Hans Ulrik Riisgård

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Filtration rate capacities in undisturbed freshwater bivalves were determined by means of two different methods (indirect “clearance” and “suction” methods) in Anodonta anatina (L.), Unio tumidus Philipsson, Unio pictorum (L.), Unio crassus Philipsson, Dreissena polymorpha (Pallas) and Sphaerium corneum (L.). In A. anatina, D. polymorpha, and S. corneum the(More)
Burrowing animals maintain contact with the water above the sediment by pumping water through a tube system and therefore measurements of water pumping rate of burrowing animals is of crucial importance for the study of many processes both within and above the sea floor. This review deals with the measuring of water pumping and the analysis of flow(More)
The exhalant jet flow of mussels in conjunction with currents and/or other mussels may strongly influence the mussels’ grazing impact. Literature values of mussel exhalant jet velocity vary considerably and the detailed fluid mechanics of the near-mussel flow generated by the exhalant jet has hitherto been uncertain. Computational modelling of this(More)
A large number of suspension-feeding aquatic animals (e.g. bivalves, polychaetes, ascidians, bryozoans, crustaceans, sponges, echinoderms, cnidarians) have specialized in grazing on not only the 2 to 200 μm phytoplankton but frequently also the 0.5 to 2 μm free-living bacteria, or they have specialized in capturing larger prey, e.g. zooplankton organisms.(More)
Based on observations of feeding structures and currents in the polychaete Spirorbis tridentatus, the entoproct Loxosoma pectinaricola and the cycliophore Symbion pandora, which all possess compound cilia, it is hypothesized that their capture mechanism is based on the catch-up principle. According to this principle, the compound cilia constitute the pump(More)
The relationship between body dry weight (W) and shell length (L) of blue mussels, Mytilus edulis, can be expressed by the condition index (CI = W/L 3) which varies from population to population and during the year. Here, we examine the influence of CI on the relationships between maximum filtration rate (F, l h−1), W (g), and L (mm) as described by the(More)
Beating cilia are important organelles for swimming in many zooplanktonic aquatic organisms, including many invertebrate larvae, rotifers and ciliates, but other planktonic organisms, such as copepods and brine shrimps, use muscle-powered swimming appendages. In recent studies we found that the temperature-dependent viscosity of seawater is the key(More)
The energy cost for various ciliary filter feeders shows that useful pump work constitutes 0.3–1.1% of the total metabolic expenditure. The ‘water processing potential’ (liters of water pumped per milliliter O2 consumed by the animal) is a useful tool for characterizing filter feeding and adaptation to the environment. The six types of ciliarycapture(More)
The effect of salinity on the filtration rate of blue mussels, Mytilus edulis, from the brackish Great Belt (Denmark) and the low-saline Central Baltic Sea, respectively, was studied. First, we measured the effect of long-term (weeks) constant ambient salinities between 5 and 30 psu on the filtration rate of M. edulis collected in the Great Belt where the(More)