Echinoderms are marine animals with a body based on a cylindrically symmetrical pattern of five, (with some exceptions), a calcareous internal skeleton and a water vascular system. They have brightly colored skin which is often hard to the touch, a large number of writhing tube-like feet and often hard spines in rows all over the body.
Species include Brittlestars, Featherstars, Starfish, Sea Cucumbers, Sand Dollars and Sea Urchins.
Turn over any rock, (not forgetting to replace it of course) and you will inevitably find a brittle star or two, even several different species together. There are a wide variety to be found here, the most common is the brittle star (Ophiothrix fragilis), which has a disc 2cm in diameter and is often pentagonal in shape, its upper surface has many minute spinelets, and some longer spinelets arranged in five radiating groups.
Also fairly widespread is the brittle star (Ophiocomina nigra) which is a black brownish color and has a disc up to 3cm in diameter and five arms up to 5 times the disc diameter. All Brittle stars are extremely fragile and arms are often broken or regenerating. Be especially careful when handling, though it is best not to, and always replace where found because opportunistic rainbow wrasse will attack almost immediately.
FEATHER STARS (Antedon bifida)
These are very common in Turkey and can be found clinging to rocks either singly or more often in groups. Ten, sometimes mobile, arms radiate from a very small green or brown colored body, they are very fragile and it is better to just observe.
SAND DOLLARS and HEART URCHINS
The tests (‘shells’) of sand dollars and heart urchins are a common sight for most divers. Less common are the animals themselves which when alive spend almost their entire life under the sand. To find and observe a live specimen takes a fair amount of patience sifting through the sandy bottom at a depth of about 12cm. They can often be detected by a conical depression in the sand above the animal.
The most common varieties in this region are the COMMON HEART URCHIN (Echinocardium cordatum) and the PURPLE HEART URCHIN (Spatangus purpureus) although other varieties can be found. These heart shaped echinoids are bilaterally symmetrical with most tube feet borne on the upper side with a few arranged below. The mouth and the anus are situated on the underside, towards the anterior and posterior ends respectively. The test is thickly covered with fine spines often with a fur like appearance and when removed from their subterranean habitat the dorsal spines become erect, and directional from front to back. Once examined be sure to replace under the sand because they are vulnerable to attack by some species of fish.
SEA CUCUMBERS (Holothuroidea)
On virtually every dive several species of sea cucumber can usually be seen. These bilateral echinoderms lack conspicuous spines, arms or rays and are usually cucumber shaped or worm like. Tube feet are present in many species arranged in five rows along the sides of the animal. The anterior mouth is surrounded by modified tube feet, and the anus is positioned posteriorly. A skeleton of loosely associated calcareous spicules is embedded in the ‘skin’. Common varieties in this region include (stichopus regalis) found generally in sandy areas and are usually between 15cm to 30cm in length, reddish brown in color with the upper side covered in warty protuberances and bumps.
Also common is the sea cucumber known as the COTTON SPINNER, (Holothuria forskali) which hides in rocky crevices during the day, often where there is a lot of wave exposure, venturing out in abundance at night. Cucumber shaped, it has a fairly well defined lower surface with three rows of suckered, locomotory tube feet. The upper surface is warty and reddish brown in color, often with white spots. If you see what appear to be spirals of sand about 5mm in diameter in coiled heaps in rocky areas, close inspection of the underside of overhanging rocks will usually reveal a hiding (or sleeping),cotton spinner. If molested this species may, in defense, eject a white sticky substance from its hind end which sets into strong thread like filaments.
WORM CUCUMBERS (Leptosynapta inhaerens) and (Labidoplax digitata)
These long, soft and slender tube like organisms are to be found usually in locations where there is an abundance of fine sediment. The body has no feet apart from 12 around the mouth modified for feeding, each of these carries 57 pairs of minute finger like branches. Minute, anchor shaped skeletal spicules used in locomotion protrude through the soft skin making it feel adhesive, (especially if you are wearing neoprene gloves). If disturbed the tentacle like feet are withdrawn and the animal contracts becoming rigid, and forming itself into a short ovoid shape.
SEA URCHINS (Class: Echinoidea)
The pollution free waters of the south western coastline provide the perfect habitat for sea urchins. Unfortunately the sea urchin population at the most popular dive sites is often reduced significantly during the tourist season as a result of the ‘less than environmentally aware’ guides from some dive centers breaking them to provide fish feeding spectacles for the ‘one day’ try divers.
Sea urchins appear at first sight to be sedentary but they can move relatively quickly on short spines located on the underside of the body. They also have many long tendrils located all over their body between their spines, each tendril terminating with a small sucker. These suckers are used for attachment to rocks to allow their five cylindrically symmetrical teeth to scrape anything edible from the surface of the rocks below. The tendrils are also used to pull small stones and shells onto the spines to provide additional protection and camouflage.
While not poisonous the fragile spines can penetrate skin easily if any pressure is exerted, usually breaking off beneath the surface of the skin. Sea urchin puncture wounds invariably become infected and treatment with proprietary sea urchin antiseptic creams, after removal of the spines, should be done as soon as possible.
BLACK SEA URCHIN (Arabacia lixula)
It seems that every shore side rock in this part of Turkey is home for the black sea urchin. They are usually between 5cm to 7cm in diameter when mature and the sharp spines are up to 3cm in length. The cleaned test of the animal is pink in color with characteristic red lines marking the position of the tube feet pores, the oral opening is larger than most other species.
LONG SPINED URCHIN (Centrostephanus longispinus)
At depths between 10 to 30 meters the long spined urchin, can be found hiding in rocky crevices, its long, hollow and slender spines are often mobile and brown in color with whitish bands. Viewed from the top a number of very mobile bright blue tipped antennae like tendrils can be seen on the body between the spines. The cleaned test is a reddish brown.
COMMON SEA URCHIN (Cidaris cidaris)
Unlike the other common species of sea urchin found in this part of Turkey, which have many spines close together making it impossible to see the test, the species cidaris cidaris has only a few thick, blunt spines terminating on the body at a raised hemispherical mound. They can only be found in deeper water at around 30m, but usually deeper and in predominantly sandy areas where they can sometimes be found in large numbers. The color of the spines, body and test is usually pink green.
STARFISH (Subphylum: Asterozoa)
There are many species of starfish to be found in Turkey, the most common being the bright orange colored (Asterias rubens) which has stiff rays tapering for most of their length to a fairly sharp point and rarely exceeding 18cms in diameter.
Less common, but often well camouflaged among rocks is the larger, spiny, green colored starfish (Marthasterias glacialis) whose rounded body has five tapering rays often slightly turned up at the tips when active. The body surface is covered in conspicuous spines surrounded by rings of small pincerlike organs (pedicellariae), tube feet bear suckers. Specimens can be found in Turkish waters up to 30cm in diameter although the species can grow to 75cm in diameter.
Also less common but sometimes to be found moving relatively quickly over sand is the SAND STAR, (Astropecten irregularis) it is light green/ brown in color with a smooth top side. Each of its five rays bear small spines forming a fringe visible from above.