Членистоногие ноги
Нога членистоногих формой соединенного придатка членистоногих является , обычно используемого для ходьбы . Многие из терминов, используемых для сегментов членистоногих ног (называемых , имеют латинское быть путаются с терминами для костей: Coxa (это означает бедра , пл . : Coxae ), Trochanter , кость ( Pl происхождение, и могут бедренная . Podomeres ) PL .
Гомологии сегментов ног между группами трудно доказать и являются источником большого аргумента. Некоторые авторы позиционируют до одиннадцати сегментов на ногу для общего предка существующих самого последнего членистоногих [ 1 ] Но современные членистоногих имеют восемь или меньше. Это было аргументировано [ 2 ] [ 3 ] То, что наследственная нога не должна была быть настолько сложной, и что другие события, такие как последовательная потеря функции hox -Gene , могут привести к параллельным достижениям сегментов ног.
У членистоногих каждый из сегментов ног формулируется со следующим сегментом в шарнирном соединении и может сгибаться только в одной плоскости. Это означает, что для достижения тех же самых движений требуется большее количество сегментов, которые возможны у животных позвоночных, которые имеют вращательные шар-шар-сокеты у основания передних и задних конечностей. [ 4 ]
Бирам и однорамный
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Придатки членистоногих могут быть либо бирим , либо однорамными . Однорамная конечность включает в себя одну серию сегментов, прикрепленных к сквозным. Однако бирамная конечность разветвляется на два, и каждая ветвь состоит из серии сегментов, прикрепленных сквозных.
Внешняя ветвь (Ramus) придаток ракообразных известна как экзопод или экзоподит , в то время как внутренняя ветвь известна как эндопод или эндоподит . Другие структуры, помимо последних двух, называются Exciets (внешние структуры) и энтизий (внутренние структуры). Экзоподиты можно легко отличить от Exciets при владении внутренней мускулатурой. Экзоподиты иногда могут отсутствовать в некоторых группах ракообразных ( амфипод и изоподы ), и они полностью отсутствуют у насекомых. [ 5 ]
Ноги насекомых и бесчисленных мириподов однорамны. У ракообразных первые антенны однорамны, но вторые антенны являются биримными, как и ноги у большинства видов.
Какое -то время владение однорамными конечностями считалось общим, полученным характером , поэтому однорамные членистоногих были сгруппированы в таксон под названием Uniramia . В настоящее время считается, что несколько групп членистоногих эволюционировали однорамные конечности независимо от предков с биримными конечностями, поэтому этот таксон больше не используется.
Chelicerata
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Ноги арахнидов отличаются от насекомых от добавления двух сегментов по обе стороны от голени, коленника между бедренной костью и голенью и плюсневой кости (иногда называемой базитарсом) между большеберцовой кости и лапкой (иногда называемой телотарсом), создавая В общей сложности семь сегментов.
Тарс пауков имеет когти в конце, а также крючок, который помогает с ускорительностью в Интернете. Ноги паука также могут выполнять сенсорные функции, с волосками, которые служат сенсорными рецепторами, а также органом на лапке, который служит рецептором влажности, известным как орган лапса . [ 6 ]
Ситуация идентична в скорпионах , но с добавлением до-тарсуса за пределами лапки. Когти Скорпиона не являются по -настоящему ногами, но являются педипальпами , другой вид придатки , который также встречается у пауков и специализируется на хищничестве и спаривании.
В Limulus нет метатарси или претенсиси, оставляя шесть сегментов на ногу.
Ракообразные
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Ноги ракообразных разделены примитивно на семь сегментов, которые не следуют системе именования, используемой в других группах. Это: Coxa, основа, Ischium, Merus, Carpus, Propodus и Dactylus. В некоторых группах некоторые сегменты конечностей могут быть объединены вместе. Коготь ( чела ) лобстера или краба образуется из -за артикуляции дактила против роста проподуса. Термы ракообразных также различаются по тому, чтобы быть биримными, тогда как все другие существующие членистоногих имеют однорамные конечности.
