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Metamorphosis in Insects

Metamorphosis in Insects. Insect life cycle Development from egg to adult and again to egg represents one life cycle or Generation Voltinisme = number of generations completed by a species per year 1. univoltine (one generation per yr) 2. bivoltine (2 generations per yr)

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Metamorphosis in Insects

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  1. Metamorphosis in Insects

  2. Insect life cycle Development from egg to adult and again to egg represents one life cycle or Generation Voltinisme = number of generations completed by a species per year 1. univoltine (one generation per yr) 2. bivoltine (2 generations per yr) 3. multivoltine (many generations per yr) 4. perennial (one generation in more than one year, e.g or large insects)

  3. ENDOCRINE- describing or relating to any gland or other group of cells that synthesizes hormones and secretes them directly into the blood, lymph, or other intercellular fluid Endocrine cells release protein and non-protein hormones Synthesis of hormones is orchestrated by the CNS Hormones effects are tissue dependent

  4. Metamorphosis in Insects The transformation of an immature insect from a larva to a pupa to an adult

  5. Evolution of Metamorphosis Complete metamorphosis occurs only in higher insects; it evolved only once Early expression of juvenile hormone suppresses the development of adult characteristics Larval and adult forms can occupy different environments and consume different food sources Lack of competition between larva and adult allows species success and diversification Metamorphosis can serve as a model for understanding how shifts in protein production can create different body forms

  6. Temperature, Light, Stress, etc. Prothoracicotropic hormone (PTTH) Juvenile Hormone (JH) Ecdysteroid Larva Adult Pupa Hormonal Control of Insect Metamorphosis Brain Corpus Allatum Prothoracic Gland

  7. Temperature, Light, Stress, etc. Control of Metamorphosis by Internal and External Factors Brain Temperature (day degrees) Critical size matched (availability of food) Light (photoperiod) Chemicals Amount of moisture Stress: mutagens, predators, etc.

  8. Regulation of JH Levels Juvenile Hormone Ecdysone Amount of Hormone Larva Pupa Adult Low = larva stage; Medium JH levels = pupa stage; No JH = adult stage Rate of release limited by synthesis Amounts of JH also regulated by protein degradation and methyltransferase levels (can be protected by JH binding proteins, degraded by JH esterase)

  9. Which Stage would You Target?

  10. Insect control by targeting metamorphosis Juvenile hormone mimic: Keep insects in larval stage -- Effective control for insects such as mosquitoes Juvenile hormone antagonist: Cause death of larva or early metamorphosis -- Effective control for crop pests such as hornworm Genes for juvenile hormone binding hormone and JH esterase have been identified

  11. Without Metamorphosis egg nymphs adult Without meta The first type is "without" metamorphosis which the wingless primitive orders such as silverfish (Thysanura) and springtails (Collembola) possess. The young resemble adults except for size.

  12. Incomplete Metamorphosis egg naiads adult Incomplete meta The second type is "incomplete" metamorphosis which is found among the aquatic insect orders such as mayflies (Ephemeroptera) and dragonflies (Odonata).

  13. Gradual Metamorphosis The third type is "gradual" metamorphosis seen in such orders as the grasshoppers (Orthoptera), termites (Isoptera), thrips (Thysanoptera), and true bugs (Hemiptera). This life cycle starts as an egg, but each growth, or nymphal stage looks similar, except it lacks wings and the reproductive capacity that the adult possesses. Gradual meta nymphs egg adult

  14. Complete Metamorphosis The fourth type is "complete" metamorphosis found in butterflies (Lepidoptera), beetles (Coleoptera), flies (Diptera), and bees, wasps, and ants (Hymenoptera). This life cycle has the four stages of egg, larva, pupa, and adult. Each stage is quite distinct. egg larvae pupa adult

  15. A parting shot… “Bear in mind that the wonderful things you learn in your schools are the work of many generations. All this is put in your hands as your inheritance in order that you may receive it, honor it, ADD TO IT, and one day faithfully hand it to your children.” • By: Albert Einstein & mam els

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