Part Two

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Crustaceans

DESCRIPTION

·         A segmented body and an exoskeleton - a supportive structure on the outside of their body

·         Exoskeleton: varies from a thin, transparent layer in some tiny crustaceans to a thick, shell-like carapace that covers the thorax in crayfish and crabs

·         Appendages on the thorax and abdomen for walking, swimming, respiration, and mating

·         In many cases, one or more of the walking legs forms a claw

DIET

·         Plant and animal debris

·         In some cases, like crabs and shrimps, other sea creatures

FAMILY

·         Over 30,000 species have been described, ranging from water fleas smaller than a pinhead to crabs weighing as much as 17kg

BREEDING

·         Female crustaceans generally lay eggs that hatch as larvae, although in some cases the eggs hatch as miniature adults

·         The females of some, such as crayfish and crabs, carry their eggs until they hatch

·         The larvae then grow into adults, forming part of the plankton while in the open sea

·         Other crustaceans, for example, opossum shrimps, carry their young with them until they can fend for themselves

·         Hatchlings grow quickly and moult frequently, first casting their shell every few hours, then every few days; as they mature, the period between moults extends to weeks and eventually longer

HABITAT

·         Live everywhere in the seas, from the ocean depths to the intertidal shores

·         Many live in fresh water, while few have land-based existence

PREDATORS   

·         Crabs and shrimps, although also crustaceans, are predators

Crab

DESCRIPTION

·         Walk sideways

·         Crabs are invertebrates, animals without a backbone

·         The have an exoskeleton (also called a carapace), an outer shell that both protects them from predators and provides support

·         Ten jointed legs, two of which have large, grasping claws (called pincers or chelipeds)

·         Flattened body

·         Two feelers (antennae)

·         Two eyes located on the ends of stalks

·         Marine crabs breathe underwater using gills, which are located in two cavities under the carapace

·         True land crabs have enlarged, modified cavities that act like lungs so that they can breathe air

DIET

·         Many crabs are omnivores (plant- and meat-eaters)

·         Others are carnivores (meat-eaters)

·         Some are herbivores (plant-eaters)

FAMILY

·         There are almost 5,000 different species of crabs

·         About 4,500 are true crabs

·         About 500 are hermit crabs (hermit crabs don’t have a very hard shell and use other animal’s old shells for protection)

HABITAT

·         Most live in the oceans

·         Many, like the robber crab, live on land

Lobster

DESCRIPTION

·         Have a tough shell (exoskeleton)

·         Lobsters are invertebrates - animals without a backbone

·         Are cold-blooded – their body temperature depends on the temperature of the water

·         4 pairs of jointed walking legs

·         A segmented body

·         Sensory antennae

·         A tail fan

·         Compound eyes on stalks

·         Most lobsters are nocturnal

·         Lobsters continue to grow throughout their lives

·         Lobsters may live to be 100 years old

·         Begins its life as a tiny, floating organism, which is a component of plankton

·         After a month of growing, it sinks to the sea floor, where it will spend most of its time hiding from predators

DIET

·         Lobsters are carnivores

·         Eat crabs, clams, worms, snails, mussels, flounder, and other lobsters

·         After it moults, the lobster eats the old shell

FAMILY

·         There are many different types, including the Maine (or American) lobster (an aggressive lobster with large front claws), the spiny lobster, and crayfish

HABITAT

·         Live on the ocean floor

PREDATORS

·         Fish (especially cod), octopi, other lobsters, and people

Prawns

DESCRIPTION

·         Three pairs of nippers of similar size

·         King prawn: about 30cm long, and translucent creamy yellow coloured with blue edges on the tail fan

·         School prawn: 16cm long, with similar blue markings on its tail to the king prawn

·         Jumbo tiger prawn: grows to 33cm and is brown with tiger-like stripes

·         Banana prawn: grows to 24cm and is cream to yellow with a reddish tinge

·         Green-tail prawn (also known as the greasyback): grows to 11 cm and is the only member of the family that spends its life in estuarine waters

BREEDING

·         Female prawns lay their eggs in spawning grounds offshore

·         The young moult through a series of larval stages while forming part of the plankton

·         After a few weeks, the young prawns swim to the sea floor and migrate into bays and estuaries, where they grow rapidly, feeding on plentiful food on the muddy bottom

·         After almost a year the prawns migrate back into deeper water, where they lay their eggs

·         Once they’ve laid their eggs most of the adults then die

HABITAT

·         Along most coasts of Australia but are rare off cool, exposed southern shores

·         Western king prawn: waters off the coasts of Western Australia, South Australia, The Northern Territory, Queensland and Asia

·         Jumbo tiger prawn: throughout Asia and around the northern coast from Shark Bay in Western Australia to Sydney

·         Banana prawn: northern Australia and Asia

·         Green-tail prawn: eastern Australia

Dugong

DESCRIPTION

·         Sometimes referred to as a sea cow

·         Mammal

·         Can weigh over 500kg

·         Grow up to 3m long

·         Have rounded, downward-facing snouts and broad, flexible mouths that are perfectly adapted for grazing on sea grasses

·         Nostrils are near the front of their heads and stay closed when the animal is underwater

·         Have dolphin-like tails

·         Skin is generally bronze-grey in colour with a pale belly – appears smooth, but a really close view reveals a rough surface covered in pits from which grow short, thick hairs

·         Use their front flippers for steering, as props when feeding, and for gripping their partner when mating

·         Large stomachs and long intestines with which to digest their food

·         They average less than 10km and hour, though they can reach 22km an hour in short bursts

