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Not only is it a totally different world
“down there”, but diving presents many biological dangers as well.
Snorkeling and scuba diving entail risks as we all know; from partial to
more decompression sickness and ills of too-fast surfacing, hazards of
travel and occasional, though rare rig failure. What is not often fully
appreciated is just how common biological hazards there are underwater.
There are several and diverse organisms to be aware of, and avoid; and
for the unfortunate, worthwhile treatments that you can employ should
you find yourself stuck, stung or bitten. Herein is my overview of these
bio-hazards by group. Benthic (Attached) Hydrozoans: A Large
Cast of “To-Be-Avoideds”
What do you think of when you hear of "dangers from the
deep blue seas", giant squids, sharks, other divers? The actual cause of
many, or most discomfort from dealing with marine life is from a group
of stinging-celled organisms called hydrozoans; in particular the
hydroids and fire-coral. The latter may serve another purpose other than
stinging like h, e double hockey sticks when they come in contact with
your skin. “Oh Christmas tree, oh…. Owwww”! Up close and
personal many Hydrozoans look like delightful little Christmas trees;
but don’t be fooled. Those tiny trees and fans pack a powerful stinging
wallop! Most attached species are a few inches in length maximum; with
some being barely visible.
Though many Hydrozoans look like “corals”; they are closer
relatives to jellyfishes; and some are indeed umbrella-like jellies.
Hydrozoans are one of three Classes of the phylum Cnidaria; the
“stinging-celled animals”; the others; Class Anthozoa making up the
mainly polypoid corals, anemones, sea fans... and Class Scyphozoa
comprising the "real" Jellyfishes that live most of their lives as
medusas, self-propelled bell-shapes. Most of the Hydrozoans are small,
obscure not-so funny to touch Christmas tree sort of affairs; they
include such notables as Portuguese Man of War, Fire
Corals, and the beautiful delicate Lace
Corals (Stylasterines) amongst their ranks. We’ll leave off with the jelly Hydrozoans, and
deal with them in a later piece. Here we’re going to just deal with
attached Hydrozoans. These are solitary and colonial animal
species, sometimes just being a branch per colony, other times being
made up of a few individuals coming together as specialized parts (like
the "Sail" in the free-living Man 'O War...). The Hydrozoa are
differentiated from the other Classes of Cnidarians by their specialized
cells, stinging and agglutinant (sticking) structures, as well as life
history. Attached, benthic hydrozoans are comprised of a
few types of polyps. The feeding ones bear retractable thin tentacles
that in turn house the stinging and sticking inclusions called
“nematocysts”.
Order Hydroida: These
are the Hydroids, the most common Hydrozoans. Most
are flexible and "tree-like" in appearance with their stinging cells
much like small leaves or ornaments. Most are separate sexes and
reproduce sexually, with mature attached colonies releasing small
umbrella-like medusae that form at the base of their "branches"... these
swim off producing either eggs or sperm, that if joined, metamorphose
into a planula larval form that if in turn is fortunate, gets blown by
currents to a suitable reef surface and attaches, becoming a new
branched colony.
There are several species of Hydroids to be found in all areas we dive;
and sometimes they occur in great abundance; though often overlooked.
Below is a smattering of types you’re likely to encounter.
Order Hydrocorallina: These are colonial
polypoid hydrozoans that secrete calcium carbonate skeletons, though
they are not true corals... The Order comprises two suborders, the Fire
Coral, Milleporina and Suborder Stylasterina: Characterized by
having a thick layer of tissue overlying their skeletons. Their
specialized feeding and defensive polyps are imbedded within star-shaped
openings in their calcareous skeletons.
Fire Coral; Millepora: the Poster Child
Hydrozoan
Found worldwide in shallow tropical seas, Millepora is that fawn-colored
furry-fuzzy stuff that divers love to hate. These stony-coral
look-a-likes incorporate single celled algae to manufacture at-times
massive colonies of reef-building limestone. Suborder Milleporina, are
the stinging fire corals. Unlike the stylasterines, their skeleton is
only covered by a thin epidermal layer; and their defensive polyps arise
from separate openings that encircle the gastrozooids (feeding polyps).
Millepora is the single genus. As you study and observe corals and
coral-like animals like the hydrozoans, you'll gain an appreciation for
the term polymorphic or "many shapes"; describing the several physical
forms a "species" can/does take dependent on nutrient and other growing
conditions; sometimes heavily branched and delicate in appearance, other
times more blade, fan-shaped and massive. The number of varieties of
Millepora are in dispute; systematists J.E.N. Veron states that there
are at least 48 nominal species; an unknown number of true species. More
to the point for our discussion is the question of "how to tell when
you're looking at a fire coral?" period. There's always the touch test;
ouch. Most of the time, the colonies are green or yellow-brown (due to
endosymbiotic zooxanthellae) fading to whitish at the tips, and "soft",
"hairy" and rounded in appearance. On very close inspection, the
arrangement of almost microscopic stinging and eating polyps can be seen
(image).
Avoiding Being Stung:
With careful placement and cover of most of your body, the only thing a
diver has to be watchful of is where they place their uncovered hands.
Note that even cloth gloved hands can and do pick up Hydrozoan stinging
structures from touching long-immersed mooring ropes, buoys and such;
and that it is VERY important to rinse these after and between dives…
and NOT touch your eyelids and other thin skin areas to avoid latent
stings. Too Late: Stung; What To Do
A likely enough source of information: Alert Diver online:
http://www.alertdiver.com/Marine_Envenomations_Jellyfish_and_Hydroid_Stings To paraphrase and add: The single best
treatment is to as quickly as possible wash the affected area with
household vinegar (which is 5% acetic acid). The type isn’t important,
but best to rinse the area rather than rub, or apply ice or freshwater…
as they cause even more stinging as nematocysts further fire into your
skin. For many folks, application of hydrocortisone cream/ointment
brings relief. If you can get to your doctor, they may prescribe a
higher dose or even orally administered steroids.
Some folks are more susceptible to these sorts of stings. Rarely a diver
will experience continuing sensation of burning, shortness of breath,
fever, nausea, vomiting… IF you experience these, or show no signs of
improvement with time, a visit to a medical facility is advised. Cloze:
What; where are the really dangerous animals in the seas; the sharky
sharks; the humongous biting morays; and stinging stingrays?! These will
be covered in later pieces, but for now, let’s focus on the much more
likely, more commonly encountered dangerous marines.
Yes; attached Hydrozoans are
beautiful, fragile and more than slightly to-highly toxic to the touch!
Watch your hands underwater... and don't touch your mucus membranes
without washing your hands after diving. Ouch! |
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