79-499: Others, see list The Phalangiidae are a family of harvestmen with about 380 known species. The best known is Phalangium opilio . Dicranopalpus ramosus is an invasive species in Europe . It is not to be confused with the harvestman family Phalangodidae , which belongs to the suborder Laniatores . The name of the type genus is derived from Ancient Greek phalangion "harvestman". This harvestmen -related article
158-456: A pre-Linnaean work). In England, the Opiliones are called harvestmen, not because they appear at that season, but from a superstitious belief that if one is killed there will be a bad harvest that year. The interfamilial relationships within Opiliones are not yet fully resolved, although significant strides have been made in recent years to determine these relationships. The following list
237-421: A C shape (see image). The location of anatomical structures can also be described in relation to different anatomical landmarks . They are used in anatomy, surface anatomy, surgery, and radiology. Structures may be described as being at the level of a specific spinal vertebra , depending on the section of the vertebral column the structure is at. The position is often abbreviated. For example, structures at
316-618: A broad range is unusual in arachnids, which are typically pure predators. Most hunting harvestmen ambush their prey, although active hunting is also found. Because their eyes cannot form images, they use their second pair of legs as antennae to explore their environment. Unlike most other arachnids, harvestmen do not have a sucking stomach or a filtering mechanism. Rather, they ingest small particles of their food, thus making them vulnerable to internal parasites such as gregarines . Although parthenogenetic species do occur, most harvestmen reproduce sexually . Except from small fossorial species in
395-407: A distance. The Opiliones are known for having exceptionally long legs relative to their body size; however, some species are short-legged. As in all Arachnida, the body in the Opiliones has two tagmata , the anterior cephalothorax or prosoma , and the posterior 10-segmented abdomen or opisthosoma . The most easily discernible difference between harvestmen and spiders is that in harvestmen,
474-456: A further defence from predators because they can twitch for 60 seconds to an hour after detachment. This can also potentially serve as deflection from an attack and deceive a predator from attacking the animal. It has been shown to be successful against ants and spiders. The legs continue to twitch after they are detached because 'pacemakers' are located in the ends of the first long segment (femur) of their legs. These pacemakers send signals via
553-740: A long period. Indeed, one species discovered in China, Mesobunus martensi , fossilized by fine-grained volcanic ash around 165 million years ago, is hardly discernible from modern-day harvestmen and has been placed in the extant family Sclerosomatidae . The Swedish naturalist and arachnologist Carl Jakob Sundevall (1801–1875) honored the naturalist Martin Lister (1638–1712) by adopting Lister's term Opiliones for this order, known in Lister's days as "harvest spiders" or "shepherd spiders", from Latin opilio , "shepherd"; Lister characterized three species from England (although not formally describing them, being
632-428: A pair median eyes also have two sets of vestigial eyes: one median pair (homologous to those of horseshoe crabs and sea spiders ), and one lateral pair (homologous to facetted eyes of horseshoe crabs and insects). This discovery suggests that the neuroanatomy of harvestmen is more primitive than derived arachnid groups, like spiders and scorpions. It also showed that the four-eyed fossil harvestman previously discovered
711-418: A predator after direct or indirect contact, including thanatosis , freezing , bobbing, autotomy , fleeing, stridulation , retaliation and chemical secretions. Some animals respond to attacks by simulating an apparent death to avoid either detection or further attacks. Arachnids such as spiders practise this mechanism when threatened or even to avoid being eaten by female spiders after mating. Thanatosis
790-617: A predator. Armored harvestmen in Laniatores can often use their modified morphology as weapons. Many have spines on their pedipalps, back legs, or bodies. By pinching with their chelicerae and pedipalps, they can cause harm to a potential predator. Also this has been proven to increase survival against recluse spiders by causing injury, allowing the harvestman to escape from predation. Harvestmen are well known for being chemically protected. They exude strongly odored secretions from their scent glands, called ozopores , that act as
869-514: A scientifically neglected group. Description of new taxa has always been dependent on the activity of a few dedicated taxonomists. Carl Friedrich Roewer described about a third (2,260) of today's known species from the 1910s to the 1950s, and published the landmark systematic work Die Weberknechte der Erde (Harvestmen of the World) in 1923, with descriptions of all species known to that time. Other important taxonomists in this field include: Since
