Early ontogeny in the siberian sturgeon

Abstract

This chapter is a synthesis of published information describing the development of Siberian sturgeon during the embryonic (from fertilization to hatching), prelarval (from hatching to the onset of exogenous feeding) and larval (from first feeding to the juvenile stage) periods. Siberian sturgeon embryos undergo holoblastic cleavage in which each cleavage divides the entire egg cytoplasm, including the yolk. Early cleavage, the end of gastrulation and the beginning of neurulation are the most critical stages during sturgeon embryogenesis, a process that is influenced by water temperature. The higher incubation temperature, the shorter time from fertilization to hatching; the optimal incubation water temperature in Siberian sturgeon is comprised between 12 and 20 °C. Morphogenesis and differentiation are more intense during the prelarval than the larval and early juvenile stages of development. Characteristically, during the prelarval period, embryonic adaptations and functions are replaced by definitive ones, such as gill respiration, exogenous feeding and active swimming. Such modifications involved dramatic alterations in the relationship of the developing fish with the environment that were reflected in morphological and morphometric changes. In addition, relevant information regarding the histological development of the digestive system and olfactory and visual systems is presented and their significance discussed in terms of early development and feeding behaviour.