Theory predicts that females should track resources while making decisions about where to reproduce, and males should track females. However, when males create the resource that females require, female settlement follows that of males. In this situation, how do individuals make settling decisions and what are the fitness consequences of these decisions? Here, I test the hypothesis that environmental factors (wind direction and velocity) affect optimal nest placement and orientation, and thus male and female settlement, in Baya weaver Ploceus philippinus colonies. Nests experimentally placed in windward locations with entrance tubes oriented toward the wind were more likely to lose clutches of artificial eggs than were nests placed in other combinations of placement and orientation. Correspondingly, males built their nests strongly clustered on the leeward side of colony trees, with entrance tubes oriented away from the wind. However, females did not discriminate amongst natural nests on the basis of nest placement or orientation. This may be because the effect of wind on the success of natural nests was small and was overwhelmed by other causes of nest loss. I suggest that, in some situations, female preference may remain undetected because the options available to females are constrained by preceding settlement decisions by males. In these cases, it is necessary to manipulate male distribution outside the range of natural variation to gain a better understanding of selective pressures imposed by female preferences. 相似文献
Gamma-aminobutyric acid (GABA), a non-proteinaceous amino acid, is reported in prokaryotes and eukaryotes, since ancient times. However, it has gained attention in the present time because of its rapid accumulation during stressed conditions in plants as well as in the cyanobacteria. In plants, it regulates the number of physiological processes such as pollen tube growth, root growth, TCA cycle, N2-metabolism, and osmoregulation. Several biotic and abiotic stresses prevail in the environment, which lead to enhanced accumulation of reactive oxygen species (ROS) thus causing oxidative damage. However, a rapid increase in the accumulation of GABA during stress in various plant forms like bacteria, cyanobacteria, fungi, and plants indicates its putative role in stress regulation and acclimation. This review summarizes the biosynthesis of GABA, its role in abiotic stress tolerance, and its crosstalk with ROS, nitric oxide, Ca+2 ions, phytohormones, and polyamines in stress acclimation.
Effect of the low level of copper exposure on nonenzymatic antioxidants was studied in a freshwater fish Channa punctatus (Bloch.). Fish were exposed to cupric chloride at the concentration of 10 ppb for 4 wk (28 d) in a static culture condition.
Copper significantly (p < 0.001) increased the serum ceruloplasmin level and total iron-binding capacity. A significant (p < 0.05) increase in reduced glutathione level was recorded in all of the tissues. With regard to nonprotein thiols, copper
decreased their level in the liver, but increased it in the gill. The protein-bound thiols remained unaltered except for an
increase in the liver. Metallothionein (MT) induction was observed in liver only. Copper exposure had no significant effect
on the ascorbic acid level and induced no lipid peroxidation over control values. It is suggested that by modulating the ceruloplasmin
level, copper indirectly protects the fish, as it facilitates conversion of pro-oxidant iron to nonoxidant iron. It also induces
an array of antioxidants that may be beneficial to fish in the case of oxidative stress resulting from chemical pollutants. 相似文献
Protoplasma - Stroke is one of the main causes of mortality and disability in most countries of the world. The only way of managing patients with ischemic stroke is the use of intravenous tissue... 相似文献