One is that they developed from gill arches, bony hoops that support the gills. The other is that they arose from a continuous single fin that once encircled fish, similar to median fins seen in the embryos of fish and amphibians. A number of recent studies revealed that several of the genes underlying the formation of paired fins also help guide the development of both gill arches and median fins, supporting both concepts for how paired fins evolved.
To shed light on the origin of paired fins, scientists analyzed the embryos of lampreys, jawless fish that diverged from other vertebrates before the evolution of paired fins.
They focused on tissue known as the somatopleure, from which paired appendages develop as outgrowths. Researchers knew that in animals such as reptiles, birds and mammals, the somatopleure helps form the body wall, the outer part of the body that encloses the body cavity. It provides supports during swimming. It creates dynamic lifting force and also helps the fish to turn left or right.
They are soft fins and located between the dorsal and caudal fins, usually very near to the caudal fin. It is mainly found in Salmonidae , Characins , and catfishes. This type of fin help to navigate the fish in rough water. The caudal fin is the primary appendage which is used for locomotion in many fishes.
The caudal fin is also known as tail fin or a median fin which is usually homocercal or heterocercal. Generally, it is a vertically expanded structure which is located at the caudal end of the body.
The base of the caudal fin is known as caudal peduncle with strong swimming muscles. In general, caudal fin acts like a propeller while the caudal peduncle functions as a motor.
The caudal fin has two lobes such as dorsal epichordal and ventral hypochordal lobe which are supported by the modified last three caudal vertebrae. The shape of the caudal fin may vary in different species from rounded to pointed, notched, emarginated, truncated, etc.
It is used to identify the fish species. Generally, fish use it for forwarding propulsion and speed. It is the most primitive type of caudal fin where the straight vertebral column divides the caudal fin into two equal lobes such as upper lobe and lower lobe. In this case, the upper lobe is known as epichordal or epicaudal and the lower lobe is called hypochordal or hypocaudal lobe.
A series of rods are arranged around the central axis of the caudal region, which support the fin membrane. Undoubtedly, during the developmental period, the caudal fin of all fishes passes through the protocercal stage. This type of fin is found in cyclostomes and the living dipnoans lungfishes. The heterocercal tail is sometimes called the shark-tail type of caudal fin. Elasmobranch cartilaginous fish and some primitive type of bony fishes contain this type of fin.
This fin has two unequal lobes where the upper smaller lobe is known as epichordal lobe and a much larger lower lobe is known as hypochordal lobe. Issue Date : July Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article.
Provided by the Springer Nature SharedIt content-sharing initiative. Skip to main content. Search SpringerLink Search. Synopsis The paired fins of the basic, ancestral type of free-swimming acanthopterygian teleost serve primarily in guiding the forward course of movement and in maneuvering within the water column. References cited Able, K. Google Scholar Andriashev, A. Google Scholar Bardach, J. Google Scholar Eschmeyer, W. Google Scholar Grenholm, A.
Google Scholar Hallacher, L. Google Scholar Kido, J. Google Scholar Longley, W. Google Scholar Matsubara, K. Google Scholar Morrill, A. Google Scholar Sakurai, Y. Google Scholar Samuel, C. Google Scholar Starks, E. Google Scholar Yabe, M. Google Scholar Download references. William A. Gosline Authors William A. Gosline View author publications. Rights and permissions Reprints and Permissions. About this article Cite this article Gosline, W. Copy to clipboard.
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