Ampullae of Lorenzini are a network of electroreceptors, sensory organs that detect electric fields in water, found in chondrichthyes (sharks, rays, and chimaeras). The ampullae are a series of symmetrical pores, concentrated around the snout and nose, connected by gel-filled canals. They can conduct electrical impulses so small, that chondrichthyes are likely to be more sensitive … [Read more…]
Elasmobranchs, including sharks, rays, and sawfishes, belong to the taxonomic subclass of cartilaginous fish Elasmobranchii. Like most chondrichthyes, they have exposed gills, no swim bladder, internal fertilization, and placoid denticles. They differ from the other subclass, chimaera (subclass: Holocephali), in that they have rigid dorsal fins, placoid denticles cover most of their bodies, and they … [Read more…]
Osteichthyes are a taxonomic grouping of bony fishes. This group includes ray-finned fishes (class: Actinopterygii) and lobe-finned fishes (class: Sarcopterygii). This highly diverse group of fishes, which contains almost all fish species, is the most diverse group of vertebrates today. Osteichthyes differ from chondrichthyes by (in most cases) possessing a bony skeleton, a swim bladder, … [Read more…]
Chondrichthyes are a taxonomic class of cartilaginous fishes that encompass sharks and rays (elasmobranchs) and chimaera. Though there are exceptions, in general, Chondrichthyes have exposed gills, no swim bladder, internal fertilization, and placoid denticles. These characteristics differentiate them from the more evolutionarily derived branch of fishes, bony fish (Osteichthyes).
Placoid denticles are found on sharks, rays, and chimaeras. Not really a true “scale,” like ctenoid or cycloid scales, placoid denticles are actually modified teeth. They have an inner tissue component, which contains both blood vessels and nerves, that is covered by a layer of dentin and an outer enamel. They form a tough protective skin … [Read more…]
This series of small bones links the swim bladder to the inner ear in Ostariophysian fish, including minnows, carp, catfishes, and characins. When a sound wave hits the swim bladder, the vibration is transferred through the Weberian apparatus to the auditory region of the inner ear. This action helps amplify sound and, as a result, … [Read more…]
The swim bladder is an air filled organ used by some fish to maintain buoyancy at a desired depth and produce or hear sound. Physostomous swim bladders are directly connected to the gastrointestinal tract so that fish with these swim bladders, such as herrings, must “gulp” air to inflate their swim bladder and “burb” or … [Read more…]
The lateral line is, literally, an observable line down both sides of a fish. It is also a sensory organ system that helps fish detect motion in the water around them. When water along the lateral line is displaced by movement or a vibration nearby, hair cells (similar in form and function to hair cells … [Read more…]
Photophores are organs that are used by fish (and invertebrates) to produce light either by chemical reaction or through symbiotic bacteria capable of bioluminescence. Most fish that use photophores live in the deep sea where light from the surface is limited. Like a firefly in the sea, some of these fish use photophores to attract … [Read more…]
Thermoregulation is the process by which an organism controls its internal temperature. Fish have many different mechanisms for regulating their temperature. Most fish are ectothermic, using their environmental temperature to manage their body temperature, but some fish are endothermic, having the metabolic ability to internally manage temperature. Poikilothermic fish are ectotherms which have no control over … [Read more…]