The effect of the presence of adult fishes, gonad homogenates, and embryo homogenates on the dispersion‐reaggregation phase during early embryonic development of the annual fish Nothobranchius korthausae

Abstract

AbstractThe effect of the presence of adults of the annual fish Nothobranchius korthausae on development of eggs of this species was investigated. If the eggs were incubated in glass tanks together with adult females, embryonic development was prolonged during the dispersion‐reaggregation phase. Furthermore, gonadal homogenates as well as homogenates of oocytes and fertilized eggs or embryos (until the prehatching stage) also caused prolongation of the dispersion‐reaggregation phase. This prolongation was attributed to a longer lasting reaggregation, although the occurrence of a brief diapause I could not be ruled out.We suggest that gonads of adult annual fishes, especially females, contain one or more pheromonelike agents that are released into the water and induce a prolongation of the dispersion‐reaggregation phase of the deposited eggs. By increasing or decreasing the amount of agent released, the adults would be able to affect embryonic development. The fact that homogenates of oocytes and fertilized eggs had the same effect on egg development indicates that also the eggs may be a source of this agent. Therefore, it probably plays a function during (normal) embryonic development.