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More About Crustaceans ...
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The crustaceans (Crustacea) are a large group of arthropods (55,000 species), usually treated as a subphylum. They include various familiar animals, such as lobsters, crabs, shrimp and barnacles. They are variously found in marine and freshwater, with a few terrestrial members (such as woodlice).
Crustaceans have 3 distinct body parts: head, thorax, and abdomen. They have two pairs of antennae on the head, compound eyes, three pairs of mouthparts and a telson. Smaller crustaceans respire through their body surface by diffusion and larger crustaceans respire with gills. Crustaceans typically have a thick carapace on the dorsal side of their body. Their appendages are typically biramous, including the second pair of antennae (but not the first).
Most crustaceans have separate sexes and are distinguished by appendages on the abdomen called swimmerets. The first (and sometimes the second) pair of swimmerets are larger on the male than on the female. Terrestrial crabs mate seasonally and return to the sea to breed. Female crabs' eggs are retained by the females until they hatch. The eggs hatch into free-swimming larvae.
Although crustaceans are rarer as fossils than trilobites are, a number of different types of crustaceans are common in the rocks of the Cretaceous period as well as those of the Caenozoic era. Most of the smaller crustaceans, such as shrimp, have an exoskeleton which is somewhat delicate and for this reason their fossil record is incomplete. However, crustaceans such as crabs and lobsters have a thicker exoskeleton which is reinforced with calcium carbonate and so their fossil record is much better. The fossil record of barnacles is scarce and little is known of their history prior to the Mesozoic era. Well preserved specimens are known from the rocks of the Cretaceous period and the Caenozoic era.
The most well known crustaceans, the malacostraca (crabs, lobsters, crayfish, shrimp), although widespread today are only found sporadically as fossils. Most of the known fossil crabs are of forms which lived on the sea-floor or in a reef environment. In rocks such as the Gault clay from the Cretaceous period and the London clay from the Eocene period in England fossil crabs may be found. The 'Lobster Bed' of the Greensand formation from the Cretaceous period which occurs at Atherfield on the Isle of Wight in England contains many well preserved examples of the small lobster Mecochirus magna. The lithographic limestones from the Jurassic period of Solnhofen in Germany have long been famed for the many exceptionally preserved crabs, lobsters and shrimp fossils they have yielded (such as Aeger, Eryon, and Pseudastacus).
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Source: Wikipedia Read more about Crustaceans
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INFO LINKS
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Common shrimp
BBC Nature: Wildfacts
Common shrimp: Facts and Pictures Read More
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Goose barnacle
BBC Nature: Wildfacts
Goose barnacle: Facts and Pictures Read More
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Crayfish
The Longpoint schoolhouse
Crayfish Read More
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Horseshoe Crab
http://www.dnr.state.md.us/
Tons of information on this crab like life history, anatomy, fishery, conservation, medical uses, raising crabs, etc. Read More
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Chinese Mitten Crab
Natural History Museum
"The Chinese mitten crab originates originates form the Far East, with a native distribution from the Province of Fukien, China". Information on classification, life history, distribution, environmental problems, etc. Read More
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Crayfish
NatureNorth
Crayfish are fairly common, but seldom seen critters Interesting narrative. Read More
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crab
BBCi
About its mechanism of protection. Easy to read Read More
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Blue Crab
National Geographic
Blue Crab fact sheet and pictures; audio clip Read More
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Krill
National Geographic
Krill fact sheet and pictures Read More
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Blue Crab
National Aquarium, Baltimore
"The blue crab, Callinectes sapidus, lives in estuaries along the eastern coasts of North and South America, from low tide to depths of 37 meters" Narrative Read More
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Fiddler Crab
Pelotes Island Nature Preserve
"Adult male fiddler crabs have one large front claw and one small one, while females and young fiddlers have two small claws. The large claw looks a bit like a fiddle". FAQs on Fiddler Crabs Read More
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Shrimp
Oceanes - the holiday designer
Brief description and categorized information about Shrimp Read More
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Mantis shrimp
Oceanes - the holiday designer
Brief description and categorized information about Mantis shrimp Read More
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Yabby
Unique Australian Animals
Categorized information on Yabby including description, habitat, feeding, etc. Has nice pictures, too. Read More
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Green Crab
Sustainable Ecosystems Institute
An article about "The European Green Crab....A New Invader". Read More
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Green Crab
AquaCulture
Find out why "The recent arrival of the green crab on the U.S. West Coast is cause for concern" . Read More
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Horseshoe Crab
Beach-Net.com
Information on mating ritual, facts and figures like "Despite their size and intimidating appearance, horseshoe crabs are not dangerous". Read More
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Horseshoe Crab
Globalclassroom.org
"The hosrseshoe crab is called a "living fossil" because it has been on earth for millions of years". Narrative on this crab. Read More
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Chinese Mittern Crab
Department of Fish and Game Bay-Delta
Information on life history, identification, pictures, regulations, etc. Read More
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Blue Crab
Blue-Crab.net
The literal translation of the scientific name may mean" the beautiful, savory swimmer" An Interesting Narrative Read More
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Red Rock Crab
http://www.shim.bc.ca
Information on habitat, food, predators, etc. Read More
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Crabs
Cyhaus.com
General Information on Crabs Read More
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Crab
Enchanted Learning.com
"Crabs are 10-legged animals that walk sideways. There are almost 5,000 different species of crabs; about 4,500 are true crabs, plus about 500 are hermit crabs (hermit crabs don't have a very hard shell and use other animals' old shells for protection). ". Information on crab diet, anatomy, breathing, etc. Find out which is the biggest crab Read More
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horseshoe crab
sentinel.com
Arthropods - Horseshoe Crabs Take a close look at the external anatomy of the horseshoe crab Read More
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Hermit Crabs
Museum Victoria
Find out about hermit crabs and false crabs "Some crustaceans that look somewhat like crabs belong to the Anomura. They differ from true crabs by having at most only three pairs of walking legs instead of four". Contains photos and information on hermit crabs and other Anomur, or False Crabs Read More
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Spider Crab
Crustacean Gallery
Information on distinguishing feature, habitat, and general biology Read More
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Chinese Mitten Crab
http://www.seerecht.org
"ecological model reflecting what is known scientifically about the Chinese mitten crab." Read More
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Fiddler Crab
http://www.public.asu.edu/
Facts on fiddler crabs Read More
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San Diego Fairy Shrimp
National Wildlife Federation
Categorized information about San Diego Fairy Shrimp Read More
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Koura - Freshwater Crayfish
Department of Conservation, New Zealand
Fact Sheet Read More
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