Мириапода
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Множество ( Millipedes , Mentipedes и их родственники) имеют семь сегментированных ходячих ног, включающих Coxa, Trochanter, Prefemur, Femur, голень, лапсы и когти Tarsal. Бесчисленные ноги показывают различные модификации в разных группах. Во всех многоногах первая пара ног модифицирована в пару ядовитых клыков, которые называются Forcipules. В большинстве Millipedes одна или две пары пешеходных ног у взрослых мужчин модифицированы в структуры передачи сперматозоидов, называемые гоноподами . В некоторых Millipedes первая пара ног у мужчин может быть уменьшена до крошечных крючков или крючков, в то время как в других первая пара может быть увеличена.
Насекомые
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Насекомые и их родственники - это гексапод, имеющие шесть ног, соединенные с грудной клеткой , каждый с пятью компонентами. Для тела они являются Coxa, Trochanter, бедренной кости, голени и Tarsus. Каждый представляет собой единый сегмент, кроме лапки, которая может быть от трех до семи сегментов, каждый из которых называется Tarsomere .
Except in species in which legs have been lost or become vestigial through evolutionary adaptation, adult insects have six legs, one pair attached to each of the three segments of the thorax. They have paired appendages on some other segments, in particular, mouthparts, antennae and cerci, all of which are derived from paired legs on each segment of some common ancestor.
Some larval insects do however have extra walking legs on their abdominal segments; these extra legs are called prolegs. They are found most frequently on the larvae of moths and sawflies. Prolegs do not have the same structure as modern adult insect legs, and there has been a great deal of debate as to whether they are homologous with them.[7] Current evidence suggests that they are indeed homologous up to a very primitive stage in their embryological development,[8] but that their emergence in modern insects was not homologous between the Lepidoptera and Symphyta.[9] Such concepts are pervasive in current interpretations of phylogeny.[10]
In general, the legs of larval insects, particularly in the Endopterygota, vary more than in the adults. As mentioned, some have prolegs as well as "true" thoracic legs. Some have no externally visible legs at all (though they have internal rudiments that emerge as adult legs at the final ecdysis). Examples include the maggots of flies or grubs of weevils. In contrast, the larvae of other Coleoptera, such as the Scarabaeidae and Dytiscidae have thoracic legs, but no prolegs. Some insects that exhibit hypermetamorphosis begin their metamorphosis as planidia, specialised, active, legged larvae, but they end their larval stage as legless maggots, for example the Acroceridae.
Among the Exopterygota, the legs of larvae tend to resemble those of the adults in general, except in adaptations to their respective modes of life. For example, the legs of most immature Ephemeroptera are adapted to scuttling beneath underwater stones and the like, whereas the adults have more gracile legs that are less of a burden during flight. Again, the young of the Coccoidea are called "crawlers" and they crawl around looking for a good place to feed, where they settle down and stay for life. Their later instars have no functional legs in most species. Among the Apterygota, the legs of immature specimens are in effect smaller versions of the adult legs.[citation needed]
Fundamental morphology of insect legs
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A representative insect leg, such as that of a housefly or cockroach, has the following parts, in sequence from most proximal to most distal:
- coxa
- trochanter
- femur
- tibia
- tarsus
- pretarsus.
Associated with the leg itself there are various sclerites around its base. Their functions are articular and have to do with how the leg attaches to the main exoskeleton of the insect. Such sclerites differ considerably between unrelated insects.[7]
Coxa
[edit]The coxa is the proximal segment and functional base of the leg. It articulates with the pleuron and associated sclerites of its thoracic segment, and in some species it articulates with the edge of the sternite as well. The homologies of the various basal sclerites are open to debate. Some authorities suggest that they derive from an ancestral subcoxa. In many species, the coxa has two lobes where it articulates with the pleuron. The posterior lobe is the meron which is usually the larger part of the coxa. A meron is well developed in Periplaneta, the Isoptera, Neuroptera and Lepidoptera.
