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Bony Fish
Jessica Harwood
Douglas Wilkin, Ph.D.
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AUTHORS
Jessica Harwood
Douglas Wilkin, Ph.D.
EDITOR
Douglas Wilkin, Ph.D.
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Printed: March 16, 2015
CONTRIBUTORS
Doris Kraus, Ph.D.
Niamh Gray-Wilson
Jean Brainard, Ph.D.
Sarah Johnson
Jane Willan
Corliss Karasov
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C HAPTER
Chapter 1. Bony Fish
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Bony Fish
• Describe the characteristics of the bony fish.
• Discuss the importance of the swim bladder and operculum.
• Distinguish ray-finned fish from lobe-finned fish.
Can fish have bones?
Of course. Many fish have bones. They serve the same function as our bones: protection and support. Notice how
the skeleton protects the fish’s brain. Also, notice the bones along the body of the fish would allow muscles to attach
to aid in movement.
Bony Fish
There are about 27,000 species of bony fish ( Figure 1.1), which are divided into two classes: ray-finned fish and
lobe-finned fish. Most bony fish are ray-finned. These thin fins consist of webs of skin over flexible spines. Lobefinned fish, on the other hand, have fins that resemble stump-like appendages.
FIGURE 1.1
Fins of bony fish: ray fin (left) and lobe fin
(right).
Characteristics of Bony Fish
Most fish are bony fish, making them the largest group of vertebrates in existence today. They are characterized by:
1. A head and pectoral girdles (arches supporting the forelimbs) that are covered with bones derived from the
skin.
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2. A lung or swim bladder, which helps the body create a balance between sinking and floating by either filling
up with or emitting gases such as oxygen.
3. Jointed, segmented rods supporting the fins.
4. A cover over the gill called the operculum, which helps them breathe without having to swim.
5. The ability to see in color, unlike most other fish.
Ray-finned Fish
The ray-finned fish have fin rays, with fins supported by bony spines known as rays. The ray-finned fish are the
dominant class of vertebrates, with nearly 99% of fish falling into this category. They live in all aquatic environments,
from freshwater and marine environments from the deep sea to the highest mountain streams.
Lobe-finned fish
The lobe-finned fish are characterized by fleshy lobed fins, as opposed to the bony fins of the ray-finned fish. There
are two types of living lobe-finned fish: the coelacanths and the lungfish. The pectoral and pelvic fins have joints
resembling those of tetrapod (four-limbed land vertebrates) limbs. These fins evolved into legs of amphibians, the
first tetrapod land vertebrates. They also possess two dorsal fins with separate bases, as opposed to the single dorsal
fin of ray-finned fish. All lobe-finned fishes possess teeth covered with true enamel.
How Big Are Bony Fish?
The ocean sunfish is the most massive bony fish in the world, up to 11 feet long and weighing up to 5,070 pounds
( Figure 1.2). Other very large bony fish include the Atlantic blue marlin, the black marlin, some sturgeon species,
the giant grouper, and the goliath grouper. The long-bodied oarfish can easily be over 30 feet long, but is not nearly
as massive as the ocean sunfish. In contrast, the dwarf pygmy goby measures only 0.6 inches. Fish can also be quite
valuable. In January 2013, at an auction in Tokyo’s Tsukiji fish market, a 222-kilogram (489-pound) tuna caught off
northeastern Japan sold for 155.4 million yen, which is $1,760,000.
FIGURE 1.2
An ocean sunfish, the most massive bony fish in the world, can reach up
to 11 feet long and weigh up to 5,070 pounds!
Summary
• The bony fish are divided into two classes: ray-finned fish and lobe-finned fish.
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Chapter 1. Bony Fish
• The bony fish are characterized by a lung or swim bladder, a cover over the gills, and bones covering the head
and pectoral girdles.
Explore More
Use the resources below to answer the questions that follow.
Explore More I
• Bony Fish (Perch) Anatomy at http://www.youtube.com/watch?v=pNZQEmGp11k (5:55)
MEDIA
Click image to the left or use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/57390
1. What is one of the purposes of the operculum?
2. What is the lateral line used for? Where is it located?
3. Not all fish have swim bladders, but, for those who do, what are they used for? Why do you think some fish
don’t have swim bladders?
Explore More II
• Pregnant Males at http://www.youtube.com/watch?v=EaOHLQy_bjU (2:25)
MEDIA
Click image to the left or use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/57391
1.
2.
3.
4.
What type of fish is a seahorse?
What is unusual about seahorse reproduction?
How wide is a seahorse’s field of vision? How is it so wide?
What do seahorses feed on?
Review
1.
2.
3.
4.
5.
What is the largest group of vertebrates in existence today?
Name three characteristics of the bony fish?
What are the two classes of the bony fish?
What is the swim bladder?
What is the operculum?
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References
1. (left) Brian Gratwicke; (right) Daniel Jolivet. The fins of a ray fin and a lobe fin fish . CC BY 2.0
2. Brian Snelson. Picture of an ocean sunfish . CC BY 2.0
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