Chapter 8Chapter 8

Marine FishesMarine Fishes

Phylum Chordata

Subphylum Vertebrata

Classification of FishesClassification of Fishes

Marine FishMarine Fish

• First vertebrates - 500 million years agoFirst vertebrates - 500 million years ago

• Oldest and largest group of vertebratesOldest and largest group of vertebrates

• 24,000 known species of fish, 15,000 marine24,000 known species of fish, 15,000 marine

• Bilateral symmetryBilateral symmetry

• EndoskeletonEndoskeleton

Vertebrates: An Vertebrates: An IntroductionIntroduction

• Have a backbone (also called Have a backbone (also called vertebral vertebral columncolumn or spine) or spine)

• The backbone encloses and protects the The backbone encloses and protects the nerve cord nerve cord or spinal cordor spinal cord

• The spinal cord ends in a brain The spinal cord ends in a brain protected by a skullprotected by a skull

Types of Marine FishTypes of Marine Fish

1.1. AgnathaAgnatha (jawless fish) (jawless fish)• HagfishHagfish• LampreysLampreys

2.2. ChondrichthyesChondrichthyes (cartilaginous fish) (cartilaginous fish)• SharksSharks• SkatesSkates• RaysRays• ratfishratfish

3.3. OsteichthyesOsteichthyes (bony fish) (bony fish)• Lobe-finned fishesLobe-finned fishes• Ray-finned fishesRay-finned fishes

Types of Marine FishTypes of Marine Fish

Class Agnatha Class Agnatha (Hagfish and Lampreys)(Hagfish and Lampreys)– Most primitive fishes living todayMost primitive fishes living today

– These These jawless fish jawless fish have a muscular, circular have a muscular, circular mouth with rows of teeth in rings and feed by mouth with rows of teeth in rings and feed by suctionsuction

– Long, cylindrical bodyLong, cylindrical body

– Lack paired fins and scales seen in other fishLack paired fins and scales seen in other fish

Types of Marine FishTypes of Marine Fish

A. Hagfishes or A. Hagfishes or ““slime eelsslime eels””– 20 species20 species– Exclusively marineExclusively marine– They feed on dead and dying fish and They feed on dead and dying fish and

marine mammalsmarine mammals– Live in burrows in soft sedimentsLive in burrows in soft sediments– Produce large quantities of Produce large quantities of mucousmucous from from

glands in the skin to protect them while glands in the skin to protect them while feedingfeeding

HagfishHagfish

Hagfish videoHagfish video

•http://www.youtube.com/watch?v=NYRr_MrjebA

Types of Marine FishTypes of Marine Fish

B. LampreyB. Lamprey– 30 species30 species– Freshwater (most) and MarineFreshwater (most) and Marine– Adults of some species live in sea, but return to Adults of some species live in sea, but return to

freshwater to breed freshwater to breed – Adults normally die after breeding.Adults normally die after breeding.– Other species live in freshwater lakesOther species live in freshwater lakes– Attach to other fish and suck their bloodAttach to other fish and suck their blood

LampreyLamprey

LampreyLamprey

•http://www.youtube.com/watch?v=x-KJZ22-wTQ

Advanced Groups of FishAdvanced Groups of Fish

• Fishes in the Chondrichthyes and Fishes in the Chondrichthyes and Osteichthyes are considered to be more Osteichthyes are considered to be more advanced. advanced.

• General Characteristics (advancements) General Characteristics (advancements) seen in these groups:seen in these groups:– Highly efficient gillsHighly efficient gills– Scales cover the body Scales cover the body – Paired fins Paired fins – A wide variety of jaw and feeding typesA wide variety of jaw and feeding types– Lateral line and other sensory organsLateral line and other sensory organs– Streamlined bodyStreamlined body

External Anatomy of More External Anatomy of More Advanced Fish GroupsAdvanced Fish Groups

• These representative fish show the position of These representative fish show the position of fins in cartilaginous and bony fish.fins in cartilaginous and bony fish.

