Sea Urchin
This animal can be seen in abundance even in the shallow waters at Pulau Kapas, out in the open during the day. Usually, they hide in nooks and crannies in the day and come out to feed at night to avoid their many predators e.g. Triggerfishes, Wrasses etc that roam the coral patches during the day. Sea urchins have long needle-like, movable spines used for protection. These are attached to the hard shell by ball and socket joints controlled by muscular attachments that allow movement. These spines in some species can puncture skin and wounds are extremely painful due to a toxin, which causes numbness, headaches, nausea and even fainting. Fortunately,, the pain subsides as the lodged spines disintegrates over time but the numbness and discoloration may be present for weeks.
 This sea urchin is very common in our reefs and can often be found in shallow waters especially at night when they come out to feed. The long, sharp spines contain toxin and puncture wounds from these creatures are extremely painful. To ease the pain, soak the wound in hot water.
The Sea urchin's body is made up of five radial segments and develops a calcareous skeleton which protects and holds 'Aristotle's lantern', the intestines and the gonads. Just before reproduction, these gonads swell up to fill the whole shell. These gonads are very much sought after by the reef fishes that feed on the creature. They are the rich, yellow, paste-like, strong odoured and is served as a delicacy which is often used to top sushi in Japanese restaurants. The delicacy is called 'uni' in Japanese.
Also relatively common on the reefs, this urchin vary in colour from white to jet black and at times have a combination of white and black bars. During the day, it retreats into holes and crevices and come out to feed on algae and small invertebrates at night. The mouth is a sophisticated apparatus connected to an internal jaw contraption called Aristotle's Lantern. They scrape with this set of horny teeth as they move along the reef, removing algae together with morsels of coral rock.
Sea Cucumbers
At a glance, sea cucumbers look like overgrown, flaccid worms. They are in fact, echinoderms and are constructed with the same pentagonal symmetry found in starfishes, chrinoids and sea urchins. These sausage shaped creatures are found on sandy bottoms, ingesting large quantities of sand as they slowly crawl along. The mouth is surrounded by tentacles that are connected to a water vascular system which enables to open and close for feeding. They relish on the rich organic film on the surface of the sandy bottom. This organic matter is digested as the sand is passed through a straight, tubular digestive tract. The processed sand particles are then excreted through the anus, leaving a trail as it crawls away.
 They have relatively no fish predators and are therefore at ease when feeding during the day. Even so, some species can discharge sticky, toxic white threads from the anus when handled or molested. There are other species that in desperate attempts to escape would expel their digestive tract, reproductive organs and even parts of the respiratory system through the anus. This distracts the predator while the creature slowly crawls away to live another day, able to regenerate all the lost organs. Most tropical sea cucumbers are toxic but they have become a lucrative commodity in the South east Asian countries where fishermen harvest these creatures for markets where Chinese communities thrive. Sea cucumbers are considered delicacies but over harvesting have wiped out many of the species in the Indo-Pacific region.
This sea cucumber is found in areas where there is heavy siltation, feeding on sand and rubble patches amongst coral reefs.
The body and tentacles of this sea cucumber is entirely black. It is very common on reef flats and can be seen in shallow waters. Smaller individuals are usually coated with sand but like the larger ones, they secrete a red toxic fluid when the outer skin is rubbed.
This sea cucumber resembles a loaf of baked bread gone wrong. Its body is covered with teat shaped papillae. When handled or attacked, the sea cucumber disintegrates and if quickly returned to the water, the process can be reversed.
These animals are frequently seen clinging to the outer surface of the barrel or encrusting sponges. This is another symbiotic relationship where the Synaptid feeds on the microscopic food that often clogs the pores of the sponge while the latter benefits from having its surface cleaned of such debris so water can circulate through its pores.
Worms
 Although not known to many of us, coral reefs like rich soil in our garden patches are abound with worms. But most times, we overlook these tiny creatures because many worm species live either in dead lower parts of the coral bases or they burrow under the sand, silt and rubble bottoms. These animals are incredibly important to the reef community. Boring worms however, do destroy large quantities of live coral by physically and methodically chewing off the coral formations. They chomp through the live corals, creating endless tunnels that run right through the reefs' foundations. In doing this, the good point is that they help pulverise reef skeletons to rubble and fine sediment, which is recycled later by new colonies of live corals. These worms play an important role in building reefs despite their destructive behaviour.
One worm that many are familiar with, not only divers but snorkellers as well… is the Christmas tree worm.
