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Underwater Wakulla- August 21, 2014
More on the Echinoderm By GREGG STANTON
Wednesday, August 20, 2014 at 5:00 pm (Updated: August 20, 5:00 pm)
Last week's Natural Wakulla column by extension director Les Harrison had a very enjoyable piece on Sand Dollars, but there is another
dimension in our waters.
Echinoderms (called "spiny skinned" creatures), which include many groups of marine animals, are
distinguished by their use of "tube feet." They move around by hydraulically latching these feet on
to the substrate and pulling. Some groups will also hold rubble or shells to their body thus providing
camouflage (a way to hide). Just pick one up (carefully) and look underneath and you will see small
translucent tubes waiving around trying to find a substrate to suck on to. This predatory group has
no blood, relying on its Vascular Water System to multi-task.
You know this group of marine invertebrates by their common name, such as Starfish, Sea Urchins,
Sea Cucumbers, Sand Dollars and Sea Biscuits. Last I recall we have at least five species off our
coast. Divers are most concerned about the spines of the Sea Urchin because they can easily
Starfish tube feet
penetrate your skin and break off. Some, like the Diadema, a black long spined Urchin found in the
Florida Keys, have fine spines that will penetrate through gloves and wet suits. Around here, our
Urchins have shorter robust spines. Lytichinas is red, and found on sand. The smaller Arbacia is black and is found on rocks.
In basic scuba class you are taught to maintain horizontal trim and not land on the substrate to avoid damaging fragile creatures and
driving these spines into you knee (as happened to a recent student on the jetties in Panama City).
Starfish are the stuff of countless beach combing, especially with kids. These five-legged creatures are known to regenerate
appendages when lost. Some have many more than five, come in many colors and become ornamental features when carefully dried
and mounted in fish nets. When diving the Antarctic, we called the local starfish marauders. They are very powerful, capable of opening
clams and in our case, experimental vials, with ease!
Sea Cucumbers look like the vegetable, but pull themselves along from the front. Like the Starfish, they eviscerate their stomach to feed.
Unlike the Starfish, if threatened, they will eviscerate the sticky, slimy stomach at you. So here is another critter to just observe, don't
touch.
Sand Dollars, Heart Urchins and Sea Biscuits reside under the sand locally. They are not easily found alive unless you probe with a
knife or gloved hand. These creatures congregate so when you find one you find many. Echinoderms are plentiful on "K" Tower, in 40-60
feet, 17 miles out from Dog Island. The urchins are on the tower, the sand dollars and biscuits are under the sand.
But you can also find them as fossils in the Miocene deposits in our caves in North Florida. As the limestone in caves is dissolved by
acid rain, fossils drop from the walls and ceiling. I know of sites where the floor is littered with spines and tests (the body) of these
creatures. We encourage folks leave them in place because they will collapse when removed from the water.
Of course many of these fine creatures or their remains are washed in on the tide and become the treasure of many salvors....
10/26/2014 12:08 PM