Times of the Islands Summer 2020

green pages newsletter of the department of environment & coastal resources
What is an anemone?
You may have seen them in the Turks & Caicos Islands
and wondered what makes these animals tick. In a lot of
ways, anemones are similar to corals, and even jellyfish—
they are all grouped into the phylum Cnidaria. Cnidarians
are considered some of the simplest organisms in the animal
kingdom because they lack what we would consider
organs. While you and I have a heart to distribute blood
throughout our bodies and lungs to transfer oxygen into
our blood, cnidarians lack these organs. Ultimately, cnidarians
are made up of just two sets of membranes, or
body parts—the epidermis (similar to our skin) and the
gastrodermis (similar to our stomach). So, if they don’t
have gills or lungs, how do cnidarians get their oxygen?
Cnidarians’ thin membranes are the key—these membranes
are in constant contact with water and allow
diffusion of oxygen into the body.
incredible acceleration that this event is considered one
of the fastest found in nature. When nematocytes on the
tentacles of a cnidarian are triggered by contact with
another object, such as a small tasty crustacean, they
launch hundreds of hooked barbs into the object and
begin releasing venom. Prey that are unfortunate enough
to be on the receiving end of these barbs are incapacitated
and then eaten by the cnidarian.
In the case of anemones, they have a mouth in the
center of an oral disc, into which their tentacles guide the
food. One species here in the Turks & Caicos Islands is
in fact a voracious eater. The Giant Caribbean Anemone,
Condylactis gigantea, is capable of eating not only crustaceans
and other invertebrates, but even small fish!
Anemone menagerie
Anemones come in countless colors, shapes and sizes,
BEN FARMER
Left: This upside-down jellyfish, genus Cassiopea, rests on the sand. Cassiopea is a cnidarian, the same phylum as anemones.
Right: This stony coral was found during a dive on the wall bordering South Caicos. Corals are cnidarians, the same phylum as anemones.
Simple yet deadly
What really sets cnidarians apart are their potent stinging
cells. If you have ever accidentally stepped on a jellyfish
on the beach or brushed against one underwater, you
may have had first-hand experience with this! These cells,
called nematocytes, are used by cnidarians to capture
their food as well as protect themselves. Nematocytes
stay spring-loaded at all times, ready to fire out with such
but perhaps the Giant Caribbean Anemone is the type
that comes to mind for most people. Even within this
species, however, exists a variety of color morphs. In
Jamaica, the Giant Caribbean Anemone has been spotted
with pink-tipped tentacles in deeper waters, and
green-tipped tentacles in shallower waters. These different
morphs might be linked to genetic differences in
how well the anemone absorbs sunlight. Many anemo-
Times of the Islands Summer 2020 41