus pelagicus seemed clear at that time (pers. comm.). However, we have demonstrated that there are four species in the P. pelagicus species complex, and it is clear that the figure of Rumphius (1705) is insufficient to identify P. pelagicus sensu stricto. This is particularly important because P. pelagicus sensu stricto and P. armatus (A. Milne-Edwards, 1861) are sympatric in northern Australia and the potential for confusion is significant, especially since Ambon is relatively near this region of sympatry. As the lectotype specimen is lost, we consider it necessary to designate a neotype for P. pelagicus .

The name Portunus denticulatus Marion de Procé, 1822 , has not been used since it was first described from Manila, the Philippines. Checks at the MNHN as well as NMCR in Manila reveal no trace of the type specimens, and from what is known, all of Marion de Procé’s material is now lost (D. Guinot, pers. comm.). On the basis of its description and the fact that we have so far identified only P. pelagicus sensu stricto from the north-west Pacific (including extensive material from Manila and Philippines), we are confident the two species are conspecific. Nonetheless, a neotype for P. denticulatus is needed to prevent future nomenclatural problems and we here designate a male specimen (119.7 × 54.0mm) (ZRC 2002.302), from Bohol, Philippines, as the neotype ( Fig. 9 ). We consider this neotype to morphologically and genetically fall within the present concept of P. pelagicus .

Cancer cedonulli Herbst, 1794 , is also regarded as a junior synonym of P. pelagicus . Herbst’s (1794) original description was too brief to be informative. However, his accompanying illustration unambiguously depicts a male with a banding pattern of broad blotches and reticulations, and with a long and slender cheliped merus — characters that are diagnostic of P. pelagicus sensu stricto. Herbst (1794) indicated only that it was collected from “Ostindien” (East Indies), an area that was considered to extend from the east coast of India to the Indo-Malaysian region. The holotype is believed to be lost; it was not listed in Sakai’s (1999) catalogue of the J. F. W. Herbst Collection in the Berlin Zoological Museum, and subsequent searches have also failed to find it (O. Coleman, pers. comm.). The east Indian Ocean and the Bay of Bengal area is likely a region of sympatry between P. pelagicus sensu stricto and P. reticulatus Herbst, 1799 (from genetic evidence), and this creates potential problems with the identity of Cancer cedonulli . Thus, a neotype is necessary to ensure there is no future taxonomic confusion. We here designate the neotype of Cancer pelagicus Linnaeus, 1758 (see above), as a simultaneous neotype of Cancer cedonulli Herbst, 1794 , making both names objective synonyms.

A subadult male specimen of P. pelagicus (NHM 80.35) (determined by Miers, date unknown), purported to be collected from Hawaii during the voyage of H. M. S. Challenger, was examined. This specimen was not listed in Miers’ (1886) “Challenger Report” on the Brachyura collected during the expedition. Barring this unpublished record, there have been no reports of P. pelagicus from the Hawaiian Islands and it is not listed in the latest checklist of Hawaiian Brachyura (http://www2.bishopmuseum.org/HBS/ invert/brachyura.htm) or mentioned in Edmondson’s (1954) study of the Portunidae of Hawaii. The main portunid utilized for food in Hawaii (although not commercially significant), is P. sanguinolentus hawaiiensis Stephenson, 1968 . Although superficially similar to P. pelagicus , especially with regards to parts of the carapace colour pattern, the morphology of P. sanguinolentus hawaiiensis is clearly closer to P. sanguinolentus (see Stephenson, 1968b). Thus we believe the Challenger specimen, though clearly referable to P. pelagicus , was probably mislabeled. The presence of P. pelagicus in Hawaii is unlikely.

Most authors (Apel & Spiridonov, 1998; Boone, 1934; Stephenson, 1972b; Stephenson & Campbell, 1959; Tirmizi & Kazmi, 1996) accept that P. pelagicus occurs in Tahiti. However, the only verified record appears to be that of Heller (1865) based on specimens collected during the Novara Expedition ( Poupin, 1996). All subsequent records have followed suit. Heller mentioned Tahiti as a locality for P. pelagicus along with others such as Singapore and India and his material is currently deposited at the Natural History Museum in Vienna. They are also damaged. There have been no subsequent published records from Tahiti, and the species has not been collected during extensive French collections made in this region over the last few decades (J. Poupin, pers. comm.). It is well documented that labels and localities from the Novara Expedition have been mixedup (see McLaughlin & Dworschak, 2001; Rathbun, 1905, 1906), and there have been instances where Heller caused confusion by quoting wrong localities. For example, he described a species of freshwater crab from Chile in South America ( Telphusa chilensis Heller, 1862 ) that later proved to belong to a genus endemic to Java and Borneo ( Ng, 1989). Large edible crabs such as P. pelagicus , that typically inhabit shallow inshore coastal waters, are seldom overlooked. We thus consider it highly unlikely that P. pelagicus occurs in French Polynesia. However, is also possible that the species may be confused with P. sanguinolentus hawaiiensis Stephenson, 1968 , a species which superficially resembles P. pelagicus and is known from Hawaii and central Pacific (unpublished data).

