Vertebrates are animals with a vertebral column, and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain.
Fish anatomy is the study of the form or morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in living fish.
Pinealocytes are the main cells contained in the pineal gland, located behind the third ventricle and between the two hemispheres of the brain. The primary function of the pinealocytes is the secretion of the hormone melatonin, important in the regulation of circadian rhythms. In humans, the suprachiasmatic nucleus of the hypothalamus communicates the message of darkness to the pinealocytes, and as a result, controls the day and night cycle. It has been suggested that pinealocytes are derived from photoreceptor cells. Research has also shown the decline in the number of pinealocytes by way of apoptosis as the age of the organism increases. There are two different types of pinealocytes, type I and type II, which have been classified based on certain properties including shape, presence or absence of infolding of the nuclear envelope, and composition of the cytoplasm.
The sea lamprey is a parasitic lamprey native to the Northern Hemisphere. It is sometimes referred to as the "vampire fish". In its original habitats, the sea lamprey coevolved with its hosts, and those hosts evolved a measure of resistance to the sea lampreys.
The brook lamprey, also known as the European brook lamprey and the western brook lamprey is a small European lamprey species that exclusively inhabits freshwater environments. The species is related to, but distinct from, the North American western brook lamprey.
The stoplight loosejaws are small, deep-sea dragonfishes of the genus Malacosteus, classified either within the subfamily Malacosteinae of the family Stomiidae, or in the separate family Malacosteidae. They are found worldwide, outside of the Arctic and Subantarctic, in the mesopelagic zone below a depth of 500 meters. This genus once contained three nominal species: M. niger, M. choristodactylus, and M. danae, with the validity of the latter two species being challenged by different authors at various times. In 2007, Kenaley examined over 450 stoplight loosejaw specimens and revised the genus to contain two species, M. niger and the new M. australis.
Mordacia praecox, the Australian brook lamprey or nonparasitic lamprey, is a freshwater species of southern topeyed lamprey that occurs in south-eastern Australia. It has a thin eel-like body around 12 to 15 cm long, with two low dorsal fins on the back half. The skin is dark blue above and grey below. Its eyes are small, and located on the top of its head. Unlike M. mordax, M. praecox has eyes that appear to have the potential for dichromatic vision despite being similarly adapted for low-light environments.
The pouched lamprey, also known as the piharau in New Zealand's North Island, korokoro,kanakana in the South Island, or wide-mouthed lamprey, is a species in the genus Geotria, which is the only genus in the family Geotriidae. The second species in the genus is the Argentinian lamprey, which was revalidated as a separate species in 2020. The pouched lamprey is native to the southern hemisphere. It spends the early part of its life in fresh water, migrating to the sea as an adult, and returning to fresh water to spawn and die.
Geotria is the only genus in the lamprey family Geotriidae. It has 2 known species: Geotria australis and Geotria macrostoma. Both species were considered conspecific until G. macrostoma was revived in a 2020 study.
The Pacific lamprey is an anadromous parasitic lamprey from the Pacific Coast of North America and Asia in an area called the Pacific Rim. It is a member of the Petromyzontidae family. The Pacific lamprey is also known as the three-tooth lamprey and tridentate lamprey.
Shark anatomy differs from that of bony fish in a variety of ways. Variation observed within shark anatomy is a potential result of speciation and habitat variation.
The silver lamprey is a lamprey commonly found in the Northern and Central United States, as well as a large part of southern Canada. Its binomial name means "sucking fish" in Greek and "one-pointed" in Latin. The silver lamprey is a member of the class Agnatha, sometimes referred to as cyclostomes (round-mouths). Other common names include: bloodsucker, blue lamprey, hitch-hiker, lamper, lamprey eel, northern lamprety. The silver lamprey should not be confused with the sea lamprey, which has caused considerable damage to native fish populations in the Great Lakes region.
Mordacia is a genus of lamprey, the sole genus of the family Mordaciidae, also known as the southern topeyed lampreys.
Mordacia lapicida, also known as the Chilean lamprey, is a species of southern topeyed lamprey endemic to southern Chile, where it can be found in riverine and marine habitats. This species is anadromous. This parasitic lamprey can reach a length of 54 centimetres (21 in) SL. Ammocoetes and adults of this species are found in rivers, and occur in fine sand along river banks. The life cycle of a Mordacia lapicida is divided into three life stages: freshwater rearing, an ocean parasite and an adult spawning stage. Once in the adult stage, individuals migrate into marine waters where they attack and attach themselves to marine fishes. For this species, metamorphosis occurs during August and March.
Marine vertebrates are vertebrates that live in marine environments, which include saltwater fish and marine tetrapods. As a subphylum of chordates, all vertebrates have evolved a vertebral column (backbone) based around the embryonic notochord, forming the core structural support of an internal skeleton, and also serves to enclose and protect the spinal cord.
Lampreys are a group of jawless fish comprising the order Petromyzontiformes. The adult lamprey is characterized by a toothed, funnel-like sucking mouth. The common name "lamprey" is probably derived from Latin lampetra, which may mean "stone licker", though the etymology is uncertain. Lamprey is sometimes seen for the plural form.
The Caspian lamprey, Caspiomyzon wagneri, is a species of lamprey native to the Caspian Sea, and a member of the Petromyzontidae family. This species is a non-parasitic lamprey that feeds on animal carcasses.
The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fish lineages belong to the Agnatha, or jawless fish. Early examples include Haikouichthys. During the late Cambrian, eel-like jawless fish called the conodonts, and small mostly armoured fish known as ostracoderms, first appeared. Most jawless fish are now extinct; but the extant lampreys may approximate ancient pre-jawed fish. Lampreys belong to the Cyclostomata, which includes the extant hagfish, and this group may have split early on from other agnathans.
Priscomyzon riniensis is an extinct lamprey that lived some 360 million years ago during the Famennian in a marine or estuarine environment in South Africa. This small agnathan is anatomically similar to the Mazon Creek lampreys, but is some 35 million years older. Its key developments included the first known large oral disc, circumoral teeth and a branchial basket.
Lampetra ayresii is a species of lamprey in the family Petromyzontidae. It is also called the river lamprey or western river lamprey. It is found in the eastern Pacific, specifically from Tee Harbor, Juneau in Alaska to the Sacramento–San Joaquin drainage in California, USA. It can survive in both marine surface waters and freshwater lakes, rivers, and creeks. In freshwater, it is found typically in the lower portions of large river systems. It is a predatory fish and feeds on fishes in the size range of 10–30 cm. It feeds by attaching to prey using its round, sucker-like mouth. Adult western river lampreys typically grow to about 21 cm (8.3 in) total length (TL), but can reach 31 cm (12 in) TL.
