Ray Finned Fish

SCIENTIFIC CLASSIFICATION:

They are actinoptergians under the class fish in vertebrates.

TIME PERIOD:

They are alive to date.

HABITAT:

The live generally in tropical waters.

DESCRIPTION:

This spiny and poisonous lionfish is just one of the 20,000 of species of actinopterygians alive. The name means "ray-finned," for unlike the Chondrichthyes, the fins of the Actinopterygii are webs of skin supported by bony or spines. Most actinopterygians have complex skeletons of true bone.

Ray-finned fishes form the major portion aquatic vertebrates today, making up about half of all vertebrate species known. They are found in every aquatic zone from the depths of the ocean to freshwater streams and even ponds; a few can crawl on land for short periods of time.

Though fish generally live in water and breathe through gills, this rule does not always apply to ray- finned fish.

A few fish like the walking catfish and the mudskipper, are able to crawl about on land, to find food or new habitats - usually due to water shortage or shortage of food. Some others, like the Siamese fighting fish, possess the ability to breath air in addition to extracting oxygen from the water with their gills. These fish are not closely related to the sarcopterygian lineage of creatures that led to air- breathing land vertebrates, but have independently evolved limited abilities to move on land and/or breathe air.

Almost all fish lay eggs, but some - including the common fishes like guppies, swordtails, and mollies - hold the eggs inside their bodies until hatching. In a few cases such as the seahorse, the male receives the eggs and keeps them inside a special pouch in his body. Such fish are said to be ovoviviparous unlike mammals, these fish do not nourish the embryos during development. Many fish do not provide parental care for their offspring, but a number do protect them in various and sometimes unique ways. In some African cichlids, for instance, the female keeps her eggs in her mouth - and after they hatch, the young are kept in her mouth as well. During times of danger, the young rush to the mother.