Ricardo Perez-Enriquez

Population Genetic Structure of Pacific White Shrimp (Litopenaeus vannamei) from Mexico to Panama: Microsatellite DNA Variation

Genetic variation and population structure of wild white shrimp (Litopenaeus vannamei) from 4 geographic locations from Mexico to Panama were investigated using 5 microsatellite DNA loci. The genetic diversity between populations was indicated by the mean number of alleles per locus and mean observed heterozygosity, which ranged from 7.4 to 8.6 and from 0.241 to 0.388, respectively. Significant departures from Hardy-Weinberg equilibrium were found at most locations at each locus, with the exception Guatemala at Pvan0013, and were caused by high heterozygote deficiencies. Genetic differences between localities were detected by pairwise comparison based on allelic and genotypic frequencies, with the exception of locus Pvan1003. Significant pairwise FST values between locations and total FST showed that the white shrimp population is structured into subpopulations. However, population differentiation does not follow an isolation-by-distance model. Knowledge of the genetic diversity and structure of L.vannamei populations will be of interest for aquaculture and fisheries management to utilize and preserve aquatic biodiversity.

Genetic Variability Assessed by Microsatellites in a Breeding Program of Pacific White Shrimp (Litopenaeus vannamei)

Genetic diversity in a shrimp-breeding program was monitored for 2 generations by microsatellite DNA markers (Pvan1578 and Pvan1815) to establish levels of variation and proceed with a selection program. An increase in the number and frequencies of some alleles in both microsatellite loci from G0 to G2 was induced by foreign sire contributions. Most common alleles and high heterozygosities (around 70% in both loci) were maintained through the generations, indicating that there had not been a significant loss of genetic variability in the breeding program. However, when compared with variability in other wild and cultured stocks, the presence of 4 main alleles at both loci may be an indication that a certain reduction in variability already was present in the line used as founder stock (G0). Therefore, it is recommended that additional genetic variability be introduced to the breeding stock by crossing it with a different line.

GENETIC STRUCTURE OF GREEN ABALONE HALIOTIS FULGENS POPULATION OFF BAJA CALIFORNIA, MEXICO

Abstract The design of appropriate management plans of the green abalone Haliotis fulgens fishery needs a better understanding of the present status of the genetic diversity of the wild stock, as well as its genetic structure. Samples from nine locations along the Baja California Peninsula, including one from an oceanic island (Isla Guadalupe), were obtained covering the areas where the commercial fishery is active. DNA was extracted from muscle tissue of 50 individuals from each location, and was used for PCR amplification of 4 microsatellites (Hka28, Hka56, Hful260, and Hful603). The number of alleles observed in all samples with Hka28 and Hka56 (23–35 and 15–19, respectively) was higher than that observed in Hful260, and Hful603 (3 and 6 alleles, respectively). A relatively high mean heterozygosity was observed in all locations with the lowest value of 0.687 in Isla Guadalupe. A deviation from Hardy-Weinberg Equilibrium (HWE) caused by a heterozygote deficiency was only observed in 2 out of 36 tests, indicating that this disequilibrium is random. An AMOVA showed a significant FST (P < 0.00196) suggesting genetic differentiation among locations. Pairwise analyses using FST and allele frequencies showed that the significant difference was caused by Isla Guadalupe, which indicates a restricted gene flow between this and the other locations. Nevertheless, no significant differences were observed among sites along the Peninsula. The implications of these results on the management of the fishery are discussed.

Isolation and cross-amplification of microsatellites in pink abalone (Haliotis corrugata)

Ten novel microsatellite loci were isolated in pink abalone, Haliotis corrugata, using (GT)15 and (CT)15 enriched genomic libraries. Two previously reported Haliotis kamtschatkana microsatellites cross‐amplified in H. corrugata. A set of 12 polymorphic microsatellites were evaluated in a wild population sample (N = 49). The number of alleles ranged from two to 55, and the observed and expected heterozygosities ranged from 0.104 to 0.939 and from 0.213 to 0.982, respectively. Significant deviations from Hardy–Weinberg equilibrium at three loci and no linkage disequilibrium were observed. Haliotis corrugata microsatellites cross‐amplified in other abalone species, two in H. fulgens, and seven in H. rufescens.

Prevalence of viral pathogens WSSV and IHHNV in wild organisms at the Pacific Coast of Mexico

This study investigated whether white spot syndrome virus and Infectious hypodermal and hematopoietic necrosis virus, can survive in wild invertebrates and vertebrates in the environment surrounding shrimp farms along the Pacific coast of Mexico. The evidences imply that both viruses have a potential of persisting in crabs, blue, white and brown shrimps. The most prevalent virus, IHHNV was present in 19.5% (344/1736) followed by WSSV in 3.6% (65/1736). Coinfection of WSSV and IHHNV was also detected in crabs, blue and white shrimps. This is the first prevalence report of WSSV and IHHNV associated with wildlife species in Mexico.

