Lake County SWCD has a crayfish tank in the Two Harbors office. Crayfish were collected during the 2017 season from the White Iron Chain of Lakes. The tank serves as a repository for animals needing further identification. Additionally, it provides live specimens for outreach and education, prompting interesting discussions in the office.
A few weeks ago, we noticed the crayfish had small white worms attached to their carapace (shell). The white worms are citellate annelids (or intermediaries between oligochaetes and leeches) in the order Branchiobdella. These “worms” attach to the crayfish with suckers. The scientific community has not reached a consensus about the relationship between the citellate annelids and their hosts – some say the relationship is parasitic, some say mutualistic. The Branchiobdella clean the crayfish’s gills, feeding on host tissue. This either benefits the crayfish by providing a “cleaning service,” or it harms them by causing constant wounding of the gills, resulting in infections and bleeding in the branchial chamber. There are no known methods of control for infected crayfish, although the Branchiobdella do seem to be geographically limited to the Northern Hemisphere. Crayfish in the SWCD office are occasionally taken out of their tank and rubbed to remove some of the Branchiobdella. Cleaning the tank and replacing water on a regular basis helps keep the population of Branchiobdella lower as well. Crayfish in the office are also fed regularly with a crayfish food pellet mix including meat, aquatic vegetation gathered in the field, and lettuce or other vegetables.
Most crayfish do not necessarily “play nice” together in the confines of a tank. There are currently 9 crayfish at Lake County SWCD, numbered so we can see how various territorial fights ensue. Stop by and see which crayfish you’ll put your bets on! Feel free to bring some lettuce or other food for the crayfish – they will eat most anything!