The study investigated the effects of environmental factors (salinity, pH, ions and activation media) on sperm motility (activation rate, duration of quick movement, and lifespan) and fertilization rate of Phascolosoma esculenta. The results showed that spermatozoa in the coelom and nephridium are able to move quickly. The optimal salinity was 14.64 to 43.35 and the optimal pH was 6.46 to 9.53 for sperm activation and motility, whereas the ranges for fertilization were narrower (18.56 to 30.3 for salinity and 6.46 to 8.61 for pH). Of the ions studied, Na+ was indispensable for sperm motility and fertilization, and Ca2+ and Mg2+ were necessary for fertilization. P. esculenta sperm could not fertilize eggs and have short lifespans in 200 to 600 mmol/L NaCl and KCl solutions. Furthermore, they could not be activated or move in 200 to 600 mmol/L CaCl2, MgSO4, and sucrose solutions.
The functional-trait approach to communities focuses on the distribution of traits and on their variations in communities along environmental gradients. We devised a pattern-oriented demarche to predict specific leaf area (SLA) distribution in three plant communities located along an environmental gradient governed by soil fertility and nutrient stress in subalpine gypsic dolines. An individual-based model incorporating physiological mechanisms simulated the growth of thirty functional groups varying in leaf traits (SLA and correlated leaf life-span) and nitrogen (N) stress tolerance which competed with their neighbours for access to light and nitrogen. The SLAs of these groups encompassed the range of SLAs measured in the sites. Leaf traits governed the daily temperature-dependent processes involved in capturing resources (N and light), biomass synthesis and loss, and the value of the parameter Nc governed the decrease in growth rate of organisms according to a decline in N supply. Biomass drove the competitive ability of each plant in its neighbourhood. A soil sub-model described the amount of available nitrogen in the soil. Simulations yielded performances of functional groups according to the availability of nitrogen in the soil. An integration function, which simulated the effects of the dominance process according to the performances of the groups, yielded the frequency distribution of the groups at the community scale. The SLAs patterns were deduced from this distribution. Comparison of simulated and measured distribution of SLA frequency (Kendall tests) showed the model’s ability to reproduce realistically SLA distributions along a nutrient gradient; measured SLA community patterns at lower, medium and higher fertility levels matched simulated SLA distribution with respectively 5 to 30, 82, and 154 kg N ha−1 year−1. These results demonstrate the efficacy of a strategy based on a pattern-oriented approach and the use of functional traits and trade-offs to predict the distributions of traits and their variations in communities along an environmental gradient.
Authors:Yasir H. Siddique, Falaq Naz, and Smita Jyoti
Siddique , Y. H. , Naz , F. , Jyoti , S. ( 2014 ) Effect of curcumin on lifespan, activity pattern, oxidative stress, and apoptosis in the brains of transgenic Drosophila model of Parkinson’s disease . BioMed Res. Int. 2014 , 1 – 6