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[Show abstract][Hide abstract] ABSTRACT: Chironomus larvae were caught in some lowland brooks and one pond in Flanders. Fourth-instar larvae were identified by means of a karyological study. It was the first time that Belgian animals were identified by using this technique. We have found one new species. Chironomus melanotus is reported from Belgium for the first time. We can also confirm the presence of two other species : Ch. plumosus and Ch. riparius.
[Show abstract][Hide abstract] ABSTRACT: Animals that dwell at different depths in the sediment, are adapted to different respiratory environments. It is possible that animals that occur deep in the sediment have a higher hemoglobin concentration than surface-dwelling animals. To test this hypothesis, hemoglobin concentrations and weights of eight chironomid species that dwell in the littoral zone were measured. High hemoglobin concentration and weight both seemed to contribute to an ability to cope with low oxygen concentrations, and determined the vertical distribution of chironomids in the sediment. A multiple regression equation, including these factors, was derived. It may be used to predict the median depth of occurrence for species that were not included in this study. High sensitivity of small animals to oxygen stress is discussed from a theoretical point of view.