Types of Marine FishTypes of Marine Fish

2. 2. Class Chondrichthyes Class Chondrichthyes – Cartilaginous fish– Cartilaginous fish•General Characteristics of Group:General Characteristics of Group:

– About 1000 speciesAbout 1000 species– Sharks, rays, skates and ratfishes Sharks, rays, skates and ratfishes – Skeleton of Skeleton of cartilagecartilage -lighter and more flexible than -lighter and more flexible than

bonebone– Movable jaws with well-developed teethMovable jaws with well-developed teeth– Placoid scales Placoid scales and paired finsand paired fins

– scales cause rough, sandpaper skinscales cause rough, sandpaper skin– SpiraclesSpiracles in many species (openings on head used to in many species (openings on head used to

bring water directly in for respiration without opening bring water directly in for respiration without opening the mouth)the mouth)

– Males in most species have projections of the anal fin Males in most species have projections of the anal fin called called claspersclaspers that are used in copulation that are used in copulation

Paired fins

Placoid scales

Class ChondrichthyesClass Chondrichthyes

SharksSharks•350 species well adapted for fast swimming (fusiform shape) and 350 species well adapted for fast swimming (fusiform shape) and predatory feedingpredatory feeding

•Some have not changed for 100 mySome have not changed for 100 my

•Caudal fin Caudal fin (tail) well developed and powerful(tail) well developed and powerful– Heterocercal Heterocercal – upper lobe longer than lower– upper lobe longer than lower

•Two dorsal fins and paired pectoral finsTwo dorsal fins and paired pectoral fins

•5-7 gill slits behind head on either side5-7 gill slits behind head on either side

•Powerful jaws with several rows of teeth that move forwardPowerful jaws with several rows of teeth that move forward

Shark Diversity

Shark Diversity

Class ChondrichthyesClass Chondrichthyes

Shark Diversity – found in all oceans and depthsShark Diversity – found in all oceans and depths•HammerheadHammerhead – wide flattened head acts as rudder and widens – wide flattened head acts as rudder and widens sensory organs for better receptionsensory organs for better reception

•SawsharksSawsharks – long, flattened head with teeth – long, flattened head with teeth

•Thresher sharks Thresher sharks – long upper lobe on tail to herd and stun fish– long upper lobe on tail to herd and stun fish

•Spined pigmy shark Spined pigmy shark – 10 inches– 10 inches

•Whale shark Whale shark – 60 feet filter feeders (plankton)– 60 feet filter feeders (plankton)

•Great white shark Great white shark – 20 feet– 20 feethttp://www.youtube.com/watch?v=n9L4Mwn6wu0

Class ChondrichthyesClass Chondrichthyes• Rays and SkatesRays and Skates

– 500 species500 species– Dorsoventrally flattenedDorsoventrally flattened– Demersal Demersal – bottom dwellers (some cover with sand and – bottom dwellers (some cover with sand and

hide)hide)– Pectoral fins flat and expanded – wingsPectoral fins flat and expanded – wings– 5 pairs of gills slits on ventral side5 pairs of gills slits on ventral side– Spiracles on dorsal sideSpiracles on dorsal side

Class ChondrichthyesClass Chondrichthyes• Rays Rays

– Large flattened teeth for feeding on molluscs and Large flattened teeth for feeding on molluscs and arthropodsarthropods

– Have long whip-like tailsHave long whip-like tails; in sting rays, there is a spine ; in sting rays, there is a spine (barb) at the base of the tail with an associated poison (barb) at the base of the tail with an associated poison glandgland

– Stepping on a ray or making contact with the ray may Stepping on a ray or making contact with the ray may eject venomous spineeject venomous spine

– Electric rays have organs that produce electricity on Electric rays have organs that produce electricity on either side of headeither side of head

Types of Rays and Types of Rays and SkatesSkates

• StingraysStingrays

• Bat ray Bat ray

• Cow nosed rayCow nosed ray

• Electric raysElectric rays

• Eagle rayEagle ray

• Bull ray (killed Steve Irwin)Bull ray (killed Steve Irwin)