Trochanter
[edit]The trochanter articulates with the coxa but usually is attached rigidly to the femur. In some insects, its appearance may be confusing; for example it has two subsegments in the Odonata. In parasitic Hymenoptera, the base of the femur has the appearance of a second trochanter.
Femur
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In most insects, the femur is the largest region of the leg; it is especially conspicuous in many insects with saltatorial legs because the typical leaping mechanism is to straighten the joint between the femur and the tibia, and the femur contains the necessary massive bipennate musculature.
Tibia
[edit]The tibia is the fourth section of the typical insect leg. As a rule, the tibia of an insect is slender in comparison to the femur, but it generally is at least as long and often longer. Near the distal end, there is generally a tibial spur, often two or more. In the Apocrita, the tibia of the foreleg bears a large apical spur that fits over a semicircular gap in the first segment of the tarsus. The gap is lined with comb-like bristles, and the insect cleans its antennae by drawing them through.
Tarsus
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The ancestral tarsus was a single segment and in the extant Protura, Diplura and certain insect larvae the tarsus also is single-segmented. Most modern insects have tarsi divided into subsegments (tarsomeres), usually about five. The actual number varies with the taxon, which may be useful for diagnostic purposes. For example, the Pterogeniidae characteristically have 5-segmented fore- and mid-tarsi, but 4-segmented hind tarsi, whereas the Cerylonidae have four tarsomeres on each tarsus.
The distal segment of the typical insect leg is the pretarsus. In the Collembola, Protura and many insect larvae, the pretarsus is a single claw. On the pretarsus most insects have a pair of claws (ungues, singular unguis). Between the ungues, a median unguitractor plate supports the pretarsus. The plate is attached to the apodeme of the flexor muscle of the ungues. In the Neoptera, the parempodia are a symmetrical pair of structures arising from the outside (distal) surface of the unguitractor plate between the claws.[11] It is present in many Hemiptera and almost all Heteroptera.[11] Usually, the parempodia are bristly (setiform), but in a few species they are fleshy.[12] Sometimes the parempodia are reduced in size so as to almost disappear.[13] Above the unguitractor plate, the pretarsus expands forward into a median lobe, the arolium.
Webspinners (Embioptera) have an enlarged basal tarsomere on each of the front legs, containing the silk-producing glands.[14]
Under their pretarsi, members of the Diptera generally have paired lobes or pulvilli, meaning "little cushions". There is a single pulvillus below each unguis. The pulvilli often have an arolium between them or otherwise a median bristle or empodium, meaning the meeting place of the pulvilli. On the underside of the tarsal segments, there frequently are pulvillus-like organs or plantulae. The arolium, plantulae and pulvilli are adhesive organs enabling their possessors to climb smooth or steep surfaces. They all are outgrowths of the exoskeleton and their cavities contain blood. Their structures are covered with tubular tenent hairs, the apices of which are moistened by a glandular secretion. The organs are adapted to apply the hairs closely to a smooth surface so that adhesion occurs through surface molecular forces.[7][15]
Insects control the ungues through muscle tension on a long tendon, the "retractor unguis" or "long tendon". In insect models of locomotion and motor control, such as Drosophila (Diptera), locusts (Acrididae), or stick insects (Phasmatodea), the long tendon courses through the tarsus and tibia before reaching the femur. Tension on the long tendon is controlled by two muscles, one in the femur and one in the tibia, which can operate differently depending on how the leg is bent. Tension on the long tendon controls the claw, but also bends the tarsus and likely affects its stiffness during walking. [16]
Variations in functional anatomy of insect legs
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The typical thoracic leg of an adult insect is adapted for running (cursorial), rather than for digging, leaping, swimming, predation, or other similar activities. The legs of most cockroaches are good examples. However, there are many specialized adaptations, including:
- The forelegs of mole crickets (Gryllotalpidae) and some scarab beetle (Scarabaeidae) are adapted to burrowing in earth (fossorial).
