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52-423: Generally organisms with a larval stage undergo metamorphosis, and during metamorphosis the organism loses larval characteristics. The word metamorphosis derives from Ancient Greek μεταμόρφωσις , "transformation, transforming", from μετα- ( meta- ), "after" and μορφή ( morphe ), "form". In insects, growth and metamorphosis are controlled by hormones synthesized by endocrine glands near

104-498: A yolk sac ), then to motile larvae (often known as fingerlings due to them roughly reaching the length of a human finger ) that have to forage for themselves after the yolk sac resorbs, and then to the juvenile stage where the fish progressively start to resemble adult morphology and behaviors until finally reaching sexual maturity . In typical amphibian development, eggs are laid in water and larvae are adapted to an aquatic lifestyle. Frogs , toads , and newts all hatch from

156-430: A black border. Additionally, tobacco hornworms have red horns, while tomato hornworms have dark blue or black horns. A mnemonic to remember the markings is tobacco hornworms have straight white lines like cigarettes, while tomato hornworms have V-shaped markings (as in "vine-ripened" tomatoes). M. sexta has mechanisms for selectively sequestering and secreting the neurotoxin nicotine present in tobacco. M. sexta

208-435: A butterfly 2 – The pupa is now spewing the thread to form chrysalis 3 – The chrysalis is fully formed 4 – Adult butterfly coming out of the chrysalis In cephalochordata , metamorphosis is iodothyronine -induced and it could be an ancestral feature of all chordates . Some fish, both bony fish (Osteichthyes) and jawless fish (Agnatha) , undergo metamorphosis. Fish metamorphosis is typically under strong control by

260-647: A complete metamorphosis, including a pupal or resting stage between the larval and adult forms. A number of hypotheses have been proposed to explain the evolution of holometaboly from hemimetaboly, mostly centering on whether or not the intermediate stages of hemimetabolous forms are homologous in origin to the pupal stage of holometabolous forms. According to a 2009 study, temperature plays an important role in insect development as individual species are found to have specific thermal windows that allow them to progress through their developmental stages. These windows are not significantly affected by ecological traits, rather,

312-410: A considerable role during physiological processes of multicellular organisms, particularly during embryogenesis , and metamorphosis. Additional research in 2019 found that both autophagy and apoptosis , the two ways programmed cell death occur, are processes undergone during insect metamorphosis. Below is the sequence of steps in the metamorphosis of the butterfly (illustrated): 1 – The larva of

364-461: A dead or dying caterpillar. The pupal stage lasts approximately 14–18 days under laboratory conditions (17 hours light, 7 hours dark, 27 °C). When reared on a short-day photoperiod (12 hours light, 12 hours dark), pupae enter a state of diapause that can last several months. During the pupal stage, structures of the adult moth form within the pupal case, which is shed during eclosion (adult emergence). Adult M. sexta have narrow wings with

416-583: A distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population. Animals in the larval stage will consume food to fuel their transition into the adult form. In some organisms like polychaetes and barnacles , adults are immobile but their larvae are mobile, and use their mobile larval form to distribute themselves. These larvae used for dispersal are either planktotrophic (feeding) or lecithotrophic (non-feeding) . Some larvae are dependent on adults to feed them. In many eusocial Hymenoptera species,

468-658: A gene called cytochrome P450 6B46 (CYP6B46) that converts nicotine into a metabolite. About 0.65% of nicotine metabolites are transported from the gut to the hemolymph , where they are reconverted to nicotine and released into the air from the tobacco hornworm's spiracles. The emitted nicotine is used as a way to deter spiders, a practice known as “toxic halitosis.” In one study, tobacco hornworms that fed from nicotine-deficient plants or expressed low levels of CYP6B46 were more susceptible to wolf spider predation. Tobacco hornworm caterpillars emit short clicking sounds from their mandibles when they are being attacked. This sound production

520-419: A more gradual metamorphosis to the migrating phase. In the pre-adult freshwater stage, the eel also has phenotypic plasticity because fish-eating eels develop very wide mandibles, making the head look blunt. Leptocephali are common, occurring in all Elopomorpha ( tarpon - and eel -like fish). Most other bony fish undergo metamorphosis initially from egg to immotile larvae known as sac fry ( fry with

