NEBRASKAland Magazine is dedicated to outstanding photography and informative writing with an engaging mix of articles and photos highlighting Nebraska’s outdoor activities, parklands, wildlife, history and people.
Issue link: http://mag.outdoornebraska.gov/i/695082
18 NEBRASKAland • JULY 2016 Under the Surface By Paula Hoppe, Certified Master Naturalist Just under the surface of a healthy pond, there are an assortment of creatures with adaptations that enable their habitation of this interface between water and air. Water striders, their long legs covered in tiny hairs, take advantage of the water's surface tension to glide about, feasting on mosquito larvae that rise to the surface to breathe. Life at the boundary layer is also fraught with the dual hazards of sky and sea. The split eyes of whirligig beetles allow them to watch for predators coming from both above and below. With their oar-like hind legs, water boatmen trawl the depths of the water, feeding on plants and algae using a soft, tubular mouth. Named for their habit of swimming upside down, water backswimmers, though similar in appearance to boatmen, are predatory, and have a piercing mouth- part which can inflict a painful bite. They eat other insects, small fish and even tadpoles. Many aquatic insects, including boatmen and backswimmers, carry oxygen on their body in the form of air bubbles, allowing them to stay submerged for long periods. Diving deeper we find voracious predators. These are the larvae of insects we might find more familiar above the water. Dragonfly and damselfly larvae, or nymphs, may spend one to three years under the surface, prowling the depths for unsuspecting prey. While hunting, the lower jaws of dragonfly nymphs reach out like an extra set of arms to grasp other insects and small fish. The caddisfly has a unique way of avoiding such predators. Using material found in its environment – sticks, pebbles and the like – it creates a cylindrical case that camouflages and protects it against attack. Midge fly larvae, sometimes called bloodworms, are an important food source for many aquatic organisms. The hemoglobin-like substance that gives them their red color aids in the absorption of oxygen from the water as they feed on algae and detritus in the hypoxic environment at the pond's bottom. Mayflies, depending upon the species, spend two weeks to two years in the water as larvae feeding on decaying plant matter. They then emerge from the water, usually en masse to complete their life cycle. Living only one to three days the adult mayfly has no mouth. Its one purpose is to find a mate and reproduce, and it dies quickly after and falls to the water, food for the many hungry mouths below. Just under the surface of a healthy pond is an amazing world of biodiversity, a complex ecosystem worthy of our attention. ■ PHOTO COURTESY OF NEBRASKALAND ARCHIVE Damselfly nymph