Chapter 18 The FishesChapter 18 The FishesZoologyZoology

Mrs. FlemingMrs. Fleming

Evolutionary perspectiveEvolutionary perspective

• Water covers over 70% of the earth.Water covers over 70% of the earth.• It is believed by some that life began It is believed by some that life began

in the water.in the water.• Water is an essential element to all Water is an essential element to all

life, land and water life.life, land and water life.• Fish dominate the watery Fish dominate the watery

environments and are the ancestors environments and are the ancestors of all other members of the of all other members of the subphylum Vertebrata.subphylum Vertebrata.

RelationshipsRelationships

• Fish belong along with the Fish belong along with the chordates in the group called the chordates in the group called the Craniata. Craniata. The name describes the The name describes the skull that surrounds the brain, skull that surrounds the brain, organs, eyes, and inner ear. organs, eyes, and inner ear.

• It is believed that fish started out It is believed that fish started out in the marine environments (salt in the marine environments (salt water) and then adapted to the water) and then adapted to the freshwater environments.freshwater environments.

Subphylum VertebrataSubphylum Vertebrata

• Breaks down into 6 categories (classes) Breaks down into 6 categories (classes)

• Class Class CephalospidomophiCephalospidomophi

• Class GnathostomataClass Gnathostomata

• Class PlacodermClass Placoderm

• Class ChondrichthyesClass Chondrichthyes

• Subclass ActinopterygiiSubclass Actinopterygii

• Subclass SarcopterygiiSubclass Sarcopterygii

• The tetrapodsThe tetrapods

The placoderms were small fish, usually only a few inches long. The mouth of these fish was interesting because as the lower jaw moved down the head shield moved up, thus giving a wide gape. They had no teeth, instead using a bony plate as a biting surface.

Fish Body Parts Fish Body Parts

Fish FinsFish Fins

Start of day 2 Start of day 2 Locomotion page 285 Locomotion page 285

• Swimming is less energetic Swimming is less energetic that humans running.that humans running.

• Fish are streamlined Fish are streamlined shaped and have mucoid shaped and have mucoid secretions that lubricate its secretions that lubricate its body surface to reduce body surface to reduce friction between the fish friction between the fish and the water. and the water.

Locomotion continued Locomotion continued • Fish move through the Fish move through the

water using their fins and water using their fins and body wall to push against body wall to push against the surrounding water.the surrounding water.

• Muscles are arranged in a Muscles are arranged in a side ways W pattern. side ways W pattern. Because they extend Because they extend posteriorly and anteriorly posteriorly and anteriorly in a zigzag fashion the in a zigzag fashion the contraction of each contraction of each muscle bundle can affect muscle bundle can affect a large portion of the a large portion of the body wall. body wall.

Body wall on both sides of the fish.

Nutrition and Digestive Nutrition and Digestive SystemSystem• The first fish were probably The first fish were probably

filter feeders and scavengers. filter feeders and scavengers. However fish nutrition However fish nutrition dramatically changed with the dramatically changed with the evolution of jaws.evolution of jaws.

• Most modern fish are Most modern fish are predators and spend most of predators and spend most of their time searching for food.their time searching for food.

• Prey varies greatly.Prey varies greatly.

Nutrition and Digestive Nutrition and Digestive SystemSystem• Some feed on vertebrates, larva, Some feed on vertebrates, larva,

plankton, other fish.plankton, other fish.

• Teeth capture and hold prey, Teeth capture and hold prey, some teeth are modified for some teeth are modified for crushing the shells of mollusks or crushing the shells of mollusks or the exoskeletons of arthropods. the exoskeletons of arthropods.

• Another method of eating is by Another method of eating is by using gill rakers that trap using gill rakers that trap plankton while the fish swim. plankton while the fish swim. Basically they swim with their Basically they swim with their mouth open and everything goes mouth open and everything goes through their gills. through their gills.

TeethTeeth

Digestive systemDigestive system

• Similar to other vertebrates.Similar to other vertebrates.• Has a stomach that stores mealsHas a stomach that stores meals• Small intestine is primary site for Small intestine is primary site for

enzyme secretions and food enzyme secretions and food digestions. Some have a spiral valve digestions. Some have a spiral valve in their intestine and others have out in their intestine and others have out pockets of the intestine called pyloric pockets of the intestine called pyloric ceca, both of these parts increase ceca, both of these parts increase absorption and secretory substances.absorption and secretory substances.

