The hollow pseudobulbs of Schomburgkia tibicinis (Orchidaceae; Central America) serve as domatia for many species of ants. The ants pack many of the pseudobulbs with debris including dead insects, plant material, and sand. Ants were fed 14C‐labelled D‐glucose in honey, killed, and placed in the pseudobulbs for up to eight weeks. Samples of plant tissue were harvested and tested for radioactivity after 1, 2, 3, 4, 6, and 8 weeks. The labelled material had moved into various parts of the plant and demonstrated direct nutrient uptake.
A quantitative description of the effects of sublethal concentrations of cadmium, chromium and zinc on the swimming activities of the bluegill is presented. Locomotor activities of fish in 0.1 and 0-25 mg 1-l cadmium are respectively 1.5 and 7.8 times the activities of control fish. Fish in 0 5 rng 1 -l cadmium, a concentration killing 30% in two weeks, were less active than controls. Fish in 0.05, 2.4 and 24.0 mg 1 chromium were respectively 1.2,3*6 and 6.5 times as active as controls. Fish in 0.1 and 5.0 mg 1-' zinc were respectively 1.3 and 3.8 times as active as controls. Thus metals effect hyperactive locomotor responses by the bluegill in a concentration-dependent relationship.
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