Freshwater fishes include all types of bony fishes and non-bony fishes such as plankton and algae. Fish are bony, meaning they lack bony digits, like the abalone. They form a sister Group to the tunics, with the exception of the beater, which is bony and has paired fins. Also included in this category are the flat-finned, sword-finned, corymeling, mollusk and tunic-hull fish and various extinct family members such as the elasmobranchians, eels, anemones and phalaropes.
Bony fishes are not true vertebrates: as they lack bones and muscles for a proper skeleton. All the same, they are true fish and are part of the fish family. Most of them have gills that must function via the gills filter system, which allows them to respire through gills instead of through their own lungs. Other gills aid these bony fishes in respiration through a siphon tube.
The most famous among the diverse set of fishes: that constitute the fauna and flora of our oceans and lakes are sharks, rays, caddisflies, damselflies, spiders, dragonfish and various species of tropical fishes. All have evolved from the same kind of aquatic animal called the Prototheria, with the distinguishing characteristics of having gills, a streamlined body shape and the absence of bones. The other defining characteristic of these fishes is their presence of organs for swimming and one or more ventricles.
Fishes are classified: by their appearances are called the Systematic System. According to Charles Darwin's theory of evolution, all forms of animals existing today are related to one another by descent, a theory also known as the Theory of Origin. A few examples of fishes with a close relationship to each other are the platypus, the echidna, the arowanas, the slipperfish and the mantis shrimp. These are not the only examples but they are the most common.
Fishes have evolved into something more than: just being beautiful or delicious-they have helped shape the world we live in by providing an important part in the food chain. They are aquatic animals and live by living on water, feeding by sucking tiny food particles that float in the water or attached to the bodies of prey. The food that they eat are mostly plants and animals submerged in the water including snails, insects, crustaceans, fish, birds, frogs, salamanders, dragonflies, butterflies and corals. All have a varied diet depending on where they live, which they hunt or eat, and how they use their fins and arms.
There are many different types of fishes: that can be divided into several families and it is pretty amazing to think about the relationships they have had with one another. Many fishes do have more than just one family member and some have been known to have more than one member from a single species. The most famous and best known family members are the Housefish (Paguristes salamander), the Cephalopod family, the Squamata (Paguristes streptacantha), the Sidewire (Hemidesmus indicus), the Ancistrella, the Charadrius, the Carp, the Parrotfish, the Rosey Yellowtail, the Razorbill, the Butterfly Fish, the Anemone Fish and the Ocellus. Some families don't have any representatives in the genus Cephalopoda.
These include the Cyprinus, the Ichtyrophi, the Trachyphyllium, the Allcaryotes, the Diogenetic, the Gemorphic, the Aniloma and the Raccoon fishes.
