Changes in egg size of plaice ( Pleuronectes platessa L.) during incubation, and the effect of fixation

Abstract

Changes in the size of plaice eggs during incubation were studied in tank experiments with 11 batches stripped from 6 individual females and fertilized artificially. Live egg size increased by 1% from fertilization to hatching. Fixation in 4% formaldehyde in sea water resulted in a decrease in egg size. This shrinkage increased with developmental stage from 0% in eggs that had just been fertilized to 1.4% in eggs prior to hatching. Mean size of fixed eggs decreased slightly but significantly by 0.7% between fertilization and hatching. The implications of these changes for studies of size-selective mortality in pelagic fish eggs are discussed.