Filter Feeding in Larval Lampetra Planeri: Effects of Size, Temperature and Particle Concentration

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Abstract
The filtration rate of differently sized larval L. planeri (Bloch) was estimated experimentally for a set of temperatures ranging from 2.5 to 25.degree. C, and for 9 different food particle concentrations at 15.degree. C. The food material presented consisted of suspended yeast. The concentration was measured indirectly as turbidity. Large larvae had a higher absolute filtration rate than small ones and were less dependent on temperature. If respiration was considered, the most economic filtration was achieved below 10.degree. C. This is in accordance with the low mean annual temperature of typical L, planeri streams. High ratio of filtration to respiration coincided with maximum food availability of the stream from which the larvae were collected. Low particle concentrations were compensated for by an increased filtration rate. In the interval between 30 and 100 mg dry weight of suspended yeast per liter, larvae increased their rates of filtration. The importance of L. planeri larvae in depleting the water of particles was minimal. Less than 1.10-4% of the water passing each meter of stream length was filtered by the lampreys.