Marine Fish

1. Marine Fish

2. Phylum Chordata • Dorsal hollow nerve cord • Pharyngeal gill slits • Notochord

3. Subphylum Vertebrata • Backbone made of hollow connecting bones (vertebrae); permits rapid efficient locomotion • Spinal cord ending in a complex brain • Bilateral symmetry • Endoskeleton

4. Fish – 58% are marine • First vertebrates to evolve • Probably evolved from invertebrate chordate – Fig. 7-50 • Most are economically important marine organisms • Used for sport & aquariums • Usually covered with scales and have fins • Poikilothermic (cold blooded) • O2 and CO2 exchange through gills

5. Three Classes of Fish • Agnatha – jawless fish

6. Jawless fish – Class Agnatha – Fig. 8-2 • Lampreys (mostly fresh H2O) & hagfish (marine) • Most primitive • Lack true jaws – feed by suction • Lack paired fins (pectoral & pelvic) & scales • Gill openings separate & external • Cartilaginous skeleton • Notochord persists throughout life

7. Three Classes of Fish • Chondrichthyes - cartilaginous fish

8. Cartilaginous Fish – Class Chondrichthyes – Fig. 8-3 – 8-7 • Sharks, skates, rays, & ratfishes • Cartilaginous skeleton – lighter & more flexible than bone • Jaws; mouth typically ventral • Notochord replaced by vertebrae in adults • Gill opening separate • Paired pectoral & pelvic fins; plus dorsal, anal, & tail fin • Tail fin usually asymmetrical • Skin has tiny pointed scales with very little overlapping – Fig. 8-8

10. Three Classes of Fish • Osteichthyes – bony fish

11. Bony Fish – C lass Osteichthyes • Spotted bass, flounder, salmon, tuna • Body skeletons • Jaws present with mouth usually terminal; provides more freedom of movement • Notochord replaced by vertebrae in adults • Gill openings all covered by a single operculum (protects) • Paired pectoral & pelvic fins (not as fleshy as sharks), dorsal, anal, & tail fins • Tail (caudal) fin is usually symmetrical • Scales are thin, flexible & overlapping and are covered by a thin layer of tissue & mucus. • Swim bladder – gas filled sac that allows fish to adjust buoyancy so it can float at any depth without exerting its’ muscles

13. http://www.youtube.com/watch?v=letqkpG3b5Q (hagfish feeding on whale carcass) • Slime, or mucus is used by many animals both on land and in the sea, but Hagfish have the outstanding ability to defend themselves by producing an incredible slime when touched. It comes from the glands along the side of their body, and within minutes literally liters of it can be produced. • http://www.youtube.com/watch?v=pmaal7Hf0WA&NR=1 (hagfish slime) • http://www.youtube.com/watch?v=yihoIvUBDM4 (manta ray feeding frenzy) • http://www.oceanfootage.com/video_clips/ST05_038 (tuna)

14. Ichthyology – Study of Fish • Body shape – Form fits function – Fig. 8-9 • Very fast swimmers, streamlined bodies, laterally compressed – tunas, sharks • Bottom dwellers – have flattened bodies • Living among vegetation or rocks – need very elongated flexible/bendable body – eel, gunnel • Slow swimmers – bodies are elongate on a vertical plane (seahorse), triangular ( trunkfish) or round (porcupine) • Shape of body can also be a form of camouflage – resembles the area in which they live

19. Ichthyology – Study of Fish • Coloration – can be used as camouflage or warning; sometimes color changes reflect mood or reproductive condition • Chromatophores – specialized pigment cells found in the skin; fish change color by contracting & expanding pigment molecules in these cells • http://video.google.com/videoplay?docid=-125655308012313047# • Aposematic (warning) coloration – warns potential predators to stay away & not attack; protects best against predators that can learn • Cryptic coloration – blending with the environment to deceive predator or prey – Fig. 8-10a

20. Aposmatic coloration

21. Ichthyology – Study of Fish • Coloration (cont.) • Disruptive coloration – presence of stripes, bars or spots that break up outline of fish making it harder to see in the dappled underwater light • Countershading – open water disguise • Silver or white bellies blend with light at surface when viewed from below • Dark blue, black, grey backs blend with bottom when viewed from above

