What is a Fish?
Fish is a kind of animals that lives and respires in water. They are vertebrates in nature and breathe through their gills which contain fins and scales. Fish constitute almost half of known species of vertebrates. An ichthyologist is a person who studies about fish. Fish are identified through their scale counts, colors, general features, amount of fins and character, maximum measurement lengthwise and distribution. In some groups, males and females have diverse shaped bodies or different colors; in other groups or species there are no visible dissimilarities. Several fish contain lungs and can breathe air, but most of them respire through their gills. As water goes by the fish, liquefied oxygen is engrossed in the blood, and also in waste goods like carbon dioxide that pass out in the water. The thin pieces of tissue which are supplied richly with blood constitute the gills of fish. The gills well sheltered by big bony plate known as operculum.
Lateral line is a paddle scales which most fish contain beside their sides, elongating starting from the head up to the tail. Beneath these scales, we can find a scheme canals filled with fluids and particular cells that transmit sensations into the brain. Objects including prey and predators are detected with the help of lateral line. You will observe that fish are slimy; this is because of the mucus that is secreted in the skin. This coating that is slimy is important since it gives protection from diseases and parasites. The coating also covers wounds to avoid infection and aid fish to move faster through the water. Some species discharge poisons or pollutants in the slime that ward off the attacking living things whilst others make use of their slime in giving food to their young.
Fish have diet also; they eat insect larvae, crustaceans, worms, algae, eggs of fish, terrestrial insects, water birds, turtles, mice and others. Fish are eaten by other fish, birds (like herons, pelicans and cormorants), snakes, turtles, crustaceans, dragonfly larvae and human beings. In some parts of the universe, there are also some animals like wild cats, wild bears and pigs that eat fish. Freshwater fish lives in all kinds of environments: rivers, streams, springs, lakes, lagoons, land, billabongs, swamps, estuaries, backwaters, dune lakes, reservoirs, drains and ponds. Several freshwater fish as well spend portion of their manner of living at the sea.
The following are some varieties of fish: Anabantids - they are the fishes which belong in the families of Anabantid Belontiidae, Helostomatidae and Osphronemidae. These are called "labyrinth fish" because of the supplementary breathing organ known as "labyrinth". Catfishes - they are identified through the barbells surrounding their mouths that permit them to look for food in gloomy situations. As replacement for scales, the skin can be covered by bony plates. Types of catfish are Cory, Whiptail and Plecto. Characins - most characins generate by means of egg-scattering. Tetra, Pacu and Hatchet fish are some kinds of characins. Cichlids - the colors, sizes and shapes of these are very huge. Angelfish is one type of this fish.