Zoology – FISHES

THINGS YOU NEED TO KNOW FROM THIS CHAPTER…

1. Classification of the fishes…
1. What phylum do fish belong in?
2. What animals belong in Superclass Agnatha?
3. What animals belong in Superclass Gnatostomata?

i. What are the Elasmobranchii?

ii. What are the Holocephali?

4. What animals belong to Class Actinopterygii?
5. What animals belong to Sarcopterygii?
1. What makes a fish a fish?
1. How many species of fishes are there?
2. What are the challenges of living in water?
3. What gives them a sense of distant touch?
2. History of fishes…
1. What was the Age of Fishes?
2. What happened to the cartilaginous fishes?
3. What are the two lines of bony fishes?
3. Superclass Agnatha include what type of fishes?
1. What class do hagfishes belong to?
2. What do hagfishes look like?
3. How and what do hagfishes eat?
4. What class do the lampray belong to?
5. What happened in the Great Lakes?
4. What class do the cartilaginous fishes belong to?
1. What term refers to the shape of shark bodies?
2. What is the shark nose called?
3. Shark tails are horizontal. What is this pattern called?
4. How do sharks hunt from a distance, as they approach, and then close-up?
5. How do sharks reproduce?
6. What is the largest group of cartilaginous fishes?
7. What are two examples of interesting rays?
5. What term refers to bony fishes?
1. When did they evolve?
2. Are they a successful group of organisms?
3. What features do they share with tetrapods?
4. What are the two major lineages? Which was more successful?
5. What increased respiratory efficiency?
6. What did the lung (and/or swimbladder) evolve from?
7. What adaptation aided food consumption?
6. What class do the ray-finned fishes belong to?
1. How many species do we find in this animal group?
2. What is the largest group of these fishes?
3. What replaced heavy dermal armor seen in their ancestor?
4. What is the function of their swim bladder?
7. What class do the lobe-finned fishes belong to?
1. Why is this small class so important to evolutionists?
2. What is so interesting about coelacanths?
8. Generalized fish knowledge…
1. How fast can fish swim?
2. What pushes a fish forward through water?
3. What resists this motion?
4. What is the side-to-side movement of the head known as?
5. Is swimming an efficient means of locomotion?
6. How do sharks keep from sinking?
7. How do fish keep from sinking?
8. What is countercurrent exchange? Is it any good?
9. What is the challenge with being a freshwater fish?
10. What is the challenge with being a saltwater fish?
11. What feeding strategies do we see in fish?
12. How do most fish reproduce and grow?

Classification

Phylum Chordata

Superclass Agnatha

Class Myxini - ___________________________

Class Cephalaspidomorphi - ___________________________

Superclass Gnathostomata

Class Chondrichthyes – ___________________________ fishes

Subclass Elasmobranchii – sharks, skates, & rays

Subclass Holocephali - chimaeras

Class Actinopterygii – ___________________________ fishes

Subclass Chondrostei – bichirs, paddlefishes, & sturgeons

Subclass Neopterygii – gars, bowfin, teleosts

Class Sarcopterygii – ___________________________ fishes

I. Diversity

A. Overview

1. A modern fish is an aquatic vertebrate with

___________________________, limbs (if present)

in the form of ___________________________, and usually with a

skin covered in ___________________________ of

___________________________ origin.

2. With over ___________________________ living species, fish

include more species than all other vertebrates combined.

3. They are adapted to live in a medium

___________________________ more dense than air.

4. They can adjust to the salt and water balance of their

environment.

5. Their gills are efficient at extracting oxygen from water that has

___________________________ the oxygen of air.

6. A ___________________________ system detects water

currents and vibrations, a sense of “distant touch.”

7. Evolution in an aquatic environment both shaped and

constrained its evolution.

II. Ancestry and Relationships of Major Groups of Fishes

A. History

1. The ______________________________________ is called the

Age of Fishes.

