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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.

Some sharks are ahead of the trend when it comes to comfort—living in their pyjamas! Meet the pyjama catshark, a nocturnal creature that spends most of the day lounging in caves or crevices, catching some z's. And with those signature pyjama stripes; it’s no wonder they’re all about napping in style!

Red stumpnose are endemic off South Africa and occur from False Bay to Margate, although they are more common south of East London.

They have steep foreheads which, in males, become increasingly pronounced and bulbous as they get older. They have strong molars which they use to crush prey such as redbait, urchins, octopuses and crabs.

Although red stumpnose are good to eat, they have been over-exploited. Presently they may only be caught once they have reached a minimum size of 30cm and anglers may only catch one fish per person per day.

Red stumpnose are currently listed as a Red species on SASSI’s Customer Seafood List, which means you should not buy or sell these fish as seafood.

Photograph by Dagny Warmerdam.

These fish use camouflage to mimic the ripple patterns in the sand caused by currents and tides.

They feed mainly on bottom-dwelling animals e.g. cracker shrimps, sea lice and molluscs.

Romans are an endemic species found on rocky reefs off southern Africa at depths from 5m to 100m.

Like other sea breams, the roman has the ability to change sex, in this instance from female to male.

The male attracts a harem of females, with which he will mate. A large male is very aggressive and will defend his harem and territory against all intruders, including competitive males.

His frantic protective behaviour attracts the attention of predators, which increases his risk of being eaten.

Should this happen, the dominant female will immediately take over his role. Sex change takes a little longer.

There are 51 species of surgeon fish, 19 of which occur in southern African waters.

Surgeon fish are so named because of the scalpel-like spines on either side of their tail fins, which are folded into a groove when not in use.

When surgeons are threatened or alarmed, they lift their scalpel spines, using them to slash at their attackers! They also use the spines to wedge themselves into cracks in the reef.

The pencilled surgeon has a single fixed spine on each side of the base of its caudal fin, which is used in defense or when fighting.

Adults live in caves on reefs at depths of up to 100m, or in open water around sea mounts and islands.

The juveniles are found in estuaries where they graze on algae-covered rocks.