• skatesskates

Cow nose rayCow nose ray

Bat rayBat ray

Eagle rayEagle ray

Bull rayBull ray

Sting raySting ray

Ray and Skate VideoRay and Skate Video

• Stingray national geographicStingray national geographic

•http://www.youtube.com/watch?v=Nbuu1Fa-c1k

Class ChondrichthyesClass Chondrichthyes

• SkatesSkates– Dorsoventrally flattened with pectoral fins modified into Dorsoventrally flattened with pectoral fins modified into

wingswings– Rays are less mobile than skatesRays are less mobile than skates– Skates have a fleshy tail and no spine on the tailSkates have a fleshy tail and no spine on the tail– Major difference:Major difference:

– Rays are Rays are viviparousviviparous (bearing live young) (bearing live young)– Skates are Skates are oviparousoviparous (laying eggs) (laying eggs)

– After fertilization, the female lays egg cases with an After fertilization, the female lays egg cases with an embryo insideembryo inside

– The embryo develops within the protection of the egg The embryo develops within the protection of the egg case for weeks to monthscase for weeks to months

– They are also demersal and feed on molluscs and They are also demersal and feed on molluscs and arthropods primarilyarthropods primarily

Mermaid’s Purse

Class ChondrichthyesClass Chondrichthyes

• Ratfishes (Chimaeras)Ratfishes (Chimaeras)– 30 species30 species– Deep water inhabitantDeep water inhabitant– One pair of gill slits is covered by a flap of One pair of gill slits is covered by a flap of

skin skin – They feed on the bottom on crustaceans and They feed on the bottom on crustaceans and

molluscs primarilymolluscs primarily– Heterocercal Heterocercal tail like in sharkstail like in sharks– Unlike others in this group, they also have Unlike others in this group, they also have

fin rays (tiny support rods) in the finsfin rays (tiny support rods) in the fins

Hydrolagus colliei

Ratfishes or chimaeras

Types of Marine FishTypes of Marine Fish• Class Osteichthyes Class Osteichthyes - The Bony Fish- The Bony Fish

– Skeleton composed of boneSkeleton composed of bone– Over 23, 000 species worldwideOver 23, 000 species worldwide– Gills used for respirationGills used for respiration– HomocercalHomocercal tail (two lobes of equal size) provides tail (two lobes of equal size) provides

forward thrustforward thrust– CycloidCycloid (smooth) or (smooth) or ctenoidctenoid (spiny) scales (spiny) scales– OperculumOperculum – boney flap protecting gills – boney flap protecting gills– Swim bladder Swim bladder – change depths (heavy skeleton– change depths (heavy skeleton))

Swim BladderSwim Bladder

• Swim bladder used for buoyancy control (some Swim bladder used for buoyancy control (some bottom dwelling fish lack swim bladder)bottom dwelling fish lack swim bladder)

• Sound, pressure detectionSound, pressure detection

• Bony fish ONLY- (ex. NOT in sharks)Bony fish ONLY- (ex. NOT in sharks)

Biology of FishesBiology of Fishes• IchthyologyIchthyology – study of fishes – study of fishes

• Body shape – related to lifestyleBody shape – related to lifestyle– FusiformFusiform – streamlined, strong, fast – streamlined, strong, fast– CompressedCompressed- thin, easy, quick short - thin, easy, quick short

burstsbursts– DepressedDepressed – flat, demersal, “fly” – flat, demersal, “fly”

through waterthrough water– Some irregular shapes can act as Some irregular shapes can act as

camouflage among seaweed, or rockscamouflage among seaweed, or rocks

Coloration

Biology of Fish - Biology of Fish - ColorationColoration

• ColorationColoration– Cryptic coloration Cryptic coloration – color to blend in with – color to blend in with

environmentenvironment– Bright colored Bright colored – chromatophores– chromatophores– Structural colors Structural colors – skin reflects only certain – skin reflects only certain

colorscolors• Shiny iridescent fishesShiny iridescent fishes

– Warning colors Warning colors – advertise they are dangerous, – advertise they are dangerous, poisonous, or taste badpoisonous, or taste bad

– Disruptive coloration Disruptive coloration – stripes break up outline of – stripes break up outline of fishfish• Difficult to pick out single fish from groupDifficult to pick out single fish from group

– CountershadingCountershading – light ventral and dark dorsal – light ventral and dark dorsal

