Nutritional status response of Daphnia laevis and Moina micura from a tropical reservoir to different algal diets: Scenedesmus quadricauda and Ankistrodesmus gracilis

The accumulation of lipid reserves was investigated in two common cladoceran species typical of neotropical freshwaters. Experiments were performed in order to measure differential accumulation of lipid reserves in response to two algal diets, S. quadricauda and A. gracilis. The larger D. laevis fed with the Ankistrodesmus diet accumulated a higher amount of total lipids. The average lipid content for both diets was 11.1 percent and 22.1 percent dry weight for Scenedesmus and Ankistrodemsus, respectively. This difference was found to be highly significant. The superior nutritional quality of A. gracilis was confirmed by the experiments using the smaller Moina micrura. This cladoceran accumulated 11.4 percent and 19.9 percent of the average dry weight of lipids from Scenedesmus and Ankistrodesmus, respectively. The study also found that most lipid reserves are concentrated as triacylglycerols in both cladocerans. The relative contribution of this class of lipids also varied according to the diet. For Daphnia, for instance, the average triacylglycerol levels varied from 6.2 to 11.0 with the Scenedesmus and Ankistrodesmus diets, respectively

Water maze learning in rats with neocortical and hippocampal lesions

Experiments were carried out in oreder to determine whether groups of rats (N+7) with unilateral or bilateral ablation of the neocortex or with removal of the neocortex plus the hippocampus of either hemisphere could learn to escape from a tank of water (57 cm in diameter) by climbing a visible platform when trained for 6 consecutive days. Comparison of the swimming escape latencies among groups showed no statistically significant differences, although over the first four trial blocks the decorticate group was slower (77.19 ñ 39.31, 52.45 ñ 32.37, 31.18 ñ 13.62 and 15.74 ñ 10.94 s, respectively) than the other groups, whose latencies ranged from abouth 70 s (the longest in the first trial block) to 8 s (the longest in the fourth trial block). Nevertheless, hemi-and bilateral decoricate rats were still able to learn the water maze task. The same was observed for hemidecorticate plus hemihippocampectomized rats. These results indicate that the neocortex and the hippocampus in the absence of the neocortex, is essential for spatial localization using a cue-learning strategy