Dietary nutrient allocation to somatic tissue synthesis in emerging subimago freshwater mayfly <Emphasis Type="Italic">Ephemera danica</Emphasis>

Background

The relative importance of nutrients derived from different sources for tissue synthesis is crucial for predicting a species responds to changes in food availability. The ecological and physiological strategies that govern the incorporation and routing of nutrients for reproduction are often well understood. However, the role and adaptive value of both species and individual variation during early life-stage remain elusive. In freshwater systems, dietary nutrient allocation to somatic tissue should be favoured when dietary source peaks and resource limitation may hinder flexible resource allocation. We used carbon and nitrogen stable isotopes (δ¹³C and δ¹⁵N) to examine metabolic nutrient routing and resource allocation from four dietary sources used to biosynthesize three somatic tissues of emerging subimago Ephemera danica. Aquatic emerging insects, such as the mayfly E. danica, are well suited for such studies. This is because, while burrowing nymph phase is a detritivores feeders with several early life-stages of metamorphosis, adult insects do not feed during this period but do utilize energy.

Results

Constructed models to predict percent proportional contribution of source to tissue showed that terrestrial detritus was the dominant nutrient source for abdomen, head and wing with mean values of 57%, 65% and 73%, respectively. There was evidence for differential resource allocation, as insect partitioned periphyton and sediment (but also seston) elements for tissue synthesis. Utilizing individual-specimen based relationship in isotope value; we derived tissue specific isotopic niche estimates, for the different tissue-source combinations.

Conclusions

Results indicate that tissue selection is crucial for isotopic ecological measurements in arthropods. Mayfly has long been used as bio-indicator of freshwater ecosystems and their larvae show rapid response to environmental changes. In light of the recent evidence of drastic reduction in flying insect mass in Germany, developing a system using isotopic tools to trace nutrient flow in this important taxon will assist conservation and management efforts.

     

Participatory Extension as Basis for the Work of Rural Extension Services in the Amazon

Public extension services play a key role in the implementation of strategies for rural development based on the sustainable management of natural resources. However, the sector suffers from restricted financial and human resources. Using experiences from participatory action research, a strategy for rural extension in the Amazon was defined to increase the efficiency and the relevance of external support for local resource users. This strategy considered activities initiated and coordinated by local people. Short-term facilitation visits provided continuous external support for the purpose of establishing locally based planning and learning mechanisms. In collaboration with the municipality of Muaná in the Eastern Amazon, the strategy was tested in two traditional communities – Monte Moriat and Boa Esperança. Both communities recognized as most important the need to reduce their dependence on açaí (Euterpe oleracea Mart.), the principal source of food and income. This forest resource has been overexploited, seriously affecting açaí stands and diminishing the forest benefits fundamental for survival. Two local groups decided to raise chickens as a way to reduce nutritional problems and as an alternative source of income. Supported by monthly, short-term planning and evaluation visits, the groups managed to achieve significant progress in their endeavor. The groups identified (1) the control of decision-making and information, and (2) the absence of external obligations to be the greatest advantages of the development initiative. The study confirmed the potential of participatory strategies for public extension in the Amazon. Special attention was given to realistically define the role of forests for local development. However, drastic measures are necessary to smooth the way for real participation in governmental and non-governmental organizations acting in the Brazilian Amazon.     

New fluoro intermediates for herbicidal sulfonylureas

New pyrimidine and triazine intermediates for herbicidal sulfonylureas are prepared as follows: 2,4-dichloro-6-methylpyrimidine is converted via a halogenation, halogen exchange and substitution sequence to 2-amino-4-trifluoromethyl-6-trifluoromethoxypyrimidine. New fluoromethyl-triazines are available starting from guanidine, trichloroacetonitrile and difluoroacetic anhydride, or alternatively from thiocarbamoyl guanidine and chlorodifluoroacetic ester ring closure. To obtain new o-fluoroalkyl-benzenesulfonamide precursors, o-chlorobenzaldehyde was fluorinated with sulfur tetrafluoride, or a bromobenzene derivative was subjected to a substitution reaction with sodium pentafluoropropionate. Sulfonylureas derived from trifluoromethylpyrimidines with an m-methylthio substituent are selective post-emergence herbicides in cotton, presumably due to sulfone metabolization. Selectivity in wheat is obtained by combining 4-methoxy-6-trifluoromethylpyrimidine with a lipophilic difluoromethyl-benzenesulfonamide moiety. Also in the difluoromethyl-triazine series, the combination with the difluoromethyl-benzenesulfonamide moiety is a good choice for wheat selectivity. Chlorodifluoromethyl- and trifluoromethyltriazines, however, combine better with an aromatic ester for best activity and selectivity in wheat. Selected compounds are undergoing broad field tests in wheat.