Episode 89
Teleost
Wed, 2017-Aug-02 01:01 UTC
Length - 4:03
Direct Link
Welcome to featured Wiki of the Day where we read the summary of the featured Wikipedia article every day.
The featured article for Wednesday, 02 August 2017 is Teleost.
The teleosts or Teleostei (Greek: teleios, "complete" + osteon, "bone") are by far the largest infraclass in the class Actinopterygii, the ray-finned fishes, and make up 96 percent of all known fish species. This diverse group arose in the Triassic period and members are arranged in about 40 orders and 448 families. Over 26,000 species have been described. Teleosts range from giant oarfish, measuring 25 ft (7.6 m) or more, and ocean sunfish weighing over 2.0 long tons; 2.2 short tons (2 t), to the minute male anglerfish Photocorynus spiniceps, just 0.24 in (6.2 mm) long. As well as torpedo-shaped fish built for speed, teleosts can be flattened vertically or horizontally, be elongated cylinders or take specialised shapes as in anglerfish and seahorses. Teleosts dominate the seas from pole to pole and inhabit the ocean depths, estuaries, rivers, lakes and even swamps.
The difference between teleosts and other bony fish lies mainly in their jaw bones; teleosts have a movable premaxilla and corresponding modifications in the jaw musculature which make it possible for them to protrude their jaws outwards from the mouth. This is of great advantage, enabling them to grab prey and draw it into the mouth. In more derived teleosts, the enlarged premaxilla is the main tooth-bearing bone and the maxilla, which is attached to the lower jaw, acts as a lever, pushing and pulling the premaxilla as the mouth is opened and closed. Other bones further back in the mouth serve to grind and swallow food. Another difference is that the upper and lower lobes of the tail (caudal) fin are about equal in size. The spine ends at the caudal peduncle, distinguishing this group from other fish in which the spine extends into the upper lobe of the tail fin.
Teleosts have adopted a range of reproductive strategies. Most use external fertilisation: the female lays a batch of eggs, the male fertilises them and the larvae develop without any further parental involvement. A fair proportion of teleosts are hermaphrodites, starting life as females and transitioning to males at some stage, with a few species reversing this process. A small percentage of teleosts are viviparous and some provide parental care with typically the male fish guarding a nest and fanning the eggs to keep them well-oxygenated.
Teleosts are economically important to humans as is shown by their depiction in art over the centuries. The fishing industry harvests them for food and anglers attempt to capture them for sport. Some species are farmed commercially, and this method of production is likely to be increasingly important in the future. Others are kept in aquariums or used in research, especially in the fields of genetics and developmental biology.
This recording reflects the Wikipedia text as of 01:01 UTC on Wednesday, 02 August 2017.
For the full current version of the article, go to http://en.wikipedia.org/wiki/Teleost.
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