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Branchiobdellae
Branchiobdellida is an order of freshwater leech-like clitellata, clitellates that are obligate Ectosymbiosis, ectosymbionts or ectoparasites, mostly of astacoidean crayfish. They are found in the Northern Hemisphere and have a Holarctic realm, holarctic distribution in East Asia, the Euro-Mediterranean region and North and Central America, with the greatest species diversity being in North and Central America. Taxonomy The exact relationship of this group of clitellates with other groups has been the subject of debate for a century or more. The American zoologist Perry C. Holt wrote his doctoral thesis on branchiobdellids and devoted his 45 years of research to the taxon. With his colleague, the American zoologist Richard L. Hoffman, he described 8 new Genus, genera and 75 new species, and re-described various other species. In 1965, he came to the conclusion that the group should be raised from a Family (biology), family to an Order (biology), order, a sister group to the Oligoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clitellata
The Clitellata are a class of annelid worms, characterized by having a clitellum - the 'collar' that forms a reproductive cocoon during part of their life cycles. The clitellates comprise around 8,000 species. Unlike the class of Polychaeta, they do not have parapodia and their heads are less developed. Characteristics Clitellate annelids are segmented worms characterised by the clitellum or girdle which is located near the head end of mature individuals. The mouth is on the ventral surface and is overhung by the prostomium (proboscis). The brain is not located in the head but in one of the body segments. The clitellum is formed by a modification of several segments, and either includes the female gonopores or is located just behind them. During copulation, this glandular tissue secretes mucus that keeps the paired individuals together while they exchange sperm. Afterwards it secretes material that forms a cocoon that encircles the animal's body and encloses the eggs and sperm. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal Crayfish
The signal crayfish (''Pacifastacus leniusculus'') is a North American species of crayfish. It was introduced to Europe in the 1960s to supplement the North European ''Astacus astacus'' fisheries, which were being damaged by crayfish plague, but the imports turned out to be a carrier of that disease. The signal crayfish is now considered an invasive species across Europe, Japan, and California, ousting native species there. Description and ecology Members of this species are typically long, although sizes up to are possible. They are bluish-brown to reddish-brown in colour, with robust, large, smooth claws. They have a white to pale blue-green patch near the claw hinge, like the white flags that signalmen used for directing trains—hence the name. The lifecycle of the signal crayfish is typical for the family Astacidae. Around 200–400 eggs are laid after mating in the autumn, and are carried under the female's tail until they are ready to hatch the following spring. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leech
Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodies that can lengthen and contract. Both groups are hermaphrodites and have a clitellum, but leeches typically differ from the oligochaetes in having suckers at both ends and in having ring markings that do not correspond with their internal segmentation. The body is muscular and relatively solid, and the coelom, the spacious body cavity found in other annelids, is reduced to small channels. The majority of leeches live in freshwater habitats, while some species can be found in terrestrial or marine environments. The best-known species, such as the medicinal leech, ''Hirudo medicinalis'', are hematophagous, attaching themselves to a host with a sucker and feeding on blood, having first secreted the peptide hirudin to prevent the blood from c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambarus Bartonii
''Cambarus bartonii'' is a species of crayfish native to eastern North America, where it is called the common crayfish or Appalachian brook crayfish. ''C. bartonii'' was the first crayfish to be described from North America, when Johan Christian Fabricius published it under the name ''Astacus bartonii'' in his 1798 work ''Supplementum entomologiae systematicae''. The locality where his specimen was captured is not known, but is thought to be near Philadelphia, Pennsylvania. ''C. bartonii'' lives in fast–flowing, cool, rocky streams as well as shallow lakes, and is found in the Canadian provinces of Ontario, Quebec and New Brunswick, and in the United States from Maine to Alabama. In the south of its range, ''C. bartonii'' is restricted to the Appalachian Mountains and their foothills. Colouration is usually plain dark brown, although mottling is occasionally seen, as is a saddle-shaped marking. Several subspecies of ''C. bartonii'' have been recognised, but it is unclear how ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Generalist And Specialist Species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources (for example, a heterotroph with a varied diet). A specialist species can thrive only in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either group, however. Some species are highly specialized (the most extreme case being monophagous, eating one specific type of food), others less so, and some can tolerate many different environments. In other words, there is a continuum from highly specialized to broadly generalist species. Description Omnivores are usually generalists. Herbivores are often specialists, but those that eat a variety of plants may be considered generalists. A well-known example of a specialist animal is the monophagous koala, which subsists almost entirely on eucalyptus leaves. The raccoon is a generalist, because it has a natural range that includes most of North ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Callinectes Sapidus
