ON THE RELATIONSHIP BETWEEN VERTICAL MICRODISTRIBUTION AND ADAPTATIONS TO OXYGEN STRESS IN LITTORAL CHIRONOMIDAE (DIPTERA)

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 concent rations and weights of eight chironomid species that dwell in the litt oral zone were measured. High hemoglobin concentration and weight both seemed to contribute to an ability to cope with low oxygen concentrat ions, and determined the vertical distribution of chironomids in the s ediment. 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 smal l animals to oxygen stress is discussed from a theoretical point of vi ew.