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#1732798671476948-516: A shield against predators; this is the most effective defense they use which creates a strong and unpleasant taste. In Cyphophthalmi the scent glands release naphthoquinones, chloro-naphthoquinones and aliphatic methyl ketones, Insidiatores use nitrogen-containing substances, terpenes, aliphatic ketones, and phenolics, while Grassatores use alkylated phenolics and benzoquinones, and Palpatores use substances like naphthoquinones, methyl- and ethyl-ketones. These secretions have successfully protected
1027-414: A standard set of terms to communicate clearly the position of a structure. Standard anatomical and zoological terms of location have been developed, usually based on Latin and Greek words, to enable all biological and medical scientists, veterinarians , doctors and anatomists to precisely delineate and communicate information about animal bodies and their organs, even though the meaning of some of
1106-403: A state in which a part further away is abnormally placed towards (varus) or away from (valgus) the midline. The terms proximal (from Latin proximus 'nearest') and distal (from Latin distare 'to stand away from') are used to describe parts of a feature that are close to or distant from the main mass of the body, respectively. Thus the upper arm in humans
1185-492: A variety of primary and secondary defences against predation, ranging from morphological traits such as body armour to behavioral responses to chemical secretions. Some of these defences have been attributed and restricted to specific groups of harvestmen. Primary defences help the harvestmen avoid encountering a potential predator and include crypsis , aposematism , and mimicry . Particular patterns or colour markings on harvestmen's bodies can reduce detection by disrupting
1264-452: A wound on the upper arm, but proximal to a wound on the lower arm. The terms are also applied to internal anatomy, such as to the reproductive tract of snails . Unfortunately, different authors use the terms in opposite senses. Some consider "distal" as further from a point of origin near the centre of the body and others as further from where the organ reaches the body's surface; or other points of origin may be envisaged. This terminology
1343-672: Is a stub . You can help Misplaced Pages by expanding it . Harvestmen The Opiliones (formerly Phalangida) are an order of arachnids , colloquially known as harvestmen , harvesters , harvest spiders , or daddy longlegs . As of July 2024 , over 6,650 species of harvestmen have been discovered worldwide, although the total number of extant species may exceed 10,000. The order Opiliones includes five suborders: Cyphophthalmi , Eupnoi , Dyspnoi , Laniatores , and Tetrophthalmi , which were named in 2014. Representatives of each extant suborder can be found on all continents except Antarctica . Well-preserved fossils have been found in
1422-572: Is a compilation of interfamilial relationships recovered from several recent phylogenetic studies, although the placement and even monophyly of several taxa are still in question. The family Stygophalangiidae (one species, Stygophalangium karamani ) from underground waters in North Macedonia is sometimes misplaced in the Phalangioidea. It is not a harvestman. Despite their long history, few harvestman fossils are known. This
1501-413: Is also employed in molecular biology and therefore by extension is also used in chemistry, specifically referring to the atomic loci of molecules from the overall moiety of a given compound. Central and peripheral refer to the distance towards and away from the centre of something. That might be an organ, a region in the body, or an anatomical structure. For example, the central nervous system and
1580-485: Is also used for two other distantly related groups of arthropods , the crane flies of the superfamily Tipuloidea , and the cellar spiders of the family Pholcidae, (commonly referred to as "daddy long-leg spiders") most likely because of their similar appearance. Harvestmen are also referred to as "shepherd spiders" in reference to how their unusually long legs reminded observers of the ways that some European shepherds used stilts to better observe their wandering flocks from
1659-427: Is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and anatomical axes . The meaning of terms that are used can change depending on whether an organism is bipedal or quadrupedal . Additionally, for some animals such as invertebrates , some terms may not have any meaning at all; for example, an animal that
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#17327986714761738-495: Is formed by extensions of the coxae of the pedipalps and the first pair of legs. Most Opiliones, except for Cyphophthalmi, have long been thought to have a single pair of camera-type eyes in the middle of the head, oriented sideways. Eyes in Cyphophthalmi, when present, are located laterally, near the ozopores. A 305-million-year-old fossilized harvestman with two pairs of eyes was reported in 2014. This find suggested that
1817-522: Is in rainforest patches in northwest Argentina which are in an area being dramatically destroyed by humans. The cave-living Picunchenops spelaeus is apparently endangered through human action. So far, no harvestman has been included in any kind of a Red List in Argentina, so they receive no protection. Maiorerus randoi has only been found in one cave in the Canary Islands . It is included in
