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Fish. What are Fish?. Fish are aquatic vertebrates (animals with backbones) with fins for appendages. They "breathe" by means of gills.
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What are Fish? • Fish are aquatic vertebrates (animals with backbones) with fins for appendages. They "breathe" by means of gills. • Fish make up the largest of the vertebrate groups with well over 20,000 species. Most taxonomists recognize 45 orders and 435 families of bony fishes. They can be found in a great variety of habitats in lakes, streams, oceans and estuaries.
Classification • Kingdom- Animalia • Phylum- Chordata • Sub Phylum- Vertebrata • Classes- Agnatha, Chondrichthyes, Osteichthyes
Characteristics of Subphylum Vertebrata • A notochord that has developed into a spinal cord protected byvertebrae and a head with a brain characterize organisms inthis subphylum. • Vertebrates consist of the most complex, large, fast, and conspicuous organisms. They include us, the organism that has had the most effect on the global biosphere. 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 mayrepresent the ancestor of bony fish/sharks. • Scientists theorize that during the Cambrian period the firstof 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.
Classification of Fish • Fish are classified according to the material which makes up their skeletons. • Sharks, skates and rays belong to a group called cartilaginous fish because their skeletons are composed entirely of cartilage. • Tropical fish are called bony fish (scientific name Osteichthyes) because they have skeletons made of bone.
Agnatha Jawless fish: Lampreys, Hagfish
Types of Agnathans • Hagfish- Ocean scavengers, not much is known about them. • Lamprey- fresh and salt water, they are parasitic and prey on other fish. * Both have cartilagenous skeletons and sucker-like mouths.
Chondricthyes Cartilagenous Fish: Shark, Ray
Chondrichthyes • Sharks are adapted for a predatory lifestyle. • Cartilage skeletons, stiff pectoral fins (speed). • No operculum, must keep moving to breathe. • Have live births. • Special scales feel like sandpaper. • Manta, and Sting Rays- live in shallow water, have mouths located on the underside, are fairly docile, wide flat bodies and wing-like fins that are flexible.
Types of Chondrichthyes • Sharks andRays- have no operculum and must keep moving to breathe. • Have different kinds of scales that feel and look more like sandpaper. • Have skeletons made of cartilage not bones.
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: • Subclass Elasmobranchiihave 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. • 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 (continued) • Sharks and rays have other interesting characteristics: • Both have lateral lines – lines of sensory hair along the length of the body that detect water motion and vibrations. • Unique to elasmobranchs 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 (continued) • Elasmobranchs differ in their reproductive strategy. • Sharks and rays produce fewer, but more mature offspring. • Most fertilize their eggs internally. • The male deposits sperm in the female via a pair of copulatory organs called claspers foundat the base of the pelvic fins. • The female lays an egg case in which the juveniles develop for up to six months at which time one or more sharks or rays emerge. • 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.
Fish Characteristics • Gills • Backbone (vertebrae) • Paired Fins • Single Loop Circulation • Two chambered heart
Types of Osteichthyes (Bony Fish) Ray Finned: • Most fish are this type • Fins are supported by bony structures called Rays. • Teleosts are the most advanced form of ray finned fish (symmetrical tails and mobile fins). Lobe Finned: • Fins are long, fleshy, muscular, supported by central core of bones. • Thought to be ancestors of amphibians. • Examples are: Coelacanth, Lungfish
Characteristics of Bony Fish • Class Osteichthyesare jawed fish with bone skeletons. • Most have a swim bladder and scales. • Most control buoyancy by adding or releasing gas to/from their swim bladder. • They control the swim bladders with oxygen gas exchanged to and from blood circulation. • Many have a special organ called the gas gland and the retemirabile that take up gases from the bloodstream for the swim bladder. • This allows many species to hover nearly motionless in midwater. • Most bony fish reproduce externally. • The female lays her eggs, the maleimmediately fertilizes them. • Their strategy is to produce a vast numberof off-spring with only a few expected to survive to maturity.
Characteristics of Bony Fish (continued) • Bony fish have characteristics for life on the reef and for life in theopen ocean: • Bony fish have lateral lines that detect watermotion and vibrations. • Most open ocean and schooling fish have a torpedo-likestreamlined shape that minimizes drag and turbulence. • This fusiform shape is spindle-like, slightly broader at thehead and a V-shaped tail. This makes them fast swimmers. • Most open-ocean and schooling fish have a lighter underside and dark topside for concealment. • Bony fish living in reefs and on the bottom usesurvival strategies more diverse and includeconcealment and armor instead of swimming. • For this reason, you see far more diversity in color,shape, and size among reef and bottom fish. Bony Fish – Half the World’s Vertebrates Chapter 5 Pages 5-74 & 5-75
Fish Respiration • Water flows over Gills as fish opens mouth and swims. • Water flows opposite direction of blood flow. • O2 diffuses from the water into the blood. • Gills are made of thousands of gill filaments. • Gills are covered by the Operculum.
Gills • Oxygen enters the bloodstream and carbon dioxide diffuses out at the gills, which are feathery structures found along the sides of the head. • The gills of a healthy fish are bright red due to the high level of oxygen in the blood that is very close to the surface of the gills. (Without oxygen, the gills would be brown.) • In bony fish, the gills are covered by a bony place called an operculum.
Skin • The skin of most bony fish is covered with bony scales that look like shingles on a roof. • Bony fish scales are waterproof and help protect the fish. • Glands in the skin in which the scales are embedded secrete a layer of mucus that covers the entire body
Mucus helps protect fish from infection. • Handling fish removes this mucus coating and can be harmful to the fish.
Shape • The shape of a fish's body tells a lot about its lifestyle. • Fish with fusiform, or streamlined, bodies are usually fast swimming predators that may swim at high speeds much of the time or are capable of great bursts of speed.
Many tropical fish are laterally compressed (flattened from side to side). • Fish with this shape are not very streamlined but they do not rely on speed for catching food or escaping from predators. • Their body shape is perfectly adapted for hiding in the cracks and crevices of rocks and reef.
They can move into these areas to hide, to escape predators or to get at food that cannot be reached by other fish. • Fish with this body shape, like angelfish, are very maneuverable and capable of short bursts of speed. • They are often camouflaged with disruptive coloration.
Other fish are flattened from top to bottom. • Fish with this body shape spend most of their time at the bottom. • They are usually camouflaged or can change color to match the bottom.
Fusiform(Streamlined) • Laterally Compressed(Flattened from side to side)
