Comparative Embryology of Five Species of Lampreys of the Upper Great Lakes

Abstract

The four species of lampreys native to the upper Great Lakes (American brook lamprey, Lampetra lamotteni; chestnut lamprey, Ichthyomyzon castaneus; northern brook lamprey, I. fossor; and silver lamprey, I. unicuspis) were collected in various stages of their life cycle and maintained in the laboratory until sexually mature. Secondary sex characters of the four native species are compared. Several batches of eggs of each species were reared at 18.4? C and their development was compared to that of the exotic sea lamprey, Petromyzon marinus. The temperature of 18.4' C was previously determined to be optimum for development of the sea lamprey. The high percentage survival of many batches of eggs of native species to prolarvae indicated that 18.4' C was near the optimum for them. Survival to the burrowing stage varied considerably among different batches of eggs from the same species; some batches failed to produce prolarvae. The staging characteristics used for the sea lamprey were applicable to the native species, except for the end point of the burrowing stage. Embryos of the native species in each stage of development appeared according to the time sequence established for the sea lamprey.