Cytogenetic and histological studies of the brook trout, Salvelinus fontinalis (Mitchill), and the Arctic char, S. alpinus (L.) hybrids

Abstract

Although brook trout and the Arctic char hybrids are able to reproduce, individuals with decreased fertility or even fish that are unable to produce any gametes have been also described. Abnormal gonadal development and disturbances in the gamete production in the char hybrid offspring may be triggered by the odd chromosome number and disturbances in their pairing during meiosis. To verify this hypothesis, cytogenetic examination and the gonadal histology analysis of the brook trout x Arctic char hybrids were carried out. Diploid chromosome number in the studied char (F 1 ) hybrids varied from 82 to 84 (FN = 99-102). Among 28 hybrids, 12 males, three females, nine intersex individuals and two sterile specimens were described. In the case of two individuals, gonads were not found. Diploid chromosome numbers in the males and intersex individuals varied from 82 to 84. Chromosome numbers in the females were 82 and 83 chromosomes. Two sterile fish exhibited karyotypes composed of 82 and 84 chromosomes. Predominance of the ovarian component in the intersex gonads and gonadal sex ratio distortion towards the males suggested hybrid females had problems with gonadal differentiation. However, the lack of the clear relationship between chromosome number and gonadal development in the studied hybrids did not support our hypothesis that odd chromosome number may be responsible for such reproductive disturbances in the hybrid individuals. We have presumed that sterility and intersexual development of the gonads may be caused by interactions between brook trout and Arctic char genes on the sex chromosomes and autosomes rather than unpairing of the parental chromosomes.

Cytogenetic identification of genomic elements of brook trout ( Salvelinus fontinalis ) in the karyotype of Arctic char ( Salvelinus alpinus ) from the aquaculture broodstock

“…Unintentional hybridization between Arctic char and brook trout may affect stocking practices. Presume problems with sex determination in hybrids results in the development of intersexual specimens as it was described among the F 1 Arctic char x brook trout individuals from the Rutki strains (Ocalewicz et al, 2014).…”

“…Unintentional hybridization between Arctic char and brook trout may affect stocking practices. Presume problems with sex determination in hybrids results in the development of intersexual specimens as it was described among the F 1 Arctic char x brook trout individuals from the Rutki strains (Ocalewicz et al, ). The observations made by Dumas et al () on the reciprocal Arctic char x brook trout hybrids confirms problems with sexual maturation of hybrid males where individuals with good spermiation and sperm quality were scarce when compared to the parental species.…”

“…aquaculture of salmonids, Arctic char, chromosome rearrangements, hybridization, interstitial telomeric sequences, karyotype variation 1993). Moreover, reciprocal and F 2 hybrids and backcrosses of Arctic char and brook trout (Salvelinus fontinalis Mitchill 1814) are fertile (Faulks & Östman, 2016;Hammar, Dempson, & Verspoor, 1991;Ocalewicz, Hliwa, Pomianowski, Lisboa, & Jankun, 2014) and the introgressive hybridization leading to incorporation of Arctic char mitochondrial genome into genome of brook trout has been reported (Bernatchez, Glemet, Wilson, & Danzmann, 1995).…”

Use of Eggs Derived From the Interspecific Charr Hybrids to Induce Androgenetic Development of the Brook Charr (Salvelinus fontinalis Mitchill 1814)

“…; Ocalewicz et al. ) none of the reciprocal nucleocytoplasmic charr hybrids was viable (Babiak et al. , present paper).…”

“…The failure of the other androgenetic experiments has been attributed to the incompatibility between the egg cytoplasm of one species and the sperm nucleus from another species (Babiak et al 2002). Although, brook charr 9 Arctic charr hybrids are viable and usually fertile (Gross et al 2004;Ocalewicz et al 2013b) none of the reciprocal nucleocytoplasmic charr hybrids was viable (Babiak et al 2002, present paper). This suggested that in the brook charr and the Arctic charr nucleocytoplasmic incompatibility is expressed when a nucleus comprising chromosomes of only one of these species is present in the cytoplasm of the other one.…”