Molecular phylogenetic analyses show that ciliate genus Pelagohalteria (Ciliophora, Spirotrichea) belongs to subclass Hypotricha instead of Oligotricha

BARROS M. B. L.; MONTEIRO DE CASTRO L. A.; HARADA M. L.; BORGES B.; PAIVA T. DA S.; KÜPPERS G. C.

Congreso; 61º Congresso Brasileiro de Genética; 2015

Oligotrichs s. l. are spirotrichous ciliates which exhibit a generally ovoid to obconical body, with reduced somatic ciliature, well developed adoral membranelles, and are adapted to life in the water column. They are bacterial feeders occurring in marine and freshwater plankton communities, but also in temporary ponds, bromeliad tanks and some edaphic environments. Traditionally, the Oligotricha included oligotrichids, choreotrichids, and halteriids. However, molecular phylogenetic analyses based on ribosomal genes have placed halteriid genera Halteria and Meseres within the Hypotricha (= Stichotrichia), thus contradicting previous morphology-based classifications, and suggesting that halteriid body architecture arose independently from oligotrichs. This is referred to in the literature as the ?Halteria paradox?. In the present study, we infer, for the first time, the phylogenetic positionof halteriid genus Pelagohalteria, based on analyses of the 18S-rDNA gene obtained from a strain of Pelagohalteria cf. cirrifera from Argentina. To do so, DNA was extracted from ethanol fixed cells, and PCR was performed with group-specific primers. The obtained 18Ssequence, 130 of other spirotrichs, representing Hypotricha (including Halteriidae) and Oligotricha, plus three outgroup sequences (Protohypotricha) were aligned using the computer program MUSCLE. The affinities of Pelagohalteria to the other terminals were hypothesized from a neighbor-joining tree, maximum-likelihood and Bayesian phylogenetic analyses, performed in MEGA, RAxML and MrBayes, respectively. In all results, Pelagohalteria clustered as sister-taxon of Halteria. Monophyly of Halteriidae had weak support and was sensitive to variations in taxa-sample. Halteriids, Pelagohalteria included,were consistently placed within the Hypotricha and distant from Oligotricha, corroborating previous molecular studies.