Experimental hybridization among five species of lampreys from the Great Lakes

Experimental hybridization among five species of lampreys of the Upper Great Lakes routinely produced embryos through stage 8, and four crosses produced embryos to the larval stage. Three critical periods in the embryogenesis of hybrid lampreys were between stages 8 and 9, among stages 10, 11, and 12, and at stage 15. Embryonic development in hybrid lamprey embryos is basically identical to that of controls and is identical to that of the sea lamprey (Petromyzon marinus). Synchrony of development was observed among stages of viable hybrids and their controls but lethal hybrids generally did not maintain such synchrony. The derivative species concept has been confirmed experimentally. Questions have been raised concerning some evidence cited in behalf of the appropriateness of the concept that nonparasitic lampreys are the derived species.