Heritabilities and genetic correlation of shell thickness and shell length growth in a mussel,Mytilus chilensis(Bivalvia:Mytilidae)

Abstract

Shell thickness in mollusks is generally considered adaptive because of their effects on fitness. However, little is known about the genetic basis of shell thickness. This is important, because the response to selection and the subsequent adaptive microevolution of a trait, such as thickness is only possible when that trait exhibits additive genetic variation. Here, we estimated the narrow-sense heritability (h 2 : ratio between additive genetic variance and phenotypic variance) for the traits 'shell thickness' and 'shell length growth' in a 34-month-old cohort of the mussel Mytilus chilensis obtained by using a half-full sib design and grown in the field. Also, phenotypic and genetic correlations were estimated between both traits. We found that h 2 showed significant values for shell thickness (0.294 AE 0.194) and length (0.731 AE 0.379). The phenotypic correlation between both traits was positive and significant; however, the genetic correlation between these traits was not. These results suggest both traits can evolve adaptively by selection, but because these traits did not show genetic correlation, it is possible that selection pressure affecting one trait may not affect the other.

A Microarray Study of Carpet-Shell Clam (Ruditapes decussatus) Shows Common and Organ-Specific Growth-Related Gene Expression Differences in Gills and Digestive Gland

“…The abundance of somatic aneuploidy has been also related to differences in growth rates in bivalves (de Sousa et al, 2011 ). Quantitative genetics studies have shown that growth rate has a significant genetic component, with heritabilities rising often over 0.4 (e.g., Wang et al, 2010 ; Kong et al, 2015 ; Guiñez et al, 2017 ). Selective breeding for increased growth rate has been usually successful (e.g., Rodrigues De Melo et al, 2016 ).…”

Deciphering mollusc shell production: the roles of genetic mechanisms through to ecology, aquaculture and biomimetics

“…It was suggested that polygenic characters governed evolution to low pH and genotype–environment interactions released ‘cryptic’ genetic variation of fitness‐related traits. Furthermore, three M. edulis generations grown in CO 2 ‐enriched conditions revealed heritable components of calcification performance in early development (Thomsen et al ., 2017) and rapid adaptation in shell thickness to this corrosive environment occurred in M. chilensis (Guiñez et al ., 2017).…”

Heritability estimates for nutritional quality‐related traits of the Pacific oyster, Crassostrea gigas

“…The heritabilities of growth, disease resistance, and shell color in aquaculture animals has been well studied (Alcapan, Nespolo, & Toro, 2007;Azema et al, 2017;Evans et al, 2009;Guinez et al, 2017;He et al, 2008;Kong et al, 2015;Wang et al, 2010), but information on nutritional quality traits in bivalves is scarce. Heritability estimates for lipid percentage range from 0.19 to 0.28 in Atlantic salmon and from 0.17 to 0.26 in Coho salmon (Sodeland et al, 2013).…”

“…Genetic and phenotypical correlations between two traits include specific quantitative trait parameters that can be applied to predict the potentiality of traits to be improved together by selective breeding and be beneficial for determining proper breeding strategies (Falconer & Mackay, 1996). The most recent heritability studies on bivalves focused on traits related to growth (Frank-Lawale & Allen, 2008;Guinez, Toro, Krapivka, Alcapan, & Oyarzun, 2017;He, Guan, Yuan, & Zhang, 2008;Kong, Li, Yu, & Kong, 2015;Li, Wang, Liu, & Kong, 2011;Wang, Du, Lu, & Liu, 2010) and resistance to bacteria and viruses (i.e., to mortality) (Azema et al, 2017;Degremont, Lamy, Pepin, Travers, & Renault, 2015). The heritabilities of lipid percentage in Atlantic salmon and Coho salmon have also been estimated (Sodeland et al, 2013).…”