Acanthoceras H. Honigmann E Urosolenia (F.E. Round & R. M. Crawford) E. Rott, H. Kling & J. Mcgregor (Coscinodiscophyceae, Bacillariophyta) das regiões centro-oeste e norte do Brasil
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Universidade Federal de Goiás
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Acanthoceras H. Honigmann and Urosolenia (F.E. Round & R. M.
Crawford) E. Rott, H. Kling & J. Mcgregor (Coscinodiscophyceae, Bacillariophyta) are planktonic
genera with cylindrical frustules, and conical valves. The small size and slightly silicified frustules
make these genera difficult to study by light microscopy analysis. Diacritical characteristics are
base on ultrastructure of the frustules. The ornamentation of valve surface is very important to the
taxonomy of the group. In Brazil few taxonomic and morphological studies have been developed
based on these genera. This work aimed to study the ultrastructural characterization of these genera
and to inventory them. The study area consists of floodplain environments on two Basin (Amazon
Basin – Amazonas and Pará States and Tocantins-Araguaia Basin – Goiás and Tocantins States).
We analyzed 454 samples (Amazon Basin n=182; Tocantins-Araguaia n= 272) in Zeis Axioscop
40 microscope, equipped with image capture Axiovision system. The ultrastructure was analyzed
in Jeol JSM 6610 scanning electron microscope. Five taxa of Urosolenia were found and studied
according to the morphology (U. amazonica, U. delicatissima, U. eriensis var. morsa, U. longiseta e
Urosolenia sp1). This genus was registered in 156 samples. A. zachariasii (Brun) Simonsen was
the only taxon of the genus Acanthoceras. Details of ultrastructure of all taxa were presented in
this study. Acanthoceras occurred in 14 samples. Both genera were present in 85% of samples
from Tocantins-Araguaia Basin. In general, representatives of Urosolenia were found in
oligotrophic environments with low pH, while Acanthoceras occurred in alkaline and highly
transparent environments, from mesotrophic to eutrophic conditions. Urosolenia was widely
distributed along the study area. U. amazonica and U. delicatissima were first records for Brazil.
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MORAIS, Raquel Rezende de. Acanthoceras H. Honigmann E Urosolenia (F.E. Round & R. M. Crawford) E. Rott, H. Kling & J. Mcgregor (Coscinodiscophyceae, Bacillariophyta) das regiões centro-oeste e norte do Brasil. Orientadora: Ina de Souza Nogueira. 2014. 81 f. Dissertação (Mestrado em Biodiversidade Vegetal) - Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, 2014.