Ontogeny of growth, respiration and feeding rate of the freshwater calanoid copepod Eudiaptomus graciloides |
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Authors: | Hamburger Kirsten; Boetius Finn |
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Institution: | Freshwater Biological Laboratory, University of Copenhagen 51 Helsingtørsgade, DK-3400 Hillerød, Denmark |
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Abstract: | The calanoid copepod, Eudiaplomus graciloides, was reared fromegg to adult on uni-algal diets (0.1. 0.5 and 2.5 mg dry wt11) using the green alga, Chlamydomonas reinhardtii,as food, or on a mixed diet consisting of Lake Esrom water filteredthrough a plankton net with pore size 45 µm and supplementedwith C. reinhardtii (2.5 mg dry wt 11). On the mixeddiet at 21.0°C growth in body dry wt (W, µg dry wt)was exponential, and the growth constants were 0.21 day1in the early to mid juvenile stage (N1 - C4) and 0.11 day1in the late juvenile to early adult stage (C4-A). At 14.5°Cthe corresponding growth rate constants were 0.10 and 0.08 day1.Similar growth rates were found at uni-algal concentrationsof 0.5 and 2.5 mg dry wt I1, and it was argued that thethreshold concentration for growth in Eudiaptomus was closeto 0.1 mg dry wt I1. The clearance (C, ml h1)of copepodites was measured on the uni-algal diets. The constantsof the regression (C = aWb) were: a = 0.125, b = 0.858 (2000C. reinhardtii ml1), a = 0.068, b = 0.849 (10 000), a= 0.028, b = 0.875 (50 000). Ingestion rates were calculatedfrom the clearances and the average algal concentrations. Atthe three food levels the average daily rations were 30, 67and 125% of body dry wt. The respiration rate (R, nl O2 h1)was measured in individuals reared on the mixed diet. The constantsof the regression (R = aWb) were: a = 4.82, b = 1.07 (nauplii,14.5°C), a = 4.17, b = 0.904 (copepodites and adults, 14.5°C),a = 6.87, b = 0.757 (copepodites and adults, 21.0°C). Nosignificant difference in the respiration rate of copepoditesreared on uni-algal diets and the mixed diet could be demonstrated.Energy budgets were calculated. The assimilation efficiencyand the gross growth efficiency of copepodites decreased markedlywith increasing food concentration, the net growth efficiencyvaried from an average of 0.44 at the lowest algal concentrationto 0.60 on the mixed diet. The results are discussed in relationto previous findings with both freshwater and marine copepods. |
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