Diversity of Tabanidae,Asilidae and Syrphidae (Diptera) in natural protected areas of Yucatan,Mexico

Although dipteran communities play a fundamental role in the ecosystem, little is known about their diversity, richness and abundance in different environments. In spite of the importance of Natural Protected Areas (NPAs) as reservoirs of biological diversity, information about community parameters of most insects, including Diptera, are practically unknown in these areas. In this study, we described and compared the composition and structure of Dipteran communities (considering Tabanidae, Asilidae and Syrphidae families) within six (NPAs) of Yucatan, Southeast Mexico, comprising four main vegetation types: seasonally flooded forest, tropical deciduous forest, semi-deciduous tropical forest and coastal dune. We used Malaise-traps to collect samples during a period of two days, twice a month, for one year (2006–2007) within each NPAs. A total of 6 910 specimens belonging to 33 genera and 78 species/morphospecies were recorded. Our results show that the four vegetation types host a vast diversity of dipterans. However, species richness, abundance, diversity and similarity were higher in the communities of tropical deciduous forests compared with those from semi-deciduous forests and coastal dune vegetation, probably as a result of microhabitat differences between sites. We highlight the role of tropical deciduous forests as a refuge for Diptera species and the importance of these forests for conservation of dipteran communities.     

Peanut nodulation kinetics in response to low pH.

In this work, the peanut nodulation kinetics by acid-sensitive and tolerant isolates under acid stress condition was analyzed. The results demonstrated that the acid pH produced a decrease in the number of nodules formed only when peanut plants were inoculated with acid-sensitive isolates but increased steadily by the addition of 10 mM Ca2+, reaching higher values than those obtained at pH 7.0. On the contrary, the peanut nodulation by acid-tolerant isolates was not affected by this stressing condition. These data suggest that acid-tolerant isolates could be used as a potential source of strains for preparing highly effective inoculants for peanut plants growing in acid soils.     

Density Gradient Centrifugation Studies on Lymphocytic Choriomeningitis Virus and on Viral Ribonucleic Acid

Lymphocytic choriomeningitis (LCM) virus, Traub strain, was purified from BHK-21 tissue culture medium. The virus was then analyzed by equilibrium centrifugation and rate zonal centrifugation in sucrose gradients. A buoyant density in sucrose of 1.18 g/ml was found and the S(20, w) value was estimated to be about 470 to 500S. Furthermore, the (3)H-uridine-labeled ribonucleic acid (RNA) from virus was extracted from LCM virus and analyzed by rate zonal centrifugation. Two major and one minor single-stranded RNA components were found with sedimentation coefficients of 28, 22, and 18S.