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Aquatic arthropods generally possess some form of gills in which gas exchange takes place by diffusing through the exoskeleton. Others may breathe atmospheric air while remaining submerged, via breathing tubes or trapped air bubbles, though some aquatic insects may remain submerged indefinitely and respire using a plastron. A number of insects ...
Fresh water hold less than 1/25th the oxygen content of air, the dissolved oxygen content being approximately 8 cm 3 /L compared to that of air which is 210 cm 3 /L. [4] Water is 777 times more dense than air and is 100 times more viscous. [4] Oxygen has a diffusion rate in air 10,000 times greater than in water. [4]
Four-stroke buccal pumping is used by some basal ray-finned fish and aquatic amphibians such as Xenopus and Amphiuma. [1] This method has several stages. These will be described for an animal starting with lungs in a deflated state: First, the glottis (opening to the lungs) is closed, and the nostrils are opened.
Aquatic animals generally conduct gas exchange in water by extracting dissolved oxygen via specialised respiratory organs called gills, through the skin or across enteral mucosae, although some are evolved from terrestrial ancestors that re-adapted to aquatic environments (e.g. marine reptiles and marine mammals), in which case they actually ...
Aquatic insects consume the stored air while under water or use it to regulate buoyancy. During a molt, air sacs fill and enlarge as the insect breaks free of the old exoskeleton and expands a new one. Between molts, the air sacs provide room for new growth—shrinking in volume as they are compressed by expansion of internal organs.
Hydra has a tubular, radially symmetric body up to 10 mm (0.39 in) long when extended, secured by a simple adhesive foot known as the basal disc. Gland cells in the basal disc secrete a sticky fluid that accounts for its adhesive properties. At the free end of the body is a mouth opening surrounded by one to twelve thin, mobile tentacles.
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Jet propulsion is a method of aquatic locomotion where animals fill a muscular cavity and squirt out water to propel them in the opposite direction of the squirting water. Most organisms are equipped with one of two designs for jet propulsion; they can draw water from the rear and expel it from the rear, such as jellyfish, or draw water from ...