Grapsinae

Sally lightfoots Grapsus grapsus, copyright Diego Delso.

Belongs within: Grapsoidea.

The Grapsinae are a group of shore crabs in which the inner half of the suborbital margin is dominated by the suborbital crest, with the true infraorbital margin ending far from the inner end of the suborbital. The Sally lightfoot Grapsus grapsus is a common species on the Pacific coast of Central and South America.

The Grapsidae: from sea to shore
Published 11 April 2012
Sally Lightfoot, Grapsus grapsus, photographed by Victor Burolla. The vernacular name refers to their walking on the points of their legs.

In a post from back in 2008, I wrote about the group of crabs known as the Grapsoidea. As described in that post, the classification of the Grapsoidea has been shuffled in recent years, and the subjects of today’s post, the Grapsidae, would have previously been classed as the Grapsinae within a larger Grapsidae. The more restricted Grapsidae has been supported by numerous recent analyses, both morphological (Karasawa & Kato 2001) and molecular (Schubart et al. 2000). Morphologically, grapsids are united by having an expanded anterolateral corner to the merus* of the third maxilliped, oblique ridges on the lateral surfaces of the meri of the pereiopods, and (in many species) oblique ridges on the dorsum of the carapace (Karasawa & Kato 2001). Studies of the larvae of grapsids have also identified distinctive characters by which grapsid larvae can be distinguished from those of other grapsoids (Cuesta & Schubart 1999).

*The merus is the first elongate segment of crustacean appendages, corresponding to the femur of other arthropods. The maxillipeds are feeding appendages; the pereiopods are the walking legs.

The Columbus crab Planes major, photographed by Denis Riek. This species comes in a wide range of colours, from brown to blue to almost white; the page linked to shows a number of examples.

Most grapsids are intertidal shore-dwellers, but there are some exceptions. Species of the genus Planes, known as Columbus crabs, are small oceanic forms. They live on objects floating in the open water: seaweed, driftwood and other debris, or even other animals such as by-the-wind sailors or turtles (Spivak & Bas 1999). Columbus crabs differ from other grapsids in having flattened pereiopod meri for swimming, and two of the three species lack oblique ridges on the carapace. The aforementioned phylogenetic analyses also agree in placing Planes as the sister group to other grapsids analysed.

Geograpsus grayi, from here.

Also distinctive are species of the genus Geograpsus which are one of a number of crab groups to have developed a terrestrial lifestyle, found on islands of the Indo-Pacific and Atlantic. In the Indo-Pacific G. crinipes, it has been shown that dense bunches of setae between the second and third walking legs are long enough to contact the ground when the animal sits back on its haunches (McLay & Ryan 1990). Water on the surface of the ground is drawn up through the setae by capillary action and conducted into the gill chamber, keeping the gills damp and functioning. Terrestrial Geograpsus retain marine larvae as do many other terrestrial crabs; the larval development has been studied for the eastern Pacific G. lividus which goes through nine larval stages (eight zoeae and the megalopa) over the period of two months (Cuesta et al. 2011). This happens to be the longest developmental pathway of any known crab: the previous confirmed maximum was eight larval stages.

Systematics of Grapsinae
<==Grapsinae
|--Leptograpsus Milne Edwards 1853B64
| `--L. variegatus (Fabricius 1793)J90 (see below for synonymy)
|--PlanesB64
| |--P. cyaneusB64
| |--P. major (Macleay 1838)TSH09
| `--P. minutus (Linnaeus 1758)B64
|--Pachygrapsus Randall 1839TSH09, B55
| |--P. crassipesGLT03
| |--P. gracilisMWW89
| |--P. marmoratus (Fabricius 1787)KK03
| |--P. maurus (Lucas 1846)KK03
| |--P. minutus Milne Edwards 1873TSH09
| `--P. transversus (Gibbes 1850)SCF02 [=Grapsus transversusB55]
`--Grapsus Lamarck 1801B55
|--G. albolineatus Latreille in Milbert 1812TSH09
|--G. grapsus (Linnaeus 1758)SCF02 [=Cancer grapsusB55]
|--G. maculatusF15
|--G. maurus Lucas 1846E12
|--G. pictusG20
|--G. tenuicrustatus (Herbst 1783)TSH09
`--G. variusR26

Leptograpsus variegatus (Fabricius 1793)J90 [=Cancer variegatusB64; incl. Sesarma pentagona Hutton 1875B64, Grapsus personatusJ90]

*Type species of generic name indicated

References

[B64] Bennett, E. W. 1964. The marine fauna of New Zealand: Crustacea Brachyura. New Zealand Department of Scientific and Industrial Research Bulletin 153: 1–120.

