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Several aquatic plants (Azolla filiculoides, Cladophora sp., Elodea sp., and Lemna sp.) were fed singly to groups of 30 juvenile Malaysian prawns (Macrobrachium rosenbergii) for 28 days, and comparisons were made with control prawns fed Ralston Purina Ration #20. The comparisons made were survival, weight change, and molting frequency. The animals ingested all diets during the experiment, though none on a plant diet fared as well as the controls in weight gains and survival by day 28. The controls increased 65% in dry weight, whereas the others lost weight. The control group had significantly higher survival by day 28, although on day 16 survival was better only than that of the Cladophora-fed group. Most deaths of plantfed prawns were in the last week of the experiment, whereas the control group had no deaths after day 9. In general, molting peaks occurred in 8–10 day cycles, and all groups molted less in the latter half of the experiment. Group percents for molting during various periods were consistently highest for controls. Molt/day, averaged over 28 days, was 7.3, 2.5, 4.0, 3.8, and 5.0% for the control, Azolla, Cladophora, Elodea, and Lemna groups, respectively. A single-species plant diet apparently did not satisfy the nutritional requirements of the prawn as indicated by increased mortality and decreased weight. |
