Studies of the Seasonal Variations in the Protochordate, Branchiostoma lanceolatum: A Cell Biology Investigation by the Use of Light and Electron Microscopes.

Abstract

The cephalochordate “Amphioxus” is considered a promising model animal for studying both the evolutionary and developmental mechanisms of vertebrates due to its unique phylogenetic position and simple body plan. In the present study, Branchiostoma lanceolatum specimens were collected almost monthly from the Red Sea shores near Fayed city. These specimens were submitted to morphological, histological, and ultrastructural investigations. In the laboratory, the males were separated from the females; the gonads of males have a white colour, while those of the females have an orange or yellow colour. The collected 3842 specimens were then submitted to morphological examinations, where they were classified – according to the gonad status – as full versus empty. From the analysis of this data, significant changes in the body length, body width, body weight gonadal length, and gonadal status, were registered in the different seasons. From these significant changes, the present study deduced that the breeding season extends through the whole year. For the testis of the male specimens, the germinal and non-