Untangling the Phylogeny of Amoeboid Protists1

ABSTRACT. The amoebae and amoeboid protists form a large and diverse assemblage of eukaryotes characterized by various types of pseudopodia. For convenience, the traditional morphology‐based classification grouped them together in a macrotaxon named Sarcodina. Molecular phylogenies contributed to the dismantlement of this assemblage, placing the majority of sarcodinids into two new supergroups: Amoebozoa and Rhizaria. In this review, we describe the taxonomic composition of both supergroups and present their small subunit rDNA‐based phylogeny. We comment on the advantages and weaknesses of these phylogenies and emphasize the necessity of taxon‐rich multigene datasets to resolve phylogenetic relationships within Amoebozoa and Rhizaria. We show the importance of environmental sequencing as a way of increasing taxon sampling in these supergroups. Finally, we highlight the interest of Amoebozoa and Rhizaria for understanding eukaryotic evolution and suggest that resolving their phylogenies will be among the main challenges for future phylogenomic analyses.     

The effect of humic acids,fractionated according to molecular mass,on the formation and mutagenicity of N-methyl-N-nitrosourea

Fractions of humic acids (HA-K⁺) of molecular mass between 500 and 300 000 and exceeding 300 000 showed a very high nitrite depleting ability, whereas the fraction of HA-K⁺ with molecular mass lower than 500 had little or no such effect. Autoclaving HA-K⁺ (121 °C, 20 min) decreased the nitrite-depleting ability to about a half. This observation correlates with the results of mutagenic studies in Arabidopsis thaliana, demonstrating the inhibitory effect of HA-K⁺ and its fractions on the formation of mutagenic N-methyl-N-nitrosourea (MNU) from the nitrosation mixture of N-methylurea and nitrite. Nonfractionated HA-K⁺ had no inhibitory effect towards the mutagenic activity of preformed direct acting MNU or towards the activation of the promutagen N-nitrosodimethylamine to a mutagenic product.     

Fine Structure of Exoerythrocytic Merozoite Formation of Plasmodium berghei in Rat Liver1

The fine structure of exoerythrocytic merogony of Plasmodium berghei was studied after perfusion-fixation of rat livers from 51 h post-inoculation onwards. Meroblast formation was effected by clefts originating from the parasite plasmalemma and by fusion of vacuoles with each other. Invaginations at the periphery resulted in labyrinthine structures providing the parasites with an enormous increase in surface area, which might facilitate exchange of metabolites. When the parasitophorous vacuole membrane collapsed, the newly formed merozoites were lying free in the hepatocytic cytoplasm, which degenerated until the merozoites were sticking together by a stroma, obviously a remnant of the host hepatocyte. Groups of merozoites, still kept together by the spongy stroma, were subsequently released in the bloodstream. At 53 h most of the developmental stages leading to the release of merozoites could be found and thereafter parasite numbers decreased while large granulomas became apparent.     

The effect of glycine,humus substances and sucrose on the growth of tomato rootsin vitro

The effect of glycine on the growth of isolated tomato roots in White’s nutrient solution was studied. It is obvious that the root tips grow better in the medium without glycine, because increasing rates of glycine produce inhibition. The growth of root explantates in nutrient media indicates a high synthetic ability of isolated roots. Optimal concentrations of humus acids in White’s nutrient solution without glycine and with glycine stimulate the growth of root explantates. It cannot be decided which of the two substances affects the root directly and which acts as a chelating agent in the medium. The effect of glycine varied, depending on the origin of sucrose used. It appears that in media containing beet sucrose, glycine is unsuitable but in media containing cane sucrose it is necessary.     

Habitat partitioning among sympatric wintering Common Eiders Somateria mollissima and King Eiders Somateria spectabilis

We studied the distribution of sympatric wintering Common Elders Somateria mollissima and King Eiders Somateria spectabilis in northern Norway in relation to the water depth and substrate type. The Common Eider selected water shallower than 10 m, mainly over kelp beds and sand/rock habitats. At the darkest time of the year, Common Elders also fed much more than expected over urchin barrens. In contrast, the King Eider usually dived deeper than 20 m, and when they arrived in December, King Eiders fed especially in areas which were dominated by cobbles. Later in the season, they dispersed into areas with other substrates but still preferred deep water. The segregation between the two species was significant both for depth and substrate type, but depth was the most important factor. The change in the use of various substrate types throughout the winter was also significantly different between the two species, thus very little interspecific competition seemed to occur.     

Trypanosomatids in ornithophilic bloodsucking Diptera

Trypanosomes are known as widespread blood parasites of birds; however, knowledge of their prevalences in vectors and their overall biodiversity is rather limited. To assess the prevalences in potential vectors, we have microscopically examined ornithophilic bloodsucking Diptera (Culicidae, Simuliidae and Hippoboscidae) for the presence of trypanosomatids in their guts. In total, 3270 specimens were dissected, namely Culex pipiens Linnaeus, 1758 (n = 898), C. modestus Ficalbi, 1890 (136), Simulium vernum (Macquart, 1838) (1455), S. angustipes Edwards, 1915 (221) and Ornithomyia avicularia (Linnaeus, 1758) (560). All insect species were found to be infected with trypanosomatids, and the prevalence ranged from 4 to 8% but reached 60% in S. vernum. Blackflies and hippoboscids exclusively harboured trypanosomes (both T. cf. avium s.s. Danilewsky, 1885; T. corvi/culicavium group in hippoboscids). Mosquitoes were infected with T. culicavium Votypka, 2012 and T. avium s. l. but also with monoxenous parasites, namely Crithidia brevicula Frolov and Malysheva, 1989, and Paratrypanosoma confusum Votypka and Lukes, 2013. Only 4% of the isolated parasite strains were monoxenous whereas the majority were avian trypanosomes, confirming the vectorial status of the studied insects.