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Leonard Howard
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OCTOPUS Found throughout the world in tropical, warm and cold temperate waters - the octopus is a bottom dweller, spending much of its life in hiding, usually in a hole among rocks.

1 OCTOPUS Found throughout the world in tropical, warm and cold temperate waters - the octopus is a bottom dweller, spending much of its life in hiding, usually in a hole among rocks. All octopus species have eight arms, each with a row of suckers. They lack a shell. They have a well-developed brain. The two large complex eyes are similar to human eyes and their vision is acute. The animals can change colour and texture of their skin rapidly. When an octopus emerges to find food such as crabs, lobster and shellfish, it often lures its victim by wiggling the tip of an arm like a worm; or it glides near and pounces on a crab, sinking its beak into the shell and injecting a poison that kills. An octopus is preyed upon in turn by a number of fishes, including the moray. The poison of the Blue-ringed octopus from Australia is dangerous to human beings. Many people either eat octopus or use them as bait. Octopus can recognise and respond to humans, clearly showing their intelligence. The colour changing ability is in cup-shaped cells called chromatophores which, when opened, show their colour. 54 Two Oceans Aquarium Volunteer Manual Module 3 INVERTEBRATES

2 SQUID (Chokka) Along the South African coast they are found in the open sea off the West and South Coasts. They aggregate or form large shoals in bays between Cape Point and Port Elizabeth in summer to breed. All squid are more slender and delicate than cuttlefish. They have eight short arms and two very long retractable tentacles round the mouth. All tentacles have suckers. Their shells are reduced to a transparent pen that lies just under the skin of the dorsal surface unlike the cuttlefish, which has a large internal shell. They have relatively long diamond-shaped fins. Squids are very active predators that feed mainly on small fish. Squid forms an important food source for fish, several shark species, sea birds and marine mammals. The diamond squid is one of the largest squid in our waters, with a body length of 1m and a mass of 20 kg. Squid used to be caught only for bait but are now popular for human consumption and are sold as calamari. Two Oceans Aquarium Volunteer Manual Module 3 INVERTEBRATES 55

CUTTLEFISH About 100 species of cuttlefish are known. Note : the name cuttlefish is sometimes given in error to the squid. Some live in shallow water on a sandy bottom of e.g. sheltered lagoons and estuaries.

3 CUTTLEFISH About 100 species of cuttlefish are known. Note : the name cuttlefish is sometimes given in error to the squid. Some live in shallow water on a sandy bottom of e.g. sheltered lagoons and estuaries. Others live in intertidal pools or gullies and reefs. Body elongate with a fin running down each side. Head has eight arms and two very long retractable tentacles, all with suckers. The cuttle bone is used to regulate buoyancy by modifying its gas and liquid content. Some cuttlefish capture fish by shooting out their tentacles with speed. Others swim over the bottom and feed, which are caught in the same manner, on invertebrates especially shrimps and crabs. They are a major food source for fishes, including the fast swimming tunny. The white internal skeletons of cuttlefish are often found washed up on our beaches. People collect these cuttlebones to put in bird cages, so that their birds can sharpen their beaks on them The dried, powdered cuttlebone is used in polishing and other industrial processes. The dried ink sacs of the animals yield a brown pigment called sepia (See species named above). 56 Two Oceans Aquarium Volunteer Manual Module 3 INVERTEBRATES

PAPER NAUTILUS (Argonauta argo) Open water at varying depths. Sometimes close to the surface. Body with eight arms. Two of which are flattened and responsible for holding the shell.

