Lethal Temperatures of the Developmental Stages of the Sea Lamprey, Petromyzon marinus L.

Of all stages of the sea lamprey, the eggs have the most exacting thermal requirements. The range of constant temperatures necessary for successful hatching is narrow, being 15–25 °C. This range may be extended to 12–26 °C and possibly beyond, if the eggs have developed to the head stage before they encounter temperature extremes.The ability to withstand high temperature characteristic of the post-embryonic stages of the species appears shortly before or after hatching.The role of temperature in the development of eggs under natural conditions is discussed.