Female Brook Trout Salvelinus Fontinalis Research Articles

Perturbation in protein expression of the sterile salmonid hybrids between female brook trout Salvelinus fontinalis and male masu salmon Oncorhynchus masou during early spermatogenesis

Most males and females of intergeneric hybrid (BM) between female brook trout (Bt) Salvelinus fontinalis and male masu salmon (Ms) Oncorhynchus masou had undeveloped gonads, with abnormal germ cell development shown by histological examination. To understand the cause of this hybrid sterility, expression profiles of testicular proteins in the BM and parental species were examined with 2-DE coupled with MALDI-TOF/TOF MS. Compared with the parental species, more than 60% of differentially expressed protein spots were down-regulated in BM. A total of 16 up-regulated and 48 down-regulated proteins were identified in BM. Up-regulated were transferrin and other somatic cell-predominant proteins, whereas down-regulated were some germ cell-specific proteins such as DEAD box RNA helicase Vasa. Other pronouncedly down-regulated proteins included tubulins and heat shock proteins that are supposed to have roles in spermatogenesis. The present findings suggest direct association of the observed perturbation in protein expression with the failure of spermatogenesis and the sterility in the examined salmonid hybrids.

Successful production of monosex female brook trout Salvelinus fontinalis using gynogenetic sex reversed males by a combination of methyltestosterone immersion and oral treatments

Recent advances towards the production of all-female populations of brook trout Salvelinus fontinalis have shown that methyltestosterone treatments applied after first feeding were not efficient in inducing masculinisation in neomales. A process to create all-female populations of brook trout using methyltestosterone was determined from 4 experiments. Different protocols of masculinisation by oral and/or hormonal immersion treatments were tested and the sex ratio of progeny produced from the cross of sex-reversed gynogenetic males with normal females was checked. No sexual dimorphism for growth was recorded, at least until two years of age. Masculinisation trials using oral treatments failed to produce any reversal of sex. Only the application of four weekly immersions beginning one week before hatching, combined with an oral treatment, provided 100% masculinisation. Gynogenetic sex-reversed males crossed with normal females produced 100% females, demonstrating the efficiency of this protocol in reversing the sex of brook trout. This result also highlights an earlier and longer period of sex lability, compared with most other Salmonids, and the need to initiate immersion treatments a long time before the initiation of gonadal differentiation.