4 PAPER NAUTILUS (Argonauta argo) Open water at varying depths. Sometimes close to the surface. Body with eight arms. Two of which are flattened and responsible for holding the shell. Only the female produces an unusual, semi-transparent floating shell. The naked male is much smaller than the female and often lives parasitically in the female s shell. The shell serves as a float, but its main function is to provide an egg chamber in which the female lays her eggs. Females normally die after reproducing. The paper nautilus is an active hunter feeding on animals like crustaceans. Some species of fish. Female paper nautilus The shell of the paper nautilus is not formed by the mantle, as in other molluscs, but is formed by glands in two of the arms. The very pretty coiled white shell is much sought-after by shell collectors. It is found on beaches along the south coast after storms at certain times of the year. Two Oceans Aquarium Volunteer Manual Module 3 INVERTEBRATES 57

5 PHYLUM ECHINODERMATA CLASS ASTEROIDEA Starfish OPHIUROIDEA Brittle Star ECHINOIDEA Sea urchins HOLOTHUROIDEA Sea Cucumbers CRINOIDEA Feather Star Flattened central body with five or more projecting arms. Under each arm lie delicate cylindrical tube feet with sucker tips. Five or more slender brittle arms arise from central round body. Body encased in a hard shell, the test. Tubefeet protrude through pores in shell. Long protective spines project from test. Sausage-shaped. Branched feeding tentacles at the front of the body. Tiny, round bodies with short hook-like limbs. Handsome crown of feather like appendages. Two Oceans Aquarium Volunteer Manual Module 3 INVERTEBRATES 58

6 PHYLUM: ECHINODERMATA STARFISH, SEA URCHIN, BRITTLE STAR, SEA CUCUMBER AND FEATHER STAR As their name implies (ekhinos = hedgehog + derma = skin), they have spicules or spines on their skins. This feature is developed to varying degrees in the different groups. CHARACTERISTICS Echinoderms have a penta- (five) radial symmetry. cylindrical feet with suckered tips that operate hydrostatically. no head or eyes. the ability to move in any direction. a spiny shell made up of patterned skeletal plates. These are joined with elastic threads that lie just below the surface, enabling the plates to continually grow. Echinoderms do not moult. The surface of the body opposite to that bearing the mouth (the arboral side) is highly textured, bumpy surface, sometimes with spines. Two Oceans Aquarium Volunteer Manual Module 3 INVERTEBRATES 59

CLASS: ASTEROIDEA STARFISH Rocky shores and subtidally on both rocks and sand. Five relatively stout, tapering arms radiating from a central disc.

Rows of tiny hydrostatically operated tube feet in a groove in each arm. The mouth is situated centrally on the under surface, while the anus is on the upper side.

They feed on a variety of animals including mussels, crabs and sponges. Spiny starfish pry open mussels by exerting a strong continuous pull with their suckered tube feet.

7 CLASS: ASTEROIDEA STARFISH Rocky shores and subtidally on both rocks and sand. Five relatively stout, tapering arms radiating from a central disc. In some starfish the rays and the disc merge together. There is a sense organ at the tip of each arm that can taste food and it is sensitive to light. Rows of tiny hydrostatically operated tube feet in a groove in each arm. The mouth is situated centrally on the under surface, while the anus is on the upper side. Most starfish in South Africa are herbivores and feed on algae. Some species are mobile scavengers or predators such as the spiny starfish. They feed on a variety of animals including mussels, crabs and sponges. Spiny starfish pry open mussels by exerting a strong continuous pull with their suckered tube feet. They feed by extruding their stomach through the mouth and food is digested outside the body. Spiny starfish attacking mussel Reef fish e.g. the Red roman. The crown-of-thorns starfish is 50 cm in diameter, has from 9 to 23 arms and spines, which are venomous and painful to human beings. The female can bear between 12 and 24 million eggs in the annual breeding season. Voracious consumer of coral polyps, this starfish can eat large amounts of coral and population explosions on the Great Barrier Reef have left great areas of damaged reef. 60 Two Oceans Aquarium Volunteer Manual Module 3 INVERTEBRATES

ADVANCED INVERTEBRATES HAVE COMPLEX BODIES AND INTERNAL SYSTEMS

ADVANCED INVERTEBRATES HAVE COMPLEX BODIES AND INTERNAL SYSTEMS Arthropoda Most successful phylum on Earth Exoskeleton chitin Striated muscle Articulation Crayfish, lobsters, shrimp, crabs Echinodermata