572-419: A relatively long, spiral‐shaped gut to digest that diet. Recent studies suggest tadpoles do not have a balanced homeostatic feedback control system until the beginning stages of metamorphosis. At this point, their long gut shortens and begins favoring the diet of insects. Rapid changes in the body can then be observed as the lifestyle of the frog changes completely. The spiral‐shaped mouth with horny tooth ridges

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624-462: A small peripheral desensitization for salicin, concluding that Schoonhoven erred, and that habituation in this case is centrally mediated. Tobacco hornworms are considered pests because they feed on the upper leaves of tobacco plants and leave green or black droppings on the plants. As adults, they do not damage plants since they feed on nectar. Tobacco hornworm larvae prefer humid environments. When dehydrated, tobacco hornworm larvae will move towards

676-428: A source of water or to an area with a high relative level of humidity. They use their antennae to locate water to drink . Nicotine is poisonous to most animals that use muscles to move because nicotine targets the acetylcholine receptor at the neuromuscular junction . However, the tobacco hornworm is capable of metabolizing nicotine from the tobacco plant and using nicotine as a defense against predators. It possesses

728-503: A steroidal glycoside found in those particular plants (del Campo et al., 2001). Salicin is a distasteful phagodeterrent , found only in Salix spp. while caffeine is a phagodeterrent that is actually toxic. Schoonhoven 1969 found that M. sexta habituation to salicin is mediated by desensitization of the deterrence associated peripheral neurons and Glendinning et al. 1999 the same for caffeine. However Glendinning et al. 2001 find only

780-585: A vertical surface at night, and can last several hours, with the male and female facing in opposite positions, their posterior ends touching. After mating, females deposit their fertilized eggs on foliage, usually on the underside of leaves. Like Drosophila melanogaster , M. sexta is commonly used as a model organism for experiments. They are frequently studied in the laboratory due to their large size and relative ease of rearing. They may be reared on host plants, such as tobacco and tobacco relatives, tomato plants, or wheat-germ-based artificial diet. Their rearing

832-431: A wing span of approximately 100 mm. M. sexta moths are nectarivorous and feed on flowers, demonstrating a remarkable ability to hover. Adults are sexually dimorphic . Males are identifiable by their broader antennae and the presence of claspers at the end of the abdomen. Female moths are typically ready to mate one week after eclosion , and do so only once. Males may mate many times. Mating generally occurs on

884-429: Is a common model organism , especially in neurobiology , due to its easily accessible nervous system and short life cycle. Due to its immense size M. sexta is big enough for medical imaging modalities (like CT , MRI , or PET ) and used as a model in imaging and gut inflammation. It is used in a variety of biomedical and biological scientific experiments. It can be easily raised on a wheat-germ-based diet. The larva

936-442: Is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects , some arachnids , amphibians , or cnidarians typically have a larval phase of their life cycle . A larva's appearance is generally very different from the adult form ( e.g. caterpillars and butterflies ) including different unique structures and organs that do not occur in

988-518: Is based on Antonio Berlese classification in 1913. There are four main types of endopterygote larvae types: Manduca sexta Manduca sexta is a moth of the family Sphingidae present through much of the Americas . The species was first described by Carl Linnaeus in his 1763 Centuria Insectorum . Commonly known as the Carolina sphinx moth and the tobacco hawk moth (as adults) and

1040-533: Is consumed. When they start to "wander", they are about to pupate, so are placed in a pupation chamber. Pupation chambers are holes drilled into a wood board. The Manduca larvae are sealed in the chamber using a stopper and allowed to pupate. After pupation, the pupae are placed in a breeding or colony chamber to eclose . Providing a cup of sugar water and a tobacco (or related) plant will allow mated females to oviposit fertile eggs, which can then be reared. When fed an artificial diet, Manduca larvae do not consume

1092-554: Is iodothyronine-induced and an ancestral feature of all chordates . All three categories of metamorphosis can be found in the diversity of insects, including no metamorphosis ("ametaboly"), incomplete or partial metamorphosis ("hemimetaboly"), and complete metamorphosis ("holometaboly"). While ametabolous insects show very little difference between larval and adult forms (also known as " direct development "), both hemimetabolous and holometabolous insects have significant morphological and behavioral differences between larval and adult forms,

