Molecular variations in Vibrio alginolyticus and V. harveyi in shrimp-farming systems upon stress

A study was performed to investigate the genomic variations in the shrimp farm isolates of Vibrio alginolyticus and V. harveyi when the isolates were subjected to environmental stress. Samples of shrimps, water and sediment were collected from Southern Indian coastal shrimp farms. Vibrio isolates were biochemically identified and confirmed using 16S rDNA and gyrB gene specific PCR. The bacterial strains were genotyped by PCR fingerprinting using GTG(5) and IS (Insertion Sequence) primers. Seven strains each of V. alginolyticus and V. harveyi were subjected to 10 passages through trypticase soya broth (TSB), which contained different NaCl concentrations (3, 6 and 8%) and trypticase soya agar (TSA). V. alginolyticus was also passaged through TSB with a 12% NaCl concentration. PCR fingerprinting, which was performed on the strains that were passaged through different salt concentrations, confirmed that V. alginolyticus and V. harveyi could affect the genomic variations, depending on the environmental conditions of the culture. The study highlights the complex genotypic variations that occur in Vibrio strains of tropical aquatic environment because of varied environmental conditions, which result in genetic divergence and/or probable convergence. Such genetic divergence and/or convergence can lead to the organismal adaptive variation, which results in their ability to cause a productive infection in aquatic organisms or generation of new strains.

Suscetibilidade dos estágios ontogenéticos: padrão osmorregulatório em camarões peneídeos e palemonídeos / Susceptibility of ontogenetic stages: osmoregulatory standard in penaeid and palaemonid shrimps / Susceptibilidad de etapas ontogenéticas: estándar osmorregulatorio en camarones peneídeos y palemonídeos

A invasão da água doce por crustáceos ocorreu repetidamente ao longo dos anos, pressionando um ajuste em seus processos fisiológicos. A habilidade de sobreviver aos diferentes ambientes foi encontrada em traços osmorregulatórios, e estão relacionadas à capacidade de regular o fluido extracelular. Portanto, o objetivo deste manuscrito é explorar os processos osmorregulatórios de camarões palemonídeos e peneídeos, visualizando um padrão na capacidade osmorregulatória em ambas as famílias e, em particular, tratar de assuntos pertinentes aos efeito no ciclo ontogenético e o efeito ocasionado pelo nitrito na hemolinfa de crustáceos. Comparando palemonídeos e peneídeos, percebe-se que o sucesso da conquista do ambiente dulcícola, e a não necessidade de hiporregulação, levou à perda dessa capacidade na maioria dos palemonídeos. Dessa forma, se supõem um ancestral com capacidade hiporregulatória, uma vez que invertebrados marinhos são, parcimoniosamente, osmoconformadores. Compara-se também que o nitrito apresenta efeito nas proteínas presentes na hemolinfa dos crustáceos quando submetidos à exposição natural ou induzida deste composto, e que a capacidade osmorregulatória é, portanto, variada de acordo com seus estágios...

The invasion of freshwater by crustaceans has occurred repeatedly over the years, pressing for an adjustment in their physiological processes. The ability to survive in different environments was found in osmoregulatory traits and is related to the ability to regulate the extracellular fluid. Therefore, the purpose of this manuscript is to explore the osmoregulatory processes in palaemonid and penaeid shrimps, which display a pattern of osmoregulatory capacity in both families and, in particular, to deal with matters related to the effects on ontogenetic cycle and the effect raised by nitrite in crustacean hemolymph. By comparing palaemonid and peneid shrimps, it is possible to note the success of conquering freshwater environment, and not the need for hypo-regulation, has led to the loss of this capability in most palaemonids. Thus, it is assumed that they share an ancestor with hypo-regulatory capacity, since marine invertebrates are sparsely osmoconformers. The article also compares that nitrite has effect on proteins present in the hemolymph of crustaceans when subjected to natural or induced exposure to these compound, and osmoregulatory capacity is therefore varied according to their stages...

La invasión del agua dulce por crustáceos ocurre repetidamente a lo largo de los años, pulsando un ajuste en sus procesos fisiológicos. La capacidad de sobrevivir en diferentes ambientes se ha encontrado en rasgos osmorregulatorios y están relacionados a la capacidad de regular el fluido extracelular. Por lo tanto, el objetivo de este manuscrito es el de explotar los procesos osmorregulatorios de camarones palemonídeos y peneídeos, se muestra un estándar en la capacidad osmorregulatoria en ambas las familias y, en especial, trata de cuestiones relativas a los efectos sobre los ciclo ontogenético y el efecto causado por nitrito en la hemolinfa de crustáceos. Comparando palemonídeos y peneídeos, se da cuenta de que el éxito de la conquista del ambiente dulcícola, y sin necesidad de hipo regulación, condujo a la pérdida de esa capacidad en la mayoría de los palemonídeos. Así, se supone un ancestral con capacidad hipo regulatoria, una vez que los invertebrados marinos son, parsimoniosamente, osmoconformadores. Se compara también que el nitrito presenta efectos en las proteínas presentes en la hemolinfa de los crustáceos cuando sometidos a la exposición natural o inducida por estes compuesto, y que la capacidad osmorregulatoria es, por lo tanto, variada de acuerdo con sus etapas...