1896-513: Is mainly due to their delicate body structure and terrestrial habitat, making them unlikely to be found in sediments. As a consequence, most known fossils have been preserved within amber . The oldest known harvestman, from the 410-million-year-old Devonian Rhynie chert, displayed almost all the characteristics of modern species, placing the origin of harvestmen in the Silurian , or even earlier. A recent molecular study of Opiliones, however, dated
1975-404: Is most likely a member of the suborder Eupnoi (true daddy-longlegs). Harvestmen have a pair of prosomatic defensive scent glands ( ozopores ) that secrete a peculiar-smelling fluid when disturbed. In some species, the fluid contains noxious quinones . They do not have book lungs , and breathe through tracheae . A pair of spiracles is located between the base of the fourth pair of legs and
2054-402: Is proximal and the hand is distal. "Proximal and distal" are frequently used when describing appendages , such as fins , tentacles , and limbs . Although the direction indicated by "proximal" and "distal" is always respectively towards or away from the point of attachment, a given structure can be either proximal or distal in relation to another point of reference. Thus the elbow is distal to
2133-515: Is radially symmetrical will have no anterior surface, but can still have a description that a part is close to the middle ("proximal") or further from the middle ("distal"). International organisations have determined vocabularies that are often used as standards for subdisciplines of anatomy. For example, Terminologia Anatomica for humans and Nomina Anatomica Veterinaria for animals. These allow parties that use anatomical terms, such as anatomists , veterinarians , and medical doctors , to have
2212-402: Is rarely used in human anatomy, apart from embryology, and refers more to the front of the face than the superior aspect of the organism. Similarly, the term "caudal" is used more in embryology and only occasionally used in human anatomy. This is because the brain is situated at the superior part of the head whereas the nose is situated in the anterior part. Thus, the "rostrocaudal axis" refers to
2291-481: Is roughly symmetrical. To do this, distinct ends of an organism are chosen, and the axis is named according to those directions. An organism that is symmetrical on both sides has three main axes that intersect at right angles . An organism that is round or not symmetrical may have different axes. Example axes are: Examples of axes in specific animals are shown below. Several terms are commonly seen and used as prefixes : Other terms are used as suffixes , added to
2370-495: Is seen with multiple long-legged species in the Leiobunum clade that either drop and run, or drop and remain motionless. This is also seen when disturbing an aggregation of multiple individuals, where they all scatter. Multiple species within the Laniatores and Dyspnoi possess stridulating organs, which are used as intraspecific communication and have also been shown to be used as a second line of defense when restrained by
2449-452: Is the voluntary amputation of an appendage and is employed to escape when restrained by a predator. Eupnoi individuals, more specifically sclerosomatid harvestmen, commonly use this strategy in response to being captured. This strategy can be costly because harvestmen do not regenerate their legs, and leg loss reduces locomotion, speed, climbing ability, sensory perception, food detection, and territoriality. Autotomised legs provide
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2528-617: Is thought to be commonly used during daylight, when they could be easily seen by any predators. Other harvestmen may exhibit mimicry to resemble other species' appearances. Some Gonyleptidae individuals that produce translucid secretions have orange markings on their carapaces . This may have an aposematic role by mimicking the colouration of glandular emissions of two other quinone-producing species. Mimicry ( Müllerian mimicry ) occurring between Brazilian harvestmen that resemble others could be explained by convergent evolution . Secondary defences allow for harvestmen to escape and survive from
2607-458: Is to the head or tail of an animal. To describe how close to the head of an animal something is, three distinct terms are used: For example, in horses , the eyes are caudal to the nose and rostral to the back of the head. These terms are generally preferred in veterinary medicine and not used as often in human medicine. In humans, "cranial" and "cephalic" are used to refer to the skull, with "cranial" being used more commonly. The term "rostral"
2686-434: Is to the midline, or the medial plane. Lateral (from Latin lateralis 'to the side') describes something to the sides of an animal, as in "left lateral" and "right lateral". Medial (from Latin medius 'middle') describes structures close to the midline, or closer to the midline than another structure. For example, in a human, the arms are lateral to the torso . The genitals are medial to
