Subject matters of experiments and observations of water animals in school aquarium II - breathing of water animals
Abstract
Aquatic animals also need oxygen to live. They have to breathe in oxygen that is dissolved in water or from the air above the water, using various structural adaptations (gill, gill chambers, skin, air tube, air bubble, special nostrils, blowhole).
Some water animals can be used in school aquaria for demonstration of various kinds of breathing. Simple diffusion over a relatively thin integument is known e.g. in sludge worms (Tubifex tubifex).
Extraction of oxygen from water using a plastron or physical gill can be presented in lesser water boatman (Corixa punctata) or bentic water bug Aphelocheirus aestivalis. Water nymphs of insect often used tracheal gills (stonefly nymphs /Plecoptera/ have gills on their thorax and mayfly nymphs /Ephemeroptera/ have gills on their abdomen).
Diving beetles (Dytiscidae) have air supply in the cavity under the elytra. Water scavenger beetles (Hydrophiliidae) replenish their air supply by breaking the surface of the water with their antennae and then holding their air supply bubbles in place using a dense mat of hair under the body.
Some animals like water scorpions (Nepa cinerea), water stick insect (Ranatra linearis) or mosquito larvae and pupae take oxygen from surface via breathing tubes (siphons). The pond snail (Lymnaea stagnalis) has a gas-filled mantel cavity and ventilation is accomplished by opening and closing movements of the apex of a muscular tube (the pneumostome) that forms the entrance to the mantel cavity.
Water spider (Argyroneta aquatica) builts diving bell under the water surface and fills it with air. In fish water flows in through the mouth, than water flows over the gills, than out of the fish.
Some fish have accessory respiratory organs, e.g. supra-branchial chamber called as labyrinthine organ (e.g. Siamese fighting fish Betta splendens, paradise fish Macropodus opercularis).
Frogs start life as aquatic tadpoles, breathing underwater through internal gills and their skin. Adult water frogs (e.g.
African clawed frog, Xenopus laevis) breath through lungs