Fitness of early life stages in F1 interspecific hybrids between Dicentrarchus labrax and D. punctatus

Abstract

-Inter-and intraspecific crossbreeding experiments were conducted to evaluate the aquaculture potential of hybrids in the genus Dicentrarchus, focusing on fertilisation and hatching success. The experimental design consisted of 24 controlled crosses in which individual and pooled fertilisations were made between wild D. labrax individuals (8 dams and 5 sires originating from West Mediterranean and Atlantic populations) and wild D. punctatus (6 sires). Three experiments were successively performed: (1) dams from the Mediterranean population, individually considered to have good egg quality, (2) dams from Mediterranean population, individually considered to have poor egg quality and (3) crossbreeding using pooled eggs from the Atlantic population. In each case, batches of these eggs were fertilized by sperm from males of the two species. Sperm cell quality (concentration and motility) was verified before experimentation in all cases and equal numbers of sperm cells from each male were used to individually (without inter-sire competition) fertilise egg batches. Through the repeated artificial crosses between female common sea bass Dicentrarchus labrax (Linnaeus 1758) and male spotted sea bass D. punctatus (Block 1792), these experiments showed that no post-zygotic reproductive barriers exist to interspecific hybridisation between these two species when using D. labrax as dams and D. punctatus as sires. Phenotypically, the F1 hybrids were easily recognisable: they inherited the characteristic black spots of D. punctatus. Furthermore, embryo survival was significantly higher in interspecific crosses compared with intraspecific controls, showing increased fitness for this trait (increased performance at early life stage). Then, the experimental breeding design validates the observation that West Mediterranean and Atlantic common sea bass populations are different. Indeed, the inter-population crosses (between West Mediterranean dams and Atlantic sires) also revealed increased fitness at early life stages in comparison with the progeny of intra-Atlantic population crosses. However, these individuals were still smaller than their interspecific counterparts. The ability to produce viable F1 hybrids will have significant implications for the practical improvement of sea bass aquaculture.

Metapopulation patterns of additive and nonadditive genetic variance in the sea bass (Dicentrarchus labrax)

“…The sire population appeared important to survival in sea bass, supporting recent evidence for a paternal role in increased survival of young fish (Álvarez & Garcia-Vazquez, 2011;Bang, Grønkjaer, Clemmesen, & Høie, 2006;Rideout, Trippel, & Litvak, 2004), but also other broadcast marine spawners (Styela plicata; Crean, Dwyer, & Marshall, 2013). A paternal influence was formerly shown for female hatching rate in sea bass, but not for survival (Ky et al, 2012;Saillant et al, 2001).…”

“…Indeed, regarding survival and female sex ratio, the reciprocal hybrid crosses available in this study did not outperform the two crosses involving parental forms, with hybrid (♂NAT × ♀WEM) > parental (♂NAT × ♀NAT) > hybrid (♂WEM × ♀NAT) > parental (♂WEM × ♀WEM) . Ky et al (2012) also reported that hybrid (♂NAT × ♀WEM) outperformed parental (♂NAT × ♀NAT) for hatching rate. Asymmetric performances of F 1 crosses are commonly reported in a wide range of organisms even though-contrary to sea bass-F 1 s rarely outcompete their parents as observed in, e.g., numerous freshwater fish species (Bolnick, Turelli, Lopez-Fernández, Wainwright, & Near, 2008;López-Fernández & Bolnick, 2007;Russell & Magurran, 2006;Schrader, Fuller, & Travis, 2013).…”

“…Each batch of eggs was then divided in 75 aliquots, which were individually fertilized (no intersire competition) with the sperm of 15 sires from each geographic origin to produce a theoretical number of 1,950 families of sea bass (26 dams × 75 sires). Sperm cell quality was checked as described in Ky, Vergnet, Molinari, Fauvel, and Bonhomme (2012) in order to retain sires with good semen quality. The fertilized eggs were mixed by sire (n = 5) × dam (n = 2) origins and incubated in 10 different incubators.…”

The contribution of ancient admixture to reproductive isolation between European sea bass lineages

“…To achieve this goal, we used different complementary approaches that collectively provided strong support for ancient introgression from the sister species D. punctatus . Despite low divergence ( d XY = 0.55%), partially overlapping range distributions, and interfertility in artificial crosses (Ky et al 2012), contemporary hybridization has not been observed in the wild between D. labrax and D. punctatus (Tine et al. 2014).…”

Indirect improvement of pearl grade and shape in farmed Pinctada margaritifera by donor “oyster” selection for green pearls

“…Oocytes were then fertilised at a ratio of 5-10 spermatozoa per oocyte. The fertilisation rate was evaluated in triplicate 3 hours later according to the methodology used for seabass fertilisation rate estimation by Ky et al (2012).…”