Sodium and nitrate favor the steady state of cyanobacteriain a semiarid ecosystem

This study characterized steady state events (SS) in a semiarid reservoir (Brazil) dominated by cyanobacteria for 130 weeks, and evaluated the influence of different abiotic variables on their occurrence. It was hypothesized that, in semiarid reservoirs, steady state events are independent from seasonality and influenced by high nutrient concentrations, and steady state periods show low variation of species. Our data revealed the occurrence of SS events in both the dry and wet seasons. Higher concentrations of nitrate and sodium together with higher values of color favored the development of SS. Species composing the SS dominated by Microcystis aeruginosa (Kützing) Kützingwas correlated with higher sulfate concentrations, while higher values of turbidity and sodium concentrations favored the SS of Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Suba Rajuand Planktothrix agardhii (Gomont) Anagnostidis and Komárek. The results supported the hypothesis and showed the importance of variables rarely evaluated in works of this nature, such as sodium and sulfate in SS establishment of cyanobacteria.

Determination of Behavior and the Stimuli-dependent Transition of the Probability of Behavioral Expression: A Study on the Fluctuation of Behavioral State as Represented by the Level of Body Movement Suppression

The behavior of most animals is extremely complex. Despite accumulating knowledge about the mechanisms of neurons and nervous systems, which regulate these complex behaviors, we have little understanding about how these mechanisms function. In the present study, we analyzed the exploratory behavior of mice repeatedly exposed to a novel context and tracked the changes in the fluctuation patterns of the accumulated level of body movement suppression (BMS). As a result, we found that the fluctuation in BMS can be divided into two phases, which show a pattern of progressive transition from the initial state to the context-dependent and stable equilibrium state. In the former, transition phase, the level of BMS was easily affected by the number of exposures and mental status of mice. However, in the latter, equilibrium phase, the level of BMS was only dependent on the environmental stimuli involved in the context. On the basis of the results, we suggests here a model that explains the determination of complex behavior observed in higher animals by means of the probability of behavioral expression.