Molecular evidence for cryptic species in <i>Pteroclava krempfi</i> (Hydrozoa, Cladocorynidae) living in association with alcyonaceans

<p>Hydrozoans are able to establish intimate relationships with several other organisms. The hydroid <i>Pteroclava krempfi</i> lives in association with different alcyonacean taxa from Indo-Pacific and Atlantic coral reefs, growing partially embedded within host tissues. In this study, we found <i>P. krempfi</i> associated with four alcyonacean hosts from the Maldives, namely <i>Sinularia</i>, <i>Sarcophyton</i>, <i>Lobophytum</i> and <i>Paraplexaura</i>, the latter representing a new record. We provided the first molecular phylogenetic evaluation of the genus <i>Pteroclava</i>. <i>Pteroclava krempfi</i> clustered with <i>Cladocoryne floccosa</i>, confirming its position into the family Cladocorynidae. We also performed the first morpho-molecular assessment of <i>P. krempfi</i> diversity. All the colonies growing on different hosts revealed polyps and medusae matching published descriptions of <i>P. krempfi</i>, showing no morphological differences. However, analysing both nuclear and mitochondrial DNA, two highly supported molecular lineages were identified. These two clades were highly divergent and were specifically associated with hosts belonging to different families (Alcyoniidae and Plexauridae). Therefore, our results suggest that <i>P. krempfi</i> from the Maldives is a complex of cryptic species in which the main diagnostic feature between different species could be the host specificity.</p

Description of <i>Turritopsoides marhei</i> sp. nov. (Hydrozoa, Anthoathecata) from the Maldives and its phylogenetic position

<p><i>Turritopsoides marhei</i>, a new species of the hydrozoan family Oceaniidae, is described from the Maldives. This species can be distinguished from the only other member of the genus by the presence of more branched colonies, branches not being adnate to pedicels, longer pedicels, larger nematocysts, nematocyst-rich nematophore-like outgrowths from pedicels, smaller male gonophores, and a different geographic distribution. This finding represents the first record of the genus outside the type locality of its type species, in Belize. Molecular phylogenetic analyses show that, as expected, <i>T. marhei</i> belongs to the clade Filifera IV. However, the phylogenetic hypothesis based on both mitochondrial and nuclear DNA sequences reveals that most of the families of this group are polyphyletic, including Oceaniidae, and suggests that the morphological characters used to discriminate among filiferan families need to be revised thoroughly.</p> <p><a href="http://zoobank.org/urn:lsid:zoobank.org:pub:CE901E0D-B125-4A87-BB97-8020C0658B5D" target="_blank">http://zoobank.org/urn:lsid:zoobank.org:pub:CE901E0D-B125-4A87-BB97-8020C0658B5D</a></p

List of specimens.

<p><b>Boldface</b> indicates newly obtained sequences.</p><p>List of specimens included in the analysis, with specimen code, locality and GenBank accession numbers, when available.</p

Morphological differences among clades.

<p>^a present study;</p><p>^b Fontana et al. 2012;</p><p>^c Montano et al. 2015.</p><p>Morphological characters of the clades resulted from the molecular analyses.</p

<i>In situ</i> photographs and microphotographs of living <i>Zanclea</i> hydroids associated with scleractinians.

<p><b>A</b>) <i>Goniastrea</i>; <b>B</b>) <i>Porites</i>; <b>C</b>) <i>Montipora</i>; <b>D</b>) <i>Acropora</i>; <b>E</b>) <i>Pavona</i>; <b>F</b>) <i>Favites</i>; <b>G</b>) <i>Dipsastrea</i>; <b>H</b>) <i>Echinopora</i>; <b>I</b>) <i>Platygyra</i>. (Scale bars: ~ 500 μm)</p

Phylogenetic tree based on the nuclear gene 28S inferred by Bayesian inference.

<p>The clade support values are <i>a posteriori</i> probabilities, bootstrap values from Maximum Likelihood, and bootstrap values from Maximum Parsimony, in this order. The node supporting the scleractinian-associated <i>Zanclea</i> clade is highlighted in red.</p

Pairwise comparisons and genetic distance.

<p>*<i>Zanclea</i> sequences from China available in GenBank.</p><p>Standard deviations are indicated in brackets.</p><p>Pairwise comparisons of genetic distance within and between species of <i>Zanclea</i> and/or clades of <i>Zanclea</i> associated with scleractinians based on the mitochondrial gene COI.</p

Phylogenetic trees and haplotype network analyses based on mithocondrial 16S and COI genes.

<p><b>A</b>) Phylogenetic tree based on the combined mitochondrial genes 16S and COI inferred by Bayesian inference. The clade support values are <i>a posteriori</i> probabilities (≥ 0.7), bootstrap values from Maximum Likelihood (≥ 70), and bootstrap values from Maximum Parsimony (≥ 70), in this order. Clades of <i>Zanclea</i> associated with scleractinians are boxed in different colors depending on the host coral genera. <b>B-C</b>) Most parsimonious median-joining networks of <i>Zanclea</i> associated with scleractinians inferred from mitochondrial genes 16S (<b>B</b>) and COI (<b>C</b>). The size of circles is proportional to the frequencies of specimens sharing the same haplotype. The colors of circles referred to clades found in 3A. *<i>Zanclea</i> sp. sequences from Fontana et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133084#pone.0133084.ref026" target="_blank">26</a>]</p

Coral-hydrozoan co-occurrence dataset from Corals hosting symbiotic hydrozoans are less susceptible to predation and disease

The dataset report detailed information about all coral colonies investigated in the study. This includes sampling region (Maldives or Saudi Arabia), a unique identifier for sampling site, depth class, coral genus, colony size class, a binary field indicating the occurrence on the colony of symbiotic hydrozoans, and 8 binary fields indicating the presence of signs of various coral health conditions, namely: coral bleaching, coral algae overgrowth, fish bites, gastropod (Drupella spp.) bites, white syndrome, brown band disease, skeleton eroding band disease, black band disease