- The raptorial forelegs of mantidflies (Mantispidae), mantises (Mantodea), and ambush bugs (Phymatinae) are adapted to seizing and holding prey in one way, while those of whirligig beetles Gyrinidae are long and adapted for grasping food or prey in quite a different way.
- The forelegs of some butterflies, such as many Nymphalidae, are reduced so greatly that only two pairs of functional walking legs remain.
- In most grasshoppers and crickets (Orthoptera), the hind legs are saltatorial; they have heavily bipinnately muscled femora and straight, long tibiae adapted to leaping and to some extent to defence by kicking. Flea beetles (Alticini) also have powerful hind femora that enable them to leap spectacularly.
- Other beetles with spectacularly muscular hind femora may not be saltatorial at all, but very clumsy; for example, particular species of bean weevils (Bruchinae) use their swollen hind legs for forcing their way out of the hard-shelled seeds of plants such as Erythrina in which they grew to adulthood.
- The legs of the Odonata, the dragonflies and damselflies, are adapted for seizing prey that the insects feed on while flying or while sitting still on a plant; they are nearly incapable of using them for walking.[7]
- The majority of aquatic insects use their legs only for swimming (natatorial), though many species of immature insects swim by other means such as by wriggling, undulating, or expelling water in jets.
Evolution and homology of arthropod legs
[edit]The embryonic body segments (somites) of different arthropods taxa have diverged from a simple body plan with many similar appendages which are serially homologous, into a variety of body plans with fewer segments equipped with specialised appendages.[17] The homologies between these have been discovered by comparing genes in evolutionary developmental biology.[18]
| Somite (body segment) |
Trilobite (Trilobitomorpha) 
|
Spider (Chelicerata) 
|
Centipede (Myriapoda) 
|
Insect (Hexapoda) 
|
Shrimp (Crustacea) 
|
|---|---|---|---|---|---|
| 1 | antennae | chelicerae (jaws and fangs) | antennae | antennae | 1st antennae |
| 2 | 1st legs | pedipalps | - | - | 2nd antennae |
| 3 | 2nd legs | 1st legs | mandibles | mandibles | mandibles (jaws) |
| 4 | 3rd legs | 2nd legs | 1st maxillae | 1st maxillae | 1st maxillae |
| 5 | 4th legs | 3rd legs | 2nd maxillae | 2nd maxillae | 2nd maxillae |
| 6 | 5th legs | 4th legs | collum (no legs) | 1st legs | 1st legs |
| 7 | 6th legs | - | 1st legs | 2nd legs | 2nd legs |
| 8 | 7th legs | - | 2nd legs | 3rd legs | 3rd legs |
| 9 | 8th legs | - | 3rd legs | - | 4th legs |
| 10 | 9th legs | - | 4th legs | - | 5th legs |
See also
[edit]References
[edit]- ^ 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. 70 (2): 236–255. doi:10.1139/z92-037.
- ^ Fryer, G. (1996). "Reflections on arthropod evolution". Biol. J. Linn. Soc. 58 (1): 1–55. doi:10.1111/j.1095-8312.1996.tb01659.x.
- ^ Schram, F. R. & S. Koenemann (2001). "Developmental genetics and arthropod evolution: part I, on legs". Evolution & Development. 3 (5): 343–354. doi:10.1046/j.1525-142X.2001.01038.x. PMID 11710766. S2CID 25997101.
- ^ Pat Willmer; Graham Stone; Ian Johnston (12 March 2009). Environmental Physiology of Animals. John Wiley & Sons. p. 329. ISBN 978-1-4443-0922-5.
