Cross breeding of different domesticated lines as a simple way for genetic improvement in small aquaculture industries: Heterosis and inbreeding effects on growth and survival rates of the Pacific blue shrimp Penaeus (Litopenaeus) stylirostris

Abstract

Two populations of the Latin American shrimp Penaeus (Litopenaeus) stylirostris domesticated in Hawaii and in New Caledonia were previously shown to be genetically differentiated and proven highly inbred. In New Caledonia, where different Vibriosis affect shrimp production and antibiotic use is banned in growing ponds, the Hawaiian population was introduced to increase the allelic variability available for local shrimp farmers and start a genetic improvement program. Growth and survival rates of the two pure populations and the two-way F1-hybrids obtained by breeding Hawaiian animals with New Caledonian animals were assessed in several simple experiments (earthen ponds, floating cages and experimental infection challenges) during two years on two successive generations. Results were very consistent: F1-hybrids growth rates in earthen ponds were 37% (± 7% SD) higher than for pure populations. Cage experiments demonstrated no competition between the different populations when reared together or separately in a common environment. The F1-hybrids also showed better survival rates in all experiments. Combining the results on growth and survival rates leads to the conclusion that biomass production is much higher with F1-hybrid populations than with pure populations using the same quantity of juveniles stocked: biomass production in ponds was increased 1.4 and 2.3 times on year 1 and year 2 respectively, and 1.9 times in floating cages. The advantage of growing F1hybrids appeared proportionally higher when environmental and sanitary conditions led to poorer survival (34% in year 2 vs. 56% in year 1). These results are a good example of performance improvement by heterosis effect and/or of performance loss due to inbreeding in the pure populations. This study demonstrates that aquaculture industries which cannot afford large selection programs may benefit from using two different inbred parental stocks to produce F1-hybrids for each commercial growout. This is notably true when only inbred populations are available, or when introduction of genetic variability from the wild or from other genetic resources represents a zoo-sanitary risk. In our case, the expected increase in L. stylirostris production could be around 85% (according to our average results) if producers keep stocking their ponds at their current densities using F1-hybrids. However, for sustainability reasons, it is advisable to stock F1-hybrid animals at lower densities, the gain in performance allowing producing the same amount of biomass with less input.

Responses of diploid and triploid Pacific oysters Crassostrea gigas to Vibrio infection in relation to their reproductive status

“…Experimental infections of aquatic animals using viruses, bacteria or parasites can be performed to fulfil different objectives: to estimate the efficiency of preventive treatments, study routes of infection, test the resistance of selected lines (Gomez-Leon et al, 2008;Goyard et al, 2008;Lallias et al, 2008) or different ploidy groups (Ching et al, 2009;O'Flynn et al, 1997), and to assess host factors linked to susceptibility (Goarant et al, 1998(Goarant et al, , 2006bLabreuche et al, 2006a). For bacteria, experimental infections are also often used to explore pathogenicity (Gay et al, 2004;Goarant et al, 2006b), coupled with phenotypic and/or molecular characterization of virulence factors.…”

Genetic Variation in Wild and Cultured Populations of the Freshwater Prawn, Macrobrachium nipponense, in China

“…It has been demonstrated that genetic diversity declines can lead to reduced growth, viability, reproductive performance, and the benefits of heterosis in some species such as shrimp (Cruz et al 2004;Goyard et al 2008). Genetic diversity declines have also been linked to biochemical disorders and deformities from lethal and sublethal recessive alleles (Dunham 2004).…”

Using microsatellite markers to identify heritability of Pacific whiteleg shrimp Litopenaeus vannamei

“…But despite the amenity of shrimp to genetic selections and due to their comparatively high fecundity, closed life, short generation time and larger genetic gain (Keys et al, 2004;Rezvani Gilkolaei et al, 2011;Farafidy et al, 2012;Szeker, 2012); commercial shrimp culture has been slow to adopt breeding-selection schemes (Goyard et al, 2008;Cock et al, 2009;Rezvani Gilkolaei et al, 2011). This reluctance has been due to the past perceptions of low genetic variation and difficulties in shrimp breeding (Benzie, 2009;Rezvani Gilkolaei et al, 2011).…”