Digestive SystemDigestive System

Circulation and Gas Circulation and Gas ExchangeExchange• All vertebrates have a closed All vertebrates have a closed

circulatory system where the circulatory system where the heart pumps blood with red heart pumps blood with red blood cells containing blood cells containing hemoglobin through a series of hemoglobin through a series of arteries, capillaries, and veins. arteries, capillaries, and veins.

• The typical fish's circulation is The typical fish's circulation is a single circuit: heart-gills-a single circuit: heart-gills-body-heart body-heart

Circulation and Gas Circulation and Gas ExchangeExchange• The fish heart proper is two-chambered, The fish heart proper is two-chambered,

consisting of an upper atrium and a lower consisting of an upper atrium and a lower ventricle. ventricle.

• Amphibians, basically, have a three-Amphibians, basically, have a three-chambered heart, two atria and one chambered heart, two atria and one ventricle; ventricle;

• Reptiles have a three- or four-chambered Reptiles have a three- or four-chambered heart; and heart; and

• Mammals and birds have a four-Mammals and birds have a four-chambered heart consisting of two atria chambered heart consisting of two atria and two ventricles. and two ventricles.

ComparisonComparison

• Amphibian Heart Mammal HeartAmphibian Heart Mammal Heart

ComparisonComparison

Circulation and Gas Circulation and Gas ExchangeExchange• The fish heart, however, has two accessory The fish heart, however, has two accessory

chambers, and all four chambers are contained chambers, and all four chambers are contained within a single pericardial sac. within a single pericardial sac.

• One accessory chamber is the thin-walled sinus One accessory chamber is the thin-walled sinus venosus, which collects blood and leads into the venosus, which collects blood and leads into the atrium; atrium;

• the other accessory chamber is the conus the other accessory chamber is the conus arteriosus, an enlargement of the main artery arteriosus, an enlargement of the main artery leading out of the ventricle. leading out of the ventricle.

• In some fishes, such as sharks, the conus In some fishes, such as sharks, the conus arteriosus is muscular and pumps blood in the arteriosus is muscular and pumps blood in the manner of the ventricle. manner of the ventricle.

Start of Day 3: Start of Day 3: ReproductionReproduction

•Most fishes are egg-layers, but many bear living Most fishes are egg-layers, but many bear living young. young.

• Live-bearing fishes may be ovoviviparous, in Live-bearing fishes may be ovoviviparous, in which the eggs essentially simply hatch within which the eggs essentially simply hatch within the female, or viviparous, in which the unborn the female, or viviparous, in which the unborn young are supplied nourishment through the young are supplied nourishment through the mother's tissues. mother's tissues.

• In some ovulation (or release of the egg) and In some ovulation (or release of the egg) and birth occur at the same time. birth occur at the same time.

• In some viviparous fishes the walls of the egg In some viviparous fishes the walls of the egg follicle are in intimate contact with the embryo, follicle are in intimate contact with the embryo, supplying it with nourishment. In the viviparous supplying it with nourishment. In the viviparous sharks, a part of the oviduct, or egg channel, is sharks, a part of the oviduct, or egg channel, is developed into a uterus, where the modified yolk developed into a uterus, where the modified yolk sacs of the young are closely joined to pockets sacs of the young are closely joined to pockets within the uterus.within the uterus.

Fish EggsFish Eggs

ReproductionReproduction• In live-bearing fishes and in some egg-In live-bearing fishes and in some egg-

layers, fertilization occurs internally, and layers, fertilization occurs internally, and methods have been evolved for methods have been evolved for introducing the sperm into the female's introducing the sperm into the female's body. body.

• In In sharks the pelvic fins of the male are sharks the pelvic fins of the male are modified into intromittent organs called modified into intromittent organs called myxoptergia, myxoptergia, and in the male and in the male topminnows topminnows the anal fin is modified into a similar-the anal fin is modified into a similar-functioning intromittent organ called the functioning intromittent organ called the gonopodium.gonopodium.Know that fins are used in the deliverance Know that fins are used in the deliverance of sperm into the female fish.of sperm into the female fish.

Stopped here on April 24Stopped here on April 24

ReproductionReproduction• At least three modes of reproduction--At least three modes of reproduction--

heterosexual, hermaphroditic, and heterosexual, hermaphroditic, and parthenogenetic-parthenogenetic--are found in fishes. -are found in fishes.

• In the most common form,In the most common form, heterosexual heterosexual reproduction, there are separate male and reproduction, there are separate male and female parentsfemale parents, but even here there is , but even here there is considerable variation. considerable variation.

