NON-B DISRUPTION IN THE WITH SHRIMP Litopenaeus vannamei

In a previous study, the frequency of three different trypsin phenotypes of Litopenaeus vannamei in aquaculture was described. Phenotype CBA was the most abundant, followed by phenotype CB, but phenotype CA decreased its frequency and was not found in shrimps after 45 days of culture (Fig 1) .

The conclusion was that shrimp with phenotype CA inexplicably die under culture conditions (Aguiñaga-Cruz et al 2017). The question was if the process of shrimp aquaculture exerts excess pressure on the CA organisms, will they die? or will they die no matter where they grow? To answer this question, the trypsin phenotype frequencies in 60 breeder shrimp of a natural population were analyzed to predict the trypsin phenotype frequency in the next generation. Then, a total of 1000 L. vannamei shrimp within the F1 generation of the same natural population weighing 2, 3, 5, 7 and 15 g were collected for 5 months, and the trypsin phenotype frequencies were recorded. The results indicate that the F1 is out of Hardy-Weinberg equilibrium, and the absence of phenotype CA in the natural population is similar to that in aquaculture (Fig 2) . In conclusion, the process of aquaculture does not exert pressure on the CA phenotype; such mortality is associated with another phenomenon not yet understood and deserving of further examination. At the moment, we know that the mortality occurs when shrimp inherit a trypsin codominant allele monomorphic called A, which act as lethal  gene, and thus, we named the phenomenon "NON-B disruption".