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.     

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.     

Riding the tide: intriguing observations of gulls resting at sea during breeding

Adult Lesser Black‐backed Gulls Larus fuscus were followed during the breeding season using a high‐resolution GPS tracking system. Little is known about the foraging movements of these birds and what they do when they are away from the colony. The study revealed intriguing yet infrequent behavioural patterns showing that birds would sit on the sea surface drifting passively with the tidal current for several hours, resting at sea rather than in the breeding colony. The potential function of the observed patterns is discussed as well as the relevance of these observations to other species.     

Two new species of Pseudoniphargus (Amphipoda), in Bermudian groundwaters*

The genus Pseudoniphargus comprises a number of stygobiont Amphipoda, distributed on both sides of the Atlantic. In Bermuda, groundwaters are inhabited by two species. P. grandimanus and P. carpalis, both new. They occur throughout the entire salinity spectrum, from infrahalne to euhaline, but are most abundant in oligohaline waters. Large adults, but no ovigerous specimens. arc found at greater distance from the sea coast than juveniles, which may indicate that Pseudoniphargus needs anchihaline/marine waters for its reproduction and that juveniles migrate inland to grow up.     

Melanins in IGR 1 Melanoma Cells

Information on the composition of melanins is obtained by analysis both of 4-amino-3-hydroxyphenylalanine (AHP) after hydriodic acid degradation and of pyrrole-2,3,5-tricarboxylic acid (PTCA) after potassium permanganate oxidation. Analysis of thiazole-4,5-dicarboxylic acid (TDCA) and pyrrole-2,3-dicarboxylic acid (PDCA) after permanganate oxidation, provides additional information on the composition, TDCA on pheomelanin residues, and PDCA on indolic residues without carboxy groups. Using model melanins formed from dopa and cysteinyldopa in different proportions, we found the TDCA/(PTCA+PDCA) ratio to yield a reliable estimate of the relative proportions of pheomelanin and eumelanin. The PDCA/PTCA ratio reflects the relationship between indole residues with and without carboxy groups. We have analyzed degradation products from cultures of IGR 1, an extensively studied melanoma cell line. Cell cultures were harvested after 2, 4, and 7 days. Culture media were changed after 2 days in all series, and also after 4 days in one series harvested at 7 days. Cells without medium change had seven times the amount of melanin found in cultures with medium change. The PDCA/PTCA ratio decreased with increasing amounts of melanin. With increased melanization, eumelanin is increased relatively more than pheomelanin. The cell content of 5-S-cysteinyldopa (5-S-CD) was similar in all cultures, while 6-hydroxy-5-methoxyindole-2-carboxylic acid (6H5MICA), a eumelanin precursor metabolite, was found in increased amounts of media of heavily pigmented cultures.