• In some live-bearing fishes, the female is In some live-bearing fishes, the female is able to store sperm for up to 8 or even 10 able to store sperm for up to 8 or even 10 months, and this sperm is used to fertilize months, and this sperm is used to fertilize new batches of eggs as they develop. In new batches of eggs as they develop. In some cases, a female may carry sperm some cases, a female may carry sperm from several males at oncefrom several males at once..

• In hermaphroditic reproduction, a In hermaphroditic reproduction, a single fish is both male and female, single fish is both male and female, produces both eggs and sperm produces both eggs and sperm (either at the same time or at (either at the same time or at different times), and mates with different times), and mates with other similar hermaphroditic fishes. other similar hermaphroditic fishes. External self-fertilization occurs in External self-fertilization occurs in one hermaphroditic fish, which sheds one hermaphroditic fish, which sheds egg and sperm simultaneously. In egg and sperm simultaneously. In another, internal self-fertilization another, internal self-fertilization may occur. In certain fishes there is may occur. In certain fishes there is a time sequence of hermaphroditism, a time sequence of hermaphroditism, young fishes reversing their sex as young fishes reversing their sex as they grow older.they grow older.

ReproductionReproduction• In parthenogenetic reproduction, In parthenogenetic reproduction,

unfertilized eggs develop into embryos. unfertilized eggs develop into embryos. This is known to exist in at least one This is known to exist in at least one fish species, fish species, Poecilia formosaPoecilia formosa, of the , of the Amazon River; however, even though Amazon River; however, even though development proceeds without development proceeds without fertilization in some of these females, fertilization in some of these females, mating with a male is still required to mating with a male is still required to stimulate egg development.stimulate egg development.

• Parental care also shows great diversity.Parental care also shows great diversity.

• Some fishes, like the Atlantic herring, Some fishes, like the Atlantic herring, form huge schools of males and females form huge schools of males and females and freely shed their eggs and sperm and freely shed their eggs and sperm (milt), and then (milt), and then abandon the eggsabandon the eggs. .

• Other fishes Other fishes build nests and care for build nests and care for both the eggs and newly hatched youngboth the eggs and newly hatched young. . Others have evolved Others have evolved methods of methods of carrying carrying the eggs with them, commonly the eggs with them, commonly in their mouths, but also in gill cavities in their mouths, but also in gill cavities or in special pouches on the bodyor in special pouches on the body. .

Plankton

Mutton Snapper

Bay anchovie

Silver Perch

DiseasesDiseases

Signs of DiseaseSigns of Disease

• Clamped fins (fins are held abnormally close to Clamped fins (fins are held abnormally close to body) body)

• The fish refuses its usual food for more than 2 The fish refuses its usual food for more than 2 days. days.

• There are visible spots, lesions, or white patches There are visible spots, lesions, or white patches on the fish. on the fish.

• The fish gasps at the surface of the water. The fish gasps at the surface of the water. • The fish floats, sinks, whirls, or swims sideways. The fish floats, sinks, whirls, or swims sideways. • The fish shimmies (moves from side to side The fish shimmies (moves from side to side

without going forward). without going forward). • A normally active fish is still. A normally active fish is still. • A normally still fish is very active. A normally still fish is very active. • The fish suddenly bloats up, and it's not due to The fish suddenly bloats up, and it's not due to

eggs or young. eggs or young. • The fish is scratching against tank decorations. The fish is scratching against tank decorations.

Live Birth of a Killer Whale

Another live birth

Baby is alive and well.

Swim Bladders and LungsSwim Bladders and Lungs

• Do fish have lungs? Sort of???Do fish have lungs? Sort of???• The Indian climbing fish is an example of a fish The Indian climbing fish is an example of a fish

that has that has pneumatic sacspneumatic sacs. . • These are ducts that connect to the esophagus or These are ducts that connect to the esophagus or

antoher part of the digestive tract. antoher part of the digestive tract. • They swallow air and it gets trapped in these sacs. They swallow air and it gets trapped in these sacs. • Then gas excahnage occurs across the vascular Then gas excahnage occurs across the vascular

surfaces. surfaces. • So the climbing fish that spends most of its time So the climbing fish that spends most of its time

on land can still breath so to speak with a strange on land can still breath so to speak with a strange form of lungform of lung. .

