Feeding behaviour and morphology of filtering combs of Daphnia galeata

Abstract

The population of Daphnia galeata Sars from the fish pond Velký Pálenec (Blatná, Czechoslovakia) living in high food conditions (7 mgC l⁻¹) was characterized by a small size of the filtering comb on the thoracic limb 3, measured as seta length, length of the base of the comb and number of setae (population 1). One month cultivation of this population in low food conditions (1.5 mgC l⁻¹) in the laboratory resulted in twofold increase in size of the filtering comb (population 2). Filtering and ingestion rates of both populations were measured at eight concentrations of food (approximately 0.025–3.2 mgC l⁻¹) using ¹⁴C labeled Scenedesmus acutus. The results show that size of the filtering combs influences considerably feeding behavior of Daphnia. The comparison of animals with the same body length suggests that the population with a large comb feeds at concentration of food below 0.4 mgC l⁻¹ more intensively and reaches the maximum of the filtering rate at a lower concentration than the population with a small comb. The situation is opposite at concentration above 0.4 mgC l⁻¹. The higher values of theoretical flow in population with a small projection of filtering area suggest that this population has to compensate disadvantage of a small comb with the higher appendages beat frequency.