31 Fish and Amphibians

Chapter 31Fishes and Amphibians

Charles Page High School

Dr. Stephen L. Cotton

Section 31-1Fishes

OBJECTIVES:–Describe the distinguishing characteristics of vertebrates.

Section 31-1Fishes

OBJECTIVES:–Explain how fishes carry out their essential life functions.

Section 31-1Fishes

OBJECTIVES:–Describe the three basic groups of fishes, and give an example of each.

Section 31-1Fishes

Is the name “Earth” appropriate for our planet, since more than 2/3 of it is water?–And, just about anywhere there is water- you can find fishes

We are studying the phylum Chordata- fish and other vertebrates have these features

Section 31-1Fishes

At some time in their life, they have:–a notochord–a hollow dorsal nerve cord–pharyngeal slits (or pouches)

In vertebrates, the notochord is replaced by the vertebral column

Section 31-1Fishes

In addition, most vertebrates have:–two sets of paired appendages–closed circulatory system with a ventral heart

–either gills or lungs for breathing

Section 31-1Fishes

Fishes- defined as aquatic vertebrates that are characterized by scales, fins, and pharyngeal gills–many varieties, such as some fish that have no scales

There are 4 living classes of vertebrates we know as fishes

Section 31-1Fishes

For our purposes, we can say that the living fishes fall into three main groups:–1. Jawless fishes–2. Bony fishes–3. Cartilaginous fishes

Section 31-1Fishes

Fishes are considered to be the most primitive living vertebrates–at first, they were odd-looking jawless creatures whose bodies were covered with bony plates

–Figure 31-3, page 681–lived in the oceans of the late Cambrian period= 540 million

Section 31-1Fishes

For over 100 million years, fishes retained the basic armored, jawless body plan–then they underwent a major adaptive radiation

–produced some jawless fishes that had little armor-ancestors of modern lamprey and hagfish

Section 31-1Fishes

Others produced were armored jawless fishes in a variety of new forms- were ultimately an evolutionary dead end

others were armored fishes that possessed a feeding adaptation that would revolutionize vertebrate evolution: these fishes had jaws

Section 31-1Fishes

Jaws are extremely important evolutionary innovations:–made it possible for vertebrates to “nibble” on plants, “munch” on other animals, and defend themselves by “biting”

Section 31-1Fishes

Another evolutionary innovation seen in early jawed fishes were paired pectoral (anterior) and pelvic (posterior) fins- attached to girdles of cartilage or bone–gave fishes more control over their movement in water

–Figure 31-4, page 681

Section 31-1Fishes

The pectoral fins and girdle also provided the “raw material” from which evolution shaped the forelimbs and shoulder bones of terrestrial vertebrates–pelvic fins and girdles were also the origins of the hindlimbs and hip bones

Section 31-1Fishes

The early jawed fishes soon disappeared; but they left behind two major classes that continued to evolve- still survive today–the cartilaginous fish, including the sharks and rays

–the bony fish, containing more than 97% of all living fish species

Section 31-1Fishes

Feeding- every mode of feeding is seen in fishes: herbivores, carnivore, parasite, filter feeder, and even detritus feeder–a single fish may exhibit several methods of feeding

Parasite: the pencil catfish lay their eggs and live in gills of other larger fishes

Section 31-1Fishes

Parasite: the male of certain anglerfish attaches permanently to the much larger female, and obtains nutrients from her blood–Figure 31-5, page 682

Filter feeders: the lamprey larvae and the manta rays; not all small however: the filter-feeding whale shark (18.5 meters)-largest fish!

Section 31-1Fishes

Adaptations for feeding are often quite remarkable:–the sawfish (relative of sharks) kills and stuns prey by slashing into a school of small fish with a long snout edged with sharp teeth- Figure 31-5, page 682

Section 31-1Fishes

Parrotfish- has teeth fused into a short beak used to bite off chunks of coral, and additional teeth in the throat that grind the chunks of coral into sand

Archerfish- shoots down insects by spitting drops of water

Section 31-1Fishes

Anglerfish- have wormlike or lighted lures used to attract prey–Figure 31-1, page 679

some deep-sea fishes have enormous jaws that allow them to swallow prey larger than themselves

Section 31-1Fishes

Most fishes do not really “chew” their food–instead, they tear their food into conveniently sized chunks, or swallow their prey whole

