An ongoing saga: Endemic branchiobdellidans (Annelida: Clitellata) on translocated commercial North American crayfish

Over the last 130 years demand for crayfish has exceeded regional supplies around the world, so stocks, primarily from North America, have been imported to satisfy this need. These demands are human based and include gastronomy, sport fishing bait, food for rearing animals, educational aides, ornamentation in waterbodies, and more recently a significant increase in pet crayfish sales. The three most common commercial species from North America are Pacifastacus leniusculus, Procambarus clarkii and Orconectes limosus, although four other species are increasing in importance as they become more widely distributed. All of these crayfish in their endemic range have been reported to carry branchiobdellidan annelids. Therefore, when the crayfish are translocated, their ectosymbionts likely accompany them. Eighty-six potentially transportable branchiobdellidans are recognized in this paper, along with the distribution of six species known to have been translocated. Moreover, branchiobdellidans endemic to the translocation regions have adopted introduced crustacean hosts, which demonstrates that branchiobdellidan host species specificity is not as restrictive as many researchers believe. On the evidence to date, these translocated branchiobdellidans appear to have the same relationship and cause the same amount of damage, if any, as those on their endemic crayfish hosts. The geographical distribution of endemic branchiobdellidan—crayfish species associations are unique to each of four disjunct regions as defined by Bănărescu: Euro-Mediterranean, East Asian, western North American and eastern North American; the latter includes eastward drainages from Canada to Costa Rica.