Genetics of two marine shrimp hatcheries of the Pacific white shrimp Litopenaeus vannamei (Boone, 1931) in Pernambuco, Brazil

Abstract

The shrimp industry has grown significantly over the past 10 years in Brazil, especially the farmed production of the exotic Pacific white shrimp, Litopenaeus vannamei. In 2004, this industry was marked by a productivity crisis, which stirred interest towards genetic improvement of shrimp stocks. Shrimp breeders importation was banned in Brazil by a govern Normative Instruction in 1997, as a sanitary precaution. Since then, broodstock replacement in hatcheries has been based on domestic stocks, raising concerns on the decline of genetic diversity and if the existing diversity would allow effective genetic improvement programs. In the present research, genetic parameters such as number of alleles, effective allele number, expected and observed heterozygosities, inbreeding coefficient, genetic differentiation index and deviation from Hardy-Weinberg equilibrium have estimated of two important commercial hatcheries in Northeast Brazil, genotyping 5 microsatellite loci. Effective allele number (3 to 10.5) and average observed and expected heterozygosities (0.480 and 0.680) were consistent with those reported for cultured and wild Penaeid populations. However, F IS positive values (0.381 for hatchery A and 0.249 for hatchery B) reflected a significant heterozygous deficiency within hatcheries (P<0.01). Nevertheless, we concluded that even after ten years of limited genetic input, it has been possible to maintain a high level of genetic variability, possibly due to the wide diverse origin of the founder broodstocks and the constant breeders exchange among hatcheries.

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“…The number of alleles for M. affinis over the five microsatellite loci ranged from 5 to 12, with varied in size from 120 to 434 bp (Table 2), which was similar to the number (2-13, 5-10, 3-12) reported by VallesJimenez et al (2005), Rezaee, Farahmand, and Nematollahi (2016), and Lima, Silva, Oliveira, Maggioni, and Coimbra (2010) for Pacific white shrimp (Litopenaeus vannamei) respectively, the number (6-14) that reported by Xu, Primavera, Pena, Pettit, Belak, and Warren (2001) for black tiger shrimp (Penaeus monodon), (5-16) by Zhang, Kong, Wang, and Wang (2010) for P. chinensis, and (5-15) by Gao et al (2008) for Chinese shrimp Fenneropenaeus chinensis. The tests for genetic differentiation showed significant allele frequency differences in all of the stock and suggested a moderate degree of similarity among the Bahrakan and Lifeh-Boosif populations of white shrimp (M. affinis) from the Persian Gulf evaluated in the current study.…”

“…Heterozygosity (H) values, is the best parameter for the measurement of genetic variation in natural populations that also known as gene diversity (Zhimin, Li, Fu-liang, & Guo-liang, 2010;Xu et al, 2001). Lima et al (2010) reported that the average observed heterozygosity for the two marine shrimp hatcheries of the Pacific white shrimp L. vannamei (Boone, 1931) ranged from 0.143 to 0.841 which was lower than the average expected heterozygosity varied from 0.377 to 0.878. Those data were consistent with our results, which indicated the two studied stocks have rich genetic diversity based on allelic variation.…”

Hsp70 gene polymorphisms in farmed marine shrimp Litopenaeus vannamei populations exposed to white spot disease and infectious myonecrosis

“…Using microsatellites, Lima et al (2008) reported F IS ranging from 013 to 0.39 in L. vannamei from Bahia State (Northeastern Brazil). Other studies conducted with L. vannamei populations from Brazilian post-larvae production laboratories showed F IS ranging from 0.00 to 0.38 (Luvesuto et al, 2007;Lima et al, 2010;Maggioni et al, 2013). Considering the history of geographical isolation, the higher F IS values observed in populations Lv-A and Lv-B from Southern Brazil are likely related to inbreeding.…”

Microsatellites as Molecular Markers with Applications in Exploitation and Conservation of Aquatic Animal Populations

“…It is recommended to maintain different and independent lines instead of one line. A high level of genetic variability among Pacific white shrimp, L. vannamei , in Pernambuco, Brazil, is sustained by the exchange of breeders between marine shrimp hatcheries [ 407 ]. In an attempt to reduce the exploitation of the humpback grouper, Cromileptes altivelis , captive breeding has been performed, and the recommendation has been made to increase the effective population size with wild fingerlings in order to avoid diversity reduction detected by microsatellites [ 408 ].…”