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Coral Reefs!
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Phylum Cnidaria and the class Anthozoa
There are over 800 known Hermatipic
species
◦ Hermatipic- reef building
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Coral reefs are the most biologically
diverse ecosystems on earth,
◦ Source of food
◦ Protect coastlines (from storms and erosion)
◦ Gives homes and spawning and nursery
grounds for fish
◦ Provide jobs to local economies from fishing,
recreation, and tourism
◦ New medicines
◦ Also known as ahermatypic
(non reef building) coral, they
do not produce a calcium
carbonate skeleton
◦ Often called octocorals
◦ Mostly colonial
◦ Contains sclerites in cells on
the outside of the colony
found in coenenchyme, (jellylike tissue) between polyps.
 Sclerites made of protein and
calcium carbonate.
◦ Some are also encrusting
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Hermatipic- Reef building coral
◦ Contains a basal plate
◦ Net benefit of the world's coral reef
ecosystems estimated to be $29.8 billion
per year
◦ Have zooxanthellae
 Deep water and some cold water corals lack
zooxanthellae
◦ Most corals feed at night
 Similar to sea anemones. Polyps extend their
tentacles to capture prey, first stinging them
with toxic nematocyst cells, then drawing
them toward their mouths.
 Also collect fine particles in mucous film which
are drawn by cilia into the polyp's mouth.
Some species are entirely mucous suspension
feeders
 Prey ranges in size from small fish to
zooplankton, depending on size of the coral
◦ Deep sea corals live on in deeper
water from 50 m to over 3,000 m
◦ A few species also live in
shallower, cold water in the
northern latitudes.
◦ Found in all oceans
◦ Like their shallow-dwelling
relatives, deep-sea corals exhibit
high biodiversity.
◦ Don’t contain zooxanthellae (no
light)
◦ Don’t know the extent of
communities because they live so
deep
 http://www.youtube.com/watch?v=P
UbaVZRIS18
◦ an algae that gives off oxygen
and other nutrients
◦ polyp gives the algae carbon
dioxide
 That is why coral reefs grow near the
surface
◦ Algae enhance the coral’s ability
to synthesize calcium carbonate
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Coral Bleaching
◦ When algae leave, due to warmer
than usual water or a change in
pH
 http://www.youtube.com/watch?v=a
EdoizgeNJk
 http://www.youtube.com/watch?v=6
0jof35WuAo
 Feed similar to sea anemones. Polyps
extend their tentacles to capture prey,
stinging them with nematocyst cells,
then drawing them toward their mouths.
 Also collect fine particles in mucous film
which are drawn by cilia into the polyp's
mouth. Some species are entirely
mucous suspension feeders
 Prey ranges in size from small fish to
zooplankton, depending on size of the
coral
Can be either asexual or sexual
 Budding- asexual
◦ new polyps bud off from parent. This occurs
when the parent polyp reaches a certain size and
divides. Continues throughout the animal's life
and produces polyps identical to the parent
polyp.
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Fragmentation- asexual
◦ Allows a portion of an entire colony to establish
a new colony. The separated individuals start
new coral colonies that are genetically identical to
the parent colony
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Broadcast Spawning
◦ 3/4ths of all stony coral species are
broadcast spawners
◦ Produce male and/or female gametes that are
released into the water in large numbers
 Allows them to spread their “children” over a broad
area.
 Have lots of kids at one time to compensate for how
many die a terrible depressing death, while their
parents watch, and cant do anything about it.
 occurs as a synchronized event, very important
because male and female corals cannot move.
 Usually occurs in response to environmental cues.
 Long-term cues may be related to temperature, day
length, or rate of temperature change.
 The short-term control is usually based on lunar cues
 http://www.youtube.com/watch?v=1aX61LzmeYA
 http://www.youtube.com/watch?v=wsaZ8-I7akg
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Remaining 1/3 of coral species
are brooders
◦ Only male gametes released into water.
◦ The gametes are negatively buoyant
and transported by waves and current
before sinking
◦ They are taken in by female coral
polyps containing egg cells fertilization
occurs inside the female coral and
produces a small planula.
◦ The planula is released through mouth
of female when it is old enough to
settle very soon after its release.
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Overtopping
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Aggression
◦ used mostly by fast growing species
◦ The faster growing coral just grows
over the other coral
◦ The covered coral gets less light
and food.
◦ involves extruded digestive
filaments and sweeper tentacles.
Typically results in the death of
some of the other’s polyps.
 http://animal.discovery.com/videotopics/wild-animals/coral-nighttimebattle.htm
◦ Cells are specialized to perform various
functions
◦ Very limited organ development
◦ Have a simple stomach (gastrovascular
cavity ) opens only on one end, and a ring
of tentacles.
◦ No central nervous system.
◦ While appearing to be a single organism,
many coral are actually a colony of many
individual, identical, coral polyps.
◦ Are only a few millimeters in diameter
◦ The polyps of hard corals sit in a calyx
that is produced by the coral with
calcium carbonate
◦ The walls surrounding the calyx are
called the theca and the bottom is the
basal plate.
◦ Basal plate is a calciferous ring with six
supporting ridges. The ridges grow
vertically and project into the base of
the polyp.
◦ Tabulae are horizontal partitions that
allow for upward growth by isolating
the surface from the skeleton.