Étude chronologique, structurale et biométrique de l'œuf et de son développement chez la petite roussette (Scyliorhinus canicula) élevée en eau de mer artificielle

Abstract

The eggs of the small spotted dogfish (Scyliorhinus canicula), developed in artificial sea water at 14 degrees C, pre-hatched after 3 to 3 1/2 months (total embryo length: 31 to 38 mm). Hatching occurred after 6 1/2 to 7 1/2 months (length of newborn: 80 to 95 mm). Egg weight first increased for 12 days and then remained constant until pre-hatching. A biometric study of the whole egg, egg case and albumen chamber showed very little variation in egg width, while egg length varied widely. As laying occurs in pairs, the secretory activity in each nidamental gland was observed to adapt to the extra volume of egg case contents in two cases where a double egg was laid with a normal one. However, the size and shape of the normal eggs of each female were generally distinctive, regardless of the contents or the external conditions. The egg case wall had three separate layers, as shown by microscopy of fresh material and experimental studies with various dyes.