CARDINAL FISH
Aptly named for its brilliant red to light pink colors, the Cardinal
fish can be easily found among the coral reefs in shallow water
areas. In most cases this family of fish will have large ctenoid
scales on their bodies but occasionally some species are found
with cycloid scales. This fish has a large head and eyes, with an
angled mouth that causes the lower part to protrude slightly. In
most cases the teeth are small lining the jaws and gums, but some
cardinal fish like those in the Cheilodipterus genus have longer
grasping teeth. They have two dorsal fins that appear to be rather
long for the size of their body as well as an anal fin with only two
spiny rays. Close inspection of a cardinal fish will show that the
lower jaw is separated and contain small, sharp teeth. The majority
of this family can be found inhabiting the waters of the
Indo-Pacific but some species prefer brackish water areas while
others only inhabit fresh water. One such species can be found in
New Guinea throughout the Lorentz River. This silvery, light
yellow species, Apogon trifasciatus, is around five inches in
length and has fins covered with cycloid scales.
One of the more interesting facts about the cardinal fish is their
common characteristic of mouth brooding. Once the eggs are
released and fertilized the female, or in some species the male,
will take the eggs in their mouth where they will incubate until
they have hatched and are ready to feed. In some species of the
cardinal fish, such as the red-orange cardinal fish that is often
found in the Mediterranean, both the male and female become
active in this process. Some cardinal fish, such as the Banggai
cardinal fish, have been successfully kept in salt water aquariums.
Studies of this beautiful fish show that part of the mating ritual
includes a kind of circling and nipping prior to the fertilization of
the eggs. Once the male of this species has received the
fertilized eggs into his mouth he will not eat until they have
hatched. During this time the female will aggressively chase away
any other fish that come too close to the male. Even after hatching
the fry remains in the males mouth for a few days before the spits
them out in groups to search for food. Studies have noted that
this process can take up to 24 days with the male refusing to eat
for around two weeks of this time.
The cardinal fish is, in most cases, a nocturnal fish ranging in size
from between two and eight inches in length. While many of these
fish bear the cardinal colors in a wide range of reds such as the
Apogon multitaeniatus which is the largest species reaching an
average length of around seven inches, there are some species
whose colors range from greenish, yellow-brown, silver, black to
pink. There are around 200 species of this fish with most living in
shallow reef areas. One species, the Astrapogon stellatus, that is
found in the Caribbean has been known when threatened by a
predator to take cover inside conch shells that are still inhabited
by their owners. In the Tonkin Gulf one of the more interesting
cardinal fish was found that had luminous organs. The Apogon
ellioti was discovered to have glandular organs within the
digestive tract that are structured similar to a reflector and lens. It
is still unknown what purpose these organs play in the life of this
species but it is known that there are other luminous species that
inhabit some of the deeper coral reef areas of the Indo-Pacific.