[B55] Bott, R. 1955. Dekapoden (Crustacea) aus El Salvador. 2. Litorale Dekapoden, außer Uca. Senckenbergiana Biologica 36: 45–70.

Cuesta, J. A., G. Guerao, C. D. Schubart & K. Anger. 2011. Morphology and growth of the larval stages of Geograpsus lividus (Crustacea, Brachyura), with the descriptions of new larval characters for the Grapsidae and an undescribed setation pattern in extended developments. Acta Zoologica 92 (3): 225–240.

Cuesta, J. A., & C. D. Schubart. 1999. First zoeal stages of Geograpsus lividus and Goniopsis pulchra from Panama confirm consistent larval characters for the subfamily Grapsinae (Crustacea: Brachyura: Grapsidae). Ophelia 51 (3): 163–176.

[E12] Evenhuis, N. L. 2012. Publication and dating of the Exploration Scientifique de l’Algérie: Histoire Naturelle des Animaux Articulés (1846–1849) by Pierre Hippolyte Lucas. Zootaxa 3448: 1–61.

[F15] Fowler, H. W. 1915. Cold-blooded vertebrates from Florida, the West Indies, Costa Rica, and eastern Brazil. Proceedings of the Academy of Natural Sciences of Philadelphia 67 (2): 244–269.

[GLT03] Glenner, H., J. Lützen & T. Takahashi. 2003. Molecular and morphological evidence for a monophyletic clade of asexually reproducing Rhizocephala: Polyascus, new genus (Cirripedia). Journal of Crustacean Biology 23: 548–557.

[G20] Goldfuss, G. A. 1820. Handbuch der Naturgeschichte vol. 3. Handbuch der Zoologie pt 1. Johann Leonhard Schrag: Nürnberg.

[J90] Jones, D. S. 1990. Annotated checklist of marine decapod Crustacea from Shark Bay, Western Australia. In: Berry, P. F., S. D. Bradshaw & B. R. Wilson (eds) Research in Shark Bay: Report of the France-Australe Bicentenary Expedition Committee pp. 169–208. Western Australian Museum.

Karasawa, H., & H. Kato. 2001. The systematic status of the genus Miosesarma Karasawa, 1989 with a phylogenetic analysis within the family Grapsidae and a review of fossil records (Crustacea: Decapoda: Brachyura). Paleontological Research 5 (4): 259–275.

[KK03] Kocataş, A., & T. Katağan. 2003. The decapod crustacean fauna of the Turkish seas. Zoology in the Middle East 29: 63–74.

McLay, C. L., & P. A. Ryan. 1990. The terrestrial crabs Sesarma (Sesarmops) impressum and Geograpsus crinipes (Brachyura, Grapsidae, Sesarminae) recorded from the Fiji Is. Journal of the Royal Society of New Zealand 20 (1): 107–118.

[MWW89] Miller, P. J., J. Wright & P. Wongrat. 1989. An Indo-Pacific goby (Teleostei: Gobioidei) from West Africa, with systematic notes on Butis and related eleotridine genera. Journal of Natural History 23: 311–324.

[R26] Risso, A. 1826. Histoire naturelle des principales productions de l’Europe méridionale et particulièrement de celles des environs de Nice et des Alpes maritimes vol. 5. F.-G. Levrault: Paris.

Schubart, C. D., J. A. Cuesta, R. Diesel & D. L. Felder. 2000. Molecular phylogeny, taxonomy, and evolution of nonmarine lineages within the American grapsoid crabs (Crustacea: Brachyura). Molecular Phylogenetics and Evolution 15 (2): 179–190.

[SCF02] Schubart, C. D., J. A. Cuesta & D. L. Felder. 2002. Glyptograpsidae, a new brachyuran family from Central America: Larval and adult morphology, and a molecular phylogeny of the Grapsoidea. Journal of Crustacean Biology 22 (1): 28–44.

Spivak, E. D., & C. C. Bas. 1999. First finding of the pelagic crab Planes marinus (Decapoda: Grapsidae) in the southwestern Atlantic. Journal of Crustacean Biology 19 (1): 72–76.

[TSH09] Titelius, M. A., A. Sampey & C. G. Hass. 2009. Crustaceans of Mermaid (Rowley Shoals), Scott and Seringapatam Reefs, north Western Australia. Records of the Western Australian Museum Supplement 77: 145–176.

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