Mottled Shore Crab
Pachygrapsus transversus
Description 2
The mottled shore crab, Pachygrapsus transversus, is a small intertidal crab belonging to the family Grapsidae. Members of this family are characterized by squarish carapaces with few spines (Voss 1980). The color of the carapace in P. transversus is dark green to black, and the surface is covered with oblique lines of fine tubercles or bumps (Abele et al. 1986, Ruppert & Fox 1988, Voss 1980). The sides converge toward the posterior end to form a trapezoidal shape, and the area between the eyes is slightly curved and bears no teeth. The claws are brownish to pink or cream, with a smooth upper surface on the movable finger. Teeth are present on the hind margins of the largest joints on the legs. Unlike many crabs, there is no sexual dimorphism in claw size, and the total body size of males is larger than females (Abele et al. 1986).
Distribution 3
The mottled shore crab can be found in all the habitats described above. However, individuals are probably most abundant among jetty rocks, on buoys and pilings near inlets.
Size 4
The maximum age of P. transversus is unknown, and the lifespan can vary with food availability and environmental factors. The mottled shore crab is a small species, with the maximum reported carapace width of only 1.7 cm (Abele 1986).
Look alikes 5
The spray crab, Plagusia depressa, is a grapsid crab with similar features to the mottled shore crab, and can be found in many of the same habitats. The carapace reaches a much larger width of about 2.4 cm, and is variously colored with shades of red, green or orange (Ruppert & Fox 1988). Unlike P. transversus, the body is nearly circular with a toothed front margin, and teeth are found on the front side of the largest segments of the walking legs.Regional Occurrence & Habitat Preference: The mottled shore crab has a wide geographic range, including: the western Atlantic from North Carolina to Uruguay, and Bermuda; the eastern Atlantic to Angola, including the Canary Islands and Cape Verde; Mediterranean; and the eastern Pacific from California to Peru, including the Galapagos Islands (Rathbun 1918). This species had also been introduced to areas such as Copenhagen (Christiansen 1969). The preferred habitat of this crab is as varied as its range. Populations are common in rocky intertidal areas, on wharf pilings and sea walls, and in swamps of the red mangrove, Rhizophora mangle (eg. Abele 1976). However, individuals may be found in virtually any sheltered marine intertidal zone at tropical and subtropical latitudes (Crane 1947).
Reproduction 6
Sexual dimorphism is mostly restricted to abdomen morphology, which is larger in females and used to carry egg broods. However, claw size also differs depending on sex, with larger claws belonging to males (Flores et al. 1998). Both males and females reach sexual maturity at a carapace width of about 0.7 cm (Abele et al. 1986). As with most decapod crustaceans, fertilization occurs during copulation. The process usually takes place at the entrance of a burrow, lasts approximately 10 seconds, and is initiated with a leg touch (Abele et al. 1986). Sperm-filled cases, called spermatophores, are transferred from the male to the female. After the eggs are fertilized, the female broods them on her abdomen until hatching. Reproduction is seasonal in some locations, and is likely linked to water temperature and food availability. In Brazil, ovigerous females were reported throughout the year (Flores et al. 1998), but were most abundant in summer months; whereas, recruitment of young was highest in winter (Flores & Negreiros-Fransozo 1999b). Reproduction occurred continuously in Panama populations, and lasted from November through March in Costa Rica (Crane 1947).
Link to Access Genomic Data 7
http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=72636&lvl=0
Sources and Credits
- (c) Bernadette, some rights reserved (CC BY-NC), uploaded by Bernadette
- (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11527430
- Adapted by matbio from a work by (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11527431
- (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11527435
- (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11527433
- Adapted by matbio from a work by (c) Smithsonian Marine Station at Fort Pierce, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/11527434
- (c) Emily Rose Sharkey, all rights reserved