Decline of genetic variability in a captive population of Pacific white shrimp Penaeus (Litopenaeus) vannamei using microsatellite and pedigree information

Background: The objective of this study was to estimate the decline of genetic variability and the changes in effective population size in three shrimp populations. One was a wild population collected at several points in the Mexican Pacific Ocean. The other two populations were different generations (7 and 9) from a captive population selected for growth and survival. Microsatellite markers and pedigree were both used to assess genetic variability and effective population size. Results: Using 26 loci, both captive populations showed a decline in the expected heterozygosity (20%) and allelic diversity indices (48 to 91%) compared to the wild population (P < 0.05). The studied captive populations did not differ significantly from each other regarding their expected heterozygosity or allelic diversity indices (P > 0.05). Effective population size estimates based on microsatellites declined from 48.2 to 64.0% in cultured populations (P < 0.05) compared to the wild population. Conclusions: An important decline of genetic variability in the cultured selected population due to domestication, and evidence of a further smaller decline in effective population size across generations in the selected population were observed when analyzing pedigree (41%) and microsatellite data (37%). Pedigree keeping is required to prevent the decline of effective population size and maintain genetic variability in shrimp breeding programs, while microsatellites are useful to assess effective population size changes at the population level.

Antibiotic resistance of Vibrio parahaemolyticus isolated from pond-reared Litopenaeus vannamei marketed in Natal, Brazil

Ten out of fifty fresh and refrigerated samples of shrimp (Litopenaeus vannamei) collected from retailers in Natal (Rio Grande do Norte, Northeastern Brazil) tested positive for Vibrio parahaemolyticus. The Kanagawa test and multiplex PCR assays were used to detect TDH and TRH hemolysins and the tdh, trh and tlh genes, respectively. All strains were Kanagawa-negative and tlh-positive. Antibiotic susceptibility testing was done for seven antibiotics by the agar diffusion technique. Five strains (50 percent) presented multiple antibiotic resistance to ampicillin (90 percent) and amikacin (60 percent), while two strains (20 percent) displayed intermediate-level resistance to amikacin. All strains were sensitive to chloramphenicol. Intermediate-level susceptibility and/or resistance to other antibiotics ranged from 10 to 90 percent, with emphasis on the observed growing intermediate-level resistance to ciprofloxacin. Half our isolates yielded a multiple antibiotic resistance index above 0.2 (range: 0.14-0.29), indicating a considerable risk of propagation of antibiotic resistance throughout the food chain.

Artificial family selection based on growth rate in cultivated lines of Litopenaeus vannamei (Decapoda, Penaeidae) from Venezuela

We investigated the effects of family selection on the growth rates of four genetic lines of Litopenaeus vannamei, the Pacific white shrimp, from Venezuela. The mean family weight at selection was 16.79 g and the mean growth rate was 0.169 g d-1 at a mean age of 138 days. The mean growth rates per generation were 0.141 g d-1 for the parental generation (P0), 0.173 g d-1 for the F1 and 0.191 g d-1 for the F2. Survival varied from 83.3 percent to 94.4%. There were statistically significant differences between lines, with lines B and C, growing at higher temperatures and lower salinities, showing the fastest growth. Regression analysis between growth rate and age for each genetic line showed high r² values, but smaller than those shown between growth rate and generation. The mean heritability (h²) estimated for growth rate was 0.25 ± 0.04, with line per generation values ranging from 0.18 to 0.38. The mean heritability for growth rate per line showed some variation but there was no correlation between heritability and growth rate. Females showed a greater gain in growth rate per generation than males due to their faster growth when they were older. This study shows the high potential of these L. vannamei populations for the future of shrimp culture in the Americas.

Genetic diversity within and between broodstocks of the white shrimp Litopenaeus vannamei (Boone, 1931) (Decapoda, Penaeidae) and its implication for the gene pool conservation

Genetic variation within and between fifteen closed broodstock lines of the Pacific white shrimp Litopenaeus vannamei, reared at different hatcheries in the Brazilian coast, was assessed by RAPD analysis. Fifty two polymorphic loci were identified when a set of five decamer primers was used in PCR. The genetic diversity analysis within lines evidenced genetic variation loss probably related to bottleneck effects and inbreeding. In addition, the genetic divergence values between the different samples appear to reflect the initial founder composition of such stocks, in some cases, sharing a common origin, suggesting a putative importance of interbreeding for the establishment of genetic improvement programs for these broodstocks. The genetic variation monitoring appears to be helpful to the gene pool conservation of this aquaculture species, mainly if considered its exotic status in Brazil and the current impossibility of new introduction of wild individuals.

