ABSTrACT. Since molecular phylogenies of stichotrich ciliates started to be published, some remarkable contradictions to morphology-based classifications have been reported, such as the Convergent Evolution of Urostylids and Uroleptids (CEUU) hyphothesis, the Halteria paradox, the polyphyly of Oxytricha and of Stichotrichia. We hypothesized the internal phylogeny of 18S-rDNA from 53 morphological species of stichotrichs and their relationships with Hypotrichia and Oligotrichia using parsimony and neighbor-joining methods, including new data from Pseudouroleptus caudatus and Strongylidium pseudocrassum. Competing phylogenetic scenarios were compared using statistical tests, and the results suggest the reconsideration of both CEUU and the position of Halteria among flexible-body oxytrichids. The polyphyly of Oxytricha was not rejected and the monophyly of Stichotrichia was accepted based on parsimony analysis if Pseudoamphisiella is considered an external (discocephalid related) taxon.

ABSTRACT. The São Gonçalo Channel is of great importance to the conservation of local biodiversity; it also is a water supply source of the city of Pelotas, Brazil, and the surrounding region. We examined the mutagenic activity of its waters. The following items were seasonally investigated in Allium cepa root radicular meristem cells: mitotic index, mitotic anomalies, interphase anomalies, and total anomalies. Water samples were collected from four different stations, Lock Dam, Santa Bárbara Channel, Pelotas Creek, and Barra do Laranjal. A drinking water negative control was used. For each sampling station, 8000 cells were counted, 2000 of which by repetition. The data were computed on a database (SPSS), and then analyzed by the chi-square test and the Mann-Whitney U-test. In 2005, the channel water provoked a significantly greater number of anomalies than the control water. The number of anomalies increased in 2007. This suggests that there was an increase in toxic substances in the channel over the years.