RESUMO Este artigo apresenta os resultados da análise estatística dos parâmetros microbiológicos, físicos e químicos relacionados à qualidade da água utilizada em campos de arroz no sul do Brasil. Os dados foram coletados durante três anos agrícolas consecutivos, dentro da estrutura de um programa abrangente de monitoramento. Os indicadores utilizados foram: potencial de hidrogênio, condutividade elétrica, turbidez, nitrogênio, fósforo, potássio, cálcio, coliformes totais e fecais. Componente Principal e Análise Discriminante indicaram diferenças consistentes entre a água de irrigação e de drenagem, da mesma forma a variação temporal demonstrou uma clara redução na concentração da maioria das variáveis analisadas. O padrão desta redução não é o mesmo nas duas regiões - isto é, a importância de cada uma das diferentes variáveis nas duas localizações é alterada. Estes resultados sugerem que as variações na qualidade da água utilizada para a irrigação do arroz foi influenciada por alguns aspectos específicos de cada região do arroz no sul do Brasil - como ação antrópica ou as condições de solo/clima em cada bacia hidrográfica.

ABSTRACT This paper presents the results of the statistical analysis of microbiological, physical and chemical parameters related to the quality of the water used in rice fields in Southern Brazil. Data were collected during three consecutive crop years, within structure of a comprehensive monitoring program. The indicators used were: potential hydrogen, electrical conductivity, turbidity, nitrogen, phosphorus, potassium, calcium, total and fecal coliforms. Principal Component and Discriminant Analysis showed consistent differences between the water irrigation and drainage, as the temporal variation demonstrated a clear reduction in the concentration of most of the variables analyzed. The pattern of this reduction is not the same in the two regions - that is, the importance of each of the different variables in the observed differentiation is modified in two locations. These results suggested that the variations in the water quality utilized for rice irrigation was influenced by certain specific aspects of each rice region in South Brazilian - such as anthropic action or soil/climate conditions in each hydrographic basin.

Bacilos entomopatogênicos são bactérias observadas principalmente no solo, consideradas importantes agentes no controle biológico de doenças e pragas da agricultura. No entanto, existem poucos estudos que relatam a influência das práticas agrícolas nas populações de Bacillus spp. Essa pesquisa objetivou avaliar a freqüência de bactérias entomopatogênicas pertencentes ao gênero Bacillus obtidas de amostras de solo coletadas no ano agrícola de 2006/2007 de diferentes sistemas de cultivo de arroz irrigado da EEA-IRGA, Cachoeirinha (RS). Foram analisadas 36 amostras de solos, oriundas de três sistemas de plantio de arroz irrigado, pré-germinado (SPG), convencional (SPC), plantio direto (SPD) e de uma área sem plantio de arroz (C). Para tanto, um grama de solo foi diluído, pasteurizado e inoculado em Ágar Nutriente (AN), incubado a 30 °C, por 24 horas. Todas as unidades formadoras de colônias bacterianas (UFC) foram repicadas em meios seletivos e as espécies, B. thuringiensis, B. sphaericus e B. cereus, foram identificadas por microscopia de contraste de fase. Os resultados revelaram que não houve diferença significativa entre os sistemas de plantio analisados. Por outro lado, a frequência de Bacillus spp. variou entre as diferentes fases do plantio de arroz nos períodos amostrados. A irrigação foi o principal fator que contribuiu para a variação da frequência dos Bacillus em sistemas de plantio de arroz irrigado da EEA-IRGA.

Entomopathogenic Bacillus are bacteria found mainly in the soil and are considered important agents in biological control of agricultural diseases and pests. However, there are fen studies describing the influence that different agricultural practices have on Bacillus spp. populations. This study proposes to determine the occurrence frequency of entomopathogenic bacteria from Bacillus genus in soil samples. These were collected during the agricultural year 2006/07 from different irrigated rice cultivation systems used in the EEA-IRGA plantations in Cachoerinha, State of Rio Grande do Sul, Brazil. We analyzed 36 soil samples taken from three irrigated rice plantation systems; (i) Pre-germinated (SPG); (ii) Conventional (SPC); and (iii) Direct plantation (SPD) and a fourth sample from a non-planted area (C). In each test one gram of soil was diluted, pasteurized and inoculated in Nutrient Agar (NA) and incubated for 24 hours at 30°C. All the bacteria colony-forming units (CFU) were transplanted to selective mediums and the B. thuringiensis, B. sphaericus and B. cereus species were identified using a phase contrast microscope. No significant differences in the occurrence frequencies were found in the soil samples of all plantation systems analyzed. On the other hand, the Bacillus spp frequency varied in the sampled period during the different growing phases of the irrigated rice in the EEA-IRGA plantations evaluated. Irrigation was the main factor contributing to variation of the Bacillus in the plantations.

No presente estudo investigamos o polimorfismo em três espécies de Chauliognathus Hentz, 1930 (Coleoptera, Cantharidae), analisando a variação geográfica no padrão de coloração dos élitros em C. flavipes, C. fallax e C. octomaculatus. Estas espécies pertencem ao complexo mülleriano chamado "amarelo-preto". São encontradas formando grandes agregados sobre as plantas que utilizam como substratos de alimentação e apresentam semelhança morfológica e para a coloração dos élitros e pronoto. Chauliognathus flavipes é a espécie mais freqüente e apresenta o maior número de padrões fenotípicos (8) seguidos de C. fallax e C. octomaculatus com seis e dois padrões respectivamente. Diferenças significativas nas freqüências dos padrões de coloração nas três espécies foram detectadas ao longo da área analisada. Em geral, as diferenças foram observadas entre as regiões do Estado do Rio Grande do Sul (p < 0,05), mas não dentro das regiões, exceto para a região Metropolitana. Nas três microregiões que formam a região Metropolitana encontrou-se uma correlação positiva entre o aumento da altitude e a diversidade em C. flavipes e C. fallax (r = 0,860, p < 0,01; r = 0,974, p < 0,01, respectivamente).

