The mechanism that enables the coexistence of apparently very similar species is fundamental in understanding the diversity of natural communities. The ranges of reactions of the three Daphnia clones in the presence of toxic compounds and fish kairomones were studied in laboratory. The ranges were based on differences in body length, spine length and fecundity (number of eggs in a brood chamber) during first three reproductions. The ranges of reactions of the three clones differed dramatically. The range of D. galeata and D. hyalina hardly overlapped, while that of a D. galeata x hyalina hybrid clone was significantly broader than the ranges of either parental species. The observed diversity of ranges of reactions probably enables the coexistence of closely related species in the variable environment of natural lakes.
The (15)N, (13)C and (1)H NMR chemical shifts were measured for methylamine in the gaseous and liquid phase. The gas to liquid shifts revel the deshielding effects for all investigated nuclei. It is shown that the hydrogen bonding is responsible for the largest changes, which are observed for the nitrogen and amino hydrogen atoms as well. The CHF-GIAO calculations indicate that the cyclic trimer of methylamine exhibits the shielding changes, which are in quantitative agreement with the gas to liquid shifts.
2,l,3-Benzoselenadiazole-5-carbaldehyde 5 has been prepared in 53% overall yield from 5-methyl-2,l,3-benzoselenadiazole 1, by a four-step synthesis. Compounds 1-5 and 2,1,3-benzo-selenadiazole 8 have been analysed by 1H, 13C, 15N and 77Se NMR spectroscopy, and structural implications are discussed. Some imines and diimines were prepared from 5, but low solubility in organic solvents made these compounds of little interest for further studies.
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