(also called Crawfish, Crawdad, Freshwater Lobster, etc.)

    Crayfish is in the Subphylum Crustacea,  Class Malacostraca, order Decapoda, constituting the superfamilies  Astacidae and Cambaridae (Northern Hemisphere) and Parastacidae (Southern Hemisphere in Australia, New Zealand, South America, and Madagascar). They are characterized by a joined head and thorax, or midsection, and a segmented body.  They grow by molting as all crustaceans do, i.e., they shed their carapace (shell) when they outgrow it, and form a new hard shell.  There are over 540 species worldwide, and nearly half of the number in North America.  Most of them live in fresh water, a few in salt water, and even in underwater caverns (including Troglobitic crayfishes). The color and size vary with species, diet, and age.  Most are red, some are green, brown, tan, or blue with black or orange markings in various combinations (except those in the caverns).  Juveniles often are light tan,  and turn deep red when grow up. The coloration depends in part on their diet, and can change with a change in diet.  Adult size is 2" to 6" for most US species.  Some Australian varieties can alos be quite big.  Among the largest is Astacopsis gouldi of Tasmania in Autralia, which may reach 40 cm and weigh about 3.5 kg (8 pounds).  The pictures of two species of Procambarus shown below.  We have been "playing" with these creatures from Louisiana (Procambarus spp.) for a while.  We "milk" them to get their digestive fluid, from which the endopeptidase astacin is isolated.
    Do you want to know what about crayfish outside our lab?  (Hmm!)

    P. clarkii addapted from Crayfish Photo Gallery             P. paeninsulanus addapted from Crayfish Photo Gallery

  You can find numerous links about crayfish, and here are a few of them that I found very interesting:

The "Crayfish Home Page" which has recently moved to
The International Association of Astacology (Yes, things about Astacus)
Some brief information and links
Several links in the "Freshwater Resources"