In the present report, we investigate polymorphism in three of the Brazilian species of Chauliognathus Hentz, 1930 (Coleoptera, Cantharidae), by analyzing the geographical color pattern variation of the elytra in C. flavipes, C. fallax and C. octomaculatus. These species belong to the mullerian complex called the "yellow-black". They are usually found in clusters on their host plants at various locations and present similarities in the external body morphology and in the color pattern of the elytra and the pronotum. Chauliognathus flavipes is the most common species with eight phenotypic classes followed by of C. fallax and C. octomaculatus with six and two phenotypic classes respectively. The analyses indicate a statistically significant difference in the frequencies of colour patterns of the three species over the entire area sampled. In general, the significant differences were observed between the regions of the State of Rio Grande do Sul (p < 0.05) but were not found within the individual regions except in the case of the Metropolitan region. That region and its three microregions demonstrated a positive co-relationship between an increase in altitude and the occurrence of diversity in C. flavipes and C. fallax (r = 0.860, p < 0.01; r = 0.974, p < 0.01, respectively).

The phylogenetic relationships of twelve species of Chauliognathus were investigated by studying the mitochondrial cytochrome oxidase I gene. A 678 bp fragment of the COI gene was sequenced to test the hypothesis that the Müllerian mimicry species of the "yellow-black" complex make up a monophyletic clade, separated from species with other colour patterns. The data set was analysed by neighbour-joining, maximum parsimony and maximum likelihood procedures. The results support a single origin of the yellow-black colour pattern during the evolution of the genus, with one main clade formed by Chauliognathus lineatus, C. tetrapunctatus, C. riograndensis, C. flavipes, C. octomaculatus, C. fallax, and another one formed by two species, C. expansus and C sp 1, plus an orange-black-coloured species. The nucleotide divergences found between C. sp 3 (black) and the other species studied fall within the level expected for species from different genera. The similarity of colour patterns of the yellow-black species has been considered an example of Müllerian mimicry by conservation of the ancestral state with some minor modifications.

Beetles of the species Chauliognathus fallax Germar 1824 are polymorphic for elytron colouration with six morphs distinguished on the basis of black pigmentation on a yellow background. We investigated samples of C. fallax taken in eight consecutive weeks aiming to determine the frequency of the morphs which were grouped, for statistical analysis, into three classes according to elytra pigmentation as well as the possible occurrence of assortative mating. Our results showed a variation in the frequency of the classes throughout the season, both in males and females, with the maximum frequency of each class at the fourth and fifth week. The three classes (A, B, C) showed the same pattern of variation, and class B was always the more frequent. To test randomness of matings two approaches were taken: in the first, we compared the frequency of each class in copulating and non-copulating insects. In the second, the frequency of each class in the whole sample was taken as the probability of occurrence of the respective class; then, using the criterion of the probability of independent events we calculated the expected proportion of copulating insects for each pair of events. Both methods gave non-significant differences, suggesting that the matings were random.

The relative population sizes of a species complex of Chauliognathus are reported, as well as their spatial distribution associated with different patches of food plants. Field work was done at Fazenda Santa Isabel, municipality of Guaíba, State of Rio Grande do Sul, Brazil. The results suggest that two mechanisms account for the reduction in food competition among the species involved: one is asynchrony in the appearance of the species in the area, and the other is aggregation in different patches of food plants. Since the species here reported show a similar colour pattern (yellow-black) the possibility of the occurrence of serial mimicry in this complex of species is dicussed.

This study presents data on morphometric variation for length and width of elytra in tive sympatric species of the genus Chauliognathus Hentz, 1830: C. flavipes Fabricius, 1781, C. octomaculatus Pie, 1915, C. expansus Waterhouse, 1878, C. fallax Germar, 1824 and C. lineatus Zwetsch & Machado, 2000. The meaning of this variation is discussed in the light of the theory of mimicry and visual communication between prey and predator. Females are larger than males in all species, except C. expansus. The analysis of variance for length of elytron as well as for width showed that the differences between species are significant for males and females; significant interaction (sex x species) was also found. The similarity in color pattern of these species, as well as similarities in the morphometric analysis, suggests that they could form a mimetic ring of the Müllerian type, which the authors suggest be called, a "yellow-black" complex.

This study presents data on the color polymorphism in Chauliognathus flavipes Fabricius 1781 (Coleoptera, Cantharidae), analysing the variations in the emergence pattern of phenotypic classes for elytra color and mating system. The frequency of the phenotypic classes varies significantly throughout the season (males:X² = 59,705; females: X² = 61,017; 10 gl; p<0.001) being similar in males and females. The frequency of classes does not differ significantly among the insects that were copulating and those that were not copulating at the time of collection, i.e., the matings are random for elytra color patterns. The variations observed in frequency of phenotypic classes are not influenced by factors associated with sex. Furthermore, the elytra color patterns probably do not influence the individuals' ability to copulate.