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External gills are the gills of an animal, most typically an amphibian, that are exposed to the environment, rather than set inside the pharynx and covered by gill slits, as they are in most fishes. Instead, the respiratory organs are set on a frill of stalks protruding from the sides of an animal's head. The axolotl has three pairs of external ...
The gill arches of bony fish typically have no septum, so that the gills alone project from the arch, supported by individual gill rays. Some species retain gill rakers . Though all but the most primitive bony fish lack a spiracle, the pseudobranch associated with it often remains, being located at the base of the operculum.
The ribs attach to the spine and there are no limbs or limb girdles. The main external features of the fish, the fins, are composed of either bony or soft spines called rays which, with the exception of the caudal fins, have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk. [2]
The gill arches of bony fish typically have no septum, so the gills alone project from the arch, supported by individual gill rays. Some species retain gill rakers. Though all but the most primitive bony fish lack spiracles, the pseudobranch associated with them often remains, being located at the base of the operculum.
It goes through paedomorphosis and retains its external gills. [4] Because skin and lung respiration alone is not sufficient for gas exchange, the common mudpuppy must rely on external gills as its primary means of gas exchange. [5] It is usually a rusty brown color [6] and can grow to an average total length (including tail) of 13 in (330 mm). [7]
In fish gills, there are two types of lamellae, primary and secondary. The primary gill lamellae (also called gill filament) extends from the gill arch, and the secondary gill lamellae extends from the primary gill lamellae. Gas exchange primarily occurs at the secondary gill lamellae, where the tissue is notably only one cell layer thick.
Branchial arches or gill arches are a series of paired bony/cartilaginous "loops" behind the throat (pharyngeal cavity) of fish, which support the fish gills. As chordates , all vertebrate embryos develop pharyngeal arches , though the eventual fate of these arches varies between taxa .
The skeleton of the head of a perch Parts of a pike's head. 1: liver, 2: gill arch, 3: palate with sharp teeth, 4: in the middle a heart, 5: fragment of spinal cord, 6: brain, 7: spherical lens, 8: scale. Fish heads, either separated or still attached to the rest of the fish, are sometimes used in culinary dishes, or boiled for fish stock.