2/9/14 Origin and Importance Evolution Marine Fish Fish were the first vertebrates to appear on Earth about 500 million years ago. Fish are the most economically important organism and are a vital source of protein for countless people and other animals. Vertebrates Bilateral Symmetry with Endoskeleton In vertebrates there is a column or spine of bones that protect a spinal cord that usually ends in a more complex brain. They are also characterized as having bilateral symmetry and an endoskeleton. Fish Numbers Taxonomy Fish are the most abundant vertebrate numbering about 24,000 species. About 58% of those species are marine. Agnatha Jawless Fish Chondrichthyes Cartilaginous Fish FISH Osteichthyes Bony Fish 1
2/9/14 Jawless Fish Teeth With No Jaw Bones Agnatha Jawless Fish Jawless fishes are the most primitive fishes living today (500 million years on Earth). They have no jaw, so they feed by suction using a circular mouth with many teeth. They have a long cylindrical body and lack paired fins and scales. Hagfish Slime Hagfish or slime eels are a species that feed mostly on dead or dying fish/whales on the bottom in depths less than 3000 ft. deep. They grow to be about 2-3 feet in length and sometimes bore into their prey and eat them from the inside out. If you go to grab one, they secrete a layer of slimy material that will get all over the would-be attacker. The slime is released from slime glands along the side of the animal. Feeding VIDEO s Slime VIDEO Lampreys Lampreys are characterized by a toothed, funnel-like sucking mouth. Lamprey means stone lickers. While lampreys are well-known for those species which bore into the flesh of other fish to suck their blood, most species of lamprey are non-parasitic and never feed on other fish. In zoology, lampreys are sometimes not considered to be true fish because of their distinctive mouth structures. Examples of Hagfish Pacific Hagfish, Atlantic Hagfish, Brown Hagfish, Cape Hagfish, Whiteface Hagfish, Shorthead Hagfish, Black Hagfish, Inshore Hagfish, and the Giant Hagfish 2
2/9/14 Chondrichthyes Cartilaginous Fish Cartilaginous Fish This group includes the sharks, rays and skates. Their skeleton is made up of cartilage, a material lighter and more flexible than bone. They have a moveable jaw with many teeth, paired lateral fins for efficient swimming and tough sandpaper like skin made of tiny scales with the same composition as teeth. Sharks, Skates and Rays Sharks Sharks are designed for fast swimming and predatory feeding and have changed little evolutionarily over the past 100 million years because the plan has been so successful. The tail fin is well developed and powerful. The upper lobe is usually longer than the lower. The upper surface has two dorsal fins, the first is usually large and triangular in shape and paired pectoral fins as well as 5-7 gill slits on each side. Upper Lobe Larger Than Lower A Need to Swim Most sharks need to swim continuously in order to pass water over the gills. If they get caught in fishing nets, they often drown. Few species like the nurse shark can lay still on the bottom and get enough oxygen without swimming. Water Enters Mouth/Gills How do gills work? Gills themselves have a car radiator-like appearance. Most fish have 4 gills on each side, consisting of a main bar-like structure that has numerous branches as that of a tree, and those branches consisting of even smaller branch-like structures. This arrangement of cells allows for a very large surface area when the gills are immersed in water. Countercurrent The efficiency of fish gills stems from a simple adaptation known as countercurrent exchange: The blood in the capillaries flows in the opposite direction from the water in the adjacent channels. Dissolved gases diffuse faster between fluids with a large difference in gas concentration (a high concentration gradient) than between fluids with only a small difference. 3
2/9/14 Countercurrents and NOT Nurse Shark Jaws and Teeth The powerful jaws have rows of sharp teeth embedded in a tough, fibrous membrane that covers the jaw. If the shark loses one, the teeth shift forward and a new tooth grows in behind it. Breathing VIDEO Shark Sizes The size of a shark varies. The spiny pygmy shark grows to about 10 inches while the whale shark can grow to almost 60 feet. Whale sharks and their friend the basking shark are filter feeders. The great white shark can grow to about 20 feet, but are not filter feeders. Shark Size Range 4
2/9/14 Where are Sharks Found? Bull Shark Economic Importance Sharks and their meat are economically important. The meat is used for food in restaurants; their oils are used for many products, and their skin, which is known as shagreen. Most are marine, but some like the bull shark have made their home in fresh water. In the orient, the fins are used in soup and some believe the cartilage may have some link to help treat cancer. Because they grow and reproduce so slow, overfishing has become a problem and many restriction have been put on fishing them. Sharks are found throughout all of the oceans at all depths, but commonly live in warm coastal waters. Finning Video Finning What Happens to the Shark http://www.cnn.com/video/#/video/tech/2008/09/16/ pip.shark.finning.cnn 5
2/9/14 All For What?...Soup Rays and Skates 100 dollars a bowl Rays and skates have a flattened body and live primarily on the bottom. Fishes that live on the bottom are called demersal. Their 5 pairs of gills are always located on the bottom side (ventral) rather than the side. Stingrays Watch the Tail Feeding in Skates and Rays Stingrays have a whip-like tail equipped with stinging spines used for defense. Poison glands produce venom that can cause serious problem for those who encounter them. Small Teeth that Crush Many feed on clams, crabs and small fishes that live in the sediment. They excavate the sediment using their pectoral fins and their teeth are modified into grinding plates that crush their prey. 6
2/9/14 Electric Rays Electric rays have special organs to produce electricity up to 200 volts. This can stun the fish for dinner and scare of would-be predators. Eagle and Manta Rays Not all rays live on the bottom. Eagle rays and manta rays fly through the water with the use of the pectoral fins. Eagle rays return to the bottom to feed while manta rays eat plankton. The manta ray can grow to a size of 23 feet from wing to wing. 7