Dorsal fin

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Dorsal fin of a shark

A dorsal fin is a

ichthyosaurs
. Most species have only one dorsal fin, but some have two or three.

Wildlife biologists often use the distinctive nicks and wear patterns which develop on the dorsal fins of large cetaceans to identify individuals in the field.

The bony or cartilaginous bones that support the base of the dorsal fin in fish are called pterygiophores.

Functions

The main purpose of the dorsal fin is to stabilize the animal against rolling and to assist in sudden turns. Some species have further adapted their dorsal fins to other uses. The

anal fin) for propulsion. In anglerfish, the anterior of the dorsal fin is modified into a biological equivalent to a fishing pole and a lure known as illicium or esca. Many catfish can lock the leading ray of the dorsal fin in an extended position to discourage predation or to wedge themselves into a crevice. Some animals have developed dorsal fins with protective functions, such as spines or venom. For example, both the spiny dogfish and the Port Jackson shark
have spines in their dorsal fins which are capable of secreting venom.

Billfish have prominent dorsal fins. Like tuna, mackerel and other scombroids, billfish streamline themselves by retracting their dorsal fins into a groove in their body when they swim.[1] The shape, size, position and colour of the dorsal fin varies with the type of billfish, and can be a simple way to identify a billfish species. For example, the white marlin has a dorsal fin with a curved front edge and is covered with black spots. The huge dorsal fin, or sail, of the sailfish is kept retracted most of the time. Sailfish raise them if they want to herd a school of small fish, and also after periods of high activity, presumably to cool down.[1][2]

  • Differences of dorsal fins of orcas between male and female
    Differences of dorsal fins of orcas between male and female
  • The dorsal fin of a white shark contains dermal fibers that work "like riggings that stabilize a ship's mast", and stiffen dynamically as the shark swims faster to control roll and yaw.[3]
    The dorsal fin of a white shark contains
    dermal fibers that work "like riggings that stabilize a ship's mast", and stiffen dynamically as the shark swims faster to control roll and yaw.[3]
  • Large retractable dorsal fin of the Indo-Pacific sailfish
    Large retractable dorsal fin of the Indo-Pacific sailfish
  • Various species of Ichthyosaurs displaying different types of dorsal fins
    Various species of
    Ichthyosaurs
    displaying different types of dorsal fins

Structure

A dorsal fin is classified as a

lepidotrichia, and the endoskeletal base with associated muscles for movement is the second.[4]

  • Dorsal fin of a perch showing the basals and radials of the pterygiophore that support the dorsal fin.
    Dorsal fin of a perch showing the basals and radials of the pterygiophore that support the dorsal fin.
  • Closeup of the dorsal fin of a common dragonet
    Closeup of the dorsal fin of a common dragonet

See also

Wikimedia Commons has media related to Dorsal fins.
Look up dorsal in Wiktionary, the free dictionary.

Notes

  1. ^
    ISBN 9780761471707
    .
  2. ^ Dement J Species Spotlight: Atlantic Sailfish (Istiophorus albicans) littoralsociety.org. Retrieved 1 April 2012.
  3. doi:10.1002/jmor.10207 pdf[permanent dead link
    ]
  4. ^
    S2CID 13621022
    .
  5. ^ a b c Barton, Michael (2007). Bond's Book of Fish (3rd ed.). The Thompson Corporation. pp. 37–39, 60–61.
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