Tag shell

Common Marine Hermit Crab

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The Common Marine Hermit Crab (Pagurus bernhardus) is a saltwater aquatic decapod (10-armed) crustacean. It is also known as the Soldier Crab.

Hermit crabs include the Marine Hermit Crab, which lives in saltwater, and the Land Hermit Crab, which is terrestrial in tropical regions.

The Common Marine Hermit Crab is a crab inside a shell – its mobile home. It finds empty mollusc shells to live in. It has a long soft body – not like land crabs which have a hard exo-skeleton – which is why it looks for a hard shell to protect it. It can put its whole body inside the shell. As it grows, it looks for larger shells.

The Common Marine Hermit Crab has a spirally-curved soft body (abdomen) with a columella on the tip, which is used to hold onto the shell it occupies. It has 10 appendages (legs, called pereiopods), but two of them are claws, called nippers, pinchers, or chelipeds. Its large black compound eyes are at the end of an eyestalk. It has gills to breathe (like fish).

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Golden Apple Snail

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The Golden Apple Snail (Pomacea canaliculata) is a freshwater South American snail. It is an aquatic gastropod mollusc (mollusk). It is also called the Channeled Apple Snail.

The Golden Apple Snail has a boneless foot with a brown globe-shaped shell, called a mantle. It has both external gills (like a fish) on the right-hand side of its body to enable it to breathe underwater, and an internal lung on the left-hand side of its body (like a frog) to enable it to breath on land. This means that the Golden Apple Snail lives in the water and on land – it is amphibious, like a frog or a toad. It also has an operculum, which is a little lid, that enables it to close the shell entrance to prevent it from drying out when it is buried in the mud during dry seasons.

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Fallacy: Tortoises will come out of their shell if they are frightened

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Tortoises and turtles will come out of their shell if frightened. This is not true. This is a fallacy.

Actually, the reverse is true. Tortoises pull their head and feet into their shell so that predators cannot harm or eat them. They are too slow to run away, so hiding in their shell is their way of protecting themselves.

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Bull-Mouth Helmet Snail

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The Bull-Mouth Helmet Snail (Cypraecassis rufa) is a large marine snail – a gastropod mollusk in the Cassidae family. It is also called a Cameo Shell.

The Bull-Mouth Helmet is a snail with its shell. The shell is shaped like a helmet. The shell is large, thick, and creamy-beige-coloured with a red-orange sheen. It is coiled with ridges (called varices) and bumps. It has a blunt knob at the narrow end (the anterior end). On the wide end (the posterior end), there is a spire and a protoconch. The shell has an orange-cream long, narrow opening.

The snail inside is a large muscular foot-shaped gastropod. The snail has a large head with eyes at the base of each of the two tentacles (like antennae).

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Bell’s Hinge-Back Tortoise

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The Bell’s Hinge-Back Tortoise (Kinixys belliana)is a reptile – it is medium-sized African chelonian.

The Bell’s Tortoise is a light brown colour. It has a hinge on the back of its top shell (carapace). It has a 90-degree hinge, which protects its back legs and tail. The hinge is a broad band of flexible connective tissue. The shell is slightly domed and elongated. It has five claws on each front foot.

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African Helmeted Terrapin

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The African Helmeted Terrapin (Pelomedusa subrufa) is also known as the Marsh Terrapin, the Crocodile Terrapin, or the African Side-Necked Terrapin. It is a semi-aquatic reptile from Africa, like tortoises and turtles – a chelonian.

The African Helmeted Terrapin looks like a helmet. Instead of its neck sticking in and out, it has a side-necked position where it places its head sideways in its shell. It black or brown shell (carapace) is slightly domed. Its tail and legs are grey-brown, and its underbelly is yellowish. The male has a long thick tail. The female has a shorter tail.

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Pancake Tortoise

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The Pancake Tortoise (Malacochersus tornieri) is a flat-shelled tortoise from southern Kenya and northern Tanzania in east Africa. It is a reptile – a chelonian.

The Pancake Tortoise has a brown carapace (upper shell) with geometric patterns and a pale-yellow plastron (lower shell). The top shell is not domed like other tortoises. It is flat, thin, and flexible. Its head, legs, and tail are brown.

It is a fast mover – faster than the larger, domed tortoises. It is a good climber, and can climb over rocky ground. For protection against predators, it hides in crevices and gaps in rocky areas.

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Giant African Land Snail

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The Giant African Land Snail (Lissachatina fulica) is a large mollusk in the Achatinidae family.

They are macrophytophagous herbivores, which means that they eat a wide range of plant material, fruit, and vegetables.

The Giant African Land Snail can grow to 7 centimetres (2.8 inches) long. The shell is conical with colours that depend on the snail’s location, diet, and surroundings.

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Chelonians – hidden neck or side neck?

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Tortoises and turtles are called Chelonia.

In the order Testudines (tortoise-like or turtle-like), there are two suborders: Cryptodira (hidden neck) and Pleurodira (side neck).

Cryptodira means that the chelonians pull their neck right into their shell—most chelonians are in this category. Their necks go in and out.

Pleurodira means that the chelonians tuck their neck sideways under their shell.

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How can you tell a male from a female tortoise?

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A tortoise is a land reptile with an exoskeleton, which is a hard shell.

In fact, there is a hard shell on the top (called a carapace) and a hard shell underneath (called a plastron).

How can you tell a male tortoise from a female tortoise? One way to tell the difference between a male and a female tortoise is to turn it around and look at the plastron – the underbelly shell.

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External Covering: from skin and scales to fur and feathers

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External covering is the outside appearance of an animal. Animals can have fur, feathers, hair, short hair, long hair, smooth hair, bristles, skin, thick skin, moist skin, dry skin, scales, waterproof scales, small scales, overlapping scales, spikes, hard shells, soft shells, smooth shells, rough shells, wool, or no covering at all.

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Iridescent scales, feathers and shells

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Iridescence means shiny with many colours. Many animals have iridescent colours.

Iridescence is structural colour from refracted light (crystals), diffraction gratings (feathers or butterfly wings), thin film (oily surfaces), multiple layer interference (nacre in shells), or 3-D arrays of spheres (opals).

The word iridescence comes from iris, the Greek word for rainbow. An iridescent object has many tones of colour. Iridescence creates colour by splitting and reflecting light from different structures – which is why it is often called structural colour.

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Tortoises and Turtles: Flat shell or domed shell?

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What is the difference between flat-shelled or dome-shelled tortoises and turtles?

The tortoise has a domed shell. The tortoise lives on land. The domed shell is heavy and acts like a shield or armour to protect them from predators.

The turtle has a flat shell. The turtle lives in water. Flat shells are lighter and better for swimming in water.

The terrapin has a flat shell. The terrapin lives partly on land and partly in the water.

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