Crustaceans ( Crustacea )

1. Crustaceans (Crustacea) Sub Phylum of Arthropoda

2. Like other arthropods, crustaceans have an exoskeleton, which they moult to grow. They are distinguished from other groups of arthropods, by the possession of biramous (two-parted) limbs, and by the nauplius form of the larvae.

3. Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult.

4. biramous limb, branches into two, and each branch consists of a series of segments attached end-to-end.

5. crabs

6. They live in all the world's oceans, in fresh water, and on land, are generally covered with a thick exoskeleton(composed primarily of calcium carbonate), and have a single pair of claws.

7. Males often have larger claws. • Another conspicuous difference is the form of the pleon (abdomen) in most male crabs, this is narrow and triangular in form, while females have a broader, rounded abdomen

9. Reproduction • When fertilization has taken place, the eggs are released onto the female's abdomen, below the tail flap, secured with a sticky material. In this location they are protected during embryonic development.

10. When development is complete, the female releases the newly hatched larvae into the water, where they are part of the plankton. • The release is often timed with the tides.

11. lobsters

12. They have long bodies with muscular tails, and live in crevices or burrows on the sea floor. Three of their five pairs of legs have claws, including the first pair, which are usually much larger than the others

13. Anatomy • Lobster anatomy includes the cephalothorax which fuses the head and the thorax, both of which are covered by a chitinous carapace, and the abdomen. The lobster's head bears antennae, mandibles and, the first and second maxillae.

14. There are two ways to tell if a lobster is a male or a female. • You may be able to  identify the sex simply by looking at its tail. Females have wider tails than males do because that is where she carries her eggs

15. The other way to determine a lobster’s sex is to look at its first pair of swimming legs. • This first pair of pleopods either will be feathery or hard; males have hard pleopods which they use to deposit sperm into the female. • Females have soft, feathery pleopods so she doesn’t hurt the eggs she will carry under her tail.

16. Reproduction • Lobsters can only mate after the female molts. Before that stage, the female release pheromones (chemicals) into the water to let nearby males know she is preparing to molt and mate

17. Once she has shed her hard exoskeleton, the male gently turns her over and pierces her abdomen with his first pair of pleopods. He deposits sperm packets into her sperm receptacles; these she will store for up to 15 months before she releases eggs

18. When the time is right, she releases the eggs which pass by the seminal receptacle and are fertilized • with the stored sperm. The female then attaches the eggs, all 5,000 plus of them, under her tail with a glue-like substance where they will stay for the next ten to eleven months.

20. crayfish

21. They breathe through feather-like gills and are found in bodies of water that do not freeze to the bottom. • They are mostly found in brooks and streams where there is fresh water running, and which have shelter against predators

22. made up of twenty body segments grouped into two main body parts, the cephalothorax and the abdomen. • Each segment may possess one pair of appendages.

24. shrimp

25. Shrimp are swimming crustaceans with long narrow muscular abdomens and long antennae. • Unlike crabs and lobsters, shrimp have well developed pleopods (swimmerets) and slender walking legs; they are more adapted for swimming than walking

26. The body of the shrimp is divided into two main parts: the head and thorax which are fused together to form the cephalothorax, and a long narrow abdomen. • The shell which protects the cephalothorax is harder and thicker than the shell elsewhere on the shrimp, and is called the carapace.

27. The rostrum(beak), eyes, whiskers and legs also issue from the carapace • Two bulbous eyes on stalks sit either side of the rostrum. • These are compound eyes which have panoramic vision and are very good at detecting movement. • Two pairs of whiskers (antennae) also issue from the head