Genetic Connectivity Among Pink Abalone Haliotis corrugata Populations

ABSTRACT The understanding of genetic connectivity among populations is important for the management of fisheries, particularly in overexploited benthic species such as the pink abalone Haliotis corrugata, which might have limited dispersal because of a short-term pelagic larval stage. Eight microsatellite DNA loci (Hco15, Hco16, Hco19, Hco22, Hco47, Hco97, Hco194, and Hka56) from specimens caught at five locations from the northeastern Pacific of Mexico and the United States were examined. H. corrugata showed a low to moderate genetic diversity. Most loci from the five sampling sites were in Hardy-Weinberg equilibrium, except for Hco47, which showed null alleles. Hierarchical AMOVA from seven loci showed highly significant population divergence between San Clemente Island and the Mexican locations (F ST = 0.021, P < 0.001) but not among Mexican subpopulations. The prevailing explanation for such divergence is the historical isolation by distance, but the presence of an oceanographic barrier (Southern California Eddy) and the insufficient mix between waters masses from both regions could preserve genetic differentiation.

Genotyping WSSV isolates from northwestern Mexican shrimp farms affected by white spot disease outbreaks in 2010-2012

White spot disease (WSD) causes high mortality in cultured shrimp throughout the world. Its etiologic agent is the white spot syndrome virus (WSSV). The genomic repeat regions ORF 75, ORF 94, and ORF 125 have been used to classify WSSV isolates in epidemiological studies using PCR with specific primers and sequencing. The present study investigated the variation in nucleotide sequences from 107, 150, and 143 isolates of WSSV collected from Litopenaeus vannamei shrimp ponds with WSD outbreaks in northwestern Mexico during the period 2010-2012, in the genomic repeat regions ORFs 75, 94, and 125, respectively. The haplotypic nomenclature for each isolate was based on the number of repeat units and the position of single nucleotide polymorphisms on each ORF. We report finding 17, 43, and 66 haplotypes of ORFs 75, 94, and 125, respectively. The study found high haplotypic diversity in WSSV using the complete sequences of ORFs 94 and 125 as independent variables, but low haplotypic diversity for ORF 75. Different haplotypes of WSSV were found from region-to-region and year-to-year, though some individual haplotypes were found in different places and in more than one growing cycle. While these results suggest a high rate of mutation of the viral genome at these loci, or perhaps the introduction of new viral strains into the area, they are useful as a tool for epidemiological surveys. Two haplotypes from some of the ORFs in the same shrimp were encountered, suggesting the possibility of multiple infections.

Assessment of Self-Recruitment in a Pink Abalone (Haliotis corrugata) Aggregation by Parentage Analyses

ABSTRACT The implementation of abalone aggregations as a tool for stock enhancement has been under discussion. For this purpose, understanding the self-recruitment capacity of managed reefs based on the amount of larval retention is an important task to evaluate potential success. Under the hypothesis that every reef is mostly self-restored within a short spatiotemporal scale because of a rather reduced planktonic period, the practice of aggregating mature adults of pink abalone in a reef would improve local recruitment. This study assessed local replenishment within an abalone reef of pink abalone Haliotis corrugata at Bahía Asunción (El Riíto reef), a location on the west coast of the Baja California Peninsula, where an aggregation of adult abalone was studied. A parentage analysis was carried out between adults transplanted to El Riíto and the juveniles collected from the same site by comparing their genetic profiles at 8 microsatellite DNA loci. The parentage tests defined successfully the status of more than 97% of the juveniles, revealing that approximately 4% of them could have been produced within the aggregation area. Because not all the potential parental abalone were collected, this self-recruitment proportion in the aggregation experiment was possibly underestimated. The suitability of parentage analyses, based on genetic markers as a robust alternative for the assessment of future aggregations, is discussed.

Morphometric analysis of population differentiation and sexual dimorphism in the blue spiny lobster Panulirus inflatus (Bouvier 1895) from NW Mexico

Population differences based on a morphometric analysis were studied in blue spiny lobster Panulirus inflatus (Bouvier 1895) from the Pacific coast of Mexico. Seventeen morphometric distances defined by eight landmarks were recorded for 129 specimens and Sheared PCA (SPCA) and Burnaby size-adjusted principal component analysis were performed. Sexual dimorphism was detected in each locality by analysis of covariance (ANCOVA), so comparison between localities were separately performed by sex. Males and females showed some geographic differences, however, the results indicate a low differentiation level. Morphometric differences between populations can be due to plasticity in response to local environmental conditions, but further analysis should to considered to a better understanding of stock structure of blue spiny lobster.

Molecular identification and morphological description of Micropogonias megalops, Cynoscion othonopterus, C. reticulatus and Menticirrhus nasus larvae, collected in the upper Gulf of California during Summer 2012

Abstract Sciaenidae fish larvae were collected from the upper Gulf of California during September 2012 using a conical net (505 μm) through surface tows. These were pre-classified into four larval morphotypes, based on external characteristics (mainly meristic and pigmentation). Partial sequences of cytochrome c oxidase, subunit 1 and 16S rRNA (16S) genes of mitochondrial DNA, were used in molecular genetic identification from each larval morphotype. Genetic results indicated the identification of four larval morphotypes as Micropogonias megalops, Cynoscion othonopterus, C. reticulatus and Menticirrhus nasus. Pigmentation patterns of larvae described after molecular genetic identification made it possible to distinguish between M. megalops, M. nasus and C. othonopterus (postflexion). However, pigmentation was not reliable for differentiating between preflexion larvae of C. othonopterus and C. reticulatus. From these results, both morphological and genetic approaches were proposed as complementary tools in taxonomic studies of ichthyoplankton, particularly in early fish larvae identification of congeneric species with similar morphological characteristics.