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Cuttlefish are related to octopus and squid. The common cuttlefish is also known as the ink-fish.

Like octopus, cuttlefish can change both their body colour and texture in response to their environment and their survival needs.

Special cells (chromatophores) located in the outer-skin layers, contain colour pigments, which the animal can alter by neural control (merely by thinking about it!). These chromatophores typically occur in red, yellow, brown, black and blue, and each can be expanded to display a large area of colour, or contracted to a tiny speck.

Common cuttlefish are the largest cuttlefish species found in southern Africa and occur from Mozambique on the east coast to the mouth of the Orange River on the west coast.

They live in sheltered lagoons and estuaries and in the open ocean to depths of 200m.

Cuttlefish have tentacles including two longer ones that are hidden in ‘’pockets’’ under the eyes. They use the long tentacles during mating and for capturing their prey.

Cuttlebones on the beach

Most people are familiar with cuttlebones, which are found washed up on the beach and given to pet birds as a dietary supplement and to sharpen their beaks.

Cuttlefish use the cuttlebone to regulate their buoyancy.

The giant spider crabs in the Atlantic Oceans Gallery were collected by Tokyo Sea Life Park in Japan and sent to the Two Oceans Aquarium.

Spider crabs are the largest crustaceans in the world – males grow to approximately 1m in length with a 4m leg stretch. These crabs live at depths of approximately 400m and in temperatures between 11ºC and 14ºC.

Marine mystery

Very little is known about the biology of giant spider crabs. It is virtually impossible to determine their age and we do not know when they reach sexual maturity. Their breeding habits are also a mystery to marine biologists.

Moult to grow

As with all crustaceans, continual growth is impossible for giant spider crabs because of their hard exo-skeletons. To grow, the crabs have to shed this exo-skeleton by moulting. This is a complicated process which can take up to two days. Each moult is potentially life-threatening as the crab can become entrapped in its old shell. Even if the moult is successful, the sheer effort is sometimes so exhausting, that the crab dies soon afterwards.

Vulnerable to predation

With its “new” soft, elastic exo-skeleton exposed, the crab is vulnerable to predation. The new exo-skeleton expands rapidly as the crab “pumps” water into it. Over time, together with a combination of enzymes and calcium carbonate, the new skeleton hardens. The water is then “pumped” out again and the crab grows into its new “coat”.

Cursed by lobster fishermen for the quantities of slime they produce when startled, these oceanic oozers secrete a white fluid which expands rapidly on contact with seawater, producing enough slime to fill a 7-litre bucket in minutes.

The sticky substance adheres to predators, forming a suffocating layer over their gills. The slime also creates problems for the hagfish itself, but it has developed a manoeuvre which allows it to escape – it knots its tail and, twisting the knot over its body, scrapes off the offending slime.

Although they look like snakes, hagfish are not snakes or eels, but belong to a unique group of animals.

They are primitive animals that have no jaws, no eyes, fins or scales. They have a cartilaginous skeleton and pouch-like gills not seen in any other living fish.

Living fossils, the species have changed little since the days of the earliest hagfish, which date back some 330 million years.

Scavengers of the deep

Hagfish have horny dental plates which rasp and tear into soft flesh, carrying pieces back into the mouth. A fang above the plates holds the live prey in place while it is shredded. Since they have no teeth hagfish cannot eat scaly fish and therefore they only feed on small live fish, on soft rotting carcasses or on animals that other animals have already opened. When larger food items are found, such as dead whales, hagfish have another strategy – they enter the giant corpse and eat the soft tissue out from within.

Hagfish play a vital role in recycling dead animals on the seabed and may occur at surprisingly high densities, with some areas having over 50 000 animals per square kilometre.

Box jellies are found off the west coast of South Africa and are often encountered in swarms by scuba divers.

Named for their ghostly, transparent bells, moon jellies have short tentacles that are armed with stinging cells or nematocysts. Fortunately, their sting is not as toxic as that of other jellies.

The longsnout pipefish (Syngnathus acus) is found throughout South African waters. It occurs in the waters off southern Africa from Walvis Bay to the Thukela Bank on the Kwa-Zulu Natal coast.

Life depends on plankton. Plankton is made up of microscopic plants (phytoplankton) and animals (zooplankton). Zooplankton feed on phytoplankton and drift with the currents.

You’re probably thinking, “Wow, look at the size of these guys! Yum!” These West Coast rock lobsters (crayfish or ‘’kreef’’ as they are known locally) are approximately 30 years old! The chances of you seeing crayfish this size in the ocean these days are minimal. Rock lobsters grow very slowly and can live to the ripe old age of 50 years or so.

Also known as the double sash butterflyfish, this is the only butterflyfish species to be found in both the Indian (warm) and the Atlantic (cold) oceans.

The South African butterflyfish is endemic to our coast..