2765-599: Is used as a second line of defence when detected by a potential predator and is commonly observed within the Dyspnoi and Laniatores suborders, with individuals becoming rigid with legs either retracted or stretched. Freezing – or the complete halt of movement – has been documented in the family Sclerosomatidae. While this can mean an increased likelihood of immediate survival, it also leads to reduced food and water intake. To deflect attacks and enhance escape, long-legged species – commonly known as daddy long-legs – from
2844-576: The Cenozoic , three from the Mesozoic , and at least seven from the Paleozoic . Anatomical terms of location Standard anatomical terms of location are used to describe unambiguously the anatomy of animals , including humans . The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position . This position provides a definition of what
2923-516: The Devonian Rhynie chert , 410 million years ago, already show characteristics like tracheae and sexual organs, indicating that the group has lived on land since that time. Despite being similar in appearance to, and often confused with, spiders, they are probably closely related to the scorpions , pseudoscorpions , and solifuges ; these four orders form the clade Dromopoda . The Opiliones have remained almost unchanged morphologically over
3002-610: The Eupnoi suborder, use two mechanisms. One is bobbing, for which these particular individuals bounce their bodies. It potentially serves to confuse and deflect any identification of the exact location of their bodies. This can be a deceiving mechanism to avoid predation when they are in a large aggregation of individuals, which are all trembling at the same time. Cellar spiders ( Pholcidae ) that are commonly mistaken for daddy long-legs (Opiliones) also exhibit this behavior when their webs are disturbed or even during courtship. Autotomy
3081-579: The Laniatores , and more than 70,000 in certain Eupnoi . Gregarious behavior is likely a strategy against climatic odds, but also against predators, combining the effect of scent secretions, and reducing the probability of any particular individual being eaten. Harvestmen clean their legs after eating by drawing each leg in turn through their jaws. Predators of harvestmen include a variety of animals, including some mammals, amphibians, and other arachnids like spiders and scorpions. Opiliones display
3160-438: The anterior superior iliac spine , the medial malleolus or the medial epicondyle . Anatomical lines are used to describe anatomical location. For example, the mid-clavicular line is used as part of the cardiac exam in medicine to feel the apex beat of the heart . Special terms are used to describe the mouth and teeth. Fields such as osteology , palaeontology and dentistry apply special terms of location to describe
3239-449: The head . Anterior (from Latin ante 'before') describes what is in front, and posterior (from Latin post 'after') describes what is to the back of something. For example, for a dog the nose is anterior to the eyes and the tail is considered the most posterior part; for many fish the gill openings are posterior to the eyes but anterior to the tail. These terms describe how close something
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3318-473: The leaf litter found in their environments. Some hard-bodied harvestmen have epizoic cyanobacteria and liverworts growing on their bodies that suggest potential benefits for camouflage against large backgrounds to avoid detection by diurnal predators. Some harvestmen have elaborate and brightly coloured patterns or appendages which contrast with the body colouration, potentially serving as an aposematic warning to potential predators. This mechanism
3397-648: The neuraxis is different between the two groups, and so is what is considered the standard anatomical position , such as how humans tend to be standing upright and with their arms reaching forward. Thus, the "top" of a human is the head, whereas the "top" of a dog would be the back, and the "top" of a flounder may be on either the left or right side. Unique terms are also used to describe invertebrates as well, because of their wider variety of shapes and symmetry. Because animals can change orientation with respect to their environment, and because appendages like limbs and tentacles can change position with respect to
3476-467: The pectoralis major muscle). In radiology , an X-ray image may be said to be "anteroposterior", indicating that the beam of X-rays, known as its projection, passes from their source to patient's anterior body wall first, then through the body to exit through posterior body wall and into the detector/film to produce a radiograph. The opposite is true for the term "posteroanterior," while side-to-side projections are known as either "lateromedial" (from
3555-415: The peripheral nervous systems . Central (from Latin centralis ) describes something close to the centre. For example, the great vessels run centrally through the body; many smaller vessels branch from these. Peripheral (from Latin peripheria , originally from Ancient Greek ) describes something further away from the centre of something. For example, the arm is peripheral to
