Marine Fish

Phylum ChordataDorsal hollow nerve cordPharyngeal gill slitsNotochord

Subphylum VertebrataBackbone made of hollow connecting bones

(vertebrae); permits rapid efficient locomotion

Spinal cord ending in a complex brainBilateral symmetryEndoskeleton

Fish – 58% are marineFirst vertebrates to evolveProbably evolved from invertebrate chordate

– Fig. 7-50Most are economically important marine

organismsUsed for sport & aquariumsUsually covered with scales and have finsPoikilothermic (cold blooded)O2 and CO2 exchange through gills

Three Classes of FishAgnatha – jawless

fish

Jawless fish – Class Agnatha – Fig. 8-2Lampreys (mostly fresh H2O) & hagfish

(marine)Most primitiveLack true jaws – feed by suctionLack paired fins (pectoral & pelvic) & scalesGill openings separate & externalCartilaginous skeletonNotochord persists throughout life

Three Classes of FishChondrichthyes -

cartilaginous fish

Cartilaginous Fish – Class Chondrichthyes – Fig. 8-3 – 8-7

Sharks, skates, rays, & ratfishesCartilaginous skeleton – lighter & more

flexible than boneJaws; mouth typically ventralNotochord replaced by vertebrae in adultsGill opening separatePaired pectoral & pelvic fins; plus dorsal,

anal, & tail finTail fin usually asymmetricalSkin has tiny pointed scales with very little

overlapping – Fig. 8-8

Three Classes of FishOsteichthyes – bony

fish

Bony Fish – C lass OsteichthyesSpotted bass, flounder, salmon, tunaBody skeletonsJaws present with mouth usually terminal;

provides more freedom of movementNotochord replaced by vertebrae in adultsGill openings all covered by a single operculum

(protects)Paired pectoral & pelvic fins (not as fleshy as

sharks), dorsal, anal, & tail finsTail (caudal) fin is usually symmetricalScales 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

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)

Ichthyology – Study of FishBody shape – Form fits function – Fig. 8-9

Very fast swimmers, streamlined bodies, laterally compressed – tunas, sharks

Bottom dwellers – have flattened bodiesLiving among vegetation or rocks – need very

elongated flexible/bendable body – eel, gunnelSlow 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

Ichthyology – Study of FishColoration – can be used as camouflage or

warning; sometimes color changes reflect mood or reproductive conditionChromatophores – 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

Aposmatic coloration

Ichthyology – Study of FishColoration (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

Ichthyology – Study of FishLocomotion – obtain food, escape from predators

& find mates; many cartilaginous fish swim to keep H2O moving over their gills to obtain O2 – Fig. 8-11Most 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

Ichthyology – Study of FishFeeding – wide variety of structural

adaptations; form fits function – Fig. 8-13Mainly carnivorousSome are filter feedershttp://www.youtube.com/watch?v=caiMgEnRw

7o (basking shark feeding)

Ichthyology – Study of FishDigestion – Fig. 8-14Mouth esophagus stomach intestine cloaca

anusStomach – chemical & mechanical breakdownIntestine – most absorption of nutrients, spiral valvew

in sharks increases surface areaCloaco – found only in cartilaginous fish, common

pathway for digestive, excretory & reproductive systemAccessory organs include pancreas & liver which

secrete digestive enzymesCarnivores tend to have shorter and straighter

intestines; plant eating fish have coiled intestines because they need more surface area to digest plants

Ichthyology – Study of FishCirculatory System – Fig. 8-15

Closed – blood always contained in vesselsTwo 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

Ichthyology – Study of FishRespiratory 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

Ichthyology – Study of FishRespiratory 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)

Ichthyology – Study of FishRespiratory 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

Ichthyology – Study of FishRegulation of the Internal Environment – Fig.

8-18Cartilaginous 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 glandBony fish – reduce osmosis

Drinks seawater Excess salt secreted by gills Excretes small amounts of concentrated salty urine

Ichthyology – Study of FishNervous 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 systemOlfactory – 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

Ichthyology – Study of FishNervous 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

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

barbels

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

http://dsc.discovery.com/videos/ultimate-guide-the-sharks-shark-smell.html

Ichthyology – Study of FishBehavior – used to adapt to physical factors;

find food, shelter; prey/predator; courtship & reproduction – Fig. 8-20 – 8-23Territoriality – 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&fea

ture=related

Ichthyology – Study of FishBehavior (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

Ichthyology – Study of FishReproduction & 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

Ichthyology – Study of FishReproduction & 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

Ichthyology – Study of FishReproduction & Life History (cont.)

Reproductive behavior – various adaptations to get individuals together Migrate Color changes to advertise readiness elaborate

courtship behaviors

Ichthyology – Study of FishReproduction & 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

Ichthyology – Study of FishReproduction & 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