CHAPTER 24: FISH

1. CHAPTER 24: FISH SPRING 2013 Wakefield

2. GENERAL INFORMATION There are three extant classes of fish: Chondrichthyes, Actinoptergyii and Sarcoptergyii (over 26,000 species in these three classes) General characteristics of all fish include: A. all are aquatic, jawed vertebrates with tetrapodlimb arrangement of paired pelvic and pectoral fins and endoskeleton made of either bone or cartilage or a combination of both. B. Epidermis covered with scales C. the development of jaws with teeth permitted predation of large and active food sources.

3. GENERAL INFORMATION D. Specialized sense organs for hearing, sight and smell evolved with a tripartite brain. Additional senses included the lateral line system and some fish groups also developed an electro-receptive system. E. Complete digestive system F. Bilateral symmetry G. Closed circulatory system H. All fish are dioecious(separate sexes)

4. GENERAL INFORMATION • All fish have a two chambered heart with one Atrium and one Ventricle J. Fish have various methods of achieving neutral buoyancy including two types of swim bladders and internal oil producing organs. ( such as the livers of sharks)

5. CLASS CHONDRICHTHYES (850 species) means “ cartilage fish” • Most are marine but 28 species live in freshwater. • This class includes species which achieve the second largest size in the animal kingdom, second only to whales. The whale shark can reach sizes in excess of 12 meters in length. • All chondrichthyians have a cartilagenous endoskeleton

6. Whale Shark

7. CLASS CHONDRICHTHYES Vertebral column D. All sharks have a heterocercaltail in which the top lobe of the tail is longer than the bottom lobe and contains the vertebra.

8. CLASS CHONDRICHTHYES E. tooth-like dermal denticles composed of a dentine center covered with enamel with distinct points on the posterior side, this is why a shark’s skin feels so abrasive. Their teeth are actually modified scales called Dermal denticlesand why their scales are called skin teeth. The name of these scales is Placoid

9. CLASS CHONDRICHTHYES F. Sharks lack a swim bladder so they achieve neutral bouyancyby maintaining a high osmotic internal pressure and having a large liver filled with a light-weight oil called squalene. They can adjust the amount of this oil in their liver to adjust their body density to ascend or descend through the water column.

10. CLASS CHONDRICHTHYESsubclass Elasmobranchii Represented by Sharks, Skates and Rays • 825 species • 9 living orders • Form and Function • Heterocercal tail • Paired fins, pectoral and pelvic, supported by an appendicular skeleton, In males, the pectoral fins are modified into claspers which are used in copulation. One or two dorsal fins, most of which have spines for defense.

12. CLASS CHONDRICHTHYESsubclass Elasmobranchii c. 5-7 gill slits, no operculum d. A pointed rostrum with a ventral mouth

13. CLASS CHONDRICHTHYESsubclass Elasmobranchii E.Have a well-developed jaw with the upper jaw unfused to the skull allowing for access to large chunks of food. Their teeth are modified scales that grow in rows with up to 7 rows of new teeth waiting to spring up into place to replace teeth lost while feeding ( most sharks and rays loose between 500 and 1200 teeth during their lifetime.

14. G. Digestive system consists of a large esophagus leading to a J-shaped stomach . A liver and pancreas empties into a short straight intestine. Attached to the intestine, is the rectal gland which controls the salt concentration of the blood. CLASS CHONDRICHTHYESsubclass Elasmobranchii F. Eyes are lidless and large with well developed vision

16. CLASS CHONDRICHTHYESsubclass Elasmobranchii 4. PREDATORY LIFE-Sharks and Rays are well-equipped for predation. They track their prey using certain senses in an orderly sequence. a. initial detection is usual from more than a kilometer away using their large olfactory organ (can detect blood 1 part in 10billion)

17. CLASS CHONDRICHTHYESsubclass Elasmobranchii b. prey may be located from fairly long distances by the lateral line system. c. at closer range, sharks switch to vision LATERAL LINE

18. AMPULLAE OF LORENZINI D. During the final stages of attack, the sharks are guided to their prey by a unique system called the Ampullae of Lorenzini( tiny jelly filled tubes on the ventral side of the rostrum) that detect electrical signals, some sharks also use this system to detect prey buried in sand.

