Rays

Rays have been around for over a million years with approximately 480 species found worldwide. Rays like sharks have a cartilaginous skeleton rather than bony one and no swim bladders. Rays are easily differentiated by the ventral position of the gill slit and the oversized pectoral fins. The odd-looking Sawfish and the Guitarfish are in fact Rays, identifiable from the ventral position of the gill slit.

All fertilisation is internal. The male has a set of claspers that is used to transfer sperms into the female. They give birth to their young fully formed and they are either able to nourish their fetal young internally or develop their eggs for internal hatching and growth until they are born. A small number of species produce leathery egg cases

• Eagle Ray (Aetobatus narinari) - 200cm

The eagle ray have large pectoral fins which are used for flapping and gliding through the water. It is easily recognisable by its pointed wings, a protruding head and spots on the body.

This ray has two venomous spines located close to the tip of the tail and can inflict much pain and should not be touched. There have been situations where local children were found sword fighting with each other using stingray tails discarded in bins by errant fishermen on beaches.

Octopuses

It's hard for many to believe that these creatures are in fact molluscs. They are classified as cephalopods, a word that means that their feet grow from the head. The octopus is considered the most intelligent of all invertebrates. It learns from experiences and adapts to situation. In a number of experiments conducted in a tank, a scientist noted that the octopus could learn to distinguish objects of different shapes. In doing this, objects were presented to the octopus, if the octopus attacked a 'wrong' shape - little electric shocks were administered but if it chose the correct object, it was then rewarded with food. It was found that after 10 to 20 trials, the octopus could recognise the differences and act correctly.

The octopus is renown for its hunting capabilities. As it does not have a skeletal structure, it is capable of squeezing into amazingly tight holes and crevices. It hunts methodically, inspecting with its tentacles and once in a while, pounces on a rock with its tentacles spread like a net to trap any prey underneath as it lands. It collects several preys in its many arms before returning into its hole to feast on its hoard, breaking into shells with its hard, chitinous beak. A solitary animal, the octopus digs his home under coral rocks and where it holds during the day. A diver or snorkeller may be able to spot an octopus lair because of its habit of tossing empty crab shells out of its hole when done. The hole is always littered with bits of carapaces etc. When retiring to bed, it often blocks the entrance of the hole with a makeshift wall of rocks.

The mating season for the octopus is a closed loop of life and death. In the male, the third right arm is modified to transfer sperm into the female. During courting and copulation, the male changes its colours and patterns dramatically. A series of colour variation from dark to pale combined with barred patterns of differing intensity is witnessed. The male inserts its third arm into her mantle where the reproductive organs are situated. After several minutes of copulation, the female breaks off its contact with the male and swims away. The female then takes on the task of caring for the eggs, constantly blowing water onto the egg clusters to aerate them and gently lifting them with her tentacle to inspect them. Some females have been seen to eat their own eggs during the period but it is now known that they only ingest the infertile ones. Just before or after spawning the female stops eating, losing weight over the six weeks of incubation period (depending on the species) and dies not long after the eggs are hatched. Females seldom live over 15months as once they mate and produce, their life cycle ends. Males cease feeding about the same time, although it can mate several times during the mating season with other females, it never lives to enjoy another season.

These reef octopuses have a life span of 1 - 3 years. This is a species commonly seen in reefs and can change its colour dramatically. Most time, the Reef Octopus is seen scuttling over corals and rocks in search of crustaceans and molluscs but sometimes when frightened, it forces a spurt of water out of its gill cavity through a muscular siphon, propelling them away from its enemy.

This small octopus usually lurks under rocks on reefs. Although only 7cm in length, this little creature can pack a powerful blow to unsuspecting divers. It has a venomous bite that has caused a few human fatalities. It should never be handled! Any person who has been bitten by this octopus will go into a cardiac arrest soon after. The best thing to do is to administer CPR to the person constantly until the paramedics arrive.

Cuttlefishes and Squids

Cuttlefishes are also considered intelligent invertebrates. They have complex brains and good vision. On a horizontal position, the cuttlefish has a 360-degree vision of its surroundings. Sometimes, snorkelling, they can be seen watching from a distance, their eyes following every move and then when satisfied it drifts away.

Cuttlefish are often found feeding alone on reef slopes especially at night when they are most active. These creatures like most cephalopods, squirt ink when they are threatened. This strong smelling, dark blob of ink distracts the predator in time for the cuttlefish to make its escape. The ink was used for writing in the old days. Unlike the supple octopus, the cuttlefish has a calcareous plate in its body. This structure is used to keep the creature afloat and also to maintain some stiffness so that it can balance when feeding vertically off the reef slopes. This calcareous plate is often fed to aviary birds to supplement their calcium intake, sold at RM2.00 per piece.

Mating for the cuttlefish is a lot of tentacle grasping affair. The male and female face each other head to head and after a series of colour demonstrations, the male copulates with female in the same manner as the octopus. Soon after, the female deposits it eggs, one by one in coral rubbles. It gently retrieves the egg from its mantle and carefully transfers and attaches the egg to the coral branches. The male hovers parallel to the female, watching the entire scenario with much interest.

Squids resemble the cuttlefish in form but are smaller and less robust than the latter. Squids are free swimming and are usually found in groups along reef edges and in shallow lagoons. They move by using the jet propulsion techniques. When hovering they utilise their lateral fins, which undulate to maintain position. The giant squid is the largest cephalopod found which grows to a length of 18m and is seldom seen as it lives in the abyss of the sea. This creature is the reason sperm whales dive deep in search of… a prey well worth the wait.

Squid fishing is extremely popular in the east coast of Peninsular Malaysia. Fishermen leave port during the night to fish for squids. Fluorescent lights are hung over the side of the boat to attract the squids and fishing lines tied with dozens of hooks are thrown over the side. When the squids approach the light, the fishermen jig the fishing line to catch them.

Illustrations provided by Dennis Ho: Underwater photography by Moti Uttam

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