2. Cartilaginous Fishes

a. They flourished during the Devonian and Carboniferous

Periods, but nearly became extinct at the end of the

Paleozoic.

b. They increased in numbers in the early Mesozoic,

radiating to form a modern

___________________________ assemblage.

3. Bony Fishes

a. These are the dominant fishes today.

b. They have two distinct lineages: the ray-fined fishes and

the lobe-finned fishes.

c. The ray-finned fishes radiated to form ______________

_____________fishes.

d. Lobe-finned fishes include the

___________________________ and the

___________________________ and are the sister group to

tetrapods.

III. Superclass Agnatha: ___________________________ Fishes

A. Overview

1. Living jawless fishes are represented by

___________________________ and

___________________________.

2. About 43 species of hagfishes are known and about 41 species

of lamprey are described.

3. Members of both groups lack jaws, internal ossification, scales or

paired fins.

4. Both groups share porelike gill openings and an eel-like body.

B. Class ___________________________: Hagfishes

1. Hagfishes are entirely ___________________________.

2. They are scavengers and predators of annelids, molluscs, dead

or dying fishes, etc.

3. The hagfish enters a dead or dying animal through an orifice or

by digging inside using keratinized plates on its tongue to rasp

away bits of flesh.

4. To provide leverage, the hagfish ties a knot in its tail and passes

it forward to press against the prey.

C. Class ___________________________ (Petromyzontes): Lampreys

1. Diversity

a. There are 22 species of lampreys in North America; half

belong to nonparasitic brookdwelling species.

2. Parasitic Lampreys

a. If marine, parasitic lampreys migrate to the sea; other

species remain in freshwater.

b. They attach to a fish by a sucker-like mouth and sharp

teeth rasp away flesh and they suck fluids.

c. When engorged, the lamprey drops off but the wound may

be fatal to the fish.

3. Sea Lamprey Invasion of the Great Lakes

a. No lampreys were in the U. S. Great Lakes west of

Niagara Falls until the ___________________________

was built in ___________________________.

b. A century later, sea lampreys were first seen in Lake Erie,

then spread to all of the U.S. Great Lakes in the 1940s.

c. Lampreys preferred ___________________________

and destroyed this commercial species.

d. They then turned to rainbow trout, whitefish, burbot,

yellow perch and lake herring.

e. After decimating these populations, they resorted to chubs

and suckers.

f. The lamprey populations declined both from depletion of

food and from control measures.

g. Chemical larvicides were used in spawning streams;

release of sterile males is also being used.

IV. Class Chondrichthyes: Cartilaginous Fishes

A. Overview

1. Nearly 850 living species are in the class Chondrichthyes.

2. Although a smaller and more ancient group, their well-developed

sense organs, powerful jaws and predaceous habits helped them

survive.

3. Although calcification may be extensive, true bone is completely

absent throughout the class.

4. Nearly all are marine; only 28 species live primarily in freshwater.

B. Subclass ___________________________: Sharks, Skates and Rays

1. Form and Function

a. Sharks are among the most gracefully streamlined of

fishes; the body is ___________________________.

b. The front of the ventral mouth is the pointed

___________________________.

c. The tail has a longer upper lobe; this pattern is called

___________________________.

d. Fins include paired pectoral and pelvic fins, one or two

median dorsal fins, a median caudal fin, and sometimes a

median anal fin.

e. In the male, the medial part of the pelvic fin is modified to

form a clasper used in copulation.

f. Paired nostrils are anterior to the mouth.

g. The lateral eyes are lidless; behind each eye is a spiracle,

a remnant of the first gill slit.

h. Sharks detect prey at a distance by large

___________________________ organs sensitive to one

part per 10 billion.

i. Prey may also be located from long distances sensing low

frequency vibrations in the lateral line.

j. At close range, sharks switch to

___________________________; most sharks have

excellent vision even in dimly lit water.

k. Up close, sharks are guided by _____________________ ___________________________ that surround all animals.

l. Upper and lower jaws are equipped with sharp, triangular

teeth that are constantly replaced.

