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48 the annulus ventralis,, is very similar between species. Now, given that, since we only have six species of crayfish in the state of Nebraska, the secondary characteristics noted above will often work with females as will the annulus ventralis. This photo illustrates the annulus ventralis of a Ringed crayfish female. The claw of the Ringed crayfish is shorter and stouter than those of the Northern or Calico crayfishes. The movable finger (dactyl) is straight in young specimens but develops a distinctive curve as they get older. The surface of the claw is smooth and there are no setae between the fingers. The size of the gap between the fingers can vary with sex and age. As a rule, larger Ringed crayfish have larger finger gaps. Form I males also develop larger gaps than females or Form II males. As you can see in the photo, the tips of the fingers of the Ringed crayfish usually have a black ring with an orange/red tip (which Rusty crayfish also have). But, I occasionally find a Ringed crayfish where the black ring is absent or barely visible. HABITATS In Oklahoma the species "seemingly prefers streams and rivers with clear water and a rather strong current". They were found living under rocks and boulders and were often abundant. 32 In Kansas they preferred to live under rocks but were also found in burrows of clay-banked streams. 247 In Missouri they preferred clear and rocky streams and rivers where it was found in rocky riffles. They were also found in pools that had enough flow to keep them free of silt. 188 A detailed study of the habitat use of the Ringed crayfish in an Ozark stream was done in Oklahoma. Here males tended to prefer slighter deeper water than females. Areas with gravel/cobble substrate were dominated by juveniles whereas adults preferred beds of vegetation (Myriophyllum). Juveniles inhabited areas of moderate velocity whereas adults occupied low velocity as well as high velocity areas. 80 The literature above says that the Ringed crayfish prefers clear, fast-flowing streams with rocky substrate. In Nebraska, my experience says otherwise. Streams in seven of the eight river basins where the Ringed crayfish is found (Niobrara, North Platte, South Platte, Middle Platte, Loup, Little Blue, and Republican) have predominately sand-beds with occasional gravels or silt. These streams tend to be clear (less than 300 ntu [nephelometric turbidity units]). Ringed crayfish here most commonly use the cover provided by overhanging grasses (especially exposed grass root mats) and vegetation along the banks. They also use beds of aquatic vegetation or algae that may be found along shorelines or in mid-channel