–Note the digestive system in Figure 31-6, page 683: Let’s examine this system

Section 31-1Fishes

Pathway:–mouth; food enters here–esophagus; short tube–stomach; food partially broken down

–pyloric ceca; between stomach and intestine; further digested

Section 31-1Fishes

Pathway:–pyloric ceca also secrete digestive enzymes and absorb nutrients from the digested food

–intestine; completes digestion; receives enzymes from liver and pancreas

–anus; eliminate undigested items

Section 31-1Fishes

The fish’s intestine is adapted in ways that help them meet their nutritional needs–herbivores typically have a longer intestine; more time and space to break down plant matter, which is difficult to digest

Section 31-1Fishes

Lampreys, cartilaginous fishes, and a few bony fish have a flap of tissue that spirals around the outside part of the intestine; this increases the surface area for nutrient absorption

Respiration- most breathe with gills on each side of the pharynx

Section 31-1Fishes

These feathery gills have many capillaries; provide a large surface area for gas exchange–most breathe by pumping water through the mouth, over the gill filaments, and out through slits in the sides of the pharynx

Section 31-1Fishes

Some fishes, such as the sharks and lampreys, have several gill slits on either side of the pharynx

in many fishes, this basic respiratory setup has been modified by the evolutionary process; skates and rays “inhale” from openings on the top side

Section 31-1Fishes

Many fishes (lungfish, gars, Siamese fighting fish) have adaptations that allow them to survive in oxygen-poor water, or in areas where water dries up–have specialized organs that serve as lungs by obtaining oxygen from the air

Section 31-1Fishes

In most air-breathing fishes, this organ is actually a modified swim bladder–the swim bladder (found in most bony fish) is a gas-filled sac that lies at the top of the body cavity just beneath the backbone- regulates buoyancy

Section 31-1Fishes

This swim bladder allows the fish to swim at different depths

Internal Transport- typically have a closed circulatory system with a heart that pumps blood- p.685–two-chambered heart: an atrium(collecting chamber), and a ventricle (pumping chamber)

Section 31-1Fishes

Blood is pumped out of the ventricle into a muscular vessel called the aorta, and then into the fine capillary network of the gills where gas exchange occurs–after gills, travels to rest of the body; collects in the veins, to the sinus venosus, then atrium

Section 31-1Fishes

Excretion- like most other aquatic forms, fishes get rid of nitrogenous wastes in the form of ammonia–some wastes diffuse through the gills; others removed by the kidneys

Section 31-1Fishes

Kidneys help fishes control the amount of water in their bodies–fishes in salt water tend to lose water by osmosis; the kidneys thus concentrate the urine to reduce water loss

–however, freshwater fishes need to pump out lots of dilute urine

Section 31-1Fishes

Response- fairly well developed nervous system organized around a brain-anterior parts are:–the olfactory lobes (smell) connected to the cerebrum

–cerebrum also helps with taking care of young; exploring areas

Section 31-1Fishes

–optic lobes- process information from the eyes

–cerebellum- coordinates body movements

–medulla- controls many internal organ functions and maintains balance

Section 31-1Fishes

Posterior to the brain is the spinal cord, which is in fact the hollow dorsal nerve cord that characterizes chordates

Figure 31-9, page 685–superbly designed sense organs to collect information about their environment

Section 31-1Fishes

Almost all fishes are active in the daylight; well developed eyes and color vision–fish active only at night, or in cloudy water, have large eyes with big pupils that gather as much light as possible

Section 31-1Fishes

Some have extraordinary senses of taste and smell–chemoreceptors located all over the head and much of the rest of the body, as well as nose and mouth; possibly on their “whiskers” like catfish

Section 31-1Fishes

Salmon can distinguish between the odor of their own home stream while still far out to sea–sharks can detect the presence of a drop of blood in 115 liters of sea water

ears are inside their heads, but do not really hear well

Section 31-1Fishes

Instead of hearing, they detect gentle currents and vibrations in the water–have lateral line system that can detect others around them; allows them to swim in orderly formations

Section 31-1Fishes

Some fishes- electric eels, catfish, and sharks- are able to detect electricity–a shark can detect one millionth of a volt, which is less than the charge produced by the nerves in an animal’s body

–help locate prey in murky water

Section 31-1Fishes

In addition, electric fishes can produce jolts of electricity (up to 650 volts) that stun or kill prey and discourage predators

