Characteristics of Crustaceans
approximately 30,000 species make up this Subphylum. Most are aquatic; of these, the majority are marine but some are found in fresh water. Members of the Subphylum include lobsters, crabs, crayfish, shrimp, copepods, barnacles, and several other groups of organisms. All have two pairs of antennae, a pair of mandibles, a pair of compound eyes (usually on stalks), and two pair of maxillae on their heads, followed by a pair of appendages on each body segment (crustacean bodies usually are made up of head, thorax, and abdomen, although the segments composing these tagmata differ among different Classes). The appendages are primitively branched (biramous), and although this condition is modified in many species, adults always have at least some biramous appendages. Crustaceans respire via gills. Like other arthropods, all have a hard but flexible exoskeleton.
Most crustaceans are free-living, but some are sessile and a few are even parasitic. Most use their maxillae and mandibles to take in food. The walking legs, including specialized chelipeds, may be used to help capture prey. Some crustaceans filter tiny plankton or even bacteria from the water; others are active predators; while still others scavenge nutrients from detritus.
Most crustaceans are dioecious. The actual mechanisms by which fertilization is achieved vary greatly. Some crustaceans hatch young that are like miniature adults; others go through a larval stage called a nauplius.
Many species, including lobsters, crayfish, barnacles, and crabs are important to human economies, some very much so. Others, such as krill, are at the base of extremely important marine food chains. Still others are crucial in recycling nutrients trapped in the bodies of dead organisms.
taken from: http://animaldiversity.org/accounts/Crustacea/
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 nozoic 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 cae 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 Meographic Limestones From The Jurassic Period Of Solnhofen In Germany Have Long Been Famed For The Many cochirus magna. The lithexceptionally preserved crabs, lobsters and shrimp fossils they have yielded (such as Aeger, Eryon, and Pseudastacus).
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 nozoic 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 cae 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 Meographic Limestones From The Jurassic Period Of Solnhofen In Germany Have Long Been Famed For The Many cochirus magna. The lithexceptionally preserved crabs, lobsters and shrimp fossils they have yielded (such as Aeger, Eryon, and Pseudastacus).
these beautiful and wonderous creatures are amazing and can do lots of things. they are large groups and almost never leaves each others sides. for example, the crab that can go on land and water they never go by themselves anywhere . shrimp there very colorful and they can go in The Antarctic Ocean And Not Be Cold. Sea Horses there AMAZING! they jump around using there tail and momentum and Speed
