Abstract
Mya arenaria is a bivalve mollusk of commercial and economic importance, currently impacted by ocean warming, acidification, and invasive species. In order to inform studies on the growth of M. arenaria, we selected and inbred a population of soft-shell clams for a fast-growth phenotype. This population displayed significantly faster growth (p < 0.0001), as measured by 35.4% greater shell size. To assess the biological basis of this growth heterosis, we characterized the complete transcriptomes of six individuals and identified differentially expressed genes by RNAseq. Pathways differentially expressed included structural gene pathways. Also differentially expressed was the nucleotide-binding oligomerization domain 2 (NOD2) receptor pathway that contributes to determination of growth, immunity, apoptosis, and proliferation. NOD2 pathway members that were upregulated included a subset of isoforms of RIPK2 (mean 3.3-fold increase in expression), ERK/MAPK14 (3.8-fold), JNK/MAPK8 (4.1-fold), and NFκB (4.08-fold). These transcriptomes will be useful resources for both the aquaculture community and researchers with an interest in mollusks and growth heterosis.
Highlights
The soft-shell clam, Mya arenaria, is an infaunal, benthic marine bivalve that inhabits soft-sediments in the intertidal and shallow subtidal zone and ranges in the northwest Atlantic from North Carolina to Labrador [1,2,3]
We examined the possibility of enhancing shell growth in M. arenaria through classic selective breeding
Selection resulted in a clam inbred line that displayed growth heterosis as assessed by shell length (SL) (Figure 1)
Summary
The soft-shell clam, Mya arenaria, is an infaunal, benthic marine bivalve that inhabits soft-sediments in the intertidal and shallow subtidal zone and ranges in the northwest Atlantic from North Carolina to Labrador [1,2,3]. One of the most abundantly fished organisms caught along the coast of North America (over 1,200 metric tons in 2014 [6]), M. arenaria is prone to overharvest [7]. In spite of their importance, clams and the entire phylum Mollusca are understudied and underrepresented in GenBank [8]
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