Page 34 - Fish and Amphibians (Britannica Illustrated Science Library)

30 LIFE IN THE WATER FISH AND AMPHIBIANS 31

You Are What You Eat DIFFERENCES

Carnivorous fish eat all sorts of species, even
though their basic diet consists of meat. They
ost fish feed in their natural environment, the larger fish eating have terminal-type mouths, muscular stomachs,
and short intestinal tracts. Herbivores feed on
the smaller ones, and the smallest sea creatures feeding on Grazers aquatic vegetation. They have a long intestinal
M marine plants. A fish's mouth gives many clues about its feeding tract compared with other fish.
This group of fish eats vegetation or FUSED TEETH
habits. Large, strong teeth indicate a diet of shellfish or coral; pointed coral in small bites. Parrotfish (Scaridae) Parrotfish have a strong beak that
teeth belong to a hunting fish; and a large mouth that is open while the fish have a horny beak made of fused teeth. enables them to bite the bony
skeleton of corals and eat the algae
They scrape the fine layer of algae and that grows on them. The beak is
swims is that of a filterer. Some species can also trap food that lives outside coral that covers rocks and then crush it actually made of individual teeth,
the water: trout, for example, hunt flies. into powder using strong plates in the arranged in a beaklike structure.
CORAL back of the throat.
Parrotfish feed
on corals.
PHARYNGEAL PLATES
After biting a clump of coral
covered with algae, the
Predators pharyngeal plates, strong
grinding structures in the throat,
crush the hard, stony pieces.
These are fish that feed on other species. They MOUTH
have teeth or fangs that help them to wound acts as a filter.
and kill their prey or to hold it fast after the As it swims
attack. Predators use their sight to hunt, along with its
mouth open,
although some nocturnal species such as
zooplankton and
moray eels use their senses of smell and small fish are PARROTFISH
touch and those of their lateral line. trapped. Scarus sp.
All predators have highly evolved
stomachs that secrete acid to
digest meat, bones, and scales.
Such fish have a shorter intestinal
tract than herbivorous species, so
digestion takes less time.
WHALE SHARK
Rhincodon typus
Types of Mouths
Filterers
PIRANHA
Pygocentrus sp. Some species have evolved to the point of being able to
take from the water only those nutrients they need for
feeding. They filter the nutrients out using their mouths
RAZOR-SHARP and gills. These species include whale sharks (Rhincodon
TEETH typus), herring (Clupea sp.), and Atlantic menhaden
Large, sharp teeth (Brevoortia tyrannus).
go along with a
predator's diet.
Terminal Superior
Plants
Symbiosis
Life in the water is based on phytoplankton,
is the interaction between two organisms that live in close cooperation. One type Inferior Protusible
of symbiosis is parasitism, in which one organism benefits and the other is which is eaten by zooplankton. These are in
harmed. An example of a parasite is the sea lamprey (Petromyzon marinus), which turn eaten by fish, all the way up
sticks to other fish and sucks their body fluids to feed itself. Another type of to the large marine species.
symbiosis is commensalism, in which one organism benefits and the other is not
harmed. An example is the remora (Remora remora), or suckerfish, which sticks Suckers
to other fish using suction disks on the end of its head. STURGEON
Species that live in the Acipenser sp.
depths, such as sturgeons
(Acipenseridae) and BARBELS
The sturgeon has a
suckerfish (Catostomidae),
SUCKERS spend their days sucking the mud prominent snout. In
They close their eyes, turn its mouth it has four
them, and push them on the seafloor. When they are cut sensitive barbels.
downward to increase the open, large amounts of mud or THE
pressure of the mouth. sand are found in the stomach and VACUUM
intestines. Digestive mechanisms Sucking fish use their
REMORA mouths like a large
process all this material and vacuum cleaner to hunt
Remora remora
absorb only what is needed. their prey.`