Effect of formalin fixation on size and weight of Atlantic wolffish (Anarhichas lupus) and spotted wolffish (Anarhichas minor) oocytes

Abstract

Oocytes were sampled from Atlantic wolffish (Anarhichas lupus) and spotted wolffish (Anarhichas minor) to investigate the effect of fixation and storage in formalin on oocyte size and weight over time. The effect of formalin on oocyte size was dependent on the original size of the oocyte. As the effect of fixation was similar for the two species, a common formula for the conversion of fixed oocyte size/weight to fresh oocyte size/weight was developed. The relationships were negative and nonlinear, the smallest oocytes increased ∼11 % in diameter and ∼15 % in weight when fixed in formalin, whereas the largest oocytes decreased about 4 % in diameter and 7 % in weight. After fixation, oocyte diameter was stable for up to 2, but not 10 years and for up to 10 years for oocytes at CA and VIT stage, respectively.