Genetic monitoring of broodstocks of the marine shrimp Litopenaeus vannamei in a closed rearing system in Pernambuco, Brazil.

Loss of genetic variability can be detrimental to a population's survival traits and fitness. These effects are likely to be maximized in shrimp closed broodstock rearing systems where post-larvae are often produced from crosses of breeders collected from an associated grow-out farm after mass selection. Longtime broodstock management in closed systems is also expected to lead to reduction in or even complete eradication of genetic variability. The present work aimed at monitoring the genetic variability of a Litopenaeus vannamei hatchery in the state of Pernambuco (Brazil), during three successive replacements, using microsatellite markers. No significant genetic diversity losses have been observed through the values of mean heterozygosity ( H_o=0.460 and H_e=0.660 in the first sample; H_o=0.420 and H_e=0.620 in the second sample; and H_o=0.600 and H_e=0.660 in the third sample). However, some alleles appear to have been lost after three replacements. The diversity level was considered to be high and is comparable to those reported for wild populations, suggesting that the original imported founder stock of Brazilian L. vannamei is likely to have had a high genetic diversity, possibly due to multiple origins. [ABSTRACT FROM AUTHOR]