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Freshwater snails are gastropod mollusks that live in fresh water. There are many different families. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs to major rivers.
Many aquatic animals have developed gills for respiration which are specifically adapted to their function. In fish, for example, they have: A large surface area to allow as much oxygen to enter the gills as possible because more of the gas comes into contact with the membrane; Good blood supply to maintain the concentration gradient needed
The oxygen affinity of the blood is related to lung volume. Where the lungs do not represent an oxygen store, the oxygen affinity is low to maximise the unloading of oxygen and to maintain a high tissue oxygen tension. Where the lungs are utilised as an oxygen store, the affinity is high and maximises uptake of oxygen from the alveolar volume. [13]
Physella acuta is a species of small, left-handed or sinistral, air-breathing freshwater snail, an aquatic gastropod mollusk in the family Physidae. Common names include European physa , tadpole snail , bladder snail , and acute bladder snail .
For example, many reservoirs in the Basin currently experience eutrophic (enrichment of a water body with nutrients) conditions, and chronically low dissolved oxygen levels. [ 9 ] [ 10 ] Such physical and chemical changes can affect feeding, respiration, and reproduction of these riffle and shoal snail species.
Insects of this type only rarely need to replenish their supply of air. [6] Other aquatic insects can remain under water for long periods due to high concentrations of hemoglobin in their hemolymph circulating freely within their body. Hemoglobin bonds strongly to oxygen molecules. [7]
A siphon is an anatomical structure which is part of the body of aquatic molluscs in three classes: Gastropoda, Bivalvia and Cephalopoda (members of these classes include saltwater and freshwater snails, clams, octopus, squid and relatives). Siphons in molluscs are tube-like structures in which water (or, more rarely, air) flows.
Some saltwater limpets such as Trimusculidae breathe air, and some freshwater limpets are descendants of air-breathing land snails (e.g. the genus Ancylus) whose ancestors had a pallial cavity serving as a lung. In these small freshwater limpets, that "lung" underwent secondary adaptation to allow the absorption of dissolved oxygen from water.