CRUSTACEANS


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Introduction to Crustaceans
== Crustaceans are members of a large class of animals with segmented bodies. Crustaceans belong to the same major division, or phylum, of the animal kingdom as insects and spiders. Included among them are lobsters, shrimp, crabs, wood lice, barnacles, water fleas, and many other animals. All told, there are about 25,000 species of crustaceans. Most of them live in the water a few such as wood lice live on land. ==

Two Values of Crustaceans: Crustaceans have many values to both humans and other animals such as  · Being a source of food. Crustaceans such as shrimps are a food source to humans and larger animals such as whales. · Crustaceans can also be a habitat for some animals. For example crabs, smaller creature can use its shell as shelter.

**The Classification of a Crustacean: **

 * ==** Kingdom: Animalia **==
 * ==** Phylum: Arthropoda **==

Body Anatomy of a Crustacean:
== Crustaceans are invertebrates with bilateral symmetry. They have a hard outer covering called the exoskeleton. The exoskeleton is also called a cuticle. It is made of a hard material called chitin. This material cannot stretch, so a growing crustacean must shed its exoskeleton in a process called molting. Underneath is a new body covering that soon hardens into a new exoskeleton. A crustacean that has just molted is soft for a day or two. A crustaceans three main body parts are the head, thorax and pleon or abdomen. These parts are made up of several segments, and each includes at least one pair of jointed limbs, or appendages. The appendages can be used for sensing the environment, catching or chewing food, breathing, walking, swimming or carrying eggs-depending on where they are placed in the body. The abdomen bears pleopods, and ends in a telson, which bears the anus, and is often flanked by uropods to form a tail fan. If a crustacean loses one of its pereiopods (these are the legs used to move) or claws it can regenerate a new one. The new limb starts to grow within a few days, and after several weeks a tiny, complete, new leg or claw is formed. After two or three months, the regenerated limb will become in the range of a limbs normal size. The feeding legs of a crustacean are called maxillipeds. The main body is an open circulatory system, where blood is pumped haemocoel by a heart near the dorsum. The alimentary canal consists of a straight tube that often has a gizzard-like "gastric mill" for grinding food and a pair of digestive glands that absorb food; this structure goes in a spiral format. Structures that function as kidneys are located near the antennae. A brain exists in the form of ganglia close to the antennae, and a collection of major ganglia is found below the gut. == == ==

The Life Cycle:
== Crustaceans reproduce by laying eggs. The eggs can be shed in the water or be carried by a female, either they could hatch in a special sac called the blood pouch. The amount and size of the eggs made by a female, all depend on the female’s size, temperature, and many other more examples. A large crab or large lobster can carry several thousands of eggs. The eggs could hatch in several weeks or even in a year. The crustaceans that live in the ocean hatch as tiny as larva which is called a nauplius. When crustaceans are still small they look nothing like the adults. ==

Habitat:
== Crustaceans live in various types of areas in the world. Their habitat may vary from saltwater, freshwater or land. Most Crustaceans are nocturnal and rest inside a crevice or spend the daytime burring themselves in the sandhiding. ==

The Movement of crustaceans:
== The limbs of crustaceans, which are tubular and jointed, are operated by internal muscles. These extend from the end of one section, along its length, to a prong from the next section which projects across the joint. When the muscle contracts between these two attachment points, the limb hinges. Such joints can only move in one plane, but crustaceans deal with that limitation by grouping two or three on a limb, sometimes close together, each working in a different plane so that the end of the limb can move in a complete circle. ==

Reproduction:
== Crustaceans are made from eggs which result from female's egg cells fertilized by a male's sperm cells. The eggs are produced in the ovaries in the female and go through oviducts to be released outside and the sperms are produced inside males’ testes. After the eggs have been fertilized and pass through the oviducts, they begin development and then hatch. == == Depending on the type of crustacean, the egg becomes detached from its’ mother within few weeks and most learn to feed, grow, swim and survive independently. After a series of transformations, the larvae becomes a miniature adult. == == Crustaceans cannot grow normally, as the same way many other animals do because of their outer skeleton. Instead they periodically shed their outer skeleton, it starts growing back rapidly and a new one grows back. While this process is taking place they hide in an isolated place. They breath in to have more space to grow. ==

Feeding:
== Crustacean's food varies from each of their species. Some eat plants, flesh, and some feed from the bottom of the ocean on anything they can find. Many of the crustaceans feed mainly on detritus, rotting leaves and scavenging protein when they can in the form of dead fish or other animals. ==

Fun facts:

 * == Did you know that crabs can dance? ==
 * == Did you ever wonder how the fiddler crab got its name? Well that's because they wave their large claw up in the air when they want to impress a female and intimidate a male, but sometimes it looks like its playing the violin. ==
 * == Some species of shrimps produce a dim light meaning they are luminescent. ==
 * == Water fleas have see-through body and only their bones and organs are visible. You can also see how their organs work and how the blood is pumped in their heart. ==
 * == The giant spider crab of Japan, the largest crustacean, can grow up to 3.7 m. ==
 * == Small crustaceans like water fleas can be even smaller than 0.2 mm. ==

Bibliography:

 * == ﻿ Crustaceans Series ==

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 * == ﻿ Invertebrates-'Crustaceans' Hard Shell Creatures of the Wet Tropic ==

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 * == Introduction to Crustaceans ==

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 * == Multiple joints allow circular movement: crustaceans ==

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 * == Crustaceans ==

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 * == Mantel L. Crustaceans. ==

United States of America: Scholastic Library Publishing Inc.

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