Buoyancy RegulationBuoyancy Regulation

• Buoyancy= how things can or do stay a float.Buoyancy= how things can or do stay a float.• Humans can because of their lungs and body Humans can because of their lungs and body

makeup.makeup.• Fish do this in one of four ways.Fish do this in one of four ways.• 1. incorporate low density compounds into their 1. incorporate low density compounds into their

tissues livers are saturated with buoyant oilstissues livers are saturated with buoyant oils• 2. use fins for lift2. use fins for lift• 3. reduction of heavy tissues, bones are less 3. reduction of heavy tissues, bones are less

dense and cartilage is only slightly heavier than dense and cartilage is only slightly heavier than waterwater

• 4. use of a swim bladder4. use of a swim bladder

Swim BladderSwim Bladder

• A fish regulates buoyancy by controlling A fish regulates buoyancy by controlling the volume of gas in its swim bladder. the volume of gas in its swim bladder.

• Fish gulp in air at the waters surface Fish gulp in air at the waters surface and forces air into their swim bladder.and forces air into their swim bladder.

• The blood also can exchange gas into The blood also can exchange gas into the swim bladder and out of it to help the swim bladder and out of it to help maintain buoyancy.maintain buoyancy.

Nervous SystemNervous System

• Consists of the brain and spinal column.Consists of the brain and spinal column.• Have sensory receptors for touch, Have sensory receptors for touch,

temperature, hearing, vision, olfaction, temperature, hearing, vision, olfaction, balance, equilibrium, detecting water balance, equilibrium, detecting water movements.movements.

• Fish have no eye lidsFish have no eye lids• Lenses are round which means that they must Lenses are round which means that they must

move them backwards and forwards to focus.move them backwards and forwards to focus.• Receptors for equilibrium, balance, and Receptors for equilibrium, balance, and

hearing are in the inner ear.hearing are in the inner ear.

Nervous SystemNervous System

• How do fish hear? How do fish hear?

• They have no middle or outer ear, so They have no middle or outer ear, so they hear from vibrations in the they hear from vibrations in the water that strike the fish and are water that strike the fish and are amplified by the swim bladder and amplified by the swim bladder and sent to the skull.sent to the skull.

• The lateral-line system is in the The lateral-line system is in the epidermis and it is a series of canals epidermis and it is a series of canals with sensory receptors. with sensory receptors.

Electric FishElectric Fish

• All organisms produce a weak All organisms produce a weak electrical field from the activities of electrical field from the activities of nerves and muscles.nerves and muscles.

• Electroreception: is the detection of Electroreception: is the detection of the electrical fields that a fish the electrical fields that a fish generates. generates.

• Over 500 species of fish can do this.Over 500 species of fish can do this.• Some fish can also generate electrical Some fish can also generate electrical

current.current.

Electric FishElectric Fish

• Muscles near the caudal fin are modified Muscles near the caudal fin are modified into organs that produce a continuous into organs that produce a continuous electrical discharge.electrical discharge.

• Current spreads between the head and the Current spreads between the head and the tail.tail.

• The most well known is the electric eel.The most well known is the electric eel.• The organs for producing the electric The organs for producing the electric

current are in the trunk. They can produce current are in the trunk. They can produce in excess of 500 volts.in excess of 500 volts.

• Can stun or kill prey.Can stun or kill prey.

Stop hereStop here

• Main Types of LitterMain Types of Litter• Type of Litter PercentageType of Litter Percentage• Fast Food Waste(33%)Fast Food Waste(33%)• Paper(29%)Paper(29%)• Aluminum(28%)Aluminum(28%)• Glass(6%)Glass(6%)• Plastic(2%)Plastic(2%)• Other(2%)Other(2%)• Source: Missouri Department of Source: Missouri Department of

Transportation (MoDOT) survey of Transportation (MoDOT) survey of Adopt-A-Highway volunteers - 1994Adopt-A-Highway volunteers - 1994

• How long does it take to decompose?How long does it take to decompose?

• ObjectDecomposition TimeObjectDecomposition Time

• Styrofoam container> 1 million yearsStyrofoam container> 1 million years

• Plastic jug1 million yearsPlastic jug1 million years

• Aluminum can200-500 yearsAluminum can200-500 years

• Disposable diaper550 yearsDisposable diaper550 years

• Tinned can90 yearsTinned can90 years

• Leather shoe45 yearsLeather shoe45 years

• Wool sock1 yearWool sock1 year

• Paper bag1 monthPaper bag1 month

• Banana peel3-4 weeksBanana peel3-4 weeks