Genetic differentiation in hatchery strains and wild
white shrimp Penaeus (Litopenaeus) vannamei
(Boone, 1931) from northwest Mexico
J. Soto-Hernández,
J.M. Grijalva-Chon-2004
Aquaculture International, 12(6):
593-601
Abstract:
Ten
enzymatic systems were analyzed to determine allozyme genetic
differentiation among three hatchery strains (A, B and C) of white shrimp, Penaeus
(Litopenaeus) vannamei, commonly used in shrimp farming in
northwest Mexico. A wild population from northern Sinaloa was used as a
reference. Fifteen loci were detected, nine of which were polymorphic (ACP-1*,
ACP-2*, AKP-2*, EST-2*, EST-3*, EST-4*,
EST-5*, LAP*, and LDH*). Polymorphism of A, B and
C were 53, 53, and 40%. The mean observed heterozygosity per locus was
0.071, 0.093, and 0.050 without any significant difference among them or
with respect to the wild population (0.056). In all samples observed
heteroxygosity was smaller than expected. The mean number of alleles per
locus was 1.8 in A and 1.87 in both B and C. Strain A was the only sample
without rare alleles. Only EST-3* and LAP* of strain A
were in Hardy-Weinberg equilibrium; the other loci were in disequilibrium in
all samples. High inbreeding values and heterozygote deficiencies were
detected in all samples. Distribution of allelic frequencies was
heterogeneous among the samples (G-test), involving all polymorphic
loci and suggesting a genetic differentiation. According to Fst, a
moderate genetic differentiation (7.4%) was detected among the samples.
Greater differences were between strains A and C. Based on genetic distance,
the samples were grouped into two pairs, B–C
and A-wild. Strain A is a young strain related to the wild sample, whereas
strains B and C have a different geographic origin than the wild sample.
(Departamento
de Investigaciones Científicas
y Tecnológicas, Universidad de Sonora, Av.
Rosales y Niños
Héroes s/n, Hermosillo, Sonora, México 83000;e-mail of J.M. Grijalva-Chon: mgrijal@guayacan.uson.mx)