3634-573: The scutum , which in most such species is fused with the carapace . Some such Opiliones only have this shield in the males. In some species, the two posterior abdominal segments are reduced. Some of them are divided medially on the surface to form two plates beside each other. The second pair of legs is longer than the others and function as antennae or feelers. In short-legged species, this may not be obvious. The feeding apparatus ( stomotheca ) differs from most arachnids in that Opiliones can swallow chunks of solid food, not only liquids. The stomotheca
3713-486: The 1990s, study of the biology and ecology of harvestmen has intensified, especially in South America . Early work on the developmental biology of Opiliones from the mid-20th century was resurrected by Prashant P. Sharma , who established Phalangium opilio as a model system for the study of arachnid comparative genomics and evolutionary-developmental biology . Harvestmen are ancient arachnids . Fossils from
3792-717: The 400-million-year-old Rhynie cherts of Scotland, and 305-million-year-old rocks in France. These fossils look surprisingly modern, indicating that their basic body shape developed very early on, and, at least in some taxa, has changed little since that time. Their phylogenetic position within the Arachnida is disputed; their closest relatives may be camel spiders (Solifugae) or a larger clade comprising horseshoe crabs, Ricinulei, and Arachnopulmonata (scorpions, pseudoscorpions, and Tetrapulmonata). Although superficially similar to and often misidentified as spiders (order Araneae ),
3871-563: The Brazilian national list of endangered species, all of them cave-dwelling: Giupponia chagasi , Iandumoema uai , Pachylospeleus strinatii and Spaeleoleptes spaeleus . Several Opiliones in Argentina appear to be vulnerable, if not endangered. These include Pachyloidellus fulvigranulatus , which is found only on top of Cerro Uritorco , the highest peak in the Sierras Chicas chain (provincia de Cordoba) and Pachyloides borellii
3950-840: The Catálogo Nacional de especies amenazadas (National catalog of threatened species) from the Spanish government. Texella reddelli and Texella reyesi are listed as endangered species in the United States. Both are from caves in central Texas . Texella cokendolpheri from a cave in central Texas and Calicina minor , Microcina edgewoodensis , Microcina homi , Microcina jungi , Microcina leei , Microcina lumi , and Microcina tiburona from around springs and other restricted habitats of central California are being considered for listing as endangered species, but as yet receive no protection. An urban legend claims that
4029-532: The Opiliones are a distinct order that is not closely related to spiders. They can be easily distinguished from long-legged spiders by their fused body regions and single pair of eyes in the middle of the cephalothorax . Spiders have a distinct abdomen that is separated from the cephalothorax by a constriction, and they have three to four pairs of eyes, usually around the margins of the cephalothorax. English speakers may colloquially refer to species of Opiliones as "daddy longlegs" or "granddaddy longlegs", but this name
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#17327986714764108-406: The abdomen, with one opening on each side. In more active species, spiracles are also found upon the tibia of the legs. They have a gonopore on the ventral cephalothorax, and the copulation is direct as male Opiliones have a penis , unlike other arachnids. All species lay eggs . Typical body length does not exceed 7 mm (0.28 in), and some species are smaller than 1 mm, although
4187-500: The animals' outlines or providing camouflage. Markings on legs can cause an interruption of the leg outline and loss of leg proportion recognition. Darker colourations and patterns function as camouflage when they remain motionless. Within the genus Leiobunum are multiple species with cryptic colouration that changes over ontogeny to match the microhabitat used at each life stage. Many species have also been able to camouflage their bodies by covering with secretions and debris from
4266-400: The body in a standing position with arms at the side and palms facing forward, with thumbs out and to the sides. Many anatomical terms can be combined, either to indicate a position in two axes simultaneously or to indicate the direction of a movement relative to the body. For example, "anterolateral" indicates a position that is both anterior and lateral to the body axis (such as the bulk of
4345-570: The body. These terms refer to the distance of a structure from the surface. Deep (from Old English ) describes something further away from the surface of the organism. For example, the external oblique muscle of the abdomen is deep to the skin. "Deep" is one of the few anatomical terms of location derived from Old English rather than Latin – the anglicised Latin term would have been "profound" (from Latin profundus 'due to depth'). Superficial (from Latin superficies 'surface') describes something near
4424-417: The closeness to the midline of the dental arch. Terms used to describe structures include "buccal" (from Latin bucca 'cheek') and "palatal" (from Latin palatum 'palate') referring to structures close to the cheek and hard palate respectively. Several anatomical terms are particular to the hands and feet. Additional terms may be used to avoid confusion when describing
