Everything about Ostariophysi totally explained
Ostariophysi is the second-largest
superorder of
fish. Members of this superorder are called
ostariophysans. This diverse group contains almost 8,000 species, about 28% of known fish species in the world and 68% of freshwater species, and are present on almost all major continents except
Antarctica. They have a number of common characteristics such as an alarm substance and a
Weberian apparatus.
The superorder is classified below:
- Series Anotophysi
- Series Otophysi (Euostariophysi)
The
monophyly of Ostariophysi has come into question with molecular evidence. Gonorynchiformes is more closely related to
Clupeiformes than Otophysi. It is possible that the Gonorynchiformes and Clupeiformes form a monophyletic group. There is evidence for a
sister group relationship between Ostariophysi and
Clupeomorpha (the taxon
Ostarioclupeomorpha, also known as
Otocephala, was coined to describe this possibly monophyletic group). It also contains the smallest species of freshwater fish,
Danionella translucida at only 12 mm in length. Some Ostariphysans have the ability to produce electricity (
Malapteruridae, Gymnotiformes).
Physical characteristics
Most species possess a swim bladder (except in
Gonorynchus). The swim bladder is usually divided into two chambers. A smaller anterior chamber is partially or completely covered by a silvery
peritoneal tunic. A larger posterior chamber may be reduced or absent in some groups. Minute, unicellular, horny projections known as "unculi" are commonly present on various body parts and are only known from ostariophysans. It is made up of a set of bones known as
Weberian ossicles, a chain of small bones that connect the auditory system to the
gas bladder of fishes.
[ The ossicles connect the gas bladder wall with Y-shaped lymph sinus that abuts the lymph-filled transverse canal joining the sacculi of the right and left ears. This allows the transmission of vibrations to the inner ear.]
In anotophysans, the three first vertebrae are specialized and associated with one or more cephalic ribs (a primitive Weberian apparatus). In the otophysans a distinct modification of the anterior four or five first vertebrae is found as well as the Weberian ossicles.[
The fully functioning Weberian apparatus consists of the swim bladder, the Weberian ossicles, a portion of the anterior vertebral column, and some muscles and ligaments. It is named after the German anatomist and physiologist Ernst Heinrich Weber who first described the Weberian ossicles.][Further Information]
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