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 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.