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Delve into the unique characteristics of sharks and rays, successful predators with cartilaginous skeletons and special senses. Learn how they play a vital role in marine ecosystems.
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Characteristics of Subphylum Vertebrata • A notochord that has developed into a spinal cord protected by vertebrae. Also contain a head with a brain.
Significance of Class Agnatha • This is the class of the jawless fish. • Species include lampreys and hagfish. • Organisms in this class are significant because they may represent the ancestor of bony fish/sharks. • Scientists theorize that during the Cambrian period the first of three gill arches on a jawless fish evolved into the first jaws. • Having jaws allowed vertebrates to become very successful predators. • Having jaws put organisms in class Chondrichthyes(sharks and rays) and class Osteichthyes(bony fish) near the top of marine food webs.
Characteristics of Sharks and Rays • Class Chondrichthyesincludes sharks, rays and their close relatives. • Sharks and rays don’t look similar on the outside, butshare a basic anatomy that classifies them together. • Sharks and rays are jawed fish, that lack a swim bladder, and have cartilaginous skeletons.
Special Attributes of Sharks and Rays • Sharks and rays are successful predators: • They have cartilaginous skeletons. • This characteristic saves energy. Saving energy is one of thethings that have made them successful predators. • Sharks have a sense of smell that detect incrediblydiluted substances. (one drop of blood in a mile of water) • Sharks have a “conveyor belt” of multiple rows of teeth. • They swing into place as old teeth wear out and fall away.
Special Attributes of Sharks and Rays • Sharks and rays have other interesting characteristics: • Both have lateral lines – lines of sensory organs along the length of the body that detect water motion and vibrations. • Unique to sharks and rays is electroreception – the ability to sense minute electricity created by muscles and nerves. • Sharks and rays have organs called ampullae of Lorenziniwhich you can see as visible pits near their snouts used to detect the electrical current.
Special Attributes of Sharks and Rays • New type of reproductive strategy. • Sharks and rays produce fewer, but more mature offspring. • Most fertilize their eggs internally. • A few shark species are ovoviviparous – the eggs hatch within the mother’s body. • They give birth to live young rather than egg cases.
The largest fish in the ocean. • Shark size ranges from hand-sized to thewhale shark – the largest fish in the ocean. • Whale sharks can reach 14 meters (46 feet). • Basking sharks can reach 10 meters (33 feet). • Megamouth sharks can reach 6 meters (20 feet). • All three are filter feeders that consume plankton.
Special Attributes of Rays • Superorder Batidoidimorpha of subclass Elasmobranchii consists of therays, which includes skates and guitarfish. • Ray anatomy is well suited to life on sandy bottoms or midwater. • Specially adapted to life in midwater are the eagle ray and manta ray. • Pectoral fins have become “wings” that stretch forward over the gills and are fused to the sides of the head. • Shoulder girdles are flattened and many bones are fused together for rigidity. • No longer need a tail for swimming, the tail has become a defensive whip in some species. • Rays literally fly through the water. • The largest rays are mantas with wingspans exceeding 8 meters (26 feet). • Like the largest shark, the mantas feed on plankton.