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1144-505: Is large, and thus it is relatively easy to dissect it and isolate its organs. M. sexta has a short life cycle, lasting about 30 to 50 days. In most areas, M. sexta has about two generations per year, but can have three or four generations per year in Florida. M. sexta eggs are spherical, approximately 1.5 millimeters in diameter, and translucent green. They typically hatch two to four days after they are laid. Eggs are normally found on

1196-421: Is outside the parental body, development is subject to many adaptations due to specific ecological circumstances. For this reason tadpoles can have horny ridges for teeth, whiskers, and fins. They also make use of the lateral line organ. After metamorphosis, these organs become redundant and will be resorbed by controlled cell death, called apoptosis . The amount of adaptation to specific ecological circumstances

1248-547: Is reabsorbed, due to the higher thyroxin concentrations required for tail resorption. Salamander development is highly diverse; some species go through a dramatic reorganization when transitioning from aquatic larvae to terrestrial adults, while others, such as the axolotl , display pedomorphosis and never develop into terrestrial adults. Within the genus Ambystoma , species have evolved to be pedomorphic several times, and pedomorphosis and complete development can both occur in some species. In newts, metamorphosis occurs due to

1300-402: Is remarkable, with many discoveries still being made. With frogs and toads, the external gills of the newly hatched tadpole are covered with a gill sac after a few days, and lungs are quickly formed. Front legs are formed under the gill sac, and hindlegs are visible a few days later. Following that there is usually a longer stage during which the tadpole lives off a vegetarian diet. Tadpoles use

1352-401: Is resorbed together with the spiral gut. The animal develops a big jaw, and its gills disappear along with its gill sac. Eyes and legs grow quickly, a tongue is formed, and all this is accompanied by associated changes in the neural networks (development of stereoscopic vision, loss of the lateral line system, etc.) All this can happen in about a day. It is not until a few days later that the tail

1404-401: Is straightforward, provided they receive a long daylight cycle (e.g., 14 hours) during development to prevent diapause . Eggs are rinsed for one to five minutes in dilute household bleach for disinfection. Eggs are placed on diet cubes or host plants. The eggs hatch and develop at different speeds depending on temperature. The larvae are moved to a fresh diet or leaves as their food spoils or

1456-851: Is the required hormone, and for adaptation to the land phase, thyroxin . External gills do not return in subsequent aquatic phases because these are completely absorbed upon leaving the water for the first time. Basal caecilians such as Ichthyophis go through a metamorphosis in which aquatic larva transition into fossorial adults, which involves a loss of the lateral line . More recently diverged caecilians (the Teresomata ) do not undergo an ontogenetic niche shift of this sort and are in general fossorial throughout their lives. Thus, most caecilians do not undergo an anuran-like metamorphosis. [REDACTED] The dictionary definition of metamorphosis at Wiktionary Larva A larva ( / ˈ l ɑːr v ə / ; pl. : larvae / ˈ l ɑːr v iː / )

1508-466: The M. sexta caterpillar has seven white diagonal lines with a black border at the first seven abdominal segments, and the horn is red or green with a red tip. The M. quinquemaculata caterpillar has V-shaped white markings with no borders at all eight of its abdominal segments, and the horn is dark blue or black in color. During the larval stage, M. sexta caterpillars feed on plants of the family Solanaceae , principally tobacco, tomatoes and members of

1560-426: The heart (aorta), which is a long, pulsating vessel running along the length of the caterpillar's dorsal side. The heart becomes visible through the skin just as the caterpillar is reaching the end of the final instar. A common biological control for hornworms is the parasitic braconid wasp Cotesia congregata , which lays its eggs in the bodies of the hornworms. The wasp larvae feed internally and emerge from

1612-507: The tobacco hornworm and the Goliath worm (as larvae), it is closely related to and often confused with the very similar tomato hornworm ( Manduca quinquemaculata ); the larvae of both feed on the foliage of various plants of the family Solanaceae . The larvae of these species can be distinguished by their lateral markings: Tomato hornworms have eight V-shaped white markings with no borders; tobacco hornworms have seven white diagonal lines with

