Clever Crustaceans, The Crab Activity Booklet ages 3-6
Crabs are crustaceans, a subphylum of the arthropods. Arthropods are invertebrates with an external skeleton, which gives them a hard exterior. Male and female crabs differ in size, shape, and color. A major difference between a male and female crab is the anatomy of their underside – the male crab has a pointy apron while the female has a rounded apron. While there are many animals with the term crab in their name, not all of them are true crabs. Interesting, isn’t it? Crabs have ten legs and are referred to as decapods. Like spiders, crabs also have legs that can bend at the joints. The front two legs of the crab are usually called claws and are not used for locomotion. The claws are also called pincers, and can be big in some crabs.
Swimming crabs use the hind legs as paddles to move when in water. Male crabs usually have blue colored claws, while female crabs have red colored. The distinct red color makes them look like they have applied red nail polish! Crabs have their eyes on the stalks, which enables them to see around even when they are under water or a rock, or in their burrow. Their eyes are made of hundreds of little lenses. A crab’s abdomen is under its main shell, unlike a lobster which has its abdomen on the back. They also have modified appendages called maxillipeds that are used for feeding. Most crabs have flattened bodies, allowing them to pass through narrow crevices and underwater pathways to escape predators.
Hermit crabs, Horseshoe crabs, Fiddler crabs, Coconut crabs, Blue crabs, and Sea Crabs.
The Hermit crab:
Hermit crabs are anomurans decapod crustaceans of the super family Paguroidea that have adapted to occupy empty scavenged mollusk shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an asymmetric abdomen concealed by a snug-fitting shell.
The Horseshoe crab:
These ocean critters predate the dinosaurs! The oldest known horseshoe crab species, was discovered by scientists in 2008 and is estimated to be nearly 450 million years old. While they’ve certainly experienced a few evolutionary adaptations, their physiology has remained largely unchanged over time.
The Fiddler crab:
A fiddler crab, sometimes known as a calling crab, may be any of more than one hundred species of semiterrestrial marine crabs in the family Ocypodidae. This entire group is composed of small crabs, the largest being slightly over two inches across. Fiddler crabs are found along sea beaches and brackish intertidal mud flats, lagoons and swamps.
The coconut crab is a species of terrestrial hermit crab, also known as the robber crab or palm thief. It is the largest terrestrial arthropod in the world, with a weight up to (9.0 lb). It can grow to up to (3 ft 3 in) in length from each tip to tip of the leg.
Blue crabs are closely related to shrimp and lobster. The blue crab has specially adapted hind legs shaped like paddles; these appendages make them excellent swimmers. Louisiana supports the largest crab production of hard blue crabs in the nation and is the number one supplier of live No. 1 male crabs in the southern states.
Sea crabs are a type of crustacean, meaning they have no backbone and are covered with a hard shell. Sea crabs live in the seas and oceans around the world, but can occasionally walk onto the shore. Although they may look a little like creepy-crawly spiders, sea crabs actually have more legs than spiders do. These crustaceans have five pairs of legs – the back four are used for walking, and the front is where their claws are located
Crabs work together to gather food and protect their families. Crabs aren’t picky eaters. They will eat everything from dead and living fish to barnacles, plants, snails, shrimp, worms and even other crabs . They use their claws to grab food particles and put the food into their mouths. This is similar to the way humans eat using their hands or utensils.
Crabs usually live in water bodies including oceans, rivers, freshwater and saltwater lakes. Most crabs prefer living in freshwater bodies. Certain species of crabs can also live on land, especially in tropical regions, and some like the Coconut crab or the Robber crab can also climb trees. The Coconut crab is the largest arthropod that lives on land. A group of coconut crabs can even break open a coconut!
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