Reproduction- in most species, there are separate males and females; some may be born male, but change into females as they age

Section 31-1Fishes

Many fishes are oviparous- which means the lay eggs–most oviparous fishes have external fertilization; some may fertilize internally, then lay fertilized eggs

–some,such as cod, do not take care of their young at all

Section 31-1Fishes

Others may care for their offspring–siamese fighting fish build nests of bubbles

–sticklebacks build nests of twigs–cichlids and catfish may hold eggs in their mouth until hatch

Section 31-1Fishes

In some of the fishes that have internal fertilization, such as guppies, the eggs will develop inside the female’s body–they are nourished by food stored in an attached yolk sac, not the mother’s body directly

–called ovoviviparous

Section 31-1Fishes

In other species, including several sharks, the young are actually nourished by the mother’s body as they develop–called viviparous, or truly live-bearing

Fascinating mating behaviors: dances, show color, building nests

Section 31-1Fishes

Jawless Fishes- those alive today are divided into 2 classes: the lampreys and hagfishes–thought to have evolved from the heavily armored, bony ancestors, these actually have no bones at all; only vertebrate with no backbone as adults; have only the notochord

Section 31-1Fishes

Lampreys- typically filter feeders as larvae, and parasites as adult–head taken up almost completely by a circular sucking disk with a round jawless mouth in the center - page 687

–attach to fishes; make wound; suck up tissues and body fluid

Section 31-1Fishes

Hagfishes- probably the most primitive vertebrates alive today–pinkish-gray wormlike bodies and 4 or 6 short tentacles around the mouth

–lack eyes; have light detecting regions around their bodies

Section 31-1Fishes

Feed on dead and decaying fish by using a toothed tongue to scrape a hole into the fish’s side–peculiar traits: secrete incredible amounts of slime; have 6 hearts; open circulation; regularly tie themselves into half-knots

Section 31-1Fishes

Class Chondrichthyes- sharks, rays, skates, sawfish and chimaeras–ancient and successful group–chondros- means cartilage; ichthys means fish

–endoskeleton built entirely out of cartilage

Section 31-1Fishes

Most also have toothlike scales covering the skin; making the sharkskin so rough that it is possible to use as sandpaper

Shark characteristics: large curved tail; round snout, mouth underneath; torpedo shape; enormous number of teeth; teeth continually replacing lost ones

Section 31-1Fishes

Not all sharks are man-eaters–some are filter feeders, others have flat teeth adapted for crushing the shells of mollusks and crustaceans

–more people are killed by lightning each year than sharks

Section 31-1Fishes

Unlike sharks, which are adapted for swimming rapidly through the water, rays and skates are adapted for living on the ocean floor–flattened from top to bottom (like squashed sharks); flap their large pectoral fins to swim

Section 31-1Fishes

Class Osteichthyes- bony fish–more species in this class than in any of the other vertebrate classes

–about 40% of all vertebrates are bony fishes

Section 31-1Fishes

Almost all bony fishes belong to the enormous group called the ray-finned fishes- anything from guppies to salmon to eels

ray-finned refers to the thin bony spines, or rays, that are connected by a thin layer of skin to form the fins

Section 31-1Fishes

The fins are adapted to a wide variety of functions:–some have them modified into poison spines

–some glide (fly) with winglike pectoral fins

–may use a suction cups to climb

Section 31-1Fishes

Only 7 living species of bony fishes are not classified as ray-finned fishes–these are the lungfishes and the coelacanth

The 6 species of lungfish alive today live in Australia, Africa, and South America

Section 31-1Fishes

Sometimes these areas are very wet, but other times very dry–when water is available, they use their gills- but often “gulp” air into a sac used as a lung

–during the dry season, they may burrow in the mud and enter a dormant state

Section 31-1Fishes

The single species of coelacanth alive today, Latimeria, is the only surviving member of the lobe-finned fishes–unlike ray-finned fish with bones in the base of the rays, lobe-finned fish have few bones in their fin bases

Section 31-1Fishes

Ancient lobe-finned fishes seemed to have lived in swampy areas where shallow pools alternated with mud flats and sand bars–they probably used their pelvic and pectoral appendages to move from pool to pool

Section 31-1Fishes

Coelacanths were thought to have disappeared with dinosaurs about 70 million years ago–in 1938 however, some fishermen caught a strange blue fish; thus, they were not extinct after all- important as they are the closest ancestors to all land vertebrates

Section 31-1Fishes

How Fishes Fit Into the World- vital parts of many biological systems as:–food for many animals–predators to control others–keep waterways clear of plants–pets; brightly colored to watch

Section 31-2Amphibians

OBJECTIVES:–Describe how a typical amphibian carries out it’s essential life functions.


