Scanning electron micrographs of the larval shell of a specimen of <i>Idas iwaotakii</i>.

<p>Pictures: (A) Dorsal view showing prodissoconch I (PI) and prodissoconch II (PII); the white arrow indicates the boundary between the dissoconch and prodissoconch, (B) Detail of PI; the grey arrow indicated of the boundary between PI and PII.</p

Dendrogram obtained from Bayesian analyses of the combined dataset of COI mtDNA and the 28S rRNA.

<p>Asterisks correspond to nodes with posterior probabilities (PP) obtained from BA analysis and bootstrap values obtained from ML analysis that are higher than 0.90 and 50%, respectively. (modified from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Lorion1" target="_blank">[7]</a>).</p

Geographical localities, substrates, depths and sequences of specimens of <i>I. iwaotakii</i> used in this study.

<p>The number of sequences is indicated in brackets. The superscripts refer to the authors of sequences. The stars indicate the sequences obtained during this study.</p

Semi-thin sections of the digestive tract of <i>Idas iwaotakii</i>.

<p>The specimen was collected on turtle bone off New Caledonia. (A) Overall view of the digestive tract (longitudinal sections). The black arrow indicates the location of microvilli in the intestine. (B) Cross section of the oesophagus lined by a stratified epithelium. (C) Cross section of the intestine. (D) Cross section of the stomach lined by a cuboidal epithelium. The white arrow indicates the gastric shield. (E) Longitudinal section of a detail of intestinal contents.</p

Population structure of <i>I. iwaotakii</i>.

<p>Left part: K2P neighbour-joining tree of unique COI haplotypes of <i>I. iwaotakii</i>. The localities at which each haplotype have been sampled is figured by a coloured circle (see legend for correspondence between localities and colours), the number of individuals sharing the same COI haplotype at each locality is given in brackets. The grey rectangles underline the haplotypes shared by the two studied regions. The scale bar represents 0.02% estimated base substitutions. The mitochondrial haplotypes of <i>I. iwaotakii</i> are divided in two clades, A’ and A’’, represented by one panel with large dots and the other one with small dots, respectively. Right part: Median-joining networks (MJN) from COI mtDNA data drawn independently for each of the two studied regions (North Western and South Western haplotypes). Size of haplotype circles is proportional to the number of specimens. Colours used to figure the localities within each region are the same of that used for the NJ tree. A small black circle represents a hypothetical haplotype. The haplotypes shared by the two studied regions are underlined using grey circles over haplotype labels.</p

Bayesian tree displaying bacterial symbionts based on the analysis of the 16S rRNA.

<p>Phylotypes associated with <i>I. iwaotakii</i> are shown in bold. Posterior probabilities (PP) and bootstrap values obtained from ML analysis are given above and below branches respectively. PP and bootstrap values lower than 0.90 and 50%, respectively, are not shown. The scale bar represents 0.5% estimated base substitution.</p

Gill filaments of <i>Idas iwaotakii</i>.

<p>(A) TEM view of gill filament of the lateral zone from a specimen of <i>I. iwaotakii</i> collected on wood off Vanuatu. Bacteria (black arrows) are located extracellularly in contact with microvilli. BL: blood lacuna; Lm: basal lamina. (B) Electron micrograph of the extracellular symbionts. Symbiotic bacteria possess a double membrane (white arrow) typical of Gram negative bacteria.</p

South Western Pacific map showing the sampling localities of mussels of <i>Idas iwaotakii</i>.

<p>Specimens from Malo and New Caledonia have already been studied by <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Lorion1" target="_blank">[7]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Lorion3" target="_blank">[30]</a>.</p

Mismatch distributions of COI haplotypes.

<p>COI haplotypes observed, simulated under a constant population size and a model of population expansion for the South-west Pacific populations of <i>A. iwaotakii</i>. Along x-axis are indicated the numbers of nucleotide differences between all pairs of sequences and on y-axis the frequencies of pairs. The table summarizes the parameters of demographic analyses under constant population size and demographic expansion. The confidence intervals at 99% of the parameters under a demographic expansion model are given in square brackets.</p

Comparison of data available for the <i>“thermophilus”</i> lineage and its sister lineage.

<p>The “<i>thermophilus</i>” lineage is represented by the dark grey rectangle and its sister lineage, corresponding to the genus <i>Idas</i>, by the light grey rectangle. Phylogenetic relationships correspond to a part of the combined COI mtDNA and 28S RNA phylogenetic tree from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Lorion1" target="_blank">[7]</a>. T: thiotrophic symbiont; M: methanotrophic symbiont. In geographical patterns section, the ovals correspond to pairs of sister-species with an allopatric distribution and location maps illustrate the allopatric distribution of these sister pairs. References: <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Lorion1" target="_blank">[7]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Won1" target="_blank">[9]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-LePennec1" target="_blank">[11]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Gustafson1" target="_blank">[14]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Duperron2" target="_blank">[16]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Craddock1" target="_blank">[24]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Won2" target="_blank">[26]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Plouviez1" target="_blank">[27]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Lorion3" target="_blank">[30]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Duperron5" target="_blank">[52]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-OluLeRoy1" target="_blank">[63]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Johnson1" target="_blank">[64]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-Faure1" target="_blank">[66]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-vonCosel2" target="_blank">[70]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-vonCosel4" target="_blank">[72]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-FialaMedioni1" target="_blank">[76]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069680#pone.0069680-OluLeRoy2" target="_blank">[83]</a>.</p