Cryptic Coloration

Bright Coloration

Structural Coloration

Warning Colors

Disruptive Coloration

Biology of Fish - Biology of Fish - LocomotionLocomotion

• Most fish exhibit an Most fish exhibit an ““s-shapeds-shaped”” swimming pattern swimming pattern– Pushes against water to move body forwardPushes against water to move body forward

• Some move a) whole body, b) tail end, C) other Some move a) whole body, b) tail end, C) other fins, d) caudal finfins, d) caudal fin

• MyomeresMyomeres – muscles run along sides of body – muscles run along sides of body

Biology of Fish - Biology of Fish - LocomotionLocomotion

• Sharks use fins for liftSharks use fins for lift

• Bony fish use swim bladderBony fish use swim bladder

• Dorsal and anal fins provide steering and Dorsal and anal fins provide steering and stability (no rolling)stability (no rolling)

• Pectoral and pelvic fins help turn, balance, Pectoral and pelvic fins help turn, balance, and brakeand brake

Biology of Fish - FeedingBiology of Fish - Feeding

• Most sharks are carnivores – bite prey Most sharks are carnivores – bite prey larger than themselveslarger than themselves

• Many Many cartilaginouscartilaginous fish are filter feeders fish are filter feeders

• Bony fish are diverse in how they feed, Bony fish are diverse in how they feed, though most are carnivorous though most are carnivorous – Protrusible Protrusible jaws allow more flexibility in jaws allow more flexibility in

feeding habitsfeeding habits

Biology of Fish - FeedingBiology of Fish - Feeding

• Different mouths have evolved for different dietsDifferent mouths have evolved for different diets– Teeth for rasping prey or biting off chunksTeeth for rasping prey or biting off chunks

– Huge mouths swallow large prey or filter feedHuge mouths swallow large prey or filter feed

– Beaks for biting hard coralBeaks for biting hard coral

– Downward pointing mouth – bottom feedersDownward pointing mouth – bottom feeders

Biology of Fish - Biology of Fish - DigestionDigestion

• Digestion accomplished with Digestion accomplished with stomach, stomach, intestine (with anus or cloaca), liver, intestine (with anus or cloaca), liver, pyloric caeca and pancreaspyloric caeca and pancreas– CloacaCloaca – one exit for feces, urine and gametes– one exit for feces, urine and gametes

• The stomach– stretch receptors in the wall The stomach– stretch receptors in the wall of the stomach indicate when a meal is of the stomach indicate when a meal is presentpresent

Biology of Fish - Biology of Fish - DigestionDigestion

• The intestine, pyloric caeca, pancreas and The intestine, pyloric caeca, pancreas and liver all secrete digestive enzymesliver all secrete digestive enzymes

• The intestines of carnivorous fish=short The intestines of carnivorous fish=short and straight and straight

• Intestines of herbivorous fish = longer and Intestines of herbivorous fish = longer and more coiledmore coiled

Biology of Fish -Biology of Fish -Circulatory SystemCirculatory System

• Fish have a Fish have a two chambered heart two chambered heart that that serves to pump blood throughout the body serves to pump blood throughout the body (in contrast to the 4 chambered heart seen (in contrast to the 4 chambered heart seen in mammals)in mammals)

Biology of Fish – Biology of Fish – Respiratory SystemRespiratory System

• Irrigation of the GillsIrrigation of the Gills– Extract oxygen from water; water flows Extract oxygen from water; water flows

over gillsover gills

Biology of Fish – Biology of Fish – Respiratory SystemRespiratory System

• Structure of GillsStructure of Gills– Gill archGill arch – supports two gill filaments – supports two gill filaments

– Gill rakers Gill rakers – block food from entering gills– block food from entering gills• Filter feeders use them to gather foodFilter feeders use them to gather food

– Gill filaments have lots of capillaries for gas Gill filaments have lots of capillaries for gas exchangeexchange• LamellaeLamellae – discs that increase surface area – discs that increase surface area

Biology of Fish – Biology of Fish – Respiratory SystemRespiratory System

• Gas ExchangeGas Exchange– Oxygen diffuses from water into capillary Oxygen diffuses from water into capillary

bloodblood• Blood flows in opposite direction of water flow called Blood flows in opposite direction of water flow called

Countercurrent System of flowCountercurrent System of flow or or Countercurrent Countercurrent ExchangeExchange