19. CLASS CHONDRICHTHYESsubclass Elasmobranchii 5. REPRODUCTION- all chondrichthyians are dioecious with internal fertilization but there are three different types of maternal support for the developing embryo. a. many elasmobranchs lay large yolky eggs immediately after fertilization, this type of maternal support is called oviparous, the eggs are housed in a capsule called a Mermaids Purse and may take up to 2 years to develop

20. CLASS CHONDRICHTHYESsubclass Elasmobranchii 5b. Some elasmobranchs retain the young in their uterus for a prolonged period while they are being nourished by their yolks and are then born alive, this type of maternal support is called ovoviviparous.

21. CLASS CHONDRICHTHYESsubclass Elasmobranchii 5C. Some species have true placental support (just like humans)this is called viviparous with live birth. d. Once maternal support for the developing embryo ends, so does all parental care.

22. CLASS CHONDRICHTHYESsubclass Elasmobranchii TYPES OF SHARKS Coastal waters are inhabited by sharks of Order Carcharhiniformes such as the hammerhead, tiger, and bull, all are known to attack humans. Pelagic sharks such as the Great White which can reach sizes to 6 meters and the Mako are some of the most dangerous to humans

24. CLASS CHONDRICHTHYESsubclass Elasmobranchii The largest fish of all is the whale shark, it is in order Orectiloboformesand is a filter feeder and not dangerous to humans at all.

25. CLASS CHONDRICHTHYESsubclass Elasmobranchii • The largest of the freshwater elasmobranchs is the sawfish which can reach up to 8 meters. The front of their skull is elongated to form a serrated toothed blade which can slash and kill prey

26. CLASS CHONDRICHTHYESsubclass Elasmobranchii • Almost one-half of all elasmobranchs are in order Rajiformes, a group made up of organisms with a dorso-ventrally flattened body and greatly enlarged pectoral fins used like wings for swimming. The gills are on the underneath side of the body but the large spiracle is on top of the head and used for primary breathing to keep from clogging the gills. Their teeth are adapted for crushing molluscs and crustaceans, their main prey.

27. CLASS CHONDRICHTHYESsubclass Elasmobranchii • The largest of this group is the Manta Ray (29’ across and 3000 lbs.) Examples include: electric rays, stingrays, devil rays, eagle rays and the terrible nightshocker.

29. CLASS CHONDRICHTHYESsubclass Holocephali • Called Chimeras ,ratfish, ghostfish • 35 species • Diverged from the earliest shark lineage over 360mya. • Similar to elasmobranchs, but have some unique features • They lack scales • Jaw fused to skull with large plates modified for crushing prey • 4 gills covered with an operculum • Lack a stomach • Deep sea benthic creatures • Long rat-like tail • Oviparous and lay mermaids purses

30. CHIMERAS OR RATFISH

31. Bony fish Class Actinoptergyii Class Sarcoptergyii

32. Class Actinoptergyii • Ray-finned fish ( 24,000 species) General characteristics • Endoskeleton of Bone • Modern fish have a Homocercal tail, some primitive forms have a heterocercal tail ( caudal fin) lungfish have a diphycercal tail

33. Class Actinoptergyii C. Scales ctenoid or cycloid in advanced forms, scales are of ganoid construction in primitive forms.

34. Class Actinoptergyii D. Respiration by gills covered with an operculum E. Neutral buoyancy is achieved with a swimbladder gas may be added or removed from the swim bladder by two methods.

35. Class Actinoptergyii E. Neutral buoyancy is achieved with a swim bladder gas may be added or removed from the swim bladder by two methods. 1. The more primitive method is with a physostomous bladder, the fish must swim to the surface to gulp air and they expel it by burping air out of the pneumatic duct that connects the swim bladder to the esophagus. 2. the more modern method is with a physoclistousbladder in which gas from the blood is absorbed or secreted as needed from a vascular area that is surrounded by a capillary bed called the retemirablewhich functions to trap gasses, primarily oxygen from the blood

36. Class Actinoptergyii F. Bony fish are usually oviparous with external fertilization G. Digestive modifications include spiral valve in ancient forms, modern fish have gastric caeca.

