The Diversity of Fishes Nearly one half of all known vertebrate species are fish. There are about 28
The Diversity of FishesNearly one half of all known vertebrate species are fish. There are about 28,000 identified species, which is more than all the mammals, birds, reptiles and amphibians combined. They occupy just about all aquatic ecosystems; from freshwater to marine (saltwater), tropical to polar, from surface to the deepest, darkest depths of the ocean floor along with everything in between. These environmental extremes along with 500 million years of evolution means that fishes represent some of the widest ranges of feeding habits, reproductive traits and social behaviors in the animal kingdom.So, what is a fish? At its most basic, a fish is defined as an aquatic vertebrate with gills and limbs that are shaped like fins. You would assume the presence of scales is another common characteristic but that is not always the case and therefore is not a definitive trait of all fish species. Most fishes have jaws but more primitive species do not, so even that is not a foolproof way to identify a fish. My hope is to explain many of these peculiar differences and to provide some interesting examples as well in future posts.Top: Leafy Sea Dragon (Phycodurus eques). The extra appendages are used only for camouflage. Native only to the southern coast of Australia.Second: American paddlefish (Polyodon spathula) Considered a “living fossil”, the elongated snout contains electroreceptors that are used for navigation and to locate prey. Many other species of fish use some form of electrolocation.Third: Red lionfish ( Pterois volitans) One of several species of venomous fishes. Their venom is used purely for defensive purposes but other venomous species do actively attack prey.Fourth: A whale shark (Rhincodon typus), the largest extant fish species on Earth at 12 m long (39 ft.) They eat nothing but plankton and other small organisms, which they catch via filter feeding.JRAImage Credits: Leafy sea dragon by Ta-graphy http://bit.ly/1SYjPmaUS Fish and Wildlife Service http://bit.ly/1VgAOnyJens Petersen http://bit.ly/1VgKGxIChristian Jensen http://bit.ly/1qHY9BRSources:fishbase.orghttp://bit.ly/22n5WAz -- source link
#science#ocean#vertebrate#evolution#lionfish#shark#whale shark#paddlefish#sea dragon#gills