Crawdads are freshwater lobsters with a fishy folk name
Crayfish, crawfish, or crawdads are freshwater crustaceans closely related to lobsters, breathing through feathery gills. The name comes from Old French escrevisse, bent toward fish by folk etymology, and Louisiana alone harvests 100 million pounds of them a year.
Crayfish belong with lobsters in the infraorder Astacidea. Four living families are recognised: Parastacidae in the Southern Hemisphere, across South America, Madagascar, and Australasia, and three northern ones, with Astacidae in western Eurasia and western North America, Cambaridae in eastern North America, and Cambaroididae in eastern Asia. Southeastern North America is the hotspot, with over 330 species. Fossil burrows from about 300 million years ago may be the work of early crayfish, and the oldest body fossils date to the Late Triassic.
Australia has over 100 species, including the three biggest: the Tasmanian giant freshwater crayfish, which can top 5 kg, the Murray crayfish at around 2.5 kg, and the marron at up to 2.2 kg. The average crayfish grows to about 17.5 cm. In Australia, New Zealand, and South Africa, though, cray usually means a saltwater spiny lobster, and freshwater kinds are called yabbies or, in New Zealand, kōura. In Britain the only native true crayfish, the white-clawed crayfish, is endangered.
They are omnivorous scavengers that live on the bottom, and their guts mostly contain fine organic mud, rich in bacteria, fungi, and algae. They eat quickly, then hide and digest for hours, and will eat their own droppings, shed shells, and each other. T. H. Huxley’s 1879 book The Crayfish simply called them detritivores.
Louisiana made the crawfish its state crustacean in 1983. In Europe, native species have been devastated by crayfish plague, a water mould that arrived with introduced North American crayfish, letting the resistant signal crayfish invade.
Source: Crayfish