– Dismisses CODismisses CO22 at same time at same time– OO22 and CO and CO22 carried by carried by hemoglobinhemoglobin– Muscles use lots of OMuscles use lots of O22 and use and use myoglobinmyoglobin

to store Oto store O22

– http://www.youtube.com/watch?v=cVFqME-NW9s

Biology of Fish – Biology of Fish – Regulation of Internal Regulation of Internal

EnvironmentEnvironment• Water is very solute-rich, fish have a Water is very solute-rich, fish have a

tendency to gain solutes and lose watertendency to gain solutes and lose water

• Fish need to have mechanisms to combat Fish need to have mechanisms to combat this issue – this is called this issue – this is called osmoregulationosmoregulation

Fluid Balance in FishFluid Balance in Fish

• Methods of Osmoregulation:Methods of Osmoregulation:– Swallow seawater but them expel the solutes Swallow seawater but them expel the solutes

in the digestive process (keep the water and in the digestive process (keep the water and lose the solutes)lose the solutes)

– Pass very little urine highly concentrated with Pass very little urine highly concentrated with solutes with very little water contentsolutes with very little water content

Fluid Balance in FishFluid Balance in Fish

• Osmoregulation cont:Osmoregulation cont:– In cartilaginous fish, the blood is kept at about In cartilaginous fish, the blood is kept at about

the same concentration as seawaterthe same concentration as seawater

– Keep urea in the bloodstream (this toxin is Keep urea in the bloodstream (this toxin is filtered out of the blood by other organs)filtered out of the blood by other organs)

– If salt enters through gills or feeding – If salt enters through gills or feeding – rectal rectal glandgland expels salt expels salt

OsmoregulationOsmoregulation

• Freshwater fish:Freshwater fish:– Water diffuses inWater diffuses in– Ions diffuse outIons diffuse out– Drink littleDrink little– Lots of dilute urineLots of dilute urine– Actively reabsorb ions by kidneys and Actively reabsorb ions by kidneys and

gillsgills

OsmoregulationOsmoregulation

• Saltwater fishSaltwater fish– Water diffuses outWater diffuses out– Ions diffuse inIons diffuse in– Drink a lotDrink a lot– Concentrated urineConcentrated urine– Actively excrete ions by kidneys, gills, Actively excrete ions by kidneys, gills,

and gutand gut

Biology of Fish - Nervous Biology of Fish - Nervous SystemSystem

• CNS – brain and spinal cord; nerves connect CNS – brain and spinal cord; nerves connect • Fish also possess Fish also possess olfactory sacs olfactory sacs (with nostrils) for (with nostrils) for

smellingsmelling– Sharks can smell blood 1 part/millionSharks can smell blood 1 part/million– Salmon – recognize smells for migrationSalmon – recognize smells for migration

• Taste buds are located in the mouth, lips, barbels Taste buds are located in the mouth, lips, barbels (organs near mouth of bottom feeders) and skin(organs near mouth of bottom feeders) and skin

Biology of Fish - Nervous Biology of Fish - Nervous SystemSystem

• All fish rely heavily on the All fish rely heavily on the lateral line lateral line systemsystem– Pores and canals lined with cells called Pores and canals lined with cells called

neuromasts that are specialized to detect neuromasts that are specialized to detect vibrationsvibrations•These vibrations can indicate a predator or These vibrations can indicate a predator or

prey or the position of other fish in a schoolprey or the position of other fish in a school

• Cartilaginous fish have Cartilaginous fish have ampullae of ampullae of LorenziniLorenzini– Detect electrical fieldsDetect electrical fields– Help some detect hidden prey in sedimentHelp some detect hidden prey in sediment

Lateral Line

nerves

Biology of Fish - Nervous Biology of Fish - Nervous SystemSystem

• In humans, the lens changes In humans, the lens changes shapeshape for focusing for focusing on itemson items

• In fish, the In fish, the positionposition of the lens changes like in a of the lens changes like in a cameracamera

• In some sharks, the eye is covered by a In some sharks, the eye is covered by a nictitating membrane nictitating membrane that covers the eye –that covers the eye –protect the eye, especially during feedingprotect the eye, especially during feeding

The Fish Nervous SystemThe Fish Nervous System

• The inner ears are set in fluid-filled The inner ears are set in fluid-filled canals with sensory cells similar to canals with sensory cells similar to the lateral line systemthe lateral line system..