24. Ichthyology – Study of Fish • Locomotion – obtain food, escape from predators & find mates; many cartilaginous fish swim to keep H2O moving over their gills to obtain O2 – Fig. 8-11 • Most fish swim in sinuous motion (S – shaped waves) that moves from head toward caudal fin • Some fish use only their fins - Fig. 8-12 • Myomeres – bands of muscles • http://www.youtube.com/watch?v=o81WIfjrt5I (shark swimming) • To aid buoyancy • Sharks have stiff pectoral fins that increase lift, asymmetric tail causes the head to be pushed upward, large amount of oil in liver causes an increase in buoyancy • Bony fish – swim bladder present, therefore fins are smaller and can be used for greater mobility

25. Ichthyology – Study of Fish • Feeding – wide variety of structural adaptations; form fits function – Fig. 8-13 • Mainly carnivorous • Some are filter feeders • http://www.youtube.com/watch?v=caiMgEnRw7o (basking shark feeding)

26. Ichthyology – Study of Fish • Digestion – Fig. 8-14 • Mouth  esophagus  stomach  intestine  cloaca  anus • Stomach – chemical & mechanical breakdown • Intestine – most absorption of nutrients, spiral valvew in sharks increases surface area • Cloaco – found only in cartilaginous fish, common pathway for digestive, excretory & reproductive system • Accessory organs include pancreas & liver which secrete digestive enzymes • Carnivores tend to have shorter and straighter intestines; plant eating fish have coiled intestines because they need more surface area to digest plants

28. Ichthyology – Study of Fish • Circulatory System – Fig. 8-15 • Closed – blood always contained in vessels • Two chambered heart – blood only passes through the heart once (single circulation) • Advantage of single circulation – all the blood going to the body has already been oxygenated in the gills • Disadvantage – after the blood passes through narrow gill capillaries the blood pressure is greatly reduced, this slows the rate of O2 delivery to the cells and limits the metabolic rate the fish can swim

30. Ichthyology – Study of Fish • Respiratory System – Fig. 8-16, 8-17 • Respiratory surface – gills, exchange of CO2 and O2; dissolved O2 from water must be constantly moved over gills • Irrigation of gills • Cartilaginous fish – water enters through mouth & spiracles; when mouth is shut contractions of the walls of pharynx and gills slits causes water to move over the gills and out • Bony fish – operculum is shut when fish opens mouth & expands pharynx causing water to be sucked in; when mouth closes, the operculum opens and water flows over the gills and out

31. Ichthyology – Study of Fish • Respiratory System (cont.) • Structure of gills • Gills supported by a gill arch • Gill racker keeps food from flowing into gills (may be specialized for filtering in filter feeders) • Gills are divided into gill filaments which contain many thin plates called lamellae (increase surface area)

33. Ichthyology – Study of Fish • Respiratory System (cont.) • Countercurrent gas exchange – an anatomical structure for manipulating a gradient so as to maximize uptake of O2 – Fig. 8-17 • The direction of blood flow through the capillaries in the lamellae is opposite that of H2O flowing over the lamellae (remember – O2 diffuses down its concentration gradient) • Hemoglobin – iron containing protein molecule in RBC’s that carry O2 & CO2 • Myoglobin – protein molecule that can store large amounts of O2

36. Ichthyology – Study of Fish • Regulation of the Internal Environment – Fig. 8-18 • Cartilaginous fish – reduce osmosis by increasing solute concentration of blood • Retain urea which causes and increase in blood solute concentration • Absorbs H2O through gills & skin • Excess salts are excreted by kidneys, intestine, & rectal gland • Bony fish – reduce osmosis • Drinks seawater • Excess salt secreted by gills • Excretes small amounts of concentrated salty urine

39. Ichthyology – Study of Fish • Nervous System & Sensory Organs – Fig. 8-19 – CNS consists of the brain & spinal cord, PNS consists of nerves extending out from the CNS to all parts of the body • Messages are relayed by electrical & chemical signals • NS integrates with the endocrine system • Olfactory – sense of smell (chemoreceptors) • Olfactory sacs on each side of the head pick up “chemical” scents in the water which triggers a signal which travels to the brain

