Denticula, Hantzschia and Tryblionella (Bacillariaceae, Bacillariophyta) from northwestern Ceará freshwaters

Abstract Diatoms constitute a representative portion of the algal community freshwater aquatic environments, but their studies are centered mostly in south and southern regions Brazil, making microalgae biodiversity water bodies semiarid practically unknown. In state Ceará, few records Bacillariaceae region generally not identified at specific level. Denticula, Hantzschia, Tryblionella worldwide distributed diatom genera that belong to family Bacillariaceae. The group is characterized by raphe located on channel, internally supported silica extensions, fibulae. This taxonomic study found northwestern Ceará state. Planktonic periphytic samples were collected four hydrographic basins, which influenced climate, northeastern Brazil. Fourteen infrageneric taxa identified, described, illustrated, all being pioneer citations for Ceará. present highlighted underestimated diversity diatoms need cover undersampled or never explored significantly contribute knowledge flora its distribution Brazilian environments.