Reproductive Ecology of Lampreys

The spawning-phase of lamprey, although the shortest, is the most commonly documented due to relatively high accessibility for observation.  Lamprey typically spawn in riffle habitats during the spring.  Nests are constructed in gravel substrate using the oral disc to move stones and the tail to fan sediment out of the nest.  Spawning nest size of individual species is a function of adult lamprey size, where smaller species construct nests in shallower water with slower flow and smaller gravel than larger species.  Spawning activity and diel behavioral patterns coincide with increases in spring water temperatures to those suitable for embryologic development (15-25 ^oC).  The mating system of lampreys is primarily polygynandrous.  Non-anadromous lamprey species generally have communal spawning associations where nests may contain 20 or more individuals of mixed gender.  Anadromous lamprey species generally spawn in groups of two to four and individual males aggressively defend nests from other males, but females may spawn in multiple nests.  Communal spawning of smaller lamprey species may be an adaptation to compensate for their small size.  A large group of small lampreys can create larger nests that contain more eggs, potentially increasing embryo survival through increased oxygenation and by overwhelming egg predators.  Multiple sensory modalities are used to coordinate reproduction.  Chemical communication is especially important where for example, spermiated male sea lamprey release mating pheromones which are highly attractive to ovulated females and induce spawning behaviors.  Once aggregated on the nest, tactile cues facilitate gender identification and help induce reproductive behaviors.  It is not yet known to what extent electroreception and auditory cues mediate lamprey reproduction.  Future research should determine how multiple modalities of communication among lampreys, such as olfactory, tactile, electroreception and auditory, are integrated to inform species recognition and mate choice, especially since paired lamprey species provide rare examples of speciation in sympatry.