摘要：A typical lamprey mating involves a female attaching to a stone near the upstream end of the nest A male then attaches to the back of the female's head and wraps his body around hers. Both vibrate vigorously as gametes are released. In some cases, a second male, the satellite, circles about the urogenital area of a mating pair at the moment of gamete release in what has been interpreted as an attempt to gain fertilizations. Analysis of videotapes of spawning Lampetra appendix in the North Branch Whitewater River in Minnesota (Mississippi River drainage) and Jambo Creek in eastern Wisconsin (Great Lakes drainage) revealed that at both sites at least 50% of matings in nests with at least three lampreys included a satellite male. Nest associations involving more that one lamprey species in the same nest are known to involve many combinations of species, but especially relevant are cases involving closely related parasitic and nonparasitic species. For example, we have observed nonparasitic Ichthyomyzon gagei and parasitic Ichthyomyzon castaneus spawning in the same nests and have observed a male I. gagei attached to a female I. castaneus. Conventional wisdom is that the size difference between parasitic and nonparasitic lampreys prevents successful mating, but a combination of interspecific nest association and satellite male behavior could conceivably permit gene flow between paired nonparasitic and parasitic forms. This combination is displayed by at least some Lampetra species.
