Einfache folientanks zur Planktonuntersuchung in situ

For studies of in situ interactions between plankton and ambient water, simple, cylindrical, 5 m deep translucent-foil tanks were constructed using polyamide and polyethylene (layers 30 and 100 μm, respectively, with polyamide layer outside). The tanks were suspended in the water by metal frames fixed to a buoy. The whole construction was anchored in an outer basin of the harbour of Helgoland, N. Sea, and was exposed to tides and waves generated by winds of up to 6 Bft (Beaufort scale). Even under these conditions the construction and its material allowed experiments lasting 2 weeks and longer, during the summer months of 1972 and 1973. The banks' volume, of about 4 m³ each permits experiments with naturally occurring concentrations of nutrients and organisms and large sampling volumes for the determination of trace components. In this way, natural plankton populations in 1972, and monocultures of different diatom species in 1973 were investigated. Under these conditions, different monocultures developed almost identically.     

Structural differences in the drone olfactory system of two phylogenetically distant Apis species, A. florea and A. mellifera

Male insects that are attracted by sex pheromones to find their female mates over long distances have specialized olfactory subsystems. Morphologically, these subsystems are characterized by a large number of receptor neurons sensitive to components of the female's pheromones and hypertrophied glomerular subunits ('macroglomeruli' or 'macroglomerular complexes') in the antennal lobes, in which the axons of the receptor neurons converge. The olfactory subsystems are adapted for an increased sensitivity to perceive minute amounts of pheromones. In Apis mellifera, drones have 18,600 olfactory poreplate sensilla per antenna, each equipped with receptor neurons sensitive to the queen's sex pheromone, and four voluminous macroglomeruli (MG1-MG4) in the antennal lobes. In contrast, we show that drones of the phylogenetically distant species, Apis florea, have only 1,200 poreplate sensilla per antenna and only two macroglomeruli in their antennal lobes. These macroglomeruli are homologous in anatomical position to the two most prominent macroglomeruli in A. mellifera, the MG1 and MG2, but they are much smaller in size. The morphological and anatomical differences described here suggest major modifications in the sex-pheromone processing subsystem of both species: (1) less pheromone sensitivity in A. florea and (2) a more complex sex-pheromone processing and thus a more complex sex-pheromone communication in A. mellifera.