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
(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.
(hagfish slime)
(manta ray feeding frenzy)
(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
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
(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
(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 – 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

43. Ichthyology – Study of Fish
Behavior – used to adapt to physical factors; find food, shelter; prey/predator; courtship & reproduction – Fig – 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

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
Viviporous – nutrition absorbed from walls of mothers reproductive tract ; live bearers