Feeding by Parasitic Lampreys: Trends and Variability

Much of what has been revealed about feeding by parasitic lampreys has been spurred by efforts to understand and manage sea lampreys in the Great Lakes.  When access by this species to the upper Great Lakes was facilitated by human activity, a scenario was created by which a relatively large lamprey was established in a system with relatively small host species with which it had not recently co-evolved.  Moreover, compared to marine populations, the sea lamprey in the Great Lakes had relatively easy access to relatively extensive spawning habitat of high quality.  It is not surprising that sea lampreys contributed to dramatic declines in several fish species in the Great Lakes.  However, although some aspects of sea lamprey feeding biology can be generalized to other species, the sheer volume of published research on the Great Lakes sea lamprey has contributed to a lack of appreciation for the diversity displayed by other lampreys. Parasitic phase lampreys vary substantially among species with respect to some aspects of their biology, including distance between spawning habitat and feeding grounds, duration of the parasitic phase, maximum body size, and diet (blood versus muscle).  Some relatively consistent aspects of feeding behavior include tendencies to forage nocturnally and to attack larger hosts selectively, but rarely do lampreys display all-or-none responses with respect to any aspects of behavior.  Host species and site selectivity on individual hosts may vary among and within species in predictable ways.  However, it is not known how a lamprey’s previous feeding experience affects its selection of subsequent hosts.  Moreover, although diversity among parasitic lampreys with respect to feeding adaptations has been recognized, diversity among host species with respect to qualities that enhance or inhibit the lamprey feeding process has not investigated in depth.