Shen (1932) described Portunus pelagicus var. sinensis from China, but most of his specimens were small (average carapace width 24.0 mm) and he did not explicitly state why he considered them to be different from P. pelagicus sensu stricto. After comparing juvenile P. pelagicus with his description and the excellent figures of P. pelagicus var. sinensis ( Shen, 1932: Pl.3 Fig. 6 , Pl. 4, Fig. 2 ), we see no significant differences and thus regard the latter as a subjective synonym of P. pelagicus sensu stricto. Shen’s (1932) record remains the only one of this species from northern China. Interestingly, P. pelagicus is not familiar to local fishermen or market traders at Qingdao, just south of Shandong, where P. trituberculatus is the dominant commercial species (unpublished data). The occurrence of several juveniles of P. pelagicus as recorded by Shen (1932) may have been due to accidental larval transport by northerly currents and the cold winters may have prevented further population establishment. It is also possible that the stated provenance of his material is wrong.

Herbst (1803: 159) compared Cancer pelagicus with C. reticulatus and C. cedonulli , but his accompanying drawing (Herbst, 1803: Pl. 8, Fig. 55) depicted Charybdis natator instead (Herbst, 1794). From his text, it is clear that he regards all three species as being highly similar and this error was most probably due to an editorial lapsus.

Bryars & Adams (1999) were the first to report the presence of two distinct forms of P. pelagicus found sympatrically in Darwin, northern Australia. One form is widely distributed all over Australia and the other was restricted to waters around Darwin. The former taxon was referred to as “ P. pelagicus ” and the latter, “ Portunus species ”. The two populations occur sympatrically in Darwin, but with differing ratios of catch abundance from two localities. From their observations, individuals of “ Portunus sp. ” were generally smaller in overall size than “ P. pelagicus ”, with the ninth epibranchial spines longer (relative to the carapace) and more curved. Some differences in dorsal pigmentation between the two forms were also observed. Additionally, they reported the existence of hybrids based on allozyme data. We checked the specimens referred by Bryars & Adams (1999) as Portunus sp. and confirmed that they are P. pelagicus as defined in the present study. The species widely distributed around Australia that they referred to as “ P. pelagicus ” is P. armatus . Interestingly, the specimen that was described as a hybrid between the two species resembled both P. armatus and P. pelagicus : there are small sharp spines in the median part of the anterior margin and four teeth along the posterior margin of the merus of the cheliped. However, the specimen was heavily parasitized by Sacculina , altering the overall shape of the abdominal segments. Based on allozyme results and our examinations, we agree with their conclusions. Klunbuga et al. (2007) reported genetic heterogeneity in P. pelagicus populations collected off Thai waters. As sites chosen were within the Gulf of Thailand and along the coast of the Andaman sea, it is likely that both P. pelagicus and P. reticulatus were analysed in the study. We were unable to confirm this as specimens analysed in their study were not deposited in any zoological collection.

Habitat. – Found in shallow sandy/muddy to sea grass lagoons and estuaries, brackish waters to a depth of 40 m ( Ng, 1998).

Distribution. – This species has the widest distribution of all four species in the complex. It has been recorded from China, Japan (Okinawa and Kyushu), Korea, Philippines, Indonesia, and westwards to at least the straits of Malacca ( Davie, 2002). There is evidence of hybridisation between P. pelagicus and P. reticulatus in the Bay of Bengal and the Andaman Sea based on COI data, but it is not known exactly where this hybridisation zone is (see general discussion). Based on our examination of material used by Bryars & Adams (1999), P. pelagicus is also present in the Northern Territory, Australia, and as mentioned, there is also some indication of occasional hybrids with P. armatus . Regrettably, attempts to collect fresh material of both species in the Northern Territory were not successful. As discussed, records of “ Portunus pelagicus ” from Hawaii and Tahiti are considered highly doubtful.

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. 8. Portunus pelagicus illustration from Rumphius (1705) from which Linnaeus based his description.

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.

Fig. 10. Colour variation in Portunus pelagicus males. A, Taiwan (specimen not preserved) (photograph: C.Y. Tsai); B, Singapore (specimen not preserved) (photograph: M. Ng).

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. 12. Portunus segnis (Forskål, 1775) (photograph based on a re-edition of the plates of Savigny by Institut d’Orient (1988), © Institut d’Orient/Naguib-Michel Sidhom, in Guinot & Cleva, 2009), Red Sea.

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. 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.