2. Reproduction and Development

a. All chondrichtheans have

___________________________ fertilization; maternal

support of the embryo is variable.

b. Those that lay large, yolky eggs immediately after

fertilization are ___________________________.

c. The embryo is nourished from the yolk for up to two years

before hatching as a miniature adult.

d. Sharks that retain embryos in the reproductive tract are

___________________________ if the embryo is nourished

by yolk.

e. True ___________________________ reproduction

occurs where embryos receive nourishment from the

maternal bloodstream from nutritive secretions of the

mother.

3. Form and Function of Rays

a. More than half of all elasmobranchs are

___________________________; most are specialized for

___________________________ life.

b. The dorsoventrally flattened body and enlarged pectoral

fins are used as wings in swimming.

c. Teeth are adapted for crushing prey: molluscs,

crustaceans and sometimes small fish.

d. ___________________________ have a whiplike tail with

spines and venom glands.

e. ___________________________ have large electric

organs on each side of the head.

IV. Osteichthyes: Bony Fishes

A. Origin, Evolution and Diversity

1. In the early to middle ___________________________, a

lineage of fishes with bony endoskeletons gave rise to a clade that

contains ___________________________ of living fishes and all

living ___________________________.

2. The features unite bony fishes and tetrapod descendants.

a. _________________________________ is present that

replaces cartilage developmentally.

b. A _______________ or ___________________________

is present that was evolved as an extension of the

___________________________.

3. By the middle of the Devonian, bony fishes developed into two

major lineages.

a. The ray-finned fishes, class Actinopterygii, radiated to

form modern bony fishes.

b. Seven species of lobe-finned fishes, class Sarcopterygii,

include lungfishes and the coelacanth.

4. The ___________________________ increased respiratory

efficiency; outward rotation helped draw water across the gills.

5. The gas-filled structure off the esophagus helped in buoyancy

and also in hypoxic waters.

6. Specialization of jaw musculature improved feeding.

VI. Class Actinopterygii: Ray-finned Fishes

A. Diversity

1. Over 23, 600 species of ray-finned fishes constitute the most

familiar bony fishes.

2. Includes 4 groups, but ___________________________ are the

Largest.

3 Teleosts

a. Teleosts constitute ___________________________ of

all living fishes and half of all vertebrates.

b. Perhaps 5,000-10,000 remain undescribed, many from

remote areas but some in North America.

c. Teleosts range from 10 millimeters to 17 meters long, and

up to 900 kilograms in weight.

d. They survive from 5,200 meters altitude in Tibet to 8,000

meters below the ocean surface.

e. Some can live in hot springs at 44^o C while others survive

under Antarctic ice at –2^o C.

f. Some live in salt concentrations three times seawater;

others in swamps devoid of oxygen.

B. Morphological Trends

1. Heavy dermal armor was replaced by light, thin, flexible

___________________________ and

___________________________.

2. Increased mobility from shedding armor helps fish avoid

predators and aided in food getting.

3. Fins changed to provide greater mobility and serve a variety of

functions: braking, streamlining and social communication.

4. The swim bladder shifted from primarily respiratory to buoyancy

in function.

VII. Class Sarcopterygii: Lobe-finned Fishes

A. Diversity

1. Only seven species are alive today; six species of lungfishes and

the coelacanth.

2. Early sarcopterygians had lungs as well as gills, and a

heterocercal tail.

3. The fleshy, paired lobes appear to have been used to scuttle

along the bottom.

4. The South American and African lungfish can live out of water for

long periods of time.

5. The Coelacanth

a. Thought to be extinct ___________________________

years, a specimen was dredged up in

___________________________.

b. Young coelacanths are born fully formed after hatching

from eggs up to nine centimeters in diameter.

