Download cowries - Two Oceans Aquarium

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COWRIES
Habitat
Coral reefs and beyond the lowest level of low tide. There are some temperate species in our
region on the South coast.
Description
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Colourful shiny egg-shaped shells.
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Operculum absent.
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The cowrie not only protrudes its mouth and tentacles, but also its mantle which extends
right over its shell completely obscuring it and giving it the brilliant gloss so prized by shell
collectors.
Feeding
Most of them browse on sponges.
Predators
Some species of fish.
Tiger Cowrie
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Did you know?
Until recently, the Fulton’s cowrie, Cyprea fultoni’s, was only found in the stomach of the
black musselcraker (Poenskop). As such, it was considered as extremely rare and was the
most expensive cowrie in the world.
Two Oceans Aquarium Volunteer Manual – Module 3 – INVERTEBRATES
49
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SLUGS AND SNAILS (NUDIBRANCHS (naked gills) – slugs)
Habitat
Rocky reefs, to a depth of about 15m.
Description
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They are the most beautiful and highly coloured invertebrates. The colour patterns of many
warn predators of their unpleasant taste.
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Lack a shell but are not entirely defenceless. (see Did You Know?)
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A second pair of tentacles (rhinophores) occurs on top of the head.
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The mantle cavity and primary gills may be lost.
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A plume of secondary gills around the anus.
Feeding
They feed on a variety of foods ranging from marine plants, bryozoa, sea anemones, small
crustaceans, hydroids, jellyfish and bluebottles.
Predators
Nudibranchs are seldom eaten.
BUBBLE SHELLS are very fragile seaslugs with a shell.
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Did you know?
Some Nudibranchs secrete toxic chemicals and should not be
handled.
Others obtain second-hand weapons by using the stinging cells of
their prey (jellyfish, bluebottles, hydroids).
Their enemies are mostly man. Humans threaten their habitat
through pollution and development of beaches.
Two Oceans Aquarium Volunteer Manual – Module 3 – INVERTEBRATES
CLASS: BIVALVIA
CHARACTERISTICS
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All species in this class have two shells enclosing the body.
Body compressed from side to side.
They have gills with cilia around the inner edge of the shell to propel water into the shell.
Lack head with tentacles, eyes and ribbon tongue (radula).
They are filter feeders.
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CLAMS, MUSSELS AND OYSTERS
Habitat
Bivalves have a diversity of habitats. Some are attached to rocks in the lower balanoid zone where
the waves break at low tide. Some species burrow into sand or mud.
Description of Black or Brown Mussels
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They have streamlined shells made up of two close-fitting halves.
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The two shells snap together using a strong ligament and they are very hard to pull apart
once closed.
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The shells are anchored to the rocks by strong byssus
threads.
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On the rocks a great many individual mussels group
together to form mussel beds.
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The largest part of the animal is the gonad (its
reproductive organ).
Feeding
Filter the water for minute particles of food (plankton).
Predators
Many fish with strong jaws feed on them, as well as lobsters, spiny starfish and octopus. The kelp
gull also preys on mussels.
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Did you know?
One mussel can pump as much as
two litres of water every hour.
Because mussels are filter feeders,
they can concentrate pollutants
and toxins in their flesh. They
should not be collected for food if
they are near a city.
Gonad – largest part of
the animal
Two Oceans Aquarium Volunteer Manual – Module 3 – INVERTEBRATES
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CLASS: POLYPLACOPHORA
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CHITONS
Habitat
Some on underside of rocks, others on exposed rock surface and the giant chiton partially or
totally buried in sand on flat rocky reefs.
Living Shores : fig 297
Description
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Oval, flattened mollusc.
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Eight, overlapping articulated plates along the back which can flex the body over the surface
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Plates surrounded by a tough leathery girdle.
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Head completely hidden beneath the girdle and lacks eyes in most.
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Remainder of the underside – broad muscular foot rimmed with small gills.
Feeding
When active they creep slowly about, rasping encrusting plants or animals from the rock surface
with their powerful file-like radula.
Predators
Any predator that is able to dislodge them from the rocks, e.g. seabirds, fish, crabs, eats chitons.
Did you know?
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Once detached from the rock, it rolls up to protect the softer body parts. This reflex
action prevents damage should the chiton be rolled around by the waves.
The giant chiton, Dinoplax gigas serves as excellent bait for white musselcracker.
Two Oceans Aquarium Volunteer Manual – Module 3 – INVERTEBRATES
CLASS: CEPHALOPODA
OCTOPUS, SQUID, CUTTLEFISH, PAPER NAUTILUS
Cephalopod means ‘head-footed’ and they are the top of the mollusc evolutionary tree.
CHARACTERISTICS
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Head and foot fused.
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Head has highly mobile tentacles with suckers.
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Most intelligent invertebrates with a well-developed brain.
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Capable of learning.
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Image forming eyes, equivalent to those of vertebrates.
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Complex buoyancy control.
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All have powerful beaks shaped much like a parrot’s beak.
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Use jet propulsion to escape predators.
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They release a black ‘ink’ into the water when fleeing an enemy or predator.
Did you know?
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Cephalopods include the
largest invertebrates the sea
has ever known.
Deep-sea squids may have
bodies 6m long with a total
length of 25 m.
Squids are fast swimming
animals. Can exceed 20 knots
(40km/h).
Two Oceans Aquarium Volunteer Manual – Module 3 – INVERTEBRATES
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