Timing of Changes in the Blood, Morphology, and Behavior of Petromyzon marinus During Metamorphosis

Abstract

Morphological, biochemical, and behavioral criteria, from samples collected from 1969 to 1971, showed that metamorphosis in P. marinus is of a relatively short duration. In an analysis of sequential catches during 1971, the first external signs of transformation were observed only in samples caught between July 12 and 26, illustrating the marked synchrony characteristic of this and subsequent developmental stages. Relative increases in size of the disc and snout were most marked from mid-August to late October. Polyacrylamide gel electrophoresis showed that the change-over from larval to adult hemoglobins took place mainly between early August and late October, the beginning and peak of this process being characterised by reduced hematocrit values. Over 95% of the animals captured at various times in the field commenced feeding on suckers (Catostomus commersoni) in the laboratory by late November or early December.