Morphology and molecular phylogeny of Novistrombidium sp. (Ciliophora, Oligotrichia) from Argentina

KÜPPERS G. C.; CLAPS M. C.; PAIVA, T. DA S.; BORGES, B. DO NASCIMENTO

Congreso; XXX Congresso Brasileiro de Zoologia; 2014

The Salado River basin located in the Buenos Aires province, Argentina, is an extreme environment with highly mineralized water as a result from the weathering of evaporitic sediments, and presents natural and artificial tributaries. Plankton samples were obtained in the course of a limnological survey in the Salado River and several of these tributaries, during March and October 2011. This work aims at describing the morphology and molecular phylogeny of Novistrombidium sp. that was found in one of these artificial channels, namely the Canal del Este in the locality of Mechita. In the laboratory, raw cultures were established with water from the sampling site and crushed wheat kernels were added to promote bacterial growing that served as food source for the ciliates. Novistrombidium sp. was studied under the stereomicroscope and the brightfield microscope by means of live observation and protargol impregnation. For silver staining, the ciliates were picked from the cultures with specially designed micropipettes and fixed in Bouin solution. About 100 cells were transferred through several mineral water bathes and finally stored in alcohol for DNA extraction and amplification. The 18S-rDNA gene sequence was used to hypothesize the phylogenetic affinities of Novistrombidium sp. among other oligotrichs by means of Bayesian inference, maximum likelihood and maximum parsimony analyses. Novistrombidium sp. measures 52 µm x 38 µm on average and has an apical protrusion surrounded by 30-35 anterior membranelles, which are separated from the 11-14 ventral membranelles by 2 thigmotactic membranelles. The girdle kinety is spiraled around the cell and the ventral kinety is located below the right end of the girdle kinety. Cortical extrusomes are distributed equidistantly, mainly along the course of the girdle kinety. The macronucleus is globular. The contractile vacuole is located anteriorly on the left, but pulsation was not observed. The phylogenetic analyses indicate that the genus Novistrombidium is polyphyletic. The sequence of Novistrombidium sp. unambiguously clustered with Parallelostrombidium sp., branching off near Novistrombidium sinicum and N. orientale. Compared to other congeners, Novistrombidium sp. from Canal del Este could represent a new species.