Blue Swimmer Crab

Portunus pelagicus
Image by Tanaka Juuyoh.

The blue swimmer crab is a tropical species of crab that has acclimatized to the cooler conditions of southern Australia.

They are found in lots of different places but they prefer sandy bottoms and sea grass meadows. Swimmer crabs are distinguished by the fact that their last pair of legs are swimming paddles.

They bury themselves leaving only their eyes, antennae, and gills exposed. They stay buried under sand or mud most of the time, particularly during the daytime and winter. They come out to feed during high tide; on various organisms such as bivalves, fish, and, to a lesser extent, macroalgae.

To mate the male swimmer crab will court a female for four to ten days – this is done by carrying her underneath him. After spawning, the larvae go through lots of different stages before taking on the adult shape.