·         Their dense bones enable them to stay on the sea bottom while feeding

·         They generally spend one to ten minutes under water before coming up for air

·         It is illegal to hunt dugongs in Australian waters – with the exception of Aboriginal and Torres Strait Islander hunters

·         Have a similar lifespan to humans

·         Dugongs reach adult size between 9 and 17 years of age

·         Though aquatic, it breathes air through lungs

·         They have a thick layer of fat giving them a distinctly rotund posture

·         Surface only to breathe, and never come onto land

·         Dugong males have ivory tusks used for fighting during male-male rivalry as well as for uprooting seagrasses

·         Young dugongs hide behind their mothers when in danger

DIET

·         Herbivore

·         Graze on seagrasses

FAMILY

·         Not related in any way to either seals or whales

·         Belongs to the order Sirenia, the sea cows

·         Only two families in this group - the manatees and the dugong

·         The dugong is the sole member of the family Dugongidae

·         Sometimes gather in herds or hundreds of individuals

·         Large groups are becoming less common as their habitat diminishes and their numbers dwindle

·         Often now found in smaller “family” groups of between one and three dugongs

BREEDING

·         give birth underwater to a single calf every three to seven years

·         Birth takes place in shallow water and the baby dugong is able to swim to the top of the water for its first breath

·         Babies are about 100 to 120cm long and weigh 20 to 30kg

·         Calf stays with its mother, drinking milk from her teats and following close by until 18 to 24 months of age

·         Calves start feeding on seagrasses when they are very young but continue to drink their mother’s milk for about a year and a half after birth

HABITAT

·         Indian Ocean and the south-western Pacific Ocean

·         Warm, shallow coastal waters

·         Northern half of Australia, from Shark Bay in the west to the Queensland - New South Wales border in the east

·         Range used to extend further down the east coast

·         Once more widely spread throughout the world

·         Only live where there is seagrass

PREDATORS

·         Humans

·         Only large sharks, Salt-water Crocodiles and Killer Whales

OTHER INFORMATION

·         The species is under threat, mainly due to habitat loss and hunting and incidental captures in fishing nets

·         Protected species in Australia

 Fairy Penguin

DESCRIPTION

·         Also known as little penguins

·         Short and stocky

·         Grow to about 40cm long

·         Weigh only 1kg

·         Uniform blue-grey above and white below

·         Start their annual moult in February

·         Their scientific name is eudyptula minor

·         Whilst on land they are very noisy, especially before their pre-dawn departure back to sea to feed

·         spend their days out at sea in groups, referred to as rafts, and at dusk they return to their burrows or rock crevice colonies

·         Short stiff feathers are kept waterproof by preening from oil glands located at the base of the tail

·         The average life-span is said to be seven years and they usually mate for life

·         Each year they will return to the same burrow and “renovate” it if it is not badly damaged

DIET

·         Catch most of their food with shallow dives (0 to 11m)

·         Also do some dives to the sea bed

·         Eat small fish such as anchovies, squid, plankton, frill, small octopi and pilchards

·         From the sea floor they may eat crab larvae, sea horses and crustaceans

·         They eat their fish whole

FAMILY

·         Colonies vary greatly in size, from only one or two pairs to around 15,000 pairs

BREEDING

·         Most breeding colonies form on offshore islands

·         females lay their eggs between August and September

·         in some years raise a further one, or even two, clutches when the first chicks have fledged

·         usually two eggs in a clutch

·         incubated by both parents for about 35 days

·         Until the chick fledges at 42 days it is fed regurgitated food by its parents, one of which is always on guard

·         Breeding is usually over by late February

·         Young penguins do not breed until they are three or four years old

·         Females arriving at the breeding colonies are met by noisy male courting displays

·         June through to August is the peak laying time

·         Eggs take 36 days to hatch

HABITAT

·         Nest under dense vegetation or rocks, or dig burrows in loose sand with their feet

·         Swim in the waters around the southern half of Australia, from northern New South Wales to Perth in Western Australia

·         along the shores of southern Australia and New Zealand

PREDATORS/THREATS

·         Sharks, seals, and killer whales are predators in the water

·         Sea eagles and large gulls are predators on land

·         Introduced species such as foxes, dogs and feral cats

·         Nest predators such as rats, snakes and lizards

·         Starvation, because penguins are dependant on other species to feed on

·         Man-made threats include pollution, oil spills, plastic, road kills, gill net fishing and loss of breeding habitat.

List of References for this page...

·        Crustaceans

Reader’s Digest (1997) Encyclopedia of Australian Wildlife. Reader’s Digest: Sydney

·        Crab

www.enchantedlearning.com/subjects/Crab.shtml

·        Lobster

www.enchantedlearning.com/subjects/invertebrates/crustacean/Lobsterprintout.shtml

·        Prawn

Reader’s Digest (1997) Encyclopedia of Australian Wildlife. Reader’s Digest: Sydney

·        Dugong

Reader’s Digest (1997) Encyclopedia of Australian Wildlife. Reader’s Digest: Sydney

http://australian-animals.net/

·        Fairy Penguin

Reader’s Digest (1997) Encyclopedia of Australian Wildlife. Reader’s Digest: Sydney

http://australian-animals.net/

View other Your Work entries...     Val's Journal      Jodie's Journal

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Part Five     Part Six     Part Seven     Part Eight     Part Nine     Part Ten     Part Eleven     Part Twelve 

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This page last updated: 17th February 2006