40. Ichthyology – Study of Fish • Nervous System & Sensory Organs (cont.) • Gustatory – sense of taste; chemorecep5ors on taste buds & barbels pick up “chemical” scents • Sight – photoreceptors (rods & cones) contain light sensitive pigments • Nictitating membrane – found in sharks (protects eye) • Pressure – lateral line – Fig. 8-19; mechanoreceptor (pressure) stimulated by water displacements caused by other animals or sounds - • Ampullae of Lorenzini – sense organ in cartilaginous fish that detects weak electrical fields • Sound – mechanoreceptors in fluid filled canals of inner ear that detect changes in pressure caused by vibrations & also are involved in equilibrium & balance

41. http://www.youtube.com/watch?v=N3CXUO0jxNQ (lateral line) barbels

42. http://dsc.discovery.com/videos/ultimate-guide-the-sharks-vibrations-and-shark-vision.htmlhttp://dsc.discovery.com/videos/ultimate-guide-the-sharks-shark-smell.htmlhttp://dsc.discovery.com/videos/ultimate-guide-the-sharks-vibrations-and-shark-vision.htmlhttp://dsc.discovery.com/videos/ultimate-guide-the-sharks-shark-smell.html

43. Ichthyology – Study of Fish • Behavior – used to adapt to physical factors; find food, shelter; prey/predator; courtship & reproduction – Fig. 8-20 – 8-23 • Territoriality – defending home areas against intruders to possibly ensure food & shelter & mates which may be limited; usually involves some type of aggressive behavior that is designed to frighten “predators”; actual fights & fatalities are rare • Schooling – well defined groups that function as well coordinated units – Why school? • Protection against predation • Increase swimming efficiency • Increase hunting efficiency • http://www.youtube.com/watch?v=25xV1IcctfA&feature=related

44. Ichthyology – Study of Fish • Behavior (cont.) • Migration – regular mass movements from one place to another; most migrations seem to be related to feeding and/or reproduction • Navigate by using geographical features, currents, salinity, chemicals, temp., earth’s magnetic field, light • Anadromous – fish that live in ocean but migrate to fresh H2O to breed – salmon – Fig. 8-23 • Catadromous – fish that live in fresh H2O but migrate to the ocean to breed – eel – Fig. 8-24

45. Ichthyology – Study of Fish • Reproduction & Life History – sexes usually separate with both sexes having paired gonads (ovaries/testes) • Reproductive systems • Cloaca – in cartilaginous fish a common pathway for digestive, excretory & reproductive system • Urogenital opening – opening for urine (excretory) & gametes (reproductive); (digestive system has separate opening – anus) • Gamete production usually happens only during certain periods of time when conditions are most favorable • Timing of gamete production is controlled by the release of sex hormones which may be triggered by some environmental factor such as temp., light, availability of food

46. Ichthyology – Study of Fish • Reproduction & Life History (cont.) • Reproductive systems (cont.) • A few are hermaphrodites (have male and female reproductive organs) • Sex reversal – males  females or females  males; probably influenced by presence or absence of hormones & pheromones

47. Ichthyology – Study of Fish • Reproduction & Life History (cont.) • Reproductive behavior – various adaptations to get individuals together • Migrate • Color changes to advertise readiness elaborate courtship behaviors

48. Ichthyology – Study of Fish • Reproduction & Life History • Mating • Copulation – transfer of sperm into females (internal fertilization); usually found in cartilaginous fish; claspers – Fig. 8-26 • Spawning – release of gametes into water (external fertilization); usually found in bony fish – Fig. 8-25 • Remember the number of gametes produced usually corresponds to parental involvement after fertilization (i.e. – large number of gametes, no parental involvement – Fig. 8-27

49. Ichthyology – Study of Fish • Reproduction & Life History • Early development • Ovoviviparous – eggs develop inside female and she gives birth to live young; nutrients are received from yolk sac, mostly cartilaginous fish – ex. Sharks • Oviparous – eggs develop free in the water; nutrients are received from yolk sac – Fig. 8-30 • http://dsc.discovery.com/videos/ultimate-guide-the-sharks-shark-birth-and-maturation.html • Viviporous – nutrition absorbed from walls of mothers reproductive tract ; live bearers