Ragged-tooth sharks, also known as grey nurse sharks in Australia and as sand tiger sharks in the USA, occur in temperate to tropical coastal waters of the Atlantic, Indian and western Pacific oceans. In South Africa they are common along the eastern and southern coasts, occurring as far west as False Bay.

Like all sharks, ragged-tooth sharks have a cartilaginous skeleton. They grow to about 3,2m in length and live for about 30 years. They reach sexual maturity after 5 years, and at approximately 2.2m in length.

Sharks’ teeth are arranged in rows which continually move slowly forward, like conveyor belts. This ensures a constant supply of sharp, new teeth and results in sharks losing and replacing thousands of teeth in a lifetime.

Shark ambassadors

These juvenile ragged-tooth sharks act as ambassadors for their species as we only display them for a short period of time before returning them to the wild. Once they reach a certain size we will release them at Buffel’s Bay (close to the Knysna/Plettenberg Bay area), where other ragged-tooth sharks of a similar age are found. All our sharks are tagged prior to their release.

Ragged-tooth shark migration in South Africa

Ragged-tooth sharks are found on the southern and eastern coasts of South Africa.

In November/December they congregate to mate on reefs in northern Eastern Cape and southern KwaZulu-Natal waters. The pregnant females then travel north as far as southern Mozambique to gestate in warmer waters. After a gestation period of 9 to 12 months, they return to the Eastern Cape (south of the Kei River) to give birth.

Some females only breed every two years.

Using satellite and ultrasonic tags, scientists have been able to gain more detailed information about the movement of ragged-tooth sharks up and down the South African coast.

A violent affair?

Mating in ragged-tooth sharks appears to be a violent affair, as the females are often badly bitten. The reason for this is that the males have to latch onto the females during copulation and they have only their mouths to do so! The eggs are fertilised internally and are enclosed in egg cases in groups of 16 to 23.

The embryos initially feed on internal supplies of yolk. Later they feed on fertilised eggs and on other developing embryos (known as intra-uterine cannibalism). As a result, only two pups are born per litter, i.e. one per oviduct.

The gestation period is 9 to 12 months, depending on the water temperature.

Reproduction

Cartilaginous fishes (including sharks, rays and skates) reproduce in one of three ways.

Oviparous – the female lays an egg case referred to as a “mermaid’s purse”. These are often found washed up along the shore. This egg case contains the embryo and yolk supply and the young shark eventually hatches out of the case. Cat sharks and shy sharks are oviparous.

Ovoviviparous – the embryo hatches from the egg inside the uterus, where it feeds off its own yolk sac until it is born. Ragged-tooth sharks are ovoviviparous. Most sharks breed in this way.

Viviparous – the embryo develops in the uterus and is fed either through a placenta or by uterine milk. Hammerhead and great white sharks are viviparous.

Conservation status

Ragged-tooth sharks are threatened around the world because they are slow to reach sexual maturity, they give birth to few young and, because of their inshore habits, they are highly vulnerable to over-fishing.

Ragged-tooth shark populations have been seriously depleted in Australia and the USA due to over-fishing. In 1984, Australian ragged-tooth sharks became the world’s first protected shark species. Today they are also protected in the USA, while in South Africa they may not be sold commercially without a permit.

The status of the South African ragged-tooth shark population was considered to be “near threatened” by an International Union for Conservation of Nature working group in 2003. However, the actual size of the population is unknown and is currently under investigation.

These deep-water rock lobsters live at depths of between 90 and 170m. Because they are deep-sea creatures, they are only caught commercially using baited lobster pots.

Commercial fisheries catch about 800 tonnes of South Coast rock lobster every year.

Are these lobster, crayfish or kreef? They are not true lobsters because they don’t have large claws. They are also not the same as the fresh-water crayfish found in Europe that do not have such gourmet appeal!

In South Africa we call them crayfish or kreef. Their correct name is rock lobster or spiny lobster.

Shed my skeleton

Like all crustaceans, rock lobsters have a hard exo-skeleton (meaning the skeleton is on the outside of the body rather than on the inside like ours). The skeleton is jointed, allowing rock lobsters to move quickly and efficiently on their 10 jointed legs. Although the hard exo-skeleton is like armour or a bullet-proof vest and protects them from predators, rock lobsters have to shed the skeleton in order to grow. This is called molting. During molting, rock lobsters are soft and vulnerable to predators until their new shell hardens.

Starfish have five arms, each with its own set of respiratory, digestive and reproductive organs!

Each arm also has hundreds of tiny tubefeet that enable the starfish to creep slowly over the reef.

Don’t worry if you see a starfish with only four or even three arms. Starfish can regrow their arms – in fact a single arm can regenerate a whole body!

Feeding inside out

The mouth is on the underside and the anus on the topside.

Starfish feed by turning their stomachs inside out and releasing enzymes to digest the food externally. It can take a starfish several hours to pull a mussel apart and slowly digest it.