Kin discrimination in juvenile Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis) - recognition cues and function

Rajakaruna, Rupika Subashini (2002) Kin discrimination in juvenile Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis) - recognition cues and function. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The ability to recognize relatives permits individuals to discriminate their kin, thereby enhancing their inclusive fitness. Many animal species, including salmonids, have the ability to recognize and discriminate kin from unrelated conspecifics. I conducted a series of experiments to examine the effect of recognition cues of genetic and environmental origin in juvenile Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis) and how kin association influences the growth of these species. In the first study (Chapter 2) I investigated the effect of diet as an environmental cue on the kin discrimination ability and found that kin discrimination in both Atlantic salmon and brook trout is influenced by dietary cues. Test fish could not discriminate kin and non-kin when the kin group was fed with a different diet and the non-kin group was fed with a similar diet. As second study, Chapter 3 dealt with a technique of isolation and characterization of MHC class II Bl locus and a brief survey of polymorphism of this locus in Atlantic salmon and brook trout collected from four different areas in Newfoundland. A high level of polymorphism both at the allelic level and in the amino acids is maintained at the MHC class II Bl locus in the two species. Using this technique I determined the genotype of kin and non-kin groups of both species and studied the influence of MHC class II Bl locus on their kin discrimination (Chapter 4). I found that MHC class II Bl locus significantly influence kin discrimination in juvenile Atlantic salmon and brook trout. The preference for individuals sharing alleles demonstrated that discrimination is taking place matching at the MHC locus. Data from the same study provided evidence for matching of the overall phenotypic similarity during discrimination. Moreover, test fish could not discriminate kin and non-kin when the kin group did not share any alleles and the non-kin group shared both alleles at the MHC locus. In the fourth study (Chapter 5) I examined the interaction of the genetic and environmental cues used in kin discrimination in juvenile Atlantic salmon. Both environmental and genetic cues were found to be equally important and the relevance of each cue is context dependent. The last experimental chapter (Chapter 6) examined the effect of kinship on growth and demonstrated that higher and less variable growth occurred in individuals reared with kin compared to individuals reared with non-kin. -- Taken together these data suggest that both genetic and environmental cues are important in kin discrimination the interaction of these cues is crucial for many cases of kin discrimination. Moreover, being cooperative and less aggressive towards kin result in direct and indirect fitness benefits to the individual.

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