New sequenced gastrotrich taxa used in this study.

<p>Sampling locations together with their respective coordinates are given as well as GenBank accession number.</p

Phylogenetic relationships of 43 Gastrotricha Macrodasyida inferred from Bayesian analysis of 18 S rDNA.

<p>The outgroup is represented by <i>Xenotrichula intermedia</i> (Chaetonotida, Xenotrichulidae). Number at nodes represents posterior probabilities.</p

Additional gastrotrich taxa used in this study.

<p>*Order Chaetonotida.</p><p>Origin, reference and GenBank accession number are given. NA, not available.</p

<i>Anandrodasys agadasys</i> ( = <i>Dactylopodola agadasys</i>) from the US Virgin Islands.

<p>A, habitus of a fully relaxed adult specimen; B, C adhesive tubes of the ventrolateral series of two different adult specimens; D, close-up of the anterior end of a fourth specimens, showing the arrangement of sensorial cilia and the insertion of the anterior adhesive tubes; E, posterior trunk region showing the female reproductive apparatus with eggs at different developing stages. DIC photomicrographs. Scale bars, A, 100 µm, B–E, 20 µm. Originally described from Australia, later the species has been reported from Panama, Red sea, Caribbean sea and Florida <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031740#pone.0031740-Hummon3" target="_blank">[6]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031740#pone.0031740-Hochberg2" target="_blank">[24]</a>. According to Hummon <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031740#pone.0031740-Hummon3" target="_blank">[6]</a> there are not morphological differences among populations. Morphology of the specimens from St John match that describe d by Hummon <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031740#pone.0031740-Hummon3" target="_blank">[6]</a>; however, we noticed some variability in the number and arrangement of the ventrolateral adhesive tubes, as testified by Figures B and C.</p

Phylogenetic relationships of 43 Gastrotricha Macrodasyida inferred from Maximum Parsimony analysis of 18 S rDNA.

<p>The outgroup is represented by <i>Xenotrichula intermedia</i> (Chaetonotida, Xenotrichulidae). Tree #1 out of 3 most parsimonious trees (length = 3746) is shown. The consistency index is (0.382720), the retention index is (0.608797), and the composite index is 0.254573 (0.232999) for all sites and parsimony-informative sites (in parentheses). Number at nodes represents bootstrap values (1000 replicates).</p