OBJECTIVES:–Compare the two major living orders of amphibians.


Class Amphibia- with about 4,000 living species, they are the smallest major group of vertebrates–range in size from a tiny tropical tree frog 1 cm long, to enormous salamanders 170 cm long


Some amphibians, such as salamanders and newts, have long tails and scuttle about on 4 legs–others, such as frogs and toads, have no tails; can leap from place to place with large hind legs


Still others , like caecilians (p.693) have no legs at all, and burrow in soil like giant worms

Although many of these animals spend a great deal of time on land, nearly all of them are restricted to moist areas, and most return to water to breed


The name amphibian refers to the double like most amphibians lead–amphi- means both; bio- means life

–larvae are fishlike aquatic animals that breathe through gills


The adults are terrestrial carnivores that breathe through lungs and skin–the majority of amphibians live in water for the first part of their life, and on land as adults

–the aquatic larvae is one reason they live in moist areas


Most important reason they live in a moist area: their eggs do not have a shell, thus tend to dry out unless found in moist areas–also, they do not have scales, fur, or any other protective covering that would help prevent drying out


Amphibians can be defined as vertebrates that are 1) aquatic as larvae and terrestrial as adults; 2) breathe with lungs as adults; 3) have a moist skin that contains many glands; and 4) lack scales and claws


Evolution of Amphibians- appeared around the end of the Devonian period, about 360 million years ago–probably evolved from lobe-finned fishes, similar to modern coelacanth, that had bones in their fin bases and lungs


The transition from water to land is no easy task- 1) gills were now useless; 2) appendages for water (fins) are too weak to support much weight on land; 3) loss of water is a constant danger; 4) vibrations in air are less than in water-difficult to detect sound and movement


Early amphibians evolved ways to correct these problems–bones of the limbs and limb girdles become stronger

–ribs form a bony cage to protect internal organs

–scales that protect skin on the underside


–Ears that used a membrane to transmit sound waves in the air into pressure waves in body fluids were added to their “lateral line” systems

–mucous glands, eyelids, and other structures that protect sense organs from drying out


Early amphibians soon underwent a major adaptive radiation–some ancient forms were huge–so numerous during the Carboniferous Period (345-285 million years ago) that it became known as the Age of Amphibians


Why were amphibians so successful?–They entered an environment nearly empty of animal life

–because plants and arthropods were already on land, there was plenty of food- with no competitors; full of empty niches


The heyday of amphibians was short-lived–climate changes caused many of the low, swampy habitats to disappear

–many amphibian groups were extinct by the end of the Permian Period, 245 million years ago


What was left after this period of extinction was four groups of land vertebrates:–the reptiles, which evolved from amphibians early in the Carboniferous Period; and three orders of small amphibians


Feeding- tadpoles (the larvae of frogs and toads) are typically filter feeders or herbivores–as herbivores, they have long, coiled intestines that break down hard-to-digest plant food

–tadpoles grow quickly before the water disappears


Feeding- adult amphibians are almost entirely carnivorous–salamanders and legless amphibians can only snap their jaws open and shut to catch prey

–frogs have a long sticky tongue specialized to capture insects


Feeding- Note Figure 31-20, page 696 that shows the digestive system of the frog–mouth; esophagus; stomach; small intestine (has digestive enzymes as well as absorbs food); large intestine (colon); cloaca (stores wastes)


There are tubes that connect the intestine with organs that also produce digestive enzymes, such as the:–liver; pancreas; and gall bladder


Respiration- adults typically breathe using lungs; mouth cavities; and skin–in frogs and toads, the lungs are reasonably well-developed and richly supplied with capillaries and folds that increase their surface area


Respiration- other amphibians may not have lungs that are well developed; many terrestrial salamanders have no lungs at all

The lining of the mouth cavity and skin is thin and richly supplied with capillaries to serve as gas-exchange organs


Respiration- tadpoles, salamander larvae, and few types of adult salamanders breathe primarily through their gills; however, they can get rid of excess carbon dioxide through their skin