 These worms make their homes on coral heads and can be easily spotted amidst the dull coloured hosts. They come in a variety of colours..yellow, blue, pink etc and are found in small groups dotted around the coral head. When settled on a suitable site, they begin to build tubes of mucus secretions mixed with mud or sand that kills the underlying polyps. Sensing an intruder, the coral speeds up new growth around the worm and the worm counters by secreting more tube material. Once comfortable with its tube, the worm sticks out its colourful tentacles to trap drifting planktonic organisms. The tentacles are light and pressure sensitive that quickly withdrawn when challenged. Try touching these bottle-brush like tentacles the next time you see them…they are quick to react, disappearing into their lairs before you can even come 4inches close to it. However, Christmas worms, like other polycheate filter feeders allow familiar, unthreatening neighbours such as cleaner shrimps to roam around them and not retreat into the tube each time there are disturbances so that they can maximise their time spent feeding when their tentacles are not curled up in its lair.
Sponges
Sponges are one of the reef's simplest and among the most primitive of organisms. These peculiar creatures were once thought to be plants but we now know that they are animals. There are approximately 5000 known species of sponges and only 150 are non-marine dwelling. They have been around for a long, long time and is dated back to the Pre-Cambrian period some 600 - 700million years ago. 400million years ago they were believed to be the dominant lifeform on reefs and were important reef builders until the hard corals took over this role.
Sponges are, in a way, the reef's water pumping and purifier machine. A single sponge can pump as much as four to five times its own volume every single minute. It has to sieve through a ton of water to extract enough food to gain an ounce of weight. The water is siphoned through the perforated covering of the sponge and passes through a series of internal canals. This labyrinth of canals is lined with tiny cells(choanocytes) and each of these contain a single hair that beats the water through. This motion creates a vacuum within the sponge that draws more water in. The body of water flowing into the canals is filtered of any bacteria and other organic debris, oxygenates the cells and removes wastes.
Sponges retain their rigid shapes by building a loose skeletal structure. This needle-like structure called spicules are made up of shards of silica or calcium carbonate and acts also as a form of protection for creatures such as shrimps, invertebrates and little fishes. Many creatures hide in sponges or on it as fish predators do not feed on these primitive animals. Moreover, the spicules tend to give them a terrible case of indigestion if ingested. Sponges also protect themselves with powerful toxins. It doesn't have to wait to be eaten before the toxins are used, they can release the poison into the water to prevent other sponges or corals from invading its space. These toxins have recently been much in the limelight amongst scientists searching for cancer cures, tumour prevention etc. Already some species are used for medicinal purposes such as the Acyclovir, which is extracted from a Caribbean sponge is used to treat herpes and encephalitis. Arabinosides is made from the sponge, Tethya crypta and is used for making antiviral medication. Their main predators are the Nudibranchs, cowries and sea urchins. Nudibranchs also use the toxin for its own benefit. They absorb the toxin into their body and recycle it to make themselves distasteful to their predators.
Sponges can produce asexually and they also mate when in season. When sponges are splintered during rough storms and from pounding waves, the splinters are washed elsewhere, where they can grow into new sponges. This special ability is used to heal wounds and broken appendages. Most sponges are hermaphrodites but do not self fertilise.
This sponge is the most recognisable species on any dive tours in our reefs. They can grow to an impressive size and specimens of 1m in height are common. Barrel sponges are often covered with white sea cucumbers.
This sponge can be found at depths between 5 and 20m. Bright and yellow orange in coloration and are generally round, hence the name.
Jellyfish
This coral when brushed against leaves a burning sensation on the skin. The stinging cells causes a painful rash on the skin and must be avoided at all times. Many are deceived by its general appearance but this coral is more closely related to the jellyfish. It is recognised by its smooth texture and mustard colour.
Another jellyfish relative that resembles a coral, this species ifs found on the ceilings of caves and as over-hangs. It forms branching fans that are in brilliant pink, red or purple.
The upside down jellyfish's arms contain zooxanthellae that needs sunlight for photosynthesis and hence, the jellyfish flips over to maximise the exposure to the sun. these jellyfishes depend on the zooxanthellae to provide them with nutrients, therefore can be seen resting upside down on the bottom.
Despite their delicate fern like appearance, this animal is packed with stinging cells that gives a burning sensation which eventually develop into welts that lasts for a few days. These are sometimes called sea ferns or sea nettles and sometimes form large garden patches and are commonly attached to rocks and corals.
Illustrations provided by Dennis Ho: Underwater photography by Moti Uttam
Corals & Fishes in Malaysia
| Corals - Hard & Soft Corals | Eels | Sharks | Rays | Octopus | Squids and Cuttlefish | Nautilus | Nudibranchs | Clams | Starfish | Brittlestars | Featherstars | Sea Urchins | Sea Cucumbers | Worms | Sponges | Jellyfish | Damselfish | Butterflyfish | Angelfish | Surgeonfish | Parrotfish | Wrasse | Triggerfish | Batfish | Trumpetfish | Squirrelfish | Catfish | Grouper | Athias | Sweetlips | Fusiliers | Puffers | Filefish | Trevally | Snappers | Scorpionfish | Cardinalfish | Goby | Barracuda | Rainbow Runner | Pompano | Bream | Goatfish |
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