Many animals have exoskeletons, which is a hard outer shell that helps protect the animal. The exoskeleton can also be used for protection against predators or to help the animal catch its prey. Some of the animals with exoskeletons include crabs, lobsters, spiders, and scorpions.
Five main Groups of Animals with Exoskeletons
Animals that have exoskeletons are invertebrates and include:
- Shelled Molluscs
- Millipedes & Centipedes
Examples of Animals with Exoskeletons
Spiny lobsters, also known as langustas, langouste, or rock lobsters, make up the family Palinuridae in the order Decapoda and infraorder Achelata. There are around 60 species of these achelate crustaceans which are split into 12 genera.
Spiny lobsters generally resemble true lobsters in terms of overall shape and having a hard carapace and exoskeleton, but can be distinguished by their very long, thick, spiny antennae, and by their lack of chelae (claws) on the first four pairs of walking legs. Mature female spiny lobsters have a small claw on their fifth pair of walking legs.
Spiny lobsters are nocturnal animals and spend the day hiding in crevices and rocks. They only occasionally venturing out at night to seek food. To deter predators, it flexes its tail to escape backwards and lets out a loud screech made by the antennae of the spiny lobsters rubbing against a smooth part of the exoskeleton.
Spiny lobsters are social animals, although recent research shows that healthy lobsters move away from infected ones, leaving the diseased lobsters to fend for themselves.
The Japanese spider crab (Macrocheira kaempferi) is a species of marine crab. It is the largest known living arthropod and has the largest leg span of any arthropod, sometimes measuring up to 12.5 feet from the tip of one front claw to the other. Japanese spider crabs live in the waters around Japan, and get their name from its resemblance to a spider.
Despite the intimidating appearance of these animals, the Japanese spider crab is harmless and is a slow-moving creature. As a decorator crab, it adorns its exoskeleton with algae and sponges to increase its camouflage to hide from predators like octopuses and fish. That being said, there are actually few predators at the depths in which they live.
Because these crabs have a hard outer shell (the exoskeleton) that does not grow, they must shed their shells. This unique molting behavior occurs for 103 minutes, in which the crab loses its mobility and starts molting its carapace rear and ends with molting its walking legs. This can be dangerous for them, as they can get stuck in their existing shells or be preyed on by other crabs during the molting period.
The Black House Spider (Badumna insignis) is a dark colored, robust spider. The female of the species measures up to 18 millimetres and is larger than the male which measures up to 9 millimetres. The carapace, the part of the exoskeleton that covers the cephalothorax (the first anterior major body section) and legs are dark brown to black and the abdomen is charcoal grey with a dorsal pattern of white markings.
Black House spiders are commonly found by homeowners in window framing, under leaves, gutters, in brickwork and among rocks and bark.
A Water Beetle is a beetle adapted to living in water. A number of different types are known, nearly all living in or on fresh water. The few marine species tend to live in the intertidal zone (also known as the ‘littoral zone’, in marine aquatic environments it is the area of the foreshore and seabed that is exposed to the air at low tide and submerged at high tide). Many water beetles carry an air bubble underneath their abdomens.
This air bubble provides both an air supply and prevents water from getting into the spiracles (small openings on the surface of some animals that usually lead to respiratory systems). Other water beetles have the surface of their exoskeleton modified to form a plastron (a thin permanent layer of air around the body of some aquatic insects).
Like all insects, the grasshoppers have three main body parts – the head, the thorax and the abdomen. They have six jointed legs, two pairs of wings and two antennae. Their body is covered with a hard exoskeleton. Grasshoppers breathe through a series of holes called ‘spiracles’ which are located along the sides of the body. Most grasshoppers are green, brown, or olive-green.
A Grasshopper is an amazing insect that can leap 20 times the length of its own body. If you or I could do that, we would be able to jump almost 40 yards!
A Grasshopper does not actually ‘jump’. What they do is use their legs as a catapult. Grasshoppers can both jump and fly and they can reach a speed of 8 miles per hour when flying. There are about 18,000 different species of grasshoppers.
Centipedes (Class Chilopoda) are fast-moving, venomous, predatory, terrestrial arthropods that have long bodies and many jointed legs. Centipedes are found primarily in tropical climates, however, they are also widely distributed in temperate zones. Despite their name ‘centipede’ (which means ‘100 legs’), all centipedes do not have 100 legs. Centipedes are invertebrates meaning ‘without a backbone or spinal column’.
Centipedes have a hard exoskeleton and jointed legs. Like the millipedes, centipedes are highly segmented (15 to 177 segments), but with only one pair of walking legs per segment (millipedes have two legs per segment). A common centipede is the house centipede (Scutigera forceps), which is about 5 centimetres (2 inches) long and has 15 pairs of legs. Some centipedes glow in the dark (like the Geophilus electricus).
About 20 families and 3,000 species of centipedes have been discovered worldwide.
Millipedes are arthropods in the class ‘diplopoda’.
This class contains around 10,000 species, 15 orders and 115 families. Millipedes are found in most parts of the world from back gardens to Rainforests, on all continents except Antarctica.
The Class Diplopoda is divided into three subclasses. The subclass ‘Penicillata’ contains 160 species millipedes whose exoskeleton is not calcified (consisting of, or containing, calcareous matter or lime salts) and which are covered in setae (a stiff hair) or bristles.
Cone snails, also known as cone shells, or cones, are a large group of small- to large-sized extremely venomous predatory sea snails, marine gastropod molluscs. There are over 900 different species of cone snails and they are typically found in warm and tropical seas and oceans worldwide. They belong to the family Conidiae.
Until fairly recently, over 600 species of cone snails were all classified under one genus Conus, in the family Conidae. However, in recent years, it was suggested that cone snails should occupy only a subfamily that should be split into a very large number of genera.
These species have shells that are more or less conical in shape (hence their common name) and many species have colorful patterning on the shell surface. All cone snails are venomous and capable of “stinging” humans. They can even be fatal when handled live. However, cone snail venom is showing great promise as a source of new, medically important substances.