The first family of predators we shall
i consider are those which most ob~en，ers are armed with chemically activated， springloaded
never suspect of predation， stinging cells， called cnidocytes， which are tipped with structure ~mallcr th m ，..，， ，
Nowba~k，qf ~ ，~r I ，，: ，
:he sunlit shallows of the tropical world are neurotoxins. While the poison darts， called then hundred~ .m，i th.，u，~，~ ~ ，. ~，. .
nematocysts， in these stinging cells Usual v cannot
:m to us gardens of coral. As we look at these penetrate human skin ( f they do， the pain is you see.
our percepnon of their life is unavoidably
~ d by our experience on land~ To the mind of temporary)， they are highly lethal to marine organisms Then lina，gine ~-tmtles， ，， ，r.xi h ，，，
the vast rock bulk beneath the rt r
tl man， a bed of corals has as its closest fishes. The tentacles capture food that is carried along would take the loquaciou， ，， ~-it~h， <，~，E，，， ，i
SUCh as zooplankton or， in the case of anemones， to The number of polvp~ > ，Inlt.h ~
a flower garden~ Both are beautiful， both are in the current-drlven waters and pass the food to the
\"ized by a profusion of color and form， both central mouth to be ingested by the coral.
ted\" in the ground~ Naturally， then， a bed of
Asimov or a Carl Sagan t ， v，，k~- d~:m l，. ， -~
Many corals also have a complete back-ur) s \"ste \"
~ colored corals just beneath the surface of ~ smlply stand in awe.
~ evokes the flower-garden image， and many survive even a complete absence -g ; 5\" m to Corals reproduce both s~xuaJlv an，/ *，c，q ~l]，
. * current-tmrne
method performs a valuable， funcri~，.. A v，~，
food. Embedded in the tissue of coral polyps are reproduction (or budd.ngi occur~ whet， ~r， m，i~
u write about the sea s creatures further this microscopic algae cells called zooxanthellae. These tiny polyp develops a bud which gr-m， r3~ht ，.~~- ，，
.n by referring to these communities of coral \" ， \"
gardens.\" plant cells gather sunlight and the coral s waste， and \" \"
This is invaluable to the dome .~r rcct-bu，/dm< ，
Ith about corals and other sessile (rooted) sea photosynthesize food and oxygen. Thus， the coral and If you were to draw on a b-，lloon a nun，b~，r ，t ，
zooxanthellae nourish each other even without other poiyps， then inflate the balloo~，， rot， mm~ed， ，t~l
is far more intricate and complex， food. It is， in fact， the zooxantheflae which Usually that the
in with， we must recall that the sea is like a give color to the coral; coral polyps themseh，es are role of budding is to fill in d~e ::at.， ~， r
n at its clearest， seawater contains quantities colorless， dome grows larger，
，lankton and zooplankton~ Phytoplankton are Another profoundly important chemical activity of open water. The resulting pelagic lap，~，， crmbk， ，，
Sexual reproduction releases eggs md ，pctm J，
Iplex communities of single- and multi- the coral polyp is the secretion of limestone (calcium to colonize new regions far downstream， ，，r ro
e-floating creatures which collect sunlight
t their nourishment via photosynthesis， carbonate) in the form of a protective cup about its repopulate areas of natural destruction.
ttlike cells are a principal source of our body. When a coral is not extending its tentacles to
feed， its body is withdrawn into and protected by the Interestingly， in certain areas wt ere men h ~ ，
(ygen supply. Most zooplankton， on the stony cup. dynamited cora reefs for fis a or con，truer.on， ，，
I. are often troy creatures who ingest The cup each coral polyp secretes is extended by the in the moon-barren craters~\" \" ~ \" \"~
kton and other zooplankton for their food. polyp over the years. The cumulative lengthening of corals seem to have difficu tv estxbl s n ~ h~ rn-
~ for ~uch sessile creatures as corals， Tridacna
uges， and tunicates (sea squirtsl to have thousands of cups by succeeding generations of corals Among the 2，500 species of coral there .~ .m
astonishing variety of shapes， sizes， and cok~r~ m
his plankton soup as a reliable food supply， creates a coral head. The base of any stony-coral -
structures they form.
structure is composed of ancestral skeletons， with the There are vast castles of tan Montastrea ~avcr~:o.
rest be stirred. The motion of the earth
CUrrent generation of live polyps inhabiting their cups corals; tortured edifices of fire coral (milleporal;
tis activity through wind and water Currents on the surface of the structure~ When you think of the dainty pink or purple Acropo，u with their delicate
e the plankton in endless cycles about the masszve size of many Coral heads， you begin to antler-like branches; and the soaring stonehcnges
basins. Plankton and ocean currents are the appreciate both the numbers and the crucial building formed by huge beds of elkhorn coral.
ival for ~he stationary creatures of the coral role of corals on a reef~ Vast accumulations of coral Then there are the gorgonians. Those ~ hich h~e
~ft， radially symmetrical ey inder containing heads form the world s coral reefs. Whole tropical the shallows， where the wave-surge is their trequem
the basic body plan of a coral polyp. The islands are composed of immense coral reefs rudely companion， have a flexible skeleton of wiry gor~oni
tad digestive tissues， plus reproductive \" thrust above the water s surface by the forces of plate which can withstand countless Wave-surg~:s without
p this cylinder is mounted a central mouth. .~，~ ~!:: teCtomcs or glaciation~ ~
mouth on the upper surface (or at least You Soon begin to appreciate the astronomical breaking. Other gorgonian corms are limited to rock
O.u_ter edge) of the cylinder is a ring of
2.~，~ numbers of coral polyps nvolved in these dry canyons in vast reef structures， canyons through wh~
{\" recitations of fact. Spend a montent on a snorkel or environment can produce fans of brilliant vdlow，
u~g tentacles. -~ ~?; -， tidal currents flow. In the South Pacific th s
scuba dive and try to count the coral polvos on a
y，h~ ~ght or a multiple of eight tentacles single coral head. There will be at least hundreds and current flow. A third type hidcs its brilliant reds， its
IrLsome corals these tentacles arc smooth ， .
~! il~gs the ten tacles of rep tst held testg tion in a his to ry 150 feet.
fagt ones 7::， n thehu~~reds ~r Thoroyalty of ~rotbe
~ a n!illion polyp the l~d，_ o，，，:c immense soft corals of
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