Development of the First Microsatellite Multiplex PCR Panel for Meagre (Argyrosomus regius), a Commercial Aquaculture Species

In this study, a microsatellite-based multiplex PCR panel for meagre (Argyrosomus regius) was developed as a useful and single tool in parental assignment and population studies. Twenty-one specific and interspecific microsatellites from different aquaculture species of meagre (Argyrosomus regius), Japanese meagre (A. japonicus), red drum (Sciaenops ocellatus) and yellow meagre (Acoupa weakfish) were assessed for genetic variability, allelic range and genotype reliability. Finally, a SuperMultiplex for Argyrosomus regius (SMAr) was designed with only the best eight microsatellite markers. The panel assessment was performed using a batch of brood stock from one company and a sample of 616 offspring. It was possible to assign 95% of the offspring to a single pair of parents using the exclusion method. It is therefore considered an easy procedure, and a powerful and low-cost tool for parental assignment to support companies’ breeding programs and to exchange information between research groups.

Phenotypic and Genetic Components for Growth, Morphology, and Flesh-Quality Traits of Meagre (Argyrosomus regius) Reared in Tank and Sea Cage

Simple Summary

Meagre is an emergent species in aquaculture, due to its fast growth rate, low feed conversion ratio, and the high quality of the product. Although advances have been achieved in its management, reproduction, and feeding, breeding programs have not yet been developed. For this reason, this study aimed to provide information about the genetic variations in growth, morphology traits, and flesh chemical composition to be included in a selective breeding program, studied in two different housing systems (cage and tank). Heritabilities for growth and morphology traits, and for fillet fat percentage were medium, revealing those traits as a possible selection criterion in a breeding program. Image analysis provided a great amount of objective information regarding the different morphological traits of the fish, where a positive and high correlation with growth traits was observed. Positive phenotypic correlation between fillet fat percentage and body weight was observed, so a selection process to improve growth rate could lead to a fish with higher fillet fat percentage.

Abstract

Meagre (Argyrosomus regius) plays an important role in the aquaculture system, with the potential for diversification of European aquaculture, and is characterized by its fast growth rate, low feed conversion ratio, and the high quality of the product. Focusing on the relevance of meagre, the aim of the study was to analyze growth performance, fish morphology, and flesh composition phenotypically and genetically to be considered as a strategy in a breeding program. For this purpose, 633 fish were raised in two different housing systems, in sea cages or in a continental tank, and when they reached harvest size, manual growth traits, automatic morphology by the image analysis program IMAFISH_ML, and flesh chemical composition (fat, protein, moisture, and collagen percentages) were measured. The fish reared in the cages showed a higher body weight and fillet fat percentage than those in the tank. Heritabilities for growth and morphology traits, and for fillet fat percentage were medium, revealing these traits as a possible selection criterion in a breeding program. Phenotypic and genetic correlations between growth and morphology traits were positive and high. Phenotypic correlations between growth or morphology traits with fillet fat percentage were positive and medium; genetic correlations were not estimated accurately.

Panmixia in a Critically Endangered Fish: The Totoaba (Totoaba macdonaldi) in the Gulf of California

Conservation of the evolutionary legacy of endangered species is a key component for long-term persistence. Totoaba is a long-lived fish endemic to the Gulf of California and is considered critically endangered. There is currently a debate concerning its conservation status and whether it can be used as a fishery resource. Unfortunately, basic information on biological and genetic population structure of the species is lacking. We sampled 313 individuals and employed 16 microsatellite loci and 3 mitochondrial DNA markers (16S, 547 pb; COI, 619 pb; control region, 650 pb) to assess population structure and demography of totoaba in the Gulf of California, with samples from locations that encompass nearly all of its recognized geographic distribution. We could not reject a hypothesis of panmixia for totoaba, using nuclear or mitochondrial markers. Demographic analysis of mtDNA suggests a sudden population expansion model. The results have important implications for totoaba conservation because poaching is a significant conservation challenge and could have additive negative effects over the single population of totoaba in the Gulf of California.

Applications of microsatellite markers in studies of genetics and breeding of fish

The microsatellite, or short sequence repeat (SSR), is a powerful genetic marker, useful in many areas of fish genetics and breeding. Polymorphic microsatellite loci have been frequently applied to the analysis of genetic diversity, population genetic structure, and genomic mapping. These co-dominant markers have also been applied to the classification and systematics, parentage identification, germplasm conservation, and breeding programme of food fish.

Development and characterization of 248 novel microsatellite markers in turbot (Scophthalmus maximus)

The turbot is a flatfish species of great relevance to marine aquaculture in Europe. Only a limited number of microsatellites have been isolated to date in this species. To increase the number of potentially useful mapping markers, we screened simple sequence repeat (SSR) - enriched genomic libraries obtained from several di-, tri-, and tetranucleotide tandem repeat motifs. A total of 248 new polymorphic microsatellites were successfully optimized. The efficiency of the protocol applied (6.4%) was higher than that in other studies of fish that used the same method. Dinucleotide and perfect microsatellites were predominant in this species; the (AC)n motif was the most frequent class of repeat. Polymorphism and structural properties at these loci, together with 30 variable loci previously reported in turbot, were evaluated in 6 wild individuals. The number of alleles per locus ranged from 2 to 10, with an average of 4.046. The microsatellite markers characterized in this study will contribute to the development of the turbot genetic map, which can be used for quantitative trait locus (QTL) identification, marker-assisted selection programs, and other applications to improve its culture.