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1664-830: The xanthophyll -which is a yellow pigment- needed to produce their green coloration; instead they appear blue. On some diets, they have very little pigment and pigment precursors, so are a very pale blue-white. As vitamin A and other carotenoids are necessary for the visual pigments ( rhodopsin ), an artificial-diet-reared hornworm may have poor vision due to lack of carotenoids in the diet. Captive-bred hornworms fed on an artificial diet are often given to insectivorous exotic animals, such as certain reptiles, fish and small mammals. They are preferred over wild-collected hornworms, which may bioaccumulate poisonous substances found in dietary plants. Hornworms, though originally bred for laboratories, are also farmed for this purpose. They are often sold already packed into pods that include everything

1716-401: The adult form. Their diet may also be considerably different. In the case of smaller primitive arachnids, the larval stage differs by having three instead of four pairs of legs. Larvae are frequently adapted to different environments than adults. For example, some larvae such as tadpoles live almost exclusively in aquatic environments, but can live outside water as adult frogs . By living in

1768-400: The body to spin their cocoons . Parasitized hornworms are often seen covered with multiple white, cottony wasp cocoons, which are often mistaken for large eggs. A wasp species, Polistes erythrocephalus , feeds on hornworm larvae. Before the larva pupates, it goes through a stage called the pre-pupa, where it shrinks considerably and prepares to pupate. Often people mistake this stage for

1820-410: The change in habitat, not a change in diet, because newt larvae already feed as predators and continue doing so as adults. Newts' gills are never covered by a gill sac and will be resorbed only just before the animal leaves the water. Adults can move faster on land than in water. Newts often have an aquatic phase in spring and summer, and a land phase in winter. For adaptation to a water phase, prolactin

1872-459: The development of adult characteristics during ecdysis . In holometabolous insects, molts between larval instars have a high level of juvenile hormone, the moult to the pupal stage has a low level of juvenile hormone, and the final, or imaginal , molt has no juvenile hormone present at all. Experiments on firebugs have shown how juvenile hormone can affect the number of nymph instar stages in hemimetabolous insects. In chordates, metamorphosis

1924-538: The eggs as larvae with external gills but it will take some time for the amphibians to interact outside with pulmonary respiration. Afterwards, newt larvae start a predatory lifestyle, while tadpoles mostly scrape food off surfaces with their horny tooth ridges. Metamorphosis in amphibians is regulated by thyroxin concentration in the blood, which stimulates metamorphosis, and prolactin , which counteracts its effect. Specific events are dependent on threshold values for different tissues. Because most embryonic development

1976-650: The evolution of metamorphosis in insects is thought to have fuelled their dramatic radiation (1,2). Some early ametabolous "true insects" are still present today, such as bristletails and silverfish . Hemimetabolous insects include cockroaches , grasshoppers , dragonflies , and true bugs . Phylogenetically, all insects in the Pterygota undergo a marked change in form, texture and physical appearance from immature stage to adult. These insects either have hemimetabolous development, and undergo an incomplete or partial metamorphosis, or holometabolous development, which undergo

2028-410: The front of the body ( anterior ). Neurosecretory cells in an insect's brain secrete a hormone, the prothoracicotropic hormone (PTTH) that activates prothoracic glands, which secrete a second hormone, usually ecdysone (an ecdysteroid ), that induces ecdysis (shedding of the exoskeleton). PTTH also stimulates the corpora allata , a retrocerebral organ, to produce juvenile hormone , which prevents

2080-431: The genus Datura . M. sexta has five larval instars, which are separated by ecdysis (molting), but may add larval instars when nutrient conditions are poor. Near the end of this stage, the caterpillar seeks a location for pupation , burrows underground, and pupates. This searching behavior is known as "wandering". The imminence of pupation—suggested behaviorally by the wandering—can be anatomically confirmed by spotting

2132-544: The larva feeds on its normal diet of plant foliage, it ingests pigmentacious carotenoids , which are primarily yellow in hue. The resulting combination is green. Under laboratory conditions—when fed a wheat-germ-based diet—larvae are turquoise in color due to the lack of carotenoids in their diet. The caterpillar stage of the tobacco hornworm is quite similar in appearance to that of the closely related tomato hornworm . The larvae of these two species can however be readily distinguished by their lateral markings. Specifically,