Behaviors in FishBehaviors in Fish

• TerritorialityTerritoriality– Some territorial all the time, others only Some territorial all the time, others only

during reproductionduring reproduction– Maintain territories by Maintain territories by ““posturingposturing””

•Raised fins, open mouth, darting, etc.Raised fins, open mouth, darting, etc.

– Fights are actually rareFights are actually rare

Territoriality

Behaviors in FishBehaviors in Fish

• SchoolingSchooling– Schooling is used by a wide variety of fishSchooling is used by a wide variety of fish– Fish appear much larger (as thus avoid Fish appear much larger (as thus avoid

detection by predators)detection by predators)– Harder for a predator to capture any one Harder for a predator to capture any one

fishfish– Because of this, many fish school as Because of this, many fish school as

juvenilesjuveniles– More efficient swimming?More efficient swimming?

Fish Schooling

Behaviors in FishBehaviors in Fish

• MigrationsMigrations– Mass movement from one place to anotherMass movement from one place to another

• Once per day, year, or lifetimeOnce per day, year, or lifetime

– Onshore to/from outshoreOnshore to/from outshore– Vertical migrationVertical migration– TransoceanicTransoceanic – tuna, salmon – tuna, salmon

Behaviors in FishBehaviors in Fish

• MigrationsMigrations– Anadromous Anadromous –sea, migrate fresh for –sea, migrate fresh for

reproduction – Pacific salmon and the Skipjack reproduction – Pacific salmon and the Skipjack tunatuna• HomingHoming behavior – sexual maturity swim up rivers or behavior – sexual maturity swim up rivers or

stream where they were bornstream where they were born

– Catadromous Catadromous – fresh, migrate marine for – fresh, migrate marine for reproduction – freshwater eels (Anguilla)reproduction – freshwater eels (Anguilla)

Reproduction and Life Reproduction and Life HistoryHistory

• Cartilaginous fish use cloaca; bony fish use urogential Cartilaginous fish use cloaca; bony fish use urogential openingopening

• Sex hormones Sex hormones control the development of sperm and control the development of sperm and eggs in fisheggs in fish

• The release of sex hormones cued by environmentThe release of sex hormones cued by environment

• Broadcast spawning is most commonBroadcast spawning is most common

• Internal fertilizationInternal fertilization– Typical among cartilaginous fish using claspersTypical among cartilaginous fish using claspers

Reproduction and Life Reproduction and Life HistoryHistory

• Some fish are hermaphroditicSome fish are hermaphroditic

• Simultaneous hermaphroditesSimultaneous hermaphrodites- produce both – - produce both – can even fertilize themselvescan even fertilize themselves

• Other species possess these structures at Other species possess these structures at different times during the life (different times during the life (sequential sequential hermaphroditeshermaphrodites))

Reproduction and Life Reproduction and Life HistoryHistory

• Types of Sequential HermaphroditesTypes of Sequential Hermaphrodites– ProtandryProtandry - male to female - male to female– ProtogynyProtogyny –female to male –female to male

Reproduction and Life Reproduction and Life HistoryHistory

• Behaviors are cues for the release of eggs Behaviors are cues for the release of eggs and sperm (this helps ensure fertilization)and sperm (this helps ensure fertilization)

• Color changes or body structure changes Color changes or body structure changes may indicate readiness for reproductionmay indicate readiness for reproduction

• Courtship behavior Courtship behavior – dances, displays, etc– dances, displays, etc

Reproduction in FishReproduction in Fish

• Depending on the species, fish can either be:Depending on the species, fish can either be:– ViviparousViviparous – young are born live – young are born live– OviparousOviparous- egg layers - egg layers – OvoviviparousOvoviviparous – eggs are kept inside and – eggs are kept inside and ““hatchhatch”” before before

being released from female reproductive tractbeing released from female reproductive tract– Most laying eggs in large numbers to not protectMost laying eggs in large numbers to not protect– Some laying eggs in small numbers will protectSome laying eggs in small numbers will protect