The effect of fish predation on Cyclops life cycle

Two populations of Cyclops abyssorum tatricus studied in neighbouring alpine lakes in Tatra Mountains (southern Poland) differed in their life cycles. In the lake with planktivorous fishes, Cyclops was typically monocyclic, with highly synchronized reproduction during two winter months, while in the fishless lake its reproduction was asynchronous and continued for six months. Direct and indirect effects of fish predation on Cyclops life cycles are discussed.     

Megachromosomes in tissue culture ofAllium

Chromosome studies have been conducted on the long-term callus cultures of threeAllium species:A. porrum (2n=32),A. tuberosum (2n=32) andA. fistulosum (2n=16). In cultures ofA. fistulosum several interesting cytological abnormalities were observed. They included direct elimination of chromatin from nuclei, multiple chromosome fusions and formation of polycentric and megachromosomes. The rate of abnormalities increased with the time of culture. Allium fistulosum may provide an excellent model system to analyse cytogenetic and molecular aspects of callus-induced genomic changes and, thus, somaclonal variation.     

E.s.r. radiation studies of erythrocyte membrane haemoglobin interaction.

The dependence of the yield of free radicals in gamma-irradiated, freeze-dried erythrocyte membranes on their haemoglobin content was studied. A non-monotonous relationship was found--different from that observed in mixtures of freeze-dried membranes and haemoglobin, which suggests the existence of radiation-energy transfer between the membranes and bound haemoglobin.