4503-421: The connection between the cephalothorax and abdomen is broad, so that the body appears to be a single oval structure. Other differences include the fact that Opiliones have no venom glands in their chelicerae and thus pose no danger to humans. They also have no silk glands and therefore do not build webs. In some highly derived species, the first five abdominal segments are fused into a dorsal shield called
4582-421: The end of words: Superior (from Latin super 'above') describes what is above something and inferior (from Latin inferus 'below') describes what is below it. For example, in the anatomical position , the most superior part of the human body is the head and the most inferior is the feet. As a second example, in humans, the neck is superior to the chest but inferior to
4661-609: The eyes in Cyphophthalmi are not homologous to the eyes of other harvestmen. Many cave-adapted species are eyeless, such as the Brazilian Caecobunus termitarum ( Grassatores ) from termite nests, Giupponia chagasi ( Gonyleptidae ) from caves, most species of Cyphophthalmi, and all species of the Guasiniidae . However, recent work studying the embryonic development of the species Phalangium opilio and some Laniatores revealed that harvestman in addition to
4740-417: The hand') is commonly used to describe the front of the hand, and dorsal is the back of the hand. For example, the top of a dog 's paw is its dorsal surface; the underside, either the palmar (on the forelimb) or the plantar (on the hindlimb) surface. The palmar fascia is palmar to the tendons of muscles which flex the fingers, and the dorsal venous arch is so named because it is on the dorsal side of
4819-490: The harvestman is the most venomous animal in the world but possesses fangs too short or a mouth too round and small to bite a human, rendering it harmless (the same myth applies to Pholcus phalangioides and the crane fly , which are both also called a "daddy longlegs"). None of the known species of harvestmen have venom glands; their chelicerae are not hollowed fangs but grasping claws that are typically very small and not strong enough to break human skin. Harvestmen are
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#17327986714764898-569: The harvestmen against wandering spiders ( Ctenidae ), wolf spiders (Lycosidae) and Formica exsectoides ants. However, these chemical irritants are not able to prevent four species of harvestmen being preyed upon by the black scorpion Bothriurus bonariensis ( Bothriuridae ). These secretions contain multiple volatile compounds that vary among individuals and clades. All troglobitic species (of all animal taxa) are considered to be at least threatened in Brazil . Four species of Opiliones are on
4977-575: The largest known species, Trogulus torosus ( Trogulidae ), grows as long as 22 mm (0.87 in). The leg span of many species is much greater than the body length and sometimes exceeds 160 mm (6.3 in) and to 340 mm (13 in) in Southeast Asia. Most species live for a year. Many species are omnivorous , eating primarily small insects and all kinds of plant material and fungi . Some are scavengers , feeding upon dead organisms, bird dung, and other fecal material. Such
5056-512: The legs. Temporal has a similar meaning to lateral but is restricted to the head. The terms "left" and "right" are sometimes used, or their Latin alternatives ( Latin : dexter , lit. 'right'; Latin : sinister , lit. 'left'). However, it is preferred to use more precise terms where possible. Terms derived from lateral include: Varus (from Latin 'bow-legged') and valgus (from Latin 'knock-kneed' ) are terms used to describe
5135-448: The level of the fourth cervical vertebra may be abbreviated as "C4", at the level of the fourth thoracic vertebra "T4", and at the level of the third lumbar vertebra "L3". Because the sacrum and coccyx are fused, they are not often used to provide the location. References may also take origin from superficial anatomy , made to landmarks that are on the skin or visible underneath. For example, structures may be described relative to
5214-401: The main body, terms to describe position need to refer to an animal when it is in its standard anatomical position . This means descriptions as if the organism is in its standard anatomical position, even when the organism in question has appendages in another position. This helps avoid confusion in terminology when referring to the same organism in different postures. In humans, this refers to
5293-571: The male is solely responsible for guarding the eggs resulting from multiple partners, often against egg-eating females , and cleaning the eggs regularly. Paternal care has evolved at least three times independently: once in the clade Progonyleptoidellinae + Caelopyginae, once in the Gonyleptinae, and once in the Heteropachylinae. Maternal care in opiliones probably evolved due to natural selection, while paternal care appears to be
