Pachygrapsus Randall, 1840

Poupin, Joseph, Davie, Peter J. F. & Cexus, Jean-Christophe, 2005, A revision of the genus Pachygrapsus Randall, 1840 (Crustacea: Decapoda: Brachyura, Grapsidae), with special reference to the Southwest Pacific species, Zootaxa 1015 (1), pp. 1-66: 6-7

publication ID

http://doi.org/ 10.11646/zootaxa.1015.1.1

publication LSID

lsid:zoobank.org:pub:67DBD7AA-FA11-4F32-811B-0A9EFF4C668F

persistent identifier

http://treatment.plazi.org/id/6C3D8794-ED42-FFFF-6C1C-F948FEA9FE10

treatment provided by

Felipe

scientific name

Pachygrapsus Randall, 1840
status

 

Pachygrapsus Randall, 1840  

Pachygrapsus Randall, 1840   (type species Pachygrapsus crassipes Randall, 1840   , subsequent designation by Kingsley, 1880; gender masculine; type locality was originally indicated as Hawaiian Is. but this is probably an error as it has not been subsequently reported from this locality; the Pacific coast of the United States is more likely).

Goniograpsus Dana, 1851   (type species Goniograpsus innotatus Dana, 1851   , a subjective junior synonym of Pachygrapsus transversus ( Gibbes, 1850)   , subsequent designation by Manning & Holthuis, 1981; gender masculine).

Diagnosis

Carapace subquadrate or with lateral margins convergent backwards; dorsal surface slightly convex, feebly or strongly striated. Anterolateral margins entire or with one or two teeth behind exorbital angles. Length of front more than half carapace width. Third maxilliped widely gaping; merus as broad as or broader than long with no oblique setal crest. Inner sub­orbital lobes small, allowing antennae to enter orbits.

Remarks

Pachygrapsus Randall   is morphologically close to Planes Bowdich, 1825   , and Metopograpsus H. Milne Edwards, 1853   . The latter two genera include species that have been sometimes placed in Pachygrapsus   . Planes   differs from Pachygrapsus   by having a more convex carapace that is subcircular, smooth or only feebly striated; a natatory fringe of setae on the propodi of the ambulatory legs; and an open­water habitat (among pelagic seaweeds or crawling on floating objects). It includes three species: P. major ( MacLeay, 1838)   , P. minutus ( Linnaeus, 1758)   , and P. marinus Ratbhun, 1914   . Planes marinus Ratbhun, 1914   is somewhat intermediate in morphology between Planes   and Pachygrapsus   . Its carapace is more subquadrate and striated, the chelae resembling those of Pachygrapsus   , and the natatory fringe of setae on the ambulatory legs can be reduced. This led Chace (1951: 72) to transfer the species to Pachygrapsus   , mentioning that, except for its much smaller size, it is very similar to Pachygrapsus crassipes Randall, 1840   . Chace (1966: 647) after observing the well­developed natatory fringes on specimens of Pachygrapsus marinus   from St. Helena I., decided that the similarities in shape of the carapace and chelae were probably not very important, and that the presence of natatory fringes and the shape of the G1 were the most important characters for defining Planes   . He thus reinstated Planes marinus   , and this generic placement is now widely accepted (see Prado & Melo, 2002). These generic changes, however, serve to highlight the close morphological relationship between Planes   and Pachygrapsus species.  

Pachygrapsus   is also morphologically close to Metopograpsus H. Milne Edwards, 1853   , the two being separated only on the basis of whether the antennae are able to enter the orbital hiatus ( Pachygrapsus   ) or are excluded ( Metopograpsus   ). This character is nevertheless not always reliable. We agree with Tesch (1918: 78), Tweedie (1949: 466, footnote), and Crosnier (1965: 25) that M. thukuhar ( Owen, 1839)   may have a distinct gap between the inner sub­orbital lobes and the outer angles of the front, and that it is thus possible for the antenna to enter the orbit. This has also been reported for M. quadridentatus Stimpson, 1858   ( Tesch, 1918; Tweedie, 1949). This minor difference between the genera led to confusion in the past. Tweedie (1936) described P. quadratus   from specimens collected from Singapore, but later realised ( Tweedie, 1949) that he had confused it with M. quadridentatus Stimpson, 1858   . Further work is needed to decide if such a variable orbital character is enough to separate Pachygrapsus Randall   and Metopograpsus H. Milne Edwards.  

Kingdom

Animalia

Phylum

Arthropoda

Class

Malacostraca

Order

Decapoda

Family

Grapsidae

Loc

Pachygrapsus Randall, 1840

Poupin, Joseph, Davie, Peter J. F. & Cexus, Jean-Christophe 2005
2005
Loc

P. quadratus

Tweedie 1936
1936
Loc

P. marinus

Ratbhun 1914
1914
Loc

Planes marinus

Ratbhun 1914
1914
Loc

Pachygrapsus marinus

Ratbhun 1914
1914
Loc

Planes marinus

Ratbhun 1914
1914
Loc

M. quadridentatus

Stimpson 1858
1858
Loc

M. quadridentatus

Stimpson 1858
1858
Loc

Metopograpsus

H. Milne Edwards 1853
1853
Loc

Metopograpsus

H. Milne Edwards 1853
1853
Loc

Goniograpsus

Dana 1851
1851
Loc

Goniograpsus innotatus

Dana 1851
1851
Loc

Pachygrapsus

Randall 1840
1840
Loc

Pachygrapsus crassipes

Randall 1840
1840
Loc

Pachygrapsus

Randall 1840
1840
Loc

Pachygrapsus

Randall 1840
1840
Loc

Pachygrapsus

Randall 1840
1840
Loc

Pachygrapsus

Randall 1840
1840
Loc

Pachygrapsus

Randall 1840
1840
Loc

Pachygrapsus

Randall 1840
1840
Loc

Pachygrapsus crassipes

Randall 1840
1840
Loc

Pachygrapsus

Randall 1840
1840
Loc

Pachygrapsus

Randall 1840
1840
Loc

Pachygrapsus

Randall 1840
1840
Loc

Planes

Bowdich 1825
1825
Loc

Planes

Bowdich 1825
1825
Loc

Planes

Bowdich 1825
1825
Loc

Planes

Bowdich 1825
1825
Loc

Planes

Bowdich 1825
1825