Diapause
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In animal
Activity levels of diapausing stages can vary considerably among species. Diapause may occur in a completely immobile stage, such as the
Embryonic diapause, a somewhat similar phenomenon, occurs in over 130 species of mammals, possibly even in humans,[3] and in the embryos of many of the oviparous species of fish in the order Cyprinodontiformes.[4]
Phases of insect diapause
Diapause in insects is a dynamic process consisting of several distinct phases. While diapause varies considerably from one taxon of insects to another, these phases can be characterized by particular sets of metabolic processes and responsiveness of the insect to certain environmental stimuli.[5] For example, Sepsis cynipsea flies primarily use temperature to determine when to enter diapause.[6] Diapause can occur during any stage of development in arthropods, but each species exhibits diapause in specific phases of development. Reduced oxygen consumption is typical as is reduced movement and feeding.[7] In Polistes exclamans, a social wasp, only the queen is said to be able to undergo diapause.[8]
Comparison of diapause periods
The sensitive stage is the period when stimulus must occur to trigger diapause in the organism. Examples of sensitive stage/diapause periods in various insects:[9]
Scientific name | Common name | Sensitive stage | Diapause |
Diatraea grandiosella | Southwestern corn borer | early larval | late larval[10] |
Sarcophaga crassipalpis | Flesh fly | early larval | pupa |
Sarcophaga argyrostoma | Flesh fly | mid to late larval | pupa |
Manduca sexta | Tobacco hornworm | late embryonic (egg) to late larval | pupa |
Leptinotarsa decemlineata |
Colorado potato beetle | early adult | late adult |
Bombyx mori | Silkworm | late embryonic (egg) to early larval | embryonic |
Lymantria dispar |
Spongy moth | late embryonic | late embryonic |
Danaus plexippus |
Monarch butterfly | early adulthood | adulthood |
Acronicta rumicis | Knott grass moth | mid larval | mid larval |
Cydia pomonella | Codling moth | early to mid larval | mid larval[11] |
Gynaephora groenlandica | Arctic woolly bear moth | mid larval | mid larval[12] |
Cuterebra fontinella | Mouse botfly | mid larval | pupa[13] |
Induction
The induction phase occurs at a genetically predetermined stage of life, and occurs well in advance of the environmental stress.
Preparation
The preparation phase usually follows the induction phase, though insects may go directly from induction to initiation without a preparation phase.
Initiation
Maintenance
During the maintenance phase, insects experience lowered metabolism and developmental arrest is maintained.[5] Sensitivity to certain stimuli which act to prevent termination of diapause, such as photoperiod and temperature, is increased. At this stage, insects are unresponsive to changes in the environment that will eventually trigger the end of diapause, but they grow more sensitive to these stimuli as time progresses.
Termination
In insects that undergo obligate diapause, termination may occur spontaneously, without any external stimuli.[5] In facultative diapausers, token stimuli must occur to terminate diapause. These stimuli may include chilling, freezing, or contact with water, depending on the environmental conditions being avoided. These stimuli are important in preventing the insect from terminating diapause too soon, for instance in response to warm weather in late fall. In the Edith's checkerspot butterfly, individuals must receive enough sunlight in order to terminate the diapause stage and become a fully grown butterfly.[18] Termination may occur at the height of unfavourable conditions, such as in the middle of winter. Over time, depth of diapause slowly decreases until direct development can resume, if conditions are favourable.
Post-diapause quiescence
Diapause frequently ends prior to the end of unfavourable conditions and is followed by a state of quiescence from which the insect can arouse and begin direct development, should conditions change to become more favourable.[5] This allows the insect to continue to withstand harsh conditions while being ready to take advantage of good conditions as soon as possible.
Regulation
Diapause in insects is regulated at several levels. Environmental stimuli interact with genetic pre-programming to affect
Environmental
Environmental regulators of diapause generally display a characteristic
Neuroendocrine
The neuroendocrine system of insects consists primarily of neurosecretory cells in the brain, the corpora cardiaca, corpora allata and the prothoracic glands.[2] There are several key hormones involved in the regulation of diapause: juvenile hormone (JH), diapause hormone (DH), and prothoracicotropic hormone (PTTH).[22]
Prothoracicotropic hormone stimulates the prothoracic glands to produce
The corpora allata is responsible for the production of
In adults, absence of JH causes degeneration of flight
Diapause hormone regulates
Tropical diapause
Diapause in the
Diapause in the tropics poses several challenges to insects that are not faced in
may still be abundant during the diapause period.Aggregations are common among diapausing tropical insects, especially in the orders
See also
- Eburia quadrigeminata, the species with the longest reported diapause among insects (up to 40 years).
- Polygonia c-album, whose larvae exhibit density-dependent polymorphism where one of two morphs is a diapausing phase.
References
- ISBN 0-521-57048-4, p 403.
- ^ a b c Tauber, M.J., Tauber, C.A., Masaki, S. (1986) Seasonal Adaptations of Insects. Oxford University Press[page needed]
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Annual aplocheiloid killifish embryos possess a rare ability among vertebrates to enter stages of developmental arrest (diapause) when subjected to adverse environmental conditions.
- ^ PMID 16332347.
- ^ Blanckenhorn, W. U. (1998). Altitudinal differentiation in the diapause response of two species of dung flies. Ecological Entomology 23, 1-8.
- ISBN 0-521-57048-4, pp. 403–404
- .
- ^ ISBN 0-521-57048-4, p 404.
- ^ Bulletin of Entomological Research (1976), 66:75–79 Cambridge University Press, