. Three leaf-like gills at the base of the abdomen obtain oxygen. Damselfly nymphs require 4 to 8 ppm of dissolved oxygen for survival. Damselfly nymphs can be distinguished from dragonfly nymphs by a narrow body with three gills extending in a tripod formation at the end of body. The three pairs of legs are long and spindly. Nymphs are predators and feed on mollusks, other insects, crustaceans, worms, and small fish. Nymphs are a food source for some fish.