A fluorescence method to detect cyanophycin in the symbiotic cyanobacterium, Anabaena azollae.

The cyanophycin content of the heterocystous nitrogen-fixing symbiotic cyanobacterium, Anabaena azollae, which inhabits an ovoid cavity in the dorsal leaf lobes of the fern, Azolla filiculoides, is seldom analyzed. To study the cyanophycin content in vegetative cells and heterocysts of A. azollae, we used three fluorochromes: aluminum trichloride, lead citrate and Wilson citroboric solution and Coomassie brilliant blue. Blue and yellow fluorescence were emitted from the polar nodes and cytoplasm cyanophycin granules of the heterocysts when stained with the three fluorochromes. The cyanophycin observed without staining or with Coomassie brilliant blue staining did not alter the results obtained using the fluorochromes. We found that aluminum trichloride, lead acetate and Wilson citroboric solution could be used to detect cyanophycin.

A study on the digestive physiology of a marine polychaete (Eulalia viridis) through microanatomical changes of epithelia during the digestive cycle.

As for many invertebrates, the gut of marine polychaete species has key physiological functions. However, studies integrating microanatomical descriptions with physiological processes are scarce. The present investigates histological, histochemical and cytological changes in the alimentary canal during the digestive cycle of the marine annelid Eulalia viridis, a species that combines opportunist scavenging, predation and cannibalistic behavior. The gut is comprised of an eversible pharynx, esophagus, intestine and rectum. Three main phases of digestion were identified, namely, resting/secretory, absorptive and excretory. The intestinal epithelium is complex and exhibited the most significant changes regarding intracellular digestion, excretion and storage. Conversely, the pharynx and esophagus were chiefly important for enzyme secretion. The results also indicate the existence of two distinct types of secretory cells in the intestine, with likely distinct physiological roles. Some similarities have been found between the intestinal epithelia and the molluscan (especially cephalopod) digestive gland, as, for instance, the shedding of apical corpuscles by digestive cells at posterior stages of digestion. The findings indicate that the digestive process in this worm is complex and related to the many physiological roles that cells need to play in the presence of reduced organ differentiation.

How symbiogenic is evolution?

When new entities are formed by the integration of individual organisms, these new entities possess characteristics which go beyond the sum of the individual properties of each element of the association, resulting in the development of new attributes and capacities as an integrated whole. In this process, these new entities also agglutinate and dynamize synergies not present in the individual organisms. In this sense, evolution is a dynamic process that evolves not in the way of perfection or progress, but in the way of adaptation to new conditions. Symbiogenesis, as an evolutionary mechanism, allows a coherent conceptual rupture with some evolutionary ideas of the past and, at the same time, shows and builds a new approach to life, based on solid evolutionary ideas, expanding evolution to an adequate level of integration with the more recent data in biology. These ideas and concepts should be integrated in a post-neodarwinian approach to evolution that needs further attention from the scientific community. The development of a Symbiogenic Theory of Evolution could contribute toward a new epistemological approach of the symbiotic phenomenon in the evolutionary context. This, in our point of view, could be the beginning of a new paradigm in science that rests almost unexplored.

Symbiogenesis: the hidden face of Constantin Merezhkowsky.

Constantin Merezhkowsky is celebrated today for his theory of symbiogenesis, postulated in the early decades of the twentieth century, particularly that chloroplasts were symbiotic cyanophytes (cyanobacteria). While biologists point singularly to what they see as his heroic achievement, its neglect and subsequent rediscovery, we introduce a broader and much more complex perspective on his science, his troubled life and career. We present a view of Merezhkowsky as zoologist, anthropologist, botanist, philosopher, and novelist. We explain the genesis of his theory of the origin of chloroplasts and of nucleus and cytoplasm as symbionts, as well as his depiction of the geo-chemical context of the origins and early evolution of life on earth. We also disclose his sordid social and political activities, his eugenics and racist writings, his paedophilia, and his metaphysics. Finally, we describe the context of his elaborate suicide in 1921.