Respiration in Aquatic Insects
Aquatic insects need oxygen too! They are equipped with a variety of adaptations that allow them to carry a supply of oxygen with them under water or to acquire it directly from their environment. Read each of the following sections to learn about these adaptations and how insects use them to obtain oxygen and maintain an aquatic lifestyle.
Many aquatic species have a relatively thin integument that is permeable to oxygen (and carbon dioxide). Diffusion of gasses through this body wall (cuticular respiration) may be sufficient to meet the metabolic demands of small, inactive insects — More about
Dissolved Oxygen especially those living in cold, fast-moving streams where there is plenty of dissolved oxygen. Larger insects, more active ones, or those living in less oxygenated water may need to rely on other adaptations (see below) to supplement cuticular respiration.
A biological gill is an organ that allows dissolved oxygen from the water to pass (by diffusion) into an organism’s body. In insects, gills are usually outgrowths of the tracheal system. They are covered by a thin layer of cuticle that is permeable to both oxygen and carbon dioxide.
In mayflies and damselflies, the gills are leaf-like in shape and located on the sides or rear of the abdomen. Fanning movements of the gills keep them in contact with a constant supply of fresh water. Stoneflies and caddisflies have filamentous gills on the thorax or abdomen. Dragonflies differ from other aquatic insects by having internal gills associated with the rectum. Water is circulated in and out of the anus by muscular contractions of the abdomen. This rectal gill mechanism doubles as a jet propulsion system. A sudden, powerful contraction of the abdomen will expel a jet of water and thrust the insect forward — a quick way to escape from predators.