Additive transcriptomic variation associated with reproductive traits suggest local adaptation in a recently settled population of the Pacific oyster, Crassostrea gigas.

Rossana Sussarellu,Virgile Quillen,Sylvie Lapègue,Christophe Lelong,Pierre Boudry,Florence Cornette,Nicolas Bierne,Arnaud Huvet,Lasse Fast Jensen

doi:10.1186/s12864-015-1972-8

Abstract

BackgroundOriginating from Northeast Asia, the Pacific oyster Crassostrea gigas has been introduced into a large number of countries for aquaculture purpose. Following introduction, the Pacific oyster has turned into an invasive species in an increasing number of coastal areas, notably recently in Northern Europe.MethodsTo explore potential adaptation of reproductive traits in populations with different histories, we set up a common garden experiment based on the comparison of progenies from two populations of Pacific oyster sampled in France and Denmark and their hybrids. Sex ratio, condition index and microarray gene expression in gonads, were analyzed in each progeny (n = 60).ResultsA female-biased sex-ratio and a higher condition index were observed in the Danish progeny, possibly reflecting an evolutionary reproductive strategy to increase the potential success of natural recruitment in recently settled population. Using multifarious statistical approaches and accounting for sex differences we identified several transcripts differentially expressed between the Danish and French progenies, for which additive genetic basis is suspected (showing intermediate expression levels in hybrids, and therefore additivity). Candidate transcripts included mRNA coding for sperm quality and insulin metabolism, known to be implicated in coordinated control and success of reproduction.ConclusionsObserved differences suggest that adaptation of invasive populations might have occurred during expansion acting on reproductive traits, and in particular on a female-biased sex-ratio, gamete quality and fertility.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1972-8) contains supplementary material, which is available to authorized users.

Highlights

Originating from Northeast Asia, the Pacific oyster Crassostrea gigas has been introduced into a large number of countries for aquaculture purpose
The invasiveness of C. gigas has been demonstrated in several countries and this species is considered as pest or noxious in an increasing number of coastal areas [13]
Sex-ratio and condition index Sex-ratio differed significantly (p

Summary

Introduction

Originating from Northeast Asia, the Pacific oyster Crassostrea gigas has been introduced into a large number of countries for aquaculture purpose. The Pacific oyster has turned into an invasive species in an increasing number of coastal areas, notably recently in Northern Europe. Feral populations of C. gigas have been reported in northern Europe [15, 16] as far north as Sweden, where dense populations of settled oysters can be observed in several shallow water sites [17] This expansion of Pacific oyster in the North Sea occurred much later after their first introduction than along the French Atlantic coast, suggesting that increase in population size may have been retarded by false or irregular recruitment depending on water temperature [15,16,17,18]. The success of the species and especially its northward expansion might be explained by climate change [20, 21] and local adaptation as well as phenotypic plasticity, or both [22]

Methods

Results

Discussion

Conclusion