Information about Arthropod Leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa (meaning hip), trochanter (compare greater trochanter and lesser trochanter), femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus (meaning finger), patella.
Homologies of leg segments between groups are difficult to prove and are the source of much argument. Some authors posit up to eleven segments per leg for the most recent common ancestor of extant arthropods [1], but modern arthropods have eight or fewer. It has been argued [2][3] that the ancestral leg need not have been so complex, and that other events, such as the successive loss of function of a Hox-gene could result in parallel gains of leg segments.
The appendages of arthropods may be either biramous or uniramous. A uniramous limb comprises a single series of segments attached end-to-end. A biramous limb, however, branches into two, and each branch consists of a series of segments attached end-to-end.
The legs of insects and myriapods are uniramous. In crustaceans, the first antennae are uniramous, but the second antennae are biramous, as are the legs in most species.
For a time, possession of uniramous limbs was believed to be a shared, derived character, so uniramous arthropods were grouped into a taxon called Uniramia. It is now believed that several groups of arthropods evolved uniramous limbs independently from ancestors with biramous limbs, so this taxon is no longer used.
The legs of insects are always found on the thorax. They have five segments per leg (coxa, trochanter, femur, tibia, tarsus), with the tarsus being divided into several sub-sections called tarsomeres. In some groups, the number of tarsomeres is important for identification to family level, for example beetles (Coleoptera), or to subfamily level among some dipteran flies (e.g. Cecidomyiidae). Tarsal claws, also called ungues (singular: unguis), may also be present [4][5].
The segmentation is similar in collembolans, in which each leg has a coxa, trochanter, femur, tibia, and a foot-complex.
In addition there is a sixth segment called pretarsus, which consists of claws and various other structures on the end of the tarsus. A pad or lobe-like structure is called an arolium when it is located between the claws, as in the case of Orthoptera (grasshoppers and crickets), or pulvillus if it is located at the base of the claws, as in Diptera (flies). These structures usually serve to increase adherence on various surfaces (as for the flies) and/or to cushion a fall, such as the jump of a grasshopper.
Insects' legs are attached to the three thoracic segments, the prothorax, mesothorax and metathorax. This terminology is also sometimes applied to the leg segments, so that the mesofemur is the femur of the second pair of legs, and the protarsus is the tarsus of the first pair of legs.
Spiders' legs differ from those of insects by the addition of two segments, the patella between the femur and the tibia, and the metatarsus (sometimes called basitarsus) between the tibia and the tarsus (sometimes called telotarsus), making a total of seven segments.
The situation is identical in scorpions, but with the addition of a pre-tarsus beyond the tarsus. The claws of the scorpion are not truly legs, but are pedipalps, a different kind of appendage that is also found in spiders and is specialised for predation.
In Limulus, there are no metatarsi or pretarsi, leaving six segments per leg.
The legs of crustaceans are divided primitively into seven segments, which do not follow the naming system used in the other groups. They are: coxa, basis, ischium, merus, carpus, propodus, and dactylus. In some groups, some of the limb segments may be fused together. The claw of a lobster or crab is formed by the articulation of the dactylus against an outgrowth of the propodus. Crustacean limbs also differ in being biramous, whereas all other extant arthropods have uniramous limbs.
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Homologies of leg segments between groups are difficult to prove and are the source of much argument. Some authors posit up to eleven segments per leg for the most recent common ancestor of extant arthropods [1], but modern arthropods have eight or fewer. It has been argued [2][3] that the ancestral leg need not have been so complex, and that other events, such as the successive loss of function of a Hox-gene could result in parallel gains of leg segments.
Biramous and uniramous
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Crustacean appendages
The legs of insects and myriapods are uniramous. In crustaceans, the first antennae are uniramous, but the second antennae are biramous, as are the legs in most species.
For a time, possession of uniramous limbs was believed to be a shared, derived character, so uniramous arthropods were grouped into a taxon called Uniramia. It is now believed that several groups of arthropods evolved uniramous limbs independently from ancestors with biramous limbs, so this taxon is no longer used.
Hexapoda
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Diagram of an insect leg
The segmentation is similar in collembolans, in which each leg has a coxa, trochanter, femur, tibia, and a foot-complex.
In addition there is a sixth segment called pretarsus, which consists of claws and various other structures on the end of the tarsus. A pad or lobe-like structure is called an arolium when it is located between the claws, as in the case of Orthoptera (grasshoppers and crickets), or pulvillus if it is located at the base of the claws, as in Diptera (flies). These structures usually serve to increase adherence on various surfaces (as for the flies) and/or to cushion a fall, such as the jump of a grasshopper.
