Pachygrapsus marmoratus
Introduction '''''Pachygrapsus marmoratus''''' is a species of crab, sometimes called the '''marbled rock crab''' or '''marbled crab''', which lives in the Black Sea, the Mediterranean Sea and parts of the Atlantic Ocean. It is dark violet brown, with yellow marbling, and with a body up to  long. A semiterrestrial omnivore, it feeds on algae and various animals including mussels and limpets.
Description ''P. marmoratus'' has a square carapace  long, which is dark violet brown with marbling in yellow. It can be distinguished from related species of ''Pachygrapsus'' in the Mediterranean Sea (''Pachygrapsus maurus'' and ''Pachygrapsus transversus'') by the presence of three teeth on each side of the carapace. It is capable of very rapid movements, and it uses this ability to dart into crevices, making it difficult to catch.Crab (Pachygrapsus marmoratus).jpg|on the Adriatic Sea coastline, CroatiaMarbled crab (Pachygrapsus marmoratus) Butrint.jpg| at Butrint in AlbaniaCrabs (Pachygrapsus marmoratus).webm|left|Video of algae grazing
Distribution It is widespread in Southern Europe, from the Black Sea to the Moroccan coast, and along the Atlantic coasts of Portugal, Spain and France, and was observed as early as 1996 as far north as Southampton in the English Channel. This range expansion may be due to the warming of the surface waters.
Ecology ''P. marmoratus'' is an omnivore, but not an opportunist; similar proportions of algae and animals are consumed however abundant they are in the habitat. The favoured animals in the diet of ''P. marmoratus'' are mussels, limpets and its own species. When attacking the limpet ''Patella depressa'', ''Pachygrapsus marmoratus'' uses a consistent method, which is usually unsuccessful. On more sheltered shores, ''P. grapsus'' eats fewer mussels, but compensates with a greater consumption of barnacles.Predators of ''Pachygrapsus marmoratus'' include the musky octopus, ''Eledone moschata''.The larvae of ''P. marmoratus'' are planktonic and may survive for up to 31 days. This results in high levels of gene flow between populations, and allows the species to rapidly colonise new areas.
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