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2184-407: The larvae are fed by female workers. In Ropalidia marginata (a paper wasp) the males are also capable of feeding larvae but they are much less efficient, spending more time and getting less food to the larvae. The larvae of some organisms (for example, some newts ) can become pubescent and do not develop further into the adult form. This is a type of neoteny . It is a misunderstanding that

2236-447: The larvae need, including food. Care is relatively easy, and animals seem to relish their bright color and flavor. M. sexta larvae grow up to 100 millimeters in length, reaching up to 20 grams. Due to their large size, they are used as alternative animal models for medical imaging modalities like computed tomography , magnetic resonance imaging , or positron emission tomography . Researchers around Anton Windfelder have established

2288-570: The larvae of M. sexta as an alternative animal model for chronic inflammatory bowel diseases or as an animal model for testing new contrast agents for radiology . Tobacco hornworms are facultative specialists; the larvae can grow and develop on any host plants. However, the larvae prefer solanaceous plants, such as tobacco and tomato plants. On these types of plants, larvae grow and develop faster. The lateral and medial sensilla styloconia (sensory receptors) on their mouthparts help them to identify solanaceous plants by recognizing indioside D ,

2340-520: The larval form always reflects the group's evolutionary history . This could be the case, but often the larval stage has evolved secondarily, as in insects. In these cases , the larval form may differ more than the adult form from the group's common origins. Within Insects , only Endopterygotes show complete metamorphosis, including a distinct larval stage. Several classifications have been suggested by many entomologists , and following classification

2392-566: The most significant being the inclusion, in holometabolous organisms, of a pupal or resting stage between the larval and adult forms. In hemimetabolous insects , immature stages are called nymphs . Development proceeds in repeated stages of growth and ecdysis (moulting); these stages are called instars . The juvenile forms closely resemble adults, but are smaller and lack adult features such as wings and genitalia. The size and morphological differences between nymphs in different instars are small, often just differences in body proportions and

2444-486: The number of segments; in later instars, external wing buds form. The period from one molt to the next is called a stadium. In holometabolous insects, immature stages are called larvae and differ markedly from adults. Insects which undergo holometabolism pass through a larval stage, then enter an inactive state called pupa (called a "chrysalis " in butterfly species), and finally emerge as adults. The earliest insect forms showed direct development ( ametabolism ), and

2496-403: The three thoracic segments bears a pair of true legs, and there is a pair of prolegs on the third, fourth, fifth, sixth, and last abdominal segments in all larval instars. The prothoracic segment bears one pair of spiracles , and additional pairs occur on each of the eight abdominal segments. The hemolymph (blood) of this species contains insecticyanin, a blue-colored biliprotein . When

2548-408: The thyroid hormone. Examples among the non-bony fish include the lamprey . Among the bony fish, mechanisms are varied. The salmon is diadromous , meaning that it changes from a freshwater to a saltwater lifestyle. Many species of flatfish begin their life bilaterally symmetrical , with an eye on either side of the body; but one eye moves to join the other side of the fish – which becomes

2600-427: The underside of foliage, but can also be found on the upper surface. M. sexta larvae are bright green in color and grow up to 100 millimeters in length. The posterior abdominal segment is tipped with a dorsocaudal horn that earns them the name "hornworm". The final instar consists of a cylindrical body covered with fine hairlike setae . The head is equipped with a pair of ocelli and chewing mouthparts . Each of

2652-456: The upper side – in the adult form. The European eel has a number of metamorphoses, from the larval stage to the leptocephalus stage, then a quick metamorphosis to glass eel at the edge of the continental shelf (eight days for the Japanese eel ), two months at the border of fresh and salt water where the glass eel undergoes a quick metamorphosis into elver, then a long stage of growth followed by

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2704-526: The windows are phylogenetically adapted to the ecological circumstances insects are living in. According to research from 2008, adult Manduca sexta is able to retain behavior learned as a caterpillar . Another caterpillar, the ornate moth caterpillar , is able to carry toxins that it acquires from its diet through metamorphosis and into adulthood, where the toxins still serve for protection against predators. Many observations published in 2002, and supported in 2013 indicate that programmed cell death plays

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