Insects' legs are attached to the three thoracic segments, the prothorax, mesothorax and metathorax. This terminology is also sometimes applied to the leg segments, so that the mesofemur is the femur of the second pair of legs, and the protarsus is the tarsus of the first pair of legs.
Chelicerata
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Diagram of a spider, with the leg segments colour-coded: coxa=grey, trochanter=red, femur=green, patella=blue, tibia=purple, metatarsus=brown, tarsus=cyan
The situation is identical in scorpions, but with the addition of a pre-tarsus beyond the tarsus. The claws of the scorpion are not truly legs, but are pedipalps, a different kind of appendage that is also found in spiders and is specialised for predation.
In Limulus, there are no metatarsi or pretarsi, leaving six segments per leg.
Crustacea
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The leg of a squat lobster, showing the segments; the ischium and merus are fused in many decapods.
Myriapoda
Millipedes, centipedes and their relatives have seven-segmented legs, comprising coxa, trochanter, prefemur, femur, tibia, tarsus, and a tarsal claw.References
1. ^ Kukalova-Peck, J. (1992). The "Uniramia" do not exist - the ground plan of the Pterygota as revealed by Permian Diaphanopterodea from Russia (Insecta, Paleodictyopteroidea). Canadian Journal of Zoology - Revue Canadienne de Zoologie 70 (2): 236–255.
2. ^ Fryer, G. (1996). Reflections on arthropod evolution. Biol. J. Linn. Soc. B 58 (1): 1–55.
3. ^ Schram, F. R. & S. Koenemann (2001). Developmental genetics and arthropod evolution: part I, on legs. Evolution & Development 3 (5): 343–354.
4. ^ Harbach, R. E. & K. L. Knight (1980). Taxonomist's Glossary of Mosquito Anatomy. Plexus, Marlton, NJ.
5. ^ Richards, O. W. & R. G. Davies (1977). Imm's General Textbook of Entomology, 10th ed. (2 Volumes). Chapman and Hall, London.
2. ^ Fryer, G. (1996). Reflections on arthropod evolution. Biol. J. Linn. Soc. B 58 (1): 1–55.
3. ^ Schram, F. R. & S. Koenemann (2001). Developmental genetics and arthropod evolution: part I, on legs. Evolution & Development 3 (5): 343–354.
4. ^ Harbach, R. E. & K. L. Knight (1980). Taxonomist's Glossary of Mosquito Anatomy. Plexus, Marlton, NJ.
5. ^ Richards, O. W. & R. G. Davies (1977). Imm's General Textbook of Entomology, 10th ed. (2 Volumes). Chapman and Hall, London.
An appendage in the broadest sense is an additional or subsidiary part existing on, or added to, something which can generally still function if the appendage has never existed or is later provided or grown, or will still perform a primary function if the appendage is removed.
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Arthropoda
Latreille, 1829
Subphyla and Classes
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Latreille, 1829
Subphyla and Classes
- Subphylum Trilobitomorpha
- Trilobita - trilobites (extinct)
- Subphylum Chelicerata
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Walking is the main form of animal locomotion on land, distinguished from running and crawling. When carried out in shallow waters, it is usually described as wading and when performed over a steeply rising object or an obstacle it becomes scrambling
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Latin}}}
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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hip is the bony projection of the femur which is known as the greater trochanter, and the overlying muscle and fat. The hip joint is the joint between the femur and acetabulum of the pelvis and its primary function is to support the weight of the body in both static
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The greater trochanter (great trochanter) of the femur is a large, irregular, quadrilateral eminence, situated at the junction of the neck with the upper part of the body.
It is directed a little lateralward and backward, and, in the adult, is about 1 cm.
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It is directed a little lateralward and backward, and, in the adult, is about 1 cm.
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The lesser trochanter (small trochanter) of the femur is a conical eminence, which varies in size in different subjects
It projects from the lower and back part of the base of the neck.
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It projects from the lower and back part of the base of the neck.
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The femur or thigh bone is the longest, most voluminous, and strongest bone of mammalian bodies. It forms part of the hip and part of the knee.
The word femur is Latin for thigh.
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The word femur is Latin for thigh.
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tibia is the larger of the two bones in the leg below the knee in vertebrates.
