The induction of polyploidy, gynogenesis and androgenesis in the European sea bass

Abstract

Precocious sexual maturation affects approximately one‐third of farmed European sea bass males which, in turn, constitute most of the farmed fish of this species. To prevent sexual maturation, and to contribute to the production of monosex stocks, chromosome set manipulation procedures have been subject to intense investigation over the last 20 years. These include the induction of poliploidy (triploidy and tetraploidy) and the production of individuals with uniparental inheritance (mito‐ and meiogynogens and androgenetics). Several studies have examined different experimental conditions in order to establish optimized protocols based on the application of pressure and temperature shocks, to retain a full set of chromosomes, thus suppressing the extrusion of the second polar body, or the first cleavage in the zygote. The use of UV irradiation has also been evaluated to inactivate the DNA of exposed gametes for the application of induced gynogenesis and androgenesis.

Triploidy in the European sea bass results in gonadal sterility in both sexes, which can be of advantage for its production in aquaculture although, only in larger fish, it may represent a superior growth. On the other hand, the maintenance of gynogenetic and androgenetic clonal founders can contribute to a better understanding of the genetic basis of many complex traits of interest for fish farming. Although the performance of fish after ploidy manipulation, concerning the growth, reproductive activity, and proportion of sexes, has been well documented, further evaluations are still required before these fish can achieve societal acceptance and be considered for their applicability to the industry. Finally, benefits, considerations and future work are under discussion