A variação genética existente dentro e entre quinze linhagens fechadas de reprodutores do camarão branco Litopenaeus vannamei, mantidas em diferentes laboratórios de larvicultura na costa brasileira, foi estudada utilizando análises RAPD. Através de um conjunto de cinco iniciadores decâmeros em PCR, foram identificados 52 locos polimórficos. A análise da diversidade genética dentro de cada linhagem evidenciou perda da variação genética provavelmente devida a efeitos de bottleneck e endocruzamento. Em adição, os valores de divergência genética entre as diferentes linhagens parecem refletir a composição inicial de fundação desses estoques, em alguns casos, compartilhando uma origem comum, sugerindo uma importância potencial do exo-cruzamento para estabelecer programas de melhoramento genético baseado nessas linhagens reprodutoras. O monitoramento da variação genética será muito útil para a conservação do conjunto gênico desta espécie de aquacultura, especialmente se for considerado seu status exótico no Brasil e que atualmente é impossível a realização de novas introduções de indivíduos selvagens.

Genetic structure of the sea-bob shrimp (Xiphopenaeus kroyeri Heller, 1862; Decapoda, Penaeidae) along the Brazilian southeastern coast

The sea-bob shrimp, Xiphopenaeus kroyeri, is one of the most important economic marine resources along the entire Brazilian coast. Nevertheless, despite its economic importance, no studies have examined the population genetics of this species. In this paper, we used ten allozyme loci to study the pattern of genetic structuring in X. kroyeri along the southeastern Brazilian coast. Seven of the ten analyzed loci were polymorphic, yielding observed heterozygosity values higher than those reported for other penaeid shrimps. The population from São Paulo was significantly different from the other two populations (Rio de Janeiro and Espírito Santo), which, in turn, seem to form a single panmitic unit. Therefore, our results clearly indicate that conservation policies for this species should consider the São Paulo population as an independent stock from those of Rio de Janeiro and Espírito Santo.

Genetic distance between broodstocks of the marine shrimp Litopenaeus vannamei (Decapoda, Penaeidae) by mtDNA analyses

In the constantly growing Brazilian shrimp industry the evaluation of genetic relationships between broodstocks is an useful tool for shrimp culture management programs. We established the genetic relationships between five broodstocks of the white marine shrimp Litopenaeus vannamei (Penaeidae) based on the sequencing of the mtDNA 16S rRNA and cytochrome oxidase I (COI) regions. Although no divergence was found between the broodstocks for the highly conservative 16S rRNA gene, we did find an 8.2 percent distance between L. vannamei and the Farfantepenaeus subtilis. Analyses of the COI region showed genetic distances of only 0.2 to 1 percent between the broodstocks, which contrasted with the 10.9 percent mean distance found between L. vannamei and F. subtilis. The small genetic distance values obtained may be related to genetic drift or a founder effect that occurred during broodstocks establishment. The mtDNA analysis was able to characterize the genetic divergence between the broodstocks studied and could be helpful for defining better management strategies of these crustacea.

Fluorescent amplified fragment length polymorphism (fAFLP) analyses and genetic diversity in Litopenaeus vannamei (Penaeidae)

The Pacific white shrimp, Litopenaeus vannamei (Penaeidae), represents about 95 percent of all Brazilian shrimp production. The Brazilian L. vannamei foundation broodstock was made up of specimens collected from different American Pacific sites, but little information was collected on the genetic structure of the broodstock. We used the fluorescence amplified fragment length polymorphism (fAFLP) method to study the genetic diversity of L. vannamei broodstock lines 03CMF1 and 03CBF1 originally produced by breeder-shrimps imported mainly from Panama and Ecuador, although wild individuals from other localities may also have been used in producing these two lines. Our results showed a total of 93 polymorphic bands ranging from 50 to 500 bp, the mean Nei's genetic diversity calculated for the total sample was 13.4 percent and identity and genetic distance analyses indicated high genetic homogeneity within and between both the broodstock lineages studied which suggests that they had similar genetic structure. These results may represent an important tool for the appropriate management of L. vannamei broodstocks.

Molecular phylogeny of penaeid shrimps inferred from two mitochondrial markers

Penaeid shrimps are an important resource in crustacean fisheries, representing more than the half of the gross production of shrimp worldwide. In the present study, we used a sample of wide-ranging diversity (41 shrimp species) and two mitochondrial markers (758 bp) to clarify the evolutionary relationships among Penaeidae genera. Three different methodologies of tree reconstruction were employed in the study: maximum likelihood, neighbor joining and Bayesian analysis. Our results suggest that the old Penaeus genus is monophyletic and that the inclusion of the Solenocera genus within the Penaeidae family remains uncertain. With respect to Metapenaeopsis monophyly, species of this genus appeared clustered, but with a nonsignificant bootstrap value. These results elucidate some features of the unclear evolution of Penaeidae and may contribute to the taxonomic characterization of this family.