Particle size effect on preferential settlement and growth rate of detritivorous chironomid larvae as influenced by food level
Vos, J. H.; Teunissen, M.; Postma, J. F.; van den Ende, F. P.
published: May 13, 2002
ArtNo. ESP141015401011, Price: 29.00 €
Sediment particle size distribution and organic matter content are thought to determine the distribution of chironomid larvae in benthic habitats. Therefore, we tested the preference of detritivorous chironomid larvae for combinations of mineral substrates with particles of different size ranges and organic content. Organic matter content was added in the form of food. We also measured growth of larvae in each substrate condition. Mineral particle size had no effect on larval growth at saturating food levels. However, at limiting food levels growth of third instar larvae was hampered by ingestion of small mineral grains (8-63 µm). Second, third and fourth instar larvae were able to construct tubes in silty and sandy substrates, but tubes in substrates with larger mineral particles (550-1200 µm) were less stable compared to those constructed from small particles. To perform preference experiments, substrates in culture chambers were modified so that conditions differed on either half of each chamber. When food was present only in one half of the culture chamber, larvae always were more abundant where food was present, regardless of particle size of the substrate. When food was present in both halves of the chamber, larvae were more abundant on the side with the higher food level, provided that the difference in food level exceeded 0.75mg/ml. When food level was below 0.075 mg/ml, larvae failed to settle or construct tubes. Food level and substrate particle size determined larval motility and preference for substrates. The influence of both factors was governed by food threshold and saturation concentrations. Food level and substrate particle size interacted to determine larval distribution and growth, but food level seemed to be the primary determinant of distribution and growth.