Clonal Atlantic salmon × brown trout hybrids produced by gynogenesis

Abstract

Clonal full‐sib progeny groups of Atlantic salmon Salmo salar × brown trout Salmo trutta hybrids were produced by gynogenesis. Eggs obtained from two 3‐year‐old Atlantic salmon (female) × brown trout (male) F 1 hybrids were activated with UV‐irradiated rainbow trout Oncorhynchus mykiss sperm. Fecundity, percentage egg activation and percentage survival to completion of yolk‐sac absorption were similar for the two females, and averaged 800 eggs kg −1 , 90 and 65%, respectively. Flow cytometric and protein electrophoretic analyses confirmed the progeny to be diploid hybrids. Isogenicity within progeny groups and to the maternal parent was indicated by identical DNA fingerprint patterns detected with multilocus oligonucleotide probes–GATA (5) and ACTG (n) . Isogenicity was also observed in the gynogenetic progeny of a third female spawned the following year. It appeared that a large portion of the oocytes in females of this hybrid underwent a premeiotic chromosome doubling, or possibly a complete suppression of meiosis. The result was ovulation of diploid eggs, each possessing a full set of both Atlantic salmon and brown trout chromosomes identical to those in the maternal somatic cells. Lines of clonal hybrids could therefore be perpetuated by gynogenesis and would have potential both as experimental animals and in commercial aquaculture.