Developmental stability and genetic heterozygosity in wild and cultured stocks of gilthead sea bream (Sparus aurata)

The present study checks on the validity of the hypothesis that heterozygos ity and the fluctuating asymmetry, FA), common measure of the developmental stability, are linked in populations of wild and cultured stocks of Sparus aurata from five countries. Muscle and liver samples were analysed for var iation in 26 allozymes and three microsatellite loci. Pectoral fin rays and upper and lower gill rakers of the first branchial arch were counted on th e left and on the right sides of each fish. Fluctuating asymmetry existed i n the majority of the samples although their values were consistently low, (0.305 +/- 0.147), but higher in the cultured samples. The allozyme heteroz ygosity values were al-ways high, but lower in the cultured samples. The mi crosatellite DNA analysis pro d similar results. Heterozygosity was higher in cultured individual,; (except for the Greek samples), These findings, se em to be early evidence that the reared samples are losing sonic genetic va riation, especially, due to the loss of the rarest alleles (which were pres ent in the wild populations). Genetic drift, probably caused by propagation practices, is most likely responsible for the decrease of (lie genetic var iation. No distinct pattern of geographic separation wa identified.