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Lacking paired fins, [20] adult lampreys have one nostril atop the head [21] and seven gill pores on each side of the head. [12] The brain of the lamprey is divided into the telencephalon, diencephalon, midbrain, cerebellum, and medulla. [22]
Because of shared features such as paired fins, the origins of the jawed vertebrates may lie close to Cephalaspidomorphi. Many biologists no longer use the name Cephalaspidomorphi because relations among Osteostraci and Anaspida are unclear, and the affinities of the lampreys are also contested.
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.
Adult river lampreys measure from 25 to 40 cm (10 to 16 in) for the sea-going forms and up to 28 cm (11 in) for the lake forms. The very elongate body is a uniform dark grey above, lightening to yellowish off-white on the sides and pure white below. Like all lampreys, these fish lack paired fins and possess a circular sucking disc instead of jaws.
The sea lamprey has an eel-like body without paired fins. Its mouth is jawless, round and sucker-like, and as wide or wider than the head; sharp teeth are arranged in many concentric circular rows around a sharp, rasp-like tongue. There are seven branchial or gill-like openings behind the eye. Sea lampreys are olive or brown-yellow on the ...
The brook lamprey (Lampetra planeri), 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 ( Lampetra richardsoni ).
Studies have found that the digestive tract of the lamprey actually shrinks and becomes functionally useless as larval lampreys enter the adult stage. The southern brook lamprey encounters a wide range of predators in its natural habitat. [7] The eggs of adults are preyed on by various species of fish and crayfish. [8]
Predation by other fish helps keep lamprey numbers under control. When the lamprey has hatched from its egg into the larvae stage, it is limited to pools or backwater areas with a sand or sandy mud bottom. [5] The young lampreys filter feed for food for around five to seven years until they are large enough to attach themselves to a host ...