Fish and Amphibians - Britannica Illustrated Science Library

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FFIISSHH
AANNDD AAMMPPHHIIBBIIAANNSS
BBrriittaannnniiccaa IIlllluussttrraatteedd SScciieennccee LLiibbrraarryy
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Fish and Amphibians
Contents
General
Characteristics
Page 6
Life in
the Water
Page 18
Diversity
Page 38
Amphibians
Page 60
People, Fish,
and Amphibians
Page 80
Water, the
VIETNAM
Along this country's nearly been in a state of crisis. In Nha Trang Bay this reason, they have developed various
200 miles (300 km) of
the growth of outside investment in survival techniques to live in such a wide
coastline live great
numbers of people who Source of Life aquaculture has limited the economic variety of places.
depend on fishing and
opportunities of the local population,
coral reefs for their
livelihood. including fishing for squid and other
species in the reefs with hook and line.
D
T In other cases, commercial fishing espite the fact that lunglike sacs
he life of marine creatures is
endangers the future of those who rely on evolved because of the difficulty of
fascinating and has always been
traditional fishing methods to make a breathing with gills in water with low
closely linked to human life. This is so
living. This is only one of the topics oxygen content, the development of these
particularly because fishing has been the
explored in this book, which also relates in sacs was also the first step toward moving
livelihood of islanders through the years.
detail many secrets of these vertebrates, onto land. Some descendants of the first fish
Yet for some time, in many areas of the
which were among the first creatures with with fleshy, jointed fins, known as lobe-fin
world—such as Nha Trang Bay, on the
skeletons to appear on the Earth. Perhaps fishes, began to find terrestrial food sources
south coast of Vietnam—this activity has
knowing more about their habits and and, with time, adapted more completely to
modes of life may move us to care for life on the planet's surface. This evolutionary
them and protect them. They are at the change—passing from an aquatic to a
mercy of variations in water conditions to terrestrial medium—constituted a true
a greater extent than humans. revolution for the life-forms that existed up
until then. The amphibians we will show you
in this book that are living today are a tiny
representation of all those that appeared
H
umans have marveled for centuries at during the Devonian Period, most of which
the fact that, after journeying across became extinct during the Triassic Period.
the ocean, salmon can find the river
where they were born. Is this navigational
ability related to the Earth's magnetic field,
A
sense of smell, instinct, or something else mphibians, especially some frog
that humans cannot even imagine? For those species, have become true specialists
interested in statistics, in the Yukon River in in the art of mimicry. One of the most
Alaska and in Canada, certain tagged fascinating examples is the European tree
Chinook salmon covered nearly 2,000 miles frog, which changes color to regulate its
(3,200 km) in 60 days. Upon entering the body temperature. On warm, dry evenings
river, the salmon stop eating and utilize the the frog rests in sunny places, and its skin is
fat they accumulated while in the ocean. pale. As its surroundings become cooler, the
After laying their eggs, many of the frog darkens to absorb heat. Although
females die. Most ocean fish seek shallow, amphibians are masters of camouflage,
nutrient-rich waters in which to lay their which protects them from predators, at
eggs. That is why coastal waters and present they are the object of worldwide
estuaries are so important to the life cycle of concern because of the dramatic decline in
many species. Another oddity of these their populations. Turn the page, and you will
animals is that they have adapted to living in discover much more about the abilities of
a variety of aquatic habitats: rivers, lakes, fish and amphibians, extraordinary creatures
estuaries, coral reefs, and the open sea. For that live right next to us.
General Characteristics
CROCODILE FISH FIN EARLIEST FORMS 8-9 CARTILAGINOUS FISH 14-15
This fish, which lives in
DISTINGUISHING FEATURES 10-11 ANATOMY 16-17
waters with abundant coral
reefs, can grow up to 21 BONY FISH 12-13
inches (54 cm) long.
F
ish were the first vertebrates fish, the earliest fish had no scales, fins, water and salt water. Their bodies are these complex creatures normally
with bony skeletons to appear or jawbone, but they did have a type of generally streamlined, being covered breathe through gills that capture
on the Earth. They doubtless dorsal fin. Over time they have been with smooth scales and having fins that oxygen dissolved in the water, and they
form the most numerous group changing in form and size to adapt to enable them to move with energy, are cold-blooded.
of vertebrates. Unlike today's different environments, in both fresh direction, and stability. In place of lungs,
8 GENERAL CHARACTERISTICS FISH AND AMPHIBIANS 9
Earliest Forms
Dunkleosteus
Dorsal
Its head was
A The Arthrodira—with a jointed protected by fin The tail was not
bout 470 million years ago, the first fish appeared. Unlike today's neck—were armored fish that strong armor. protected by
STREAMLINED SHAPE predominated in the late Devonian scales.
fish, they did not have a jawbone, fins, or scales. Hard plates
The shape of Pteraspis Period. The Devonian predator
covered the front part of the fish and formed a protective shield. shows that it was an Dunkleosteus was an arthrodiran
excellent swimmer. placoderm that lived over 300 million
They also had a solid, flexible dorsal spine that allowed them to propel
years ago. Its head was encased in This area of the body
themselves. Later, in the Silurian Period, fish appeared that had a an impressive set of plates 1.2 inches had neither armor
(3 cm) thick, with razor-sharp bony nor scales.
jawbone. Known as the gnathostomata, they were large predators.
plates that served as teeth.
FIERCE JAW It had a lobed tail, similar
Dunkleosteus was a to a shark's tail, which
fierce predator that indicates that it was a
CONICAL NOSE EYES devoured any type of powerful swimmer.
Pteraspis Its streamlined shape Very small,
prey, including sharks.
helped the fish move. located on both DORSAL SPIKE
The fish without a jawbone, sides of the head. Located on the fish's
Pteraspis, was about 6.5 back, it worked like a
inches (16 cm) long and lived in dorsal fin. It also had strong
the seas of Europe, Asia, and North jaws with bony teeth.
America. These fish were most
abundant during the Devonian Period.
They had bodies with armor that DORSAL SPINES
covered their heads, and they had a These helped the fish
streamlined shape. The shell had a co- to stay balanced while
nical nose that helped the fish to move. swimming.
16 feet
(5 m)
6.5 inches (16 cm)
WING SHIELD
LENGTH OF THE FISH
Scientific Pteraspis
name
MOUTH
TAIL
Diet Small organisms Having no jawbone,
The shape of the tail
they fed on small
Habitat Sea, then rivers and lakes helped balance the
organisms.
Range Europe, Asia, North America weight of the armor.
Period Early Devonian
cranium
EVOLUTION OF THE JAWBONE
The development of the jawbone was a The evolution of the jawbone LATERAL LINE
long evolutionary process that involved modified the configuration Sensory organs are
changes in the diet of fish to include not of the skull. present on both sides
only small organisms but also other fish. of the body and on top
of the armor.
PRIMITIVE
1
VERTEBRATE
The first fish Marine
had no jawbone. lamprey Fossil Chimaeriformes Cheirolepis Pycnodus Sole
Fish with lungs appeared
in the Mesozoic Era Evolution Holocephali Cheirolepididae Pycnodontiformes Holostei Teleostei
2 ELASMOBRANCHIMORPH (200 million years ago). Wing shield
The formation of the Similar to amphibians, these In the Devonian Period (Pteraspis) Dunkleosteus Sharks and rays Eusthenopteron Chondrostei NEOPTERYGII
jawbone permitted new Placoderms species breathe with lungs ocean fish began to
feeding habits, and the and are now considered diversify. Coelacanths appeared,
Placoderms Elasmobranchii Sarcopterygii
fish evolved from living fossils. The line as well as the earliest bony fish
Lamprey
herbivore to carnivore. through the center of the and the first cartilaginous fish, ACTINOPTERYGII
Acanthodii
pfihsho'tso laotf etrhael lfionses.il is the itnhcel utdhirnege smhaairnk sg.r Ionu pths iso fperiod Jawless CARTILAGINOUS FISH BONY FISH Devonian
fish
BONY FISH gnathostomad fish also
3
They already had a FOSSILIZED appeared: the placoderms, GNATHOSTOMATA
specialized jawbone Modern fish LUNGFISH SCALES chondrichthyes, and THIS PERIOD SAW AN EXPLOSION IN
like fish of today. Dipterus valenciennesi osteichthyes. VERTEBRATA THE DIVERSITY OF FISH SPECIES.
10 GENERAL CHARACTERISTICS FISH AND AMPHIBIANS 11
Distinguishing Features
Near- Jawless Fish
S fossils Of the ancient agnathans, considered
imilar characteristics define nearly all fish, with a few rare exceptions. These aquatic the first living vertebrates, only
Choanichthyes lampreys and hagfish are left.
animals are designed to live underwater, and they have a jawbone and lidless eyes and are (Sarcopterygii) are archaic
bony fish with fleshy fins. SEA LAMPREY
cold-blooded. They breathe through gills and are vertebrates—that is, they have a spinal Some of them were the first Lampetra sp.
animals with lungs. Only a
column. They live in the oceans, from the poles to the equator, as well as in bodies of few species survive. Its round, toothed mouth
fresh water and in streams. Some fish migrate, but very few can pass from salt allows it to suck the blood of
fish of various species. There
water to fresh water or vice versa. Their fins enable them to swim and move COELACANTH are also freshwater lampreys.
Latimeria chalumnae
in different directions. Animals such as dolphins, seals, and whales are This species was thought
at times mistaken for fish, but they are actually mammals. to have gone extinct
millions of years ago,
until one was discovered
Just Cartilage
ANTERIOR alive off the coast of South
DORSAL FIN Africa in 1938; more of
This fin has stiff these fish were found later. Cartilaginous fish, such as rays and
HEAD PECTORAL FIN rays and has a sharks, have extremely flexible
One of the three Symmetrical, relatively small, stabilizing skeletons with little or no bone.
EYES main divisions of and with a radial structure function. SCALES
On the side of the its body The scales are POSTERIOR
NASAL PITS head, protected by imbricateΩthat DORSAL FIN
Also called fatty membranes is, they overlap This soft-structured RAY
nares; lie on one another. fin is located Raja miraletus
ethiteh ehre asdide of bfient wanede nth teh eta dilo.rsal Its large fins send
currents of water
carrying plankton and
small fish to its mouth.
The ray is very fast.
LATERAL LINE
Fish have sensory organs
all along this line.
With Spines
MOUTH
The angle of the mouth Osteichthyes is the most numerous
affects what the fish class of fish. The skeleton has some
can eat. level of calcification.
OPERCULUM
A bony flap that covers GILLS ATLANTIC MACKEREL
the gills and helps The fish's Scomber scombrus
regulate water flow breathing organs PELVIC FINS
These permit the fish This fish has no teeth. It lives in
to swim upward and temperate waters, and its meat is
downward. considered delicious. It can live
ANAL FIN
Soft, with a row for more than 10 years.
of finlets
TAIL MUSCLE
This is the
Gill Breathing strongest muscle
in the fish. CAUDAL FIN
Gills are the organs that fish It moves from side
use to breathe. They are made Filaments Water flow to side, propelling
Gill raker Oxygenated the fish forward.
of filaments linked by the gill arches. blood
The fish uses its gills to take in
oxygen dissolved in the water. In Action Water Open Water Closed
Through a process known as diffusion,
mouth mouth
oxygen is transferred to the blood, Capillary Water enters the mouth and
which has a lower concentration of Oedpgeen ionfg t ahte tubes felxotwrasc ot voexry tgheen ,g tilhlse. wAfatteerr tihse gills Pharynx 25,000
oxygen than the water. In this way
operculum Blood expelled through the gill slits.
the fish oxygenates its blood, flow
which then circulates to the rest of
Gills
its body. In most bony fish Operculum us Is the number of known fish
(taohnsedt emeixcoihuttsth hty,h esrspo)lu iwtgsha i tntehtroe f tlgowiwllo ss s liitntrs et.ahmrosu,gh Gill arch Gill filament Dbleoooxdygenated Filaments Ooppeennisn gasn dw chleorsee sw tahteer exits Esophag Coploesrecdulum Ooppeernculum shpaelfc ioefs a, lml cahkoinrgd autpe nsepaercliye so.ne