Respiration- because they do not have the necessary chest and stomach muscles, frogs cannot inhale and exhale as we do–they fill their mouth with air; close their mouth; force air back through an opening called the glottis into the lungs


Respiration- frogs can also direct some of the air they take in to a pair of expandable vocal sacs in the rear of the mouth–Figure 31-21, page 697–frogs “croak” by forcing air from these sacs over vocal cords, both directions, even under water


Internal Transport- the circulatory system in the adult amphibians is closely linked to the development of lungs

Adults have a “double-loop”–First loop carries oxygen-poor blood from heart to lungs; then oxygen-rich blood back to heart


–Second loop transport the oxygen-rich blood from the heart to the rest of the body; and oxygen-poor blood from the body back to the heart

Thus, blood travels through the heart twice in one circulation; hence the name double-loop


Amphibian heart has 3 separate chambers:–left atrium; right atrium, and ventricle

blood returning from the body collects in a large vein called the vena cava


The vena cava and other veins that drain the head and skin empty into the sinus venosus, which empties into the right atrium

blood returning from the lungs in the pulmonary vein enters into the left atrium


When the atria contract, they empty the blood into a single ventricle–then it pumps blood into a single large vessel called the bulbus cordus, which divides into a series of aortic arches that lead to major body arteries


A three-chambered heart is much better than the fishes two-chambered heart; it allows a return to the heart for an extra burst of power before going to the body

tadpoles have two-chamber heart much like bony fishes; become adults- it changes to 3-chamber


Excretion- use kidneys to eliminate waste from bloodstream–these lie against the dorsal body wall

–filter nitrogenous wastes–the urine travels through tubes (ureters) to the cloaca; here it can be stored or eliminated


Response- have well developed nervous and sensory systems–eyes are large, and move in the sockets quite well; surface of eye is protected from damage under water and kept moist on land by a transparent nictitating membrane located inside the eyelid- which can also close


Ears are quite sensitive, even though they have no external sound collectors–a variety of croaks, peeps, and other calls to find a mate; thus hearing is vital to their survival and reproduction


Response to adverse environmental conditions is done in a variety of ways:–no internal mechanism for regulating body temperature (they are called “cold-blooded”), but find a sheltered spot or enter a dormant state


Amphibians are clawless, soft-skinned- ways of protection?–Some hide; others run quickly; some are well-camouflaged; may produce distasteful or toxic chemicals (Fig. 31-23, p.698)

–the more toxic amphibians usually have warning coloration


Reproduction- male climbs on the female’s back and squeezes–in response, the female releases many eggs, which are then fertilized by the male- external fertilization

–Figure 31-24, page 699


The frog embryos are surrounded by a sticky, transparent jelly that attaches the egg mass to underwater plants, as well as nourishes the embryo–typically hatch into tadpoles after one to three weeks


Not all amphibians have external fertilization and are oviparous like frogs–many do have internal fertilization, and are either oviparous, ovoviviparous, or viviparous


Parental care varies- this is a way of ensuring that more young will survive–carry and incubate the young in their mouth, vocal sac, or stomach

–may carry them on legs or back until eggs are ready to hatch


Health Link: the old wive’s tale that toads cause warts probably came about because of the warty appearance of a toad’s skin

In fact, viruses cause warts, not toads


Salamanders- these amphibians keep their tails even as adults–both adult and larvae are carnivores

–fossils forms may have been more then 3 meters; modern forms about 15 centimeters


Salamanders- hatch as fully aquatic larvae with gills; as adults, they live in most woods under rocks and rotting logs

some, such as the mud puppy and axolotl never lose their gills; live in water all their life


The crimson-spotted newt switches back and forth between water and land–starts as aquatic larvae; emerge and live on land as a form called the red eft; then changes color to green with red spots; returns to water to breed


Frogs and Toads- frogs are more closely tied to water, and spend much of their time in or near ponds and streams; toads are better adapted to land because their warty skin helps conserve water- often live in most woods under rocks and rotting logs


How Amphibians Fit Into the World:–adults prey on insects–tadpoles devour large amounts of algae

–eat frog legs?–toxins on arrow tips


How Amphibians Fit Into the World:–toxins give us clues to nervous systems

–salamanders regenerate; frogs cannot- Why?

31 Fish and Amphibians

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