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In humans
The tibia or shin bone, in human anatomy, is found medial (towards the middle) and anterior (towards the front) to the other such bone, the fibula...... Click the link for more information.
tarsi are the cluster of bones in the foot between the tibia and fibula and the metatarsus. The bones of the tarsus do not belong to individual toes, whereas those of the metatarsus do. The joint between the tibia and fibula and the tarsus is called the ankle.
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The ischium forms the lower and back part of the hip bone. It is situated below the ilium. The word comes from the Greek ischion, meaning "hip." (Taber's, 1985)
It is divisible into three portions:
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It is divisible into three portions:
- Body of ischium
- Superior ramus of the ischium
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The metatarsus consists of the five long bones of the foot, which are numbered from the medial side (ossa metatarsalia I.-V.); each presents for examination a body and two extremities. These are analogous to the metacarpals of the hand.
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carpus is the cluster of bones in the hand between the radius and ulna and the metacarpus. The bones of the carpus do not belong to individual fingers, whereas those of the metacarpus do. The joint between the radius and ulna and the carpus is called the wrist.
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A finger is a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates. Normally humans have five digits on each hand (exceptions are polydactyly, hypodactyly and digit loss).
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The patella or kneecap is a thick, triangular bone which articulates with the femur and covers and protects the front of the knee joint. It is the largest sesamoid bone in the human body.
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The most recent common ancestor (MRCA) of any set of organisms is the most recent individual from which all organisms in the group are directly descended. The term is most frequently used of humans.
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Arthropoda
Latreille, 1829
Subphyla and Classes
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Latreille, 1829
Subphyla and Classes
- Subphylum Trilobitomorpha
- Trilobita - trilobites (extinct)
- Subphylum Chelicerata
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A homeobox is a DNA sequence found within genes that are involved in the regulation of development (morphogenesis) of animals, fungi and plants. Genes that have a homeobox are called homeobox genes and form the homeobox gene family.
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Parallelism may refer to:
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- Angle of parallelism, the angle at one vertex of a right hyperbolic triangle that has two hyperparallel sides
- Conscious parallelism, price-fixing between competitors in an oligopoly that occurs without an actual spoken agreement between the
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Cladistics is a philosophy of classification that arranges organisms only by their order of branching in an evolutionary tree and not by their morphological similarity, in the words of Luria et al. (1981).
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Thee Uniramia are a major group of Arthropoda, consisting of organisms with an exoskeleton, jointed appendages, and with legs that do not branch, namely the Hexapoda (insects and allies) and Myriapoda (centipedes, millipedes, and related forms).
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Insecta
Linnaeus, 1758
Orders
Subclass Apterygota
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Linnaeus, 1758
Orders
Subclass Apterygota
- * Archaeognatha (bristletails)
- * Thysanura (silverfish)
- * Infraclass Paleoptera (Probably paraphyletic)
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thorax is a division of an animal's body that lies between the head and the abdomen.
In mammals, the thorax is the region of the body formed by the sternum, the thoracic vertebrae and the ribs. It extends from the neck to the diaphragm, not including the upper limbs.
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In mammals, the thorax is the region of the body formed by the sternum, the thoracic vertebrae and the ribs. It extends from the neck to the diaphragm, not including the upper limbs.
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family (Latin: familia, plural familiae) is a rank, or a taxon in that rank. Exact details of formal nomenclature depend on the Nomenclature Code which applies.
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family (Latin: familia, plural familiae) is a rank, or a taxon in that rank. Exact details of formal nomenclature depend on the Nomenclature Code which applies.
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Diptera
Linnaeus, 1758
Suborders
Nematocera (includes Eudiptera)
Brachycera
True flies are insects of the Order Diptera (Greek: di = two, and pteron
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Linnaeus, 1758
Suborders
Nematocera (includes Eudiptera)
Brachycera
True flies are insects of the Order Diptera (Greek: di = two, and pteron
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Cecidomyiidae
Subfamilies
Cecidomyiidae (sometimes misspelled Cecidomyidae) is the correct name for the insects known as gall midges or gall gnats.
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Subfamilies
- Cecidomyiinae
- Lestremiinae
- Porricondylinae
Cecidomyiidae (sometimes misspelled Cecidomyidae) is the correct name for the insects known as gall midges or gall gnats.
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Orthoptera
Latreille, 1793
Extant suborders and superfamilies
Suborder Ensifera
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Latreille, 1793
Extant suborders and superfamilies
Suborder Ensifera
- Grylloidea
- Hagloidea
- Rhaphidophoroidea
- Schizodactyloidea
- Stenopelmatoidea
- Tettigonioidea
- Acridoidea
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