37. Liver 2. swim bladder 3. roe 4. pyloric caeca 5. Stomach 6. intestine

38. Class Actinoptergyii H. Reproductive system of bony fish is usually either oviparous ( egglayers) or ovoviviparous ( live-bearers) There are no viviparous bony fish. Males have a genital pore for release of sperm and urine. Ovoviviparous male species have a gonopodiumwhich is a modified anal fin for internal fertilization. Bony fish have no cloacabut separate urogenital and anal openings. Male sex organ in bony fish-the gonopodium

39. Class Actinoptergyiisubclass Chondrosteai • Means cartilage bone 1. this is an ancient group of fish that have many shark-like characteristics such as a heterocercal tail, a spiral valve in the intestine . Endoskeleton primarly of cartilage, scales ganoid in shape. 2. Examples include sturgeon, paddlefish and the Bichirof Africa which also possesses a lung.

40. Class Actinoptergyiisubclass Chondrosteai

41. Class Actinoptergyiisubclass Neoptergii B. Means “new fin” 1. one main group, the teolosts are made up of all the modern ray-finned fish with a bony endoskeleton, a homocercal tail, and scales in shape either ctenoid or cycloid. 2. The second small group of ray-finned fish is make up of the Gar and Bowfin, both of which are freshwater and predatory with large teeth and ganoidscales.

42. Class Actinoptergyiisubclass Chondrosteai

43. Class Sarcoptergii Means “lobed fined” 6 species of lungfish and 2 species of Coelacanth General Characteristics: A. tail is diphycercal B. skin is embedded with scales called Cosminemade of a dentine center covered with thin enamel much like human teeth. C. Intestine with a spiral valve D. Gill slits with an operculum E. Swimbladder is vascular and can function as a lung. In the coelacanth, it is filled with fat.

44. Class Sarcoptergii Of the six surviving species of Lungfish, two are in one genus and found in Australia. These lungfish depend on gill respiration and cannot survive for very long out of water. • The two species of African lungfish and the two species of South American lungfish live in freshwater streams and ponds that dry up in the dry season and they can live out of water for long periods of time, up to four years, they bury in the mud and form a slime cocoon.

45. Class Sarcoptergii The Coelacanth is called a “fossil fish” because they were thought to be extinct for 70mya until one was brought up in a deep sea drift net off the coast of So. Africa in the 1940’s. A second type possibly a new species was caught in 1998n off the coast of Indonesia. These fish are large headed and heavy bodied with fleshy lobed appendages that they use to walk on the bottom of the ocean. They have an oil filled swim bladder and have the largest eggs of any known fish, over 9 cm in diameter. The eggs hatch internally.

46. Osmotic regulation • Freshwater fish are hyperosmotic regulators because freshwater is extremely dilute and the salt conc. of the body of freshwater fish is much higher so water tends to flow into their bodies, defenses include an opistonephric kidney which produces a very dilute urine and salt absorbing cells in the gills move salt from the water to the blood. Also, they never have to take a drink. • Saltwater fish are hypoosmotic regulators with a different set of problems. Because they live in a salty medium with a higher conc. of salt than their blood, they tend to lose water and gain salt so they risk dying of dehydration. To compensate, the marine fish drink seawater constantly and the gills secrete the salt through salt-secretory cells in the gills.

47. Responses to stimuli • Electrotaxis-attract or repelled by electrical currents • Phototaxis-feeding in daylight hours • Chemotaxis-scent trails in water- feed or breed • rheotaxis-orient headfirst into water currents

48. TYPES OF SYMBIOSIS Symbiosis is the close association between individuals of two or more species • Commensalism-a relationship in which individuals of one species benefit while the individuals of the other species remain unaffected. Ex. Shark and remora • Mutualism-a relationship involving the mutual exploitation and mutual benefit of two or more species. Ex. Rasses and grouper • Parasitism-a type of symbiosis in which one species, the parasite, lives at the expense of the other species, the host. Ex. Candiru and human

49. Migration There are two types of migration undertaken by fish. • Anadromousmigration occurs when adult organisms live in freshwater but return to the ocean to spawn Ex. Eels • Catadromous migration occurs when adult organisms spend their life at sea but swim up freshwater rivers to spawn. Ex. salmon