Genus Ecballocystis was proposed by Bohlin in 1897 starting from the description of type species Ecballocystis pulvinata, gathered in Brazil (Rio Grande do Sul State). Genus is considered of rare occurrence in the world. In Brazil, the species E. pulvinata has been cited more frequently. Several specimens identified as E. pulvinata gathered from different streams were taxonomically evaluated through morphometrical studies, and the occurrence of the species in relation to some environmental variables was verified. Considerable morphological amplitude was verified in the populations evaluated, probably related to the environmental variations. The characteristic that varied more was the chloroplasts number, suggesting that this attribute is not a reliable taxonomic character. All samples of E. pulvinata were gathered in rocky bed and fast current streams (38.5-75.0 cm s-1) indicating that these habitat conditions are the most appropriate to its development.
Brazil; Ecballocystis; morphometry; stream; taxonomy
