Spawning and Embryonic Development of the Least Brook Lamprey (Lampetra aepyptera)

Abstract. The reproductive biology of lampreys is of special interest given the group has retained many developmental features reminiscent of the earliest vertebrates. Herein I report spawning behavior in the Least Brook Lamprey (Lampetra aepyptera) from southern Indiana and provide descriptions of its embryonic development. Nesting activities began in mid-March when water temperatures ranged from 10 to 12 C, as two or more individuals dug out shallow depressions in loose gravel immediately above riffles. Communal spawning groups (>10 individuals) subsequently formed at the nest sites when the water temperature rose above 12 C. Embryos generated from the gametes of spawning adults underwent gastrulation 72 h after fertilization, neurulation after 6 d, and hatched after 14 d. Prolarvae developed melanophores 19 d after fertilization, eyespots were visible by 20 d, and the velum began to beat 25 d after fertilization. Expulsion of yolk from the intestine and filter feeding occurred 26 d after fertilization. Embryonic development in L. aepyptera largely matches the embryonic stages established for the Sea Lamprey (Petromyzon marinus), with subtle differences in the sequence of specific developmental features. These descriptions clarify conflicting accounts of spawning activities for L. aepyptera and provide staging criteria for future investigations into its embryonic development.