Portunus, WEBER, 1795

Koch, Milan, Spiridonov, Vassily A. & Ďuriš, Zdeněk, 2023, Revision of the generic system for the swimming crab subfamily Portuninae (Decapoda: Brachyura: Portunidae) based on molecular and morphological analyses, Zoological Journal of the Linnean Society 197, pp. 127-175 : 161-163

PORTUNUS WEBER, 1795

( FIGS 3C, 4B, 15)

= Portunus Weber, 1795 (type species Cancer pelagicus Linnaeus, 1758 , designation by Rathbun, 1926; gender masculine) [Opinion 394]; see Holthuis (1952).

Full synonymy: see Ng et al. (2008): 152 [ Portunus (Portunus) ].

Included species: Thirteen.

Portunus armatus (A. Milne-Edwards, 1861)

= Neptunus armatus A. Milne-Edwards, 1861 Portunus convexus De Haan, 1835

= Neptunus sieboldi A. Milne-Edwards, 1861 Portunus hawaiiensis Stephenson, 1968

Portunus madagascariensis (Hoffman, 1874)

= Neptunus madagascariensis Hoffmann, 1874 Portunus pelagicus (Linnaeus, 1758)

= Cancer pelagicus Linnaeus, 1758 [Opinion 394]

= Cancer pelagicus Forskål, 1775 [pre-occupied name, primary junior homonym of Cancer pelagicus Linnaeus, 1758 ]

= Cancer cedonulli Herbst, 1794

= Portunus denticulatus Marion de Procé, 1822

= Portunus (Portunus) pelagicus var. sinensis Shen, 1932

Portunus pubescens ( Dana, 1852)

= Lupa pubescens Dana, 1852

= Neptunus tomentosus Haswell, 1881

Portunus reticulatus (Herbst, 1799)

= Cancer reticulatus Herbst, 1799

Portunus rufiarcus Davie, 1987

Portunus sanguinolentus (Herbst, 1783)

= Cancer sanguinolentus Herbst, 1783

= Cancer gladiator Fabricius, 1793

= Callinectes alexandri Rathbun, 1907

=? Cancer raihoae Curtiss, 1938

Portunus serratifrons ( Montrouzier, 1865)

= Neptunus serratifrons Montrouzier, 1865 Portunus sayi (Gibbes, 1850)

= Lupa sayi Gibbes, 1850

= Portunus tropicalis Marion de Procé, 1822

= Lupea pudica Gerstaecker, 1856

= Lupea parvula Desbonne , in Desbonne & Schramm, 1867

Portunus segnis (Forskål, 1775)

= Cancer segnis Forskål, 1775

= Portunus mauritianus Ward, 1942

Portunus trituberculatus (Miers, 1876)

= Neptunus trituberculatus Miers, 1876

Diagnosis: Carapace ( Fig. 15A) usually broadly hexagonal, much broader than long, width (without lateral teeth)-to-length ratio> 1.5. Dorsal surface finely granulated, with regions feebly demarcated, sometimes with narrow rows of granules in their centres. Urogastric depression distinctly anterior (rarely slightly posterior) to half length of carapace. Front ( Fig. 15B) with four triangular or rounded teeth; median ones may be extremely reduced. Supraorbital margin with two short fissures; infraorbital margin with shallow lateral notch. Epistome apophysis well developed, may be producing medially as prominent spine far overreaching submedian frontal teeth. Anterolateral margin with nine spiniform teeth; teeth of anterior series (except last tooth) short, subequal in size; last tooth distinctly larger, lateral. Posterolateral junction of carapace rounded. Most of the sutures on thoracic sternum indistinct ( Fig. 15C), thoracic sternites generally smooth. Merus of third maxilliped with anteroexternal angle rounded or subrectangular, not produced laterally. Chelipeds usually stout; merus with posterior border subparallel to anterior (or convex), bearing three or four spines on anterior border, and unarmed or with one spine distally on posterior border. Carpus with a spine and carinae on outer face; in a few cases, carina ends in an additional spinule. Chelae ( Fig. 15D) slightly inaequal, heterodontic upper surface of palm with two distal teeth; molariform tooth present proximally at cutting edge of dactylys of larger chela. Dactyli of pereiopods 2–4 relatively broad, lanceolate, leaf-like or cultriform, indistinctly costate, densely setose on ventral margin. Merus of pereiopod 5 subquadrate, only little longer than broad or, more rarely, elongate, distinctly longer than broad, without a spine on posterior margin. Male pleon ( Figs 3C, 15C) narrowly triangular, almost smooth. Pleomeres 2 and 3 with low keels, in some species not visible in ventral view; lateral margins of pleomere 3 straight or concave; terminal part of posterior thoracic episternite fills interspace between anterior margin of pleomere 3 and thoracic sternite 8; third to fifth pleomeres fused, without remaining sutures but with indistinct transverse keels; combined part distinctly longer than sixth pleomere, the latter with lateral margins convergent distally; telson triangular and rounded, subequal or shorter than sixth pleomere. First male gonopod ( Fig. 15E) with short and robust transverse base and long, string-like distal part, basally curved and broadly arching anteriorly, touching medially; apices straight, reaching telson basis. Female vulva ( Fig. 4B) in form of a transverse slit or rounded, located in medial part of proximal portion of sternite, with long axis subparallel or oblique to anterior margin of sternite.

