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metamorphosis in vertebrates

metamorphosis in vertebrates



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Matamorphosis Matamorphosis Presentation Transcript

  • 1
  • •Metamorphosis •Types of metamorphosis •Hypermetamorphosis •Metamorphosis in insects •Metamorphosis in amphibians •Advantages of metamorphosis 2
  • Define: The process of transformation from an immature form to an adult form in two or more distinct stages. Description :The word "metamorphosis" derives from Greek μεταμόρφωσις, "transformation, transforming The term is use for exclusive, and is not applied to general aspects of cell growth, including rapid growth spurts. 3 .
  • Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Example:Some insects, amphibians, molluscs, crustaceans, Cnidarians, echinoderms and tunicates undergo metamorphosis 4
  • Including: Butterflies 5
  • There are following types of metamorphosis 1) 2) Incomplete or direct or simple metamorphosis.. Complete or Complex or Indirect Metamorphosis 6
  • A life cycle which is characterized by the absence of a pupal stage between the immature and adult stages is called incomplete metamorphosis. Hemimetabola:The group of the insects undergoing this type of metamorphosis is also called Hemimetabola. 7
  •  Egg  Nymph  Adult 8
  •  EGG A female insect lays eggs. These eggs are often covered by an egg case which protects the eggs and holds them together. 9
  •  NYMPH      The eggs hatch into nymphs. Nymphs looks like small adults, but usually don't have wings. Insect nymphs eat the same food that the adult insect eats. Nymphs shed or molt their exoskeletons (outer casings made up of a hard substance called chitin) and replace them with larger ones several times as they grow. Most nymphs molt 4-8 times. 10
  • These nymphs resemble their parents very much in their structure of body (mouth parts, simple and compound eyes, antennae, legs etc). Similarly, they have the same mode of life, feeding habits, food and habitat. The difference between the nymphs and adults is that the nymphs do not process wings and reproductive organs until they turn into full-grown adults. Besides, nymphs are smaller in size and shape. The wings develop gradually from a small wing pads in the nymphs to a fully developed functional wings in matured adults. This type of metamorphosis is therefore, also called gradual metamorphosis. 11
  • Growth of Nymph:The nymphs grow in size and shape by the process of moulting. . There is no resting or transitional phase for transformation into adult. e.g. dragonflies, damselflies, grasshoppers, cockroach, cri ckets, aphids, jassids, bugs etc. 12
  • Exopterygota:The wings development takes place externally in nymph stage and hence the group of insect which show this phenomenon is called Exopterygota. Secondarily wingless insects :In few Exopterygota insects, the wings may be lost or may not develop at all. But there are rudiments of wings in the form of wing pad/ buds in these insects and hence these insects are called secondarily wingless insects. for example, head louse, bed etc. 13
  • Aberrant Hemimetabola:A few insects their developmental period, pass through a stage called incipient or false pupal stage (comparable to pupa of Holometabola) before emerging as an adults. Such deviation from Hemimetabola is called aberrant Hemimetabola. Example:White flies and thrips. In dragonflies the nymphs are aquatic while the adults are aerial and therefore this group is called Hemimetabola. 14
  •   ADULT The insects stop molting when they reach their adult size. By this time, they have also grown wings. 15
  • Examples Orders Mayflies Ephemeroptera Dragonflies Odonata Stoneflies Plecoptera 16
  • 17
  • Complete Metamorphosis:The complete form of metamorphosis in which an insect passes through four separate stages of growth, as embryo, larva, pupa, and adult. Holometabola:The group of insects undergoing this type of metamorphosis is also called holometabola. The insects in this type complete their postembryonic development by assuming much striking morphological changes. In order to attain maturity, this insect pass through four different stages . 18
  •  Egg  Larva  Pupa  Adult 19
  • A complete metamorphosis has four stages: 20
  • EGG The female lays eggs. 21
  •  LARVA   Larva hatch from the eggs. They do not look like adult insects. They usually have a worm-like shape. Caterpillars, maggots, and grubs are all just the larval stages of insects. Larvae molt their skin several times and they grow slightly larger. 22
  • The larva differs from its parents in the structure, food, feeding habits, mode of life and habitat. The larvae may have biting type of mouthparts, while adults may have different mouthparts such as siphoning type. Similarly they do not have compound eyes but possesses simple ocelli. Some of the larvae have only three pairs of thoracic legs (beetles & weevils) while in other there may be one or more pairs of abdominal legs in addition to thoracic legs (butterflies & month). In some larvae legs are altogether absent (flies). 23
  • There are no external signs of presence of wing pads or buds on the larvae. However, these pads are present inside the body cavity in thoracic region. These wing pads develop internally hence; this group of insects is called Endopterygota. 24
  • Pupa For transformation into adults the larva has to pass through a resisting phase or transitional phase called pupa. 25
  • Feeding and movement ceases and metabolic activities are lowered down during the pupal stage but conspicuous changes in morphological forms in the development of wings and reproductive organs occur in the pupal stage. Adult The adult come out of the pupal covering with development of compound eyes, antennae, thoracic legs, wings reproductive organs and changes in mouth parts. 26
