The warm waters of coral reefs are rich in marine life. Odd shapes, bright colors and
distinctive color patterns enhance the appearance as well as the survival of many of
the animals that live there. Parrotfish are among the most colorful fish found on reefs.
Their unusual mouth is formed by large teeth that are fused together. The teeth's
resemblance to the beak of tropical birds earned this group the nickname "parrotfish."
These reef fish graze on algae that cover the surfaces of rocks and dot the re ef
bottom. While a parrot's strong beak is used to crack open nuts and seeds of rainforest
plants, parrotfish use their teeth to bite off pieces of stony coral. This may seem like
an unappetizing meal, but some parrotfish seem to prefer it.
It is not the hard coral skeleton that provides nourishment, but the soft bodied
structures coral polyps that grow on the surface of the skeleton. The polyps look like
miniature sea anemones, except that most live connected together in colonies contain
ing hundreds of individuals. Living in coral polyp cells are single-celled algae known
as zooxanthellae. Zooxanthellae are the reason why parrotfish eat coral! Any coral
skeletal material that is swallowed is crushed by the grinding action of special teet h
found in the parrotfish's throat called the pharyngeal mill.This makes its way through
the fish's digestive system and is deposited on the reef as white coral sand. Some fish
return to the same spot to release their waste products which form small hills of sand.
It has been estimated that parrotfish produce as much as one ton of coral sand per acre
of reef each year.
Classification and Characteristics
Early scientists identified over 350 different kinds of parrotfish, but it is now known
that there are only 80 members of Family Scaridae. The early confusion came about
because these fish have a number of color phases which look quite different. There is
still some disagreement, but among Atlantic species most people recognize two major
genera, Scarus and Sparisoma. Sparisoma is restricted to the Caribbean, while Scarus
is found in all tropical seas and even the Mediterranean Sea. Two smaller genera,
Cryptotomus and Nicholsina are also found in the Caribbean. Close relatives of
parrotfishes are the wrasses. Wrasses also have "buckteeth" but they are not fused
together like parrotfishes'. However, wrasses are not plant eaters and feed on
zooplankton an d larger invertebrates. Aside from eating coral polyps and perhaps an
occasional mollusk, parrotfish are algae eaters.
The different types of parrotfish can be told apart by the way in which their upper and
lower teeth meet. Scarus have teeth that most closely resemble a parrot's beak. The
upper teeth stick out and cover up the lower. They are also large fish , sometim es
reaching four feet, bright and colorful and known to swim in schools. Some male
Scarus develop a hump on their foreheads, which is especially noticeable in the blue
humphead parrotfish. In Sparisoma, however, the upper teeth fit inside of the lower
tee th. They are usually small fish, under one foot in length. They are less colorful,
mostly reds, browns and grays and swim alone or in small groups. Cryptotomus and
Nicholsina, which have a more cigar shape like the wrasses, do not have teeth that
overlap at all. Instead, their teeth are more distinct, and not completely fused into a
beak.
In general, parrotfish have large, thick scales, strong enough to stop a heavy spear in
some species. The scales have been used to decorate basketwork and shellflower
arrangements. Many Caribbean and Indo-Pacific parrotfish are eaten. In Hawaii, they
a re called ohu, palukaluka and lauia and eaten raw. At one time, Hawaiians
considered the parrotfish so special that only royalty could touch them.
Adaptations and Reproduction
At night, parrotfish do not graze, but sleep on the reef bottom. Some bury in the sand
like wrasses. Others, certain species of Scarus, have developed the unique ability to
enclose themselves in a see-through covering at night called a mucus cocoon. Th e
cocoon is secreted in just thirty minutes and provides excellent protection from night
predators such as moray eels. It seems to prevent other animals from picking up the
scent of parrotfish. In addition to being produced at night, it is thought that a mucus
cocoon is also made if there is not enough oxygen in the water.
Parrotfish have a number of other interesting features, some of which are shared by
the wrasses. Both of these families of fish use the same method of swimming in which
the pectoral fins, found just behind the gills, are used in a manner similar to row ing.
These fins make quick up-and-down movements to propel wrasses and parrotfish
forward, whereas most other fish rely on their caudal or tails fins. However, parrotfish
do use their bluntly shaped tails when they need a quick burst of speed.
In 1968 is was found that parrotfish, like wrasses, can undergo sex reversal. In this
case, a female fish becomes a male. Therefore, parrotfish can be born male and
remain male throughout their lives (primary males) or they can be born female and
chang e sex and color to become a male (secondary males). Secondary males are
sometimes called supermales or terminal males. Females and primary males look
alike and are red, gray, brown and black. Secondary males are bright green, blue, red
and yellow. There a re also some species that maintain the same colors throughout
their lifetime. As if this is not confusing enough, some parrotfish can change their
colors to match the surroundings.
Various color phases are also seen in wrasses, some are associated with sex change
and others are not. Among blueheaded wrasses, primary males and females are
yellow, sometimes with a black stripe. When he reaches a certain size, the primary
male may c hange colors and become a supermale. The supermale has a blue head,
black stripe and greenish-blue body. Supermales maintain a harem of females with
which they mate. They also establish a site just for spawning and other males are not
allowed to enter thi s territory. If the colorful supermale is removed from the harem,
the most aggressive female, usually the largest, immediately begins to dominate the
harem. Within two to four days, this female has changed color and sex to become a
blueheaded supermale. T he new male can now fertilize the eggs of the harem
members. In some species of wrasses, it is simply the largest female who changes sex.
Although they are not known to have harems, it is possible that dominance and size
plays a part in sex reversal among the parrotfishes as well.
Parrotfish spawn or produce eggs all year round, although this activity is more
frequent in the summer. Some species move to specific areas to spawn, typically into
deeper areas of the reef. Supermales pair up with one female to spawn, while primary
ma les mate with small groups containing one female and several males. After
spawning, they return to the shallow water at night. Fertilized eggs hatch after 25
hours. The larvae are only 1.7 mm long and have no eyes, mouth or pigment. A mouth
does not appear until the third day after hatching. It is not known how long the larval
stage lasts in these anim als.