Systematic position: Based on the present molecular results and a morphological comparison, Portunus is closely related to Callinectes . Spiridonov et al. (2014) presented Portunus , Callinectes and Atlantic Arenaeus as key members of the subfamily Portunidae , with unresolved positions for other species of Portunus (s.l.) diagnosed by being relatively large swimming forms sharing leaf-like walking dactyli, the lack of conspicuous granular patches on the carapace and slender gonopods. The other ‘ Portunus ’ species were separated into multiple subgenera (see listing by Ng et al., 2008), some of which have since been raised to generic level ( Mantelatto et al., 2009; Nguyen & Ng, 2010; Chertoprud et al., 2012; Spiridonov et al., 2014). Here, they are all nested inside a major monophyly as part of an unresolved basal polytomy together with Portunus – Callinectes , Achelous , Lupocyclinae and the Thalamitinae clades ( Fig. 1).

Remarks: From 24 species of Portunus (Portunus) as listed by Ng et al. (2008), the present generic reassignment reduces this to 13 species. Portunus mauritianus Ward, 1942 had already been synonymized with P. (P.) segnis by Ng et al. (2008); three species ( P. asper , P. gibbessi and P. rufiremus ) were transferred to Achelous by Mantelatto et al. (2009) and four others ( P. acuminatus , P. affinis , P. minimus and P. xantusii ) by Mantelatto (2018); and P. floridanus has recently been transferred to Achelous by Marco-Herrero et al. (2021). The remaining four species ( P. anceps , P. hastatus , P. inaequalis and P. ventralis ) are assigned to Achelous in this study (see above). Portunus serratifrons ( Montrouzier, 1865) was already suggested to be a juvenile Scylla serrata by A. Milne-Edwards (1873), but it is still listed herein as a valid species of Portunus , albeit rather provisionally. The generic affiliation of P. madagascariensis (Hoffmann, 1877) needs to be re-examined owing to its close similarity to P. sanguinolentus . The species is thus here provisionally regarded as valid.

Portunus mokyevskyi Zarenkov, 1970 was listed in the subgenus Portunus by Ng et al. (2008) on the basis of the original description ( Zarenkov, 1970). The holotype of this species, a juvenile male measuring 19.0 mm × 29.2 mm (ZMMU Ma 2177, Indonesia, North Sulawesi, Amurang, littoral, 18 December 1962, O. B. Mokievsky lgt.), was examined by one of us (V.A.S.). The general morphology and smoothness of the carapace, the presence of two spines on the posterior margin of the cheliped merus and the pattern of heterodonty (i.e. Keenan et al., 1998; Spiridonov et al., 2014) undoubtedly indicate that it belongs to Scylla De Haan, 1833 ( Necronectinae ); the shape of the frontal lobes and the pattern of spines on the carpus and palm of chelipeds allow us to identify it as Scylla tranquebarica (Fabricius, 1798) (sensu Keenan et al., 1998) , under which species we here formally synonymize it.

Except for P. madagascariensis and P.serratifrons , for which original descriptions were too brief (Montrousier, 1865; Hoffman, 1874), two groups of species may be recognized among the remaining ten species of Portunus based on their morphology [i.e. the P. convexus group (together with P. pubescens , P. rufiarcus and P. sayi ) and the P. pelagicus group (with the six remaining species)]. There are differences in the shape of the morphology of the carapace and chelipeds. Given that our molecular analysis does not cover members of the P. convexus group, the congeneric status of its three species needs to be confirmed in the future.

Size: The genus includes the group of medium-sized species P. pubescens (maximum size CL × CW 25.0 mm × 45.0 mm; Crosnier, 1962), P. convexux (30.4 mm × 51.6 mm; our data, SMF male), P.rufiarcus (CW 27.1 mm, the only known specimen, holotype; Davie, 1987) and P. sayi (37.1 mm × 76.1 mm; Rathbun, 1930). The maximum known sizes of the remaining larger species reach distinctly higher v a l u e s, e.g. C L × C W: 6 1.5 m m × 1 3 6.0 m m i n P. sanguinolentus (see Apel & Spiridonov, 1998), 77.2 mm × 163.4 mm in P. reticulatus (see Lai et al., 2010), 82.0 mm × 188.0 mm in P. trituberculatus (see Yang et al., 2012) and CW 173 mm in P. armatus (female MNHN-IU-2018-1413).

Ecological notes: Portunus spp. are generally shallow-water dwellers, confined mostly to the intertidal and upper subtidal zones, preferring sandy substrates but also occurring on other types of substrates, notably seagrass meadows; larger-sized species are known for their complex migration pattern and frequent occurrence in the outer parts of estuaries. Portunus sanguinolentus and especially P. sayi are commonly associated with flotsam, thus travelling large distances over deep waters (reviewed by Spiridonov, 2013). Portunus sayi is likely to reproduce when living on floating sargassum ( Verrill, 1908; Rathbun, 1930).

Geographical range: Indo-West Pacific (majority o f s p p.); t r o p i c a l w e s t e r n A t l a n t i c (P. s a y i); Mediterranean Sea ( P. segnis, Lessepsian migrant from the Red Sea, now common Mediterranean species; Lai et al., 2010).