  •        Examples:Butterflies moths beetle weevils, flies honeybees wasps mosquitoes 27
  • Examples Orders Lacewing Neuroptera Beetles Coleoptera Scorpionfly Mecoptera Coddisfly Trichoptera Moths, Butterflies Lepidoptera Flies Diptera Fleas Siphonaptera Wasps, Bees Hymenoptera 28
  • A kind of complete metamorphosis in which the different larval instars represents two or more different forms of larva. This is specialized type of metamorphosis found in higher orders of Endopterygota insects. The first instars larva is active and usually campodaeiform and the subsequent larval instars are vermiform or scarabaeiform. . e.g. blister beetles 29
  • The life cycle of the striped blister-beetle Epicauta vittata illustrates the hypermetamorphosis through which the blisterbeetles pass. Explanation : The female deposits her eggs in a mass of a hundred or more in a hole in the soil. They hatch into very active larvae each of which is known as a triungulin. 30
  •   The triungulin has long legs and runs about in search of eggs of grasshoppers. It feeds ravenously on the eggs and in about eight days molts to the second stage, called the caraboid stage. Because it then resembles the larva of a carabid beetle. In another week it molts and assumes the appearance of a scarabaeid larva and is therefore called the scarabaeidoid stage of the second larva. In a short time it molts again to the ultimate stage of the second larva. 31
  • Metamorphosis in beetle 32
  • In about ten days more it molts again and becomes the pseudo-pupa or the coarcate larva. This form usually hibernates and in the spring transforms to the third larval stage.  In a few days this larva transforms to the pupa in an earthen cell. in five or six days the pupa transforms to the adult beetle (imago).  33
  • All insects in the Pterygota undergo a marked change in form, texture and physical appearance or metamorphosis, from immature to adult. These insects either have hemimetabolous development, and undergo an incomplete Metamorphosis. Or have a pupal stage and shows a complete metamorphosis.  34
  • In holometabolous insects, immature stages are called larvae, and differ markedly from the adults.  Insects which undergo holometabolism pass through a larval stage, then enter an inactive state called pupa, or chrysalis, and finally emerge as adults.  This process is called "complete" metamorphosis. 35
  • It is theorized that the pupal stage is the evolutionary compaction of all the nymphal stages of their hemimetabolous ancestors, while the larval stage is an extended, mobile form of the developing embryo. 36
  •   In hemimetabolous insects, immature stages are called nymphs. Development proceeds in repeated stages of growth and ecdysis; these stages are called instars.   The juvenile forms closely resemble adults', but are smaller and lack adult features such as wings and genitalia. This process is known as "partial" or "incomplete" metamorphosis. 37
  •  The differences between nymphs in different instars are small, often just differences in body proportions and the number of segments, although external wing buds will form in later instars. 38
  • Insect growth and metamorphosis are controlled by hormones synthesized by endocrine glands near the front of the body.  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.  39
  •   PTTH also stimulates the corpora allata, a retrocerebral organ, to produce juvenile hormone (JH), which prevents the development of adult characteristics during ecdysis. In holometabolous insects, molts between larval instars have a high level of JH, the moult to the pupal stage has a low level of JH, and the final, or imaginal, molt has no JH present at all. 40
  •    In typical amphibian development, eggs are laid in water and larvae are adapted to an aquatic lifestyle Frogs, toads, and newts all hatch from the egg as larvae with external gills but it would take some while 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 41
  • 42
  • In frogs tadpole is hatched from egg.  The external gills of the newly hatched tadpole are covered with a gill sac.  Front legs are formed under the gill sac, and hind legs 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 a relatively long, spiral‐shaped gut to digest that diet.  43
  • Rapid changes in the body can then be observed as the lifestyle of the frog changes completely.  The animal develops a big jaw, and its gills disappear along with its gill sac  The spiral‐shaped mouth with horny tooth ridges is resorbed together with the spiral gut.. Eyes and legs grow quickly, a tongue is formed, and all this is accompanied by associated changes in the neural networks  44
  •   Both bony fish (Osteichyes) and non-bony fish (Agnatha), undergo metamorphosis. Fish metamorphosis is typically under strong control by the thyroid hormone. Examples :Among the non-bony fish the lamprey show metamorphosis. 45
  • In holometabolous insects, larvae enjoy in only eating and growing, while adults are responsible for producing offspring and they don't eat much in some Species.  Pupal is the intermediate stage during this larvae and adults don’t share food source so there is no food competition.  And there is a division of labor, growing and reproduction separately.  46
  • Living in different habitat is another amazing thing that only larvae can do through metamorphosis. For example:- mosquito larvae live in the water, while adult can fly around and find blood  REFERENCES   Slide share - See more at: orphosis-a-remarkablechange#sthash.awpbnim5.dpuf 47