''Callinectes sapidus'' (from the Ancient Greek ,"beautiful" + , "swimmer", and Latin , "savory"), the blue crab, Atlantic blue crab, or regionally as the Chesapeake blue crab, is a species of crab native to the waters of the western Atlantic Ocean and the Gulf of Mexico, and introduced internationally. ''C. sapidus'' is of considerable culinary and economic importance in the United States, particularly in Louisiana, the Carolinas, the Chesapeake Bay, Delaware, and New Jersey. It is the Maryland state crustacean and the state's largest commercial fishery. Due to overfishing and environmental pressures some of the fisheries have seen declining yields, especially in the Chesapeake Bay fishery. Unlike other fisheries affected by climate change, blue crab is expected to do well; warming causes better breeding conditions, more survivable winters, and a greater range of habitable areas in the Atlantic coast. Whether this will have negative effects on the surrounding ecosystems ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isopoda
Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, and five pairs of branching appendages on the abdomen that are used in respiration. Females brood their young in a pouch under their thorax. Isopods have various feeding methods: some eat dead or decaying plant and animal matter, others are grazers, or filter feeders, a few are predators, and some are internal or external parasites, mostly of fish. Aquatic species mostly live on the seabed or bottom of freshwater bodies of water, but some taxa can swim for a short distance. Terrestrial forms move around by crawling and tend to be found in cool, moist places. Some species are able to roll themselves into a ball as a defense mechanism or to conserve moisture. There are over 10,000 identified species of isopod worldwide, with around 4,50 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shrimp
Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are referred to as "shrimp". More narrow definitions may be restricted to Caridea, to smaller species of either group or to only the marine species. Under a broader definition, ''shrimp'' may be synonymous with prawn, covering stalk-eyed swimming crustaceans with long, narrow muscular tails (abdomens), long whiskers ( antennae), and slender legs. Any small crustacean which resembles a shrimp tends to be called one. They swim forward by paddling with swimmerets on the underside of their abdomens, although their escape response is typically repeated flicks with the tail driving them backwards very quickly. Crabs and lobsters have strong walking legs, whereas shrimp have thin, fragile legs which they use primarily for perching.Rudloe & Rudloe (2009 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crab
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the world's oceans, in freshwater, and on land, are generally covered with a thick exoskeleton, and have a single pair of pincers. They first appeared during the Jurassic Period. Description Crabs are generally covered with a thick exoskeleton, composed primarily of highly mineralized chitin, and armed with a pair of chelae (claws). Crabs vary in size from the pea crab, a few millimeters wide, to the Japanese spider crab, with a leg span up to . Several other groups of crustaceans with similar appearances – such as king crabs and porcelain crabs – are not true crabs, but have evolved features similar to true crabs through a process known as carcinisation. Environment Crabs are found in all of the world's oceans, as well as in fresh w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chela (organ)
A chela ()also called a claw, nipper, or pinceris a pincer (biology), pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are called chelipeds. Another name is ''claw'' because most chelae are curved and have a sharp point like a claw. Chelae can be present at the tips of arthropod legs as well as their pedipalps. Chelae are distinct from spider chelicerae in that they do not contain venomous glands and cannot distribute venom. See also * Pincer (biology) * Pincer (tool) References Arthropod anatomy {{Arthropod-anatomy-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carapace
A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron. Crustaceans In crustaceans, the carapace functions as a protective cover over the cephalothorax (i.e., the fused head and thorax, as distinct from the abdomen behind). Where it projects forward beyond the eyes, this projection is called a rostrum (anatomy), rostrum. The carapace is Calcification, calcified to varying degrees in different crustaceans. Zooplankton within the phylum Crustacea also have a carapace. These include Cladocera, ostracods, and Isopoda, isopods, but isopods only have a developed "cephalic shield" carapace covering the head. Arachnids In arachnids, the carapace is formed by the fusion of prosomal tergites into a single Plate (animal anatomy), plate which carries the e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anus
The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, depending on the type of animal, includes: matter which the animal cannot digest, such as bones; Summary at food material after the nutrients have been extracted, for example cellulose or lignin; ingested matter which would be toxic if it remained in the digestive tract; and dead or excess gut bacteria and other endosymbionts. Amphibians, reptiles, and birds use the same orifice (known as the cloaca) for excreting liquid and solid wastes, for copulation and egg-laying. Monotreme mammals also have a cloaca, which is thought to be a feature inherited from the earliest amniotes via the therapsids. Marsupials have a single orifice for excreting both solids and liquids and, in females, a separate vagina for reproduction. Female placental mamm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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