5372-435: The males defend territories. In some species, males also exhibit post-copulatory behavior in which the male specifically seeks out and shakes the female's sensory leg. This is believed to entice the female into mating a second time. The female lays her eggs shortly after mating to several months later. Some species build nests for this purpose. A unique feature of harvestmen is that some species practice parental care, in which
5451-456: The mouth and teeth. This is because although teeth may be aligned with their main axes within the jaw, some different relationships require special terminology as well; for example, teeth also can be rotated, and in such contexts terms like "anterior" or "lateral" become ambiguous. For example, the terms "distal" and "proximal" are also redefined to mean the distance away or close to the dental arch , and "medial" and "lateral" are used to refer to
5530-424: The nerves to the muscles to extend the leg and then the leg relaxes between signals. While some harvestman's legs twitch for a minute, others have been recorded to twitch up to an hour. The twitching has been hypothesised to function as an evolutionary advantage by keeping the attention of a predator while the harvestman escapes. Individuals that are able to detect potential threats can flee rapidly from attack. This
5609-584: The origin of the order at about 473 million years ago (Mya), during the Ordovician. No fossils of the Cyphophthalmi or Laniatores much older than 50 million years are known, despite the former presenting a basal clade , and the latter having probably diverged from the Dyspnoi more than 300 Mya. Naturally, most finds are from comparatively recent times. More than 20 fossil species are known from
5688-400: The outer surface of the organism. For example, in skin , the epidermis is superficial to the subcutis . These two terms, used in anatomy and embryology , describe something at the back ( dorsal ) or front/belly ( ventral ) of an organism. The dorsal (from Latin dorsum 'back') surface of an organism refers to the back, or upper side, of an organism. If talking about
5767-402: The outside of the left or right side of the body toward the inside) or "mediolateral"(from the inside of that side of the body toward the outside. The same logic is applied to all planes of the body and, thus top-to-bottom or bottom-to-top X-ray projections are known as "superoinferior" and "inferosuperior," respectively. However, within the diagnostic imaging industry, for this particular example,
5846-746: The result of sexual selection. Depending on circumstances such as temperature, the eggs may hatch at any time after the first 20 days, up to about half a year after being laid. Harvestmen variously pass through four to eight nymphal instars to reach maturity, with most known species having six instars. Most species are nocturnal and colored in hues of brown, although a number of diurnal species are known, some of which have vivid patterns in yellow, green, and black with varied reddish and blackish mottling and reticulation. Many species of harvestmen easily tolerate members of their own species, with aggregations of many individuals often found at protected sites near water. These aggregations may number 200 individuals in
5925-442: The skull, the dorsal side is the top. The ventral (from Latin venter 'belly') surface refers to the front, or lower side, of an organism. For example, in a fish, the pectoral fins are dorsal to the anal fin , but ventral to the dorsal fin . The terms are used in other contexts; for example dorsal and ventral gun turrets on a bomber aircraft. Specific terms exist to describe how close or far something
6004-437: The suborder Cyphophthalmi, where the males deposit a spermatophore , mating involves direct copulation. The females store the sperm, which is aflagellate and immobile, at the tip of her ovipositor. The eggs are fertilized during oviposition. The males of some species offer a secretion (nuptial gift) from their chelicerae to the female before copulation. Sometimes, the male guards the female after copulation, and in many species,
6083-460: The surfaces of the hand and what is the "anterior" or "posterior" surface. The term "anterior", while anatomically correct, can be confusing when describing the palm of the hand; Similarly is "posterior", used to describe the back of the hand and arm. This confusion can arise because the forearm can pronate and supinate and flip the location of the hand. For improved clarity, the directional term palmar (from Latin palma 'palm of
6162-429: The terms "cranial" (towards the head) and "caudal" (towards the tail, or, downwards, away from the head) are known interchangeable alternatives to the previous two projection terms. Combined terms were once generally hyphenated, but the modern tendency is to omit the hyphen. Anatomical terms describe structures with relation to four main anatomical planes : The axes of the body are lines drawn about which an organism
6241-404: The terms often is context-sensitive. Much of this information has been standardised in internationally agreed vocabularies for humans ( Terminologia Anatomica ) and animals ( Nomina Anatomica Veterinaria ). Different terms are used for groups of creatures with different body layouts, such as bipeds (creatures that stand on two feet, such as humans) and quadrupeds . The reasoning is that
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