- ^ Geoff A. Boxshall & Damià Jaume (2009). "Exopodites, Epipodites and Gills in Crustaceans" (PDF). Arthropod Systematics & Phylogeny. 67 (2). Museum für Tierkunde Dresden: 229–254. doi:10.3897/asp.67.e31699. Archived (PDF) from the original on 2019-04-26. Retrieved 2012-01-14.
- ^ Pechmann, Matthias (November 2010). "Patterning mechanisms and morphological diversity of spider appendages and their importance for spider evolution". Arthropod Structure & Development. 39 (6): 453–467. doi:10.1016/j.asd.2010.07.007. PMID 20696272. Retrieved 20 August 2020.
- ^ Jump up to: a b c d Richards, O. W.; Davies, R.G. (1977). Imms' General Textbook of Entomology: Volume 1: Structure, Physiology and Development Volume 2: Classification and Biology. Berlin: Springer. ISBN 0-412-61390-5.
- ^ Panganiban, Grace; Nagy, Lisa; Carroll, Sean B. (1994). "The role of the Distal-less gene in the development and evolution of insect limbs". Current Biology. 4 (8): 671–675. doi:10.1016/S0960-9822(00)00151-2. PMID 7953552. S2CID 22980014.
- ^ Suzuki, y; Palopoli, MF (октябрь 2001 г.). «Эволюция брюшных придаток насекомых: гомологичные или конвергентные признаки PROLEGS?». Dev Genes Evol . 211 (10): 486–92. doi : 10.1007/s00427-001-0182-3 . PMID 11702198 . S2CID 1163446 .
- ^ Galis, Frietson (1996). "The evolution of insects and vertebrates: homeobox genes and homology". Trends in Ecology & Evolution. 11 (10): 402–403. doi:10.1016/0169-5347(96)30038-4. PMID 21237897.
- ^ Jump up to: a b Friedemann, Katrin; Spangenberg, Rico; Yoshizawa, Kazunor; Beutel, Rolf G. (2013). "Evolution of attachment structures in the highly diverse Acercaria (Hexapoda)" (PDF). Cladistics. 30 (2): 170–201. doi:10.1111/cla.12030. PMID 34781597. S2CID 86195785. Archived from the original (PDF) on 25 January 2014. Retrieved 25 January 2014.
- ^ Schuh, Randall T. & Slater, James Alexander (1995). True Bugs of the World (Hemiptera:Heteroptera): Classification and Natural History. Ithaca, New York: Cornell University Press. p. 46. ISBN 978-0-8014-2066-5.
- ^ Goel, S. C. (1972). "Notes on the structure of the unguitractor plate in Heteroptera (Hemiptera)". Journal of Entomology Series A, General Entomology. 46 (2): 167–173. doi:10.1111/j.1365-3032.1972.tb00124.x.
- ^ Ross, Edward S. (1991). "Embioptera". In Naumann, I. D.; Carne, P. B.; et al. (eds.). The Insects of Australia. Volume 1 (2 ed.). Melbourne University Press. pp. 405–409.
- ^ Stanislav N Gorb. "Biological attachment devices: exploring nature's diversity for biomimetics Phil. Trans. R. Soc. A 2008; 366(1870): 1557-1574 doi:10.1098/rsta.2007.2172 1471-2962
- ^ RADNIKOW, G.; BÄSSLER, U. (1991-05-01). "Function of a Muscle Whose Apodeme Travels Through a Joint Moved by Other Muscles: Why the Retractor Unguis Muscle in Stick Insects is Tripartite and has no Antagonist". Journal of Experimental Biology. 157 (1): 87–99. doi:10.1242/jeb.157.1.87. ISSN 0022-0949.
- ^ Novartis Foundation; Hall, Brian (2008). Homology. John Wiley. p. 29. ISBN 978-0-470-51566-2.
- ^ Brusca, RC; Brusca, GJ (1990). Беспозвоночные . Sinauer Associates. п. 669 .
