What do lampreys not have

Some species are anadromous, migrating to coastal seas when mature and only returning to reproduce. Lamprey larvae have a low tolerance for high water temperature, hence they are not found in tropical regions. Of these, the majority 10 species are listed as Least Concern LC. While one species, the Ukrainian migratory lamprey Eudontomyzon sp. This means that once downloaded, content can be modified and improved to complement a particular course. This requires, however, that improvements are recycled back into the OER community.

All content present at the time of download must be accordingly credited and, in turn, novel content must be appropriately licensed. Hammerhead shark : Hammerhead sharks tend to school during the day and hunt prey at night. As members of Chondrichthyes, their skeletons are composed of cartilage.

Most cartilaginous fishes live in marine habitats, although a few species live in fresh water for part or all of their lives. Most sharks are carnivores that feed on live prey, either swallowing it whole or using their jaws and teeth to tear it into smaller pieces.

Shark teeth probably evolved from the jagged scales that cover their skin called placoid scales. Some species of sharks and rays are suspension feeders that feed on plankton. Sharks have well-developed sense organs that aid them in locating prey, including a keen sense of smell and electroreception. Organs called ampullae of Lorenzini enable sharks to detect the electromagnetic fields that are produced by all living things, including their prey.

Only aquatic or amphibious animals possess electroreception. Sharks, together with most fishes and aquatic and larval amphibians, also have a sense organ called the lateral line, which is used to detect movement and vibration in the surrounding water.

Rays and skates comprise more than species and are closely related to sharks. They can be distinguished from sharks by their flattened bodies, pectoral fins that are enlarged and fused to the head, and gill slits on their ventral surface. Like sharks, rays and skates have a cartilaginous skeleton. Most species are marine and live on the sea floor, with nearly a worldwide distribution. Members of the clade Osteichthyes, also called bony fish, are characterized by a bony skeleton.

The vast majority of present-day fish belong to this group, which consists of approximately 30, species, making it the largest class of vertebrates in existence today.

Nearly all bony fish have an ossified skeleton with specialized bone cells osteocytes that produce and maintain a calcium phosphate matrix. A few groups of Osteichthyes, such as sturgeons and paddlefish, have primarily cartilaginous skeletons, but retain some bony elements.

The skin of bony fish is often covered by overlapping scales. Skin glands secrete mucus that reduces drag when swimming and aids the fish in osmoregulation.

Like sharks, bony fish have a lateral line system that detects vibrations in water. All bony fish use gills for gas exchange.

Water is drawn over gills that are located in chambers covered and ventilated by a protective, muscular flap called the operculum. Many bony fish also have a swim bladder, a gas-filled organ that helps to control the buoyancy of the fish. The defining features of the living jawless fishes are the lack of jaws and lack of paired lateral appendages fins. They also lack internal ossification and scales, although these are not defining features of the clade.

Some ostracoderms, also unlike living jawless fishes, may have had paired fins. Fossils of the genus Haikouichthys from China, with an age of about million years, show many typical vertebrate characteristics including paired eyes, auditory capsules, and rudimentary vertebrae. Figure 1. Pacific hagfish are scavengers that live on the ocean floor. The class Myxini includes at least 70 species of hagfishes—eel-like scavengers that live on the ocean floor and feed on living or dead invertebrates, fishes, and marine mammals Figure 1.

Although they are almost completely blind, sensory barbels around the mouth help them locate food by smell and touch. They feed using keratinized teeth on a movable cartilaginous plate in the mouth, which rasp pieces of flesh from their prey.

These feeding structures allow the gills to be used exclusively for respiration, not for filter feeding as in the urochordates and cephalochordates.

Hagfishes are entirely marine and are found in oceans around the world, except for the polar regions. The sea lamprey control program, administered by the Great Lakes Fishery Commission, relies on exploiting sea lamprey vulnerability when they are congregated in Great Lakes tributaries, at either the larval or adult stages of their life cycle. Lampricides—pesticides selective to lampreys and the primary sea lamprey control tactic—are deployed to kill larval sea lampreys in the tributaries, while a combination of barriers and traps are used to prevent the upstream migration and reproduction of adult sea lampreys.

See Sea Lamprey Control in the Great Lakes for more information on the various sea lamprey control techniques. Sea Lamprey. How do sea lampreys kill fish? Where are sea lampreys found? What is the impact of the sea lamprey invasion?