WATCH THIS VIDEO OF MUDSKIPPERS: http://youtu.be/KurTiX4FDuQ

VIII. Structural and Functional Adaptations of Fishes

A. Locomotion in Water

1. Speed

a. Most fishes swim maximally at _____________________

______________________________________________; a

larger fish therefore swims faster.

b. Short bursts of speed are possible for a few seconds.

2. Mechanism

a. The trunk and tail musculature propels a fish.

b. Fish ___________________________ move backward

against the water, producing a reactive force with two parts.

c. The thrust pushes the fish forward and overcomes

___________________________.

d. The lateral force makes the fish’s head, this is called

“___________________________”; a large and rigid head

minimizes yaw.

e. The swaying body generates too much drag for fast

speed.

f. Fast fish are less flexible and generate all thrust with their

tails.

3. Economy

a. Swimming is the most economical form of motion because

water buoys the animal.

b. The energy cost per kilogram of body weight for traveling

one kilometer is 0.39 Kcal for swimming, 1.45 Kcal for flying

and 5.43 for walking.

B. Neutral Buoyancy and the Swim Bladder

1. Fish are slightly heavier than water.

2. To keep from sinking, a shark must continually move

___________________________; fins keep it “angled up.”

3. The ___________________________, as a gas-filled space, is

the most efficient flotation device.

4. A fish can control depth by adjusting the volume of gas in the

swim bladder.

5. Due to pressure, as a fish descends, the bladder is compressed

making the total density of the fish greater.

6. As a fish ascends, the bladder expands making the fish lighter

and it will rise ever faster.

C. Respiration

1. The gills are inside the pharyngeal cavity and covered with a

movable flap, the ___________________________.

2. The operculum protects the delicate gill filaments and

streamlines the body.

3. Pumping action by the operculum helps move water through the

gills.

4. Water flow is opposite to the blood flow; this

___________________________ exchange maximizes exchange

of gases.

D. Osmotic Regulation

1. Freshwater has far less salt than is in fish blood; water tends to

enter the body of the fish and salt is lost by diffusion.

2. The scaled and mucous-covered body is mostly impermeable,

but gills allow water and salt fluxes.

3. Freshwater fishes are hyperosmotic regulators.

a. The opisthonephric kidney pumps excess water out.

b. Special salt-absorbing cells located in epithelium actively

move salt ions from the water to the fishes’ blood.

4. Marine bony fishes are hypoosmotic regulators.

a. Marine fishes have a much lower blood salt concentration

than in the seawater around them.

b. Therefore they tend to lose water and gain salt; the

marine fish risks “drying out.”

c. To compensate for water loss, a marine teleost drinks

seawater; this brings in more unneeded salt.

d. Unneeded salt is carried by the blood to the gills and

secreted by special salt-secretory cells.

E. Feeding Behavior

1. Fish devote most of their time to searching for food to eat and

eating.

2. Most fish are ___________________________ that feed on

zooplankton, insect larvae and other aquatic animals.

3. Most fish do not chew food since it would block water flow across

the gills.

4. Some fish are ___________________________ and eat plants

and algae; they are crucial intermediates in the food chain.

5. __________________________________________________

are a third group and crop the abundant microorganisms of the sea.

6. Many of the plankton feeders swim in large schools and use the

gill rakers to strain food.

7. ___________________________ can feed on both plant and

animal food.

8. ___________________________ feed on organic debris.

9. ___________________________ fishes suck the body fluids of

other fishes.

F. Reproduction and Growth

1. Most fishes are dioecious with external fertilization and external

development.

2. Freshwater fishes may have elaborate mating dances before

spawning.

3. An egg soon takes up water, the outer layer hardens and

cleavage occurs.

4. The blastoderm develops and the yolk is consumed.

5. The fish hatches carrying a semitransparent yolk sac to supply

food until it can forage.

6. Growth is temperature dependent; warmer fish grow more

rapidly.

7. Most fish continue to grow throughout life and do not stop at

maturity.