Fickle or Faithful: The Roles of Host and Environmental Context in Determining Symbiont Composition in Two Bathymodioline Mussels

PLoS One. 2015 Dec 28;10(12):e0144307. doi: 10.1371/journal.pone.0144307. eCollection 2015.

Abstract

The Mediterranean Sea and adjoining East Atlantic Ocean host a diverse array of small-sized mussels that predominantly live on sunken, decomposing organic remains. At least two of these, Idas modiolaeformis and Idas simpsoni, are known to engage in gill-associated symbioses; however, the composition, diversity and variability of these symbioses with changing habitat and location is poorly defined. The current study presents bacterial symbiont assemblage data, derived from 454 pyrosequencing carried out on replicate specimens of these two host species, collected across seven sample sites found in three oceanographic regions in the Mediterranean and East Atlantic. The presence of several bacterial OTUs in both the Mediterranean Sea and eastern Atlantic suggests that similar symbiont candidates occur on both sides of the Strait of Gibraltar. The results reveal markedly different symbiotic modes in the two species. Idas modiolaeformis displays high symbiont diversity and flexibility, with strong variation in symbiont composition from the East Mediterranean to the East Atlantic. Idas simpsoni displays low symbiont diversity but high symbiont fidelity, with a single dominant OTU occurring in all specimens analysed. These differences are argued to be a function of the host species, where subtle differences in host evolution, life-history and behaviour could partially explain the observed patterns. The variability in symbiont compositions, particularly in Idas modiolaeformis, is thought to be a function of the nature, context and location of the habitat from which symbiont candidates are sourced.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacteria / genetics*
  • Bacteria / isolation & purification*
  • Base Sequence
  • Biodiversity
  • Gibraltar
  • Mediterranean Sea
  • Mytilidae / microbiology*
  • RNA, Ribosomal, 16S / genetics
  • Sequence Analysis, DNA
  • Symbiosis / physiology*

Substances

  • RNA, Ribosomal, 16S

Grants and funding

Sample collection and analyses were supported by the CARCACE project (PTDC/MAR/099656 /2008, co-financed by Fundacão para a Ciência e a Tecnologia, FCT); the European Regional Development Fund through COMPETE (FCOMP-01-0124-FEDER-010569); the European Commission Seventh Framework Programme (FP7/2007–2013) under the HERMIONE project contract 226354; the French ANR DeepOases; GDRE—DIWOOD; CHEMECO ESF EURODEEP (EURODEEP/0001/2007); ITN SYMBIOMICS; UPMC (University Pierre and Marie Currie), Foundation TOTAL and the Institut Universitaire de France. SRL was also supported by a PhD grant from the MARES Joint Doctorate programme selected under Erasmus Mundus coordinated by Ghent University (FPA 2011-0016), KS was funded through a PhD grant from the Marie Curie Actions Initial Training Network (ITN) SYMBIOMICS (contract number 264774), and CFR was supported by a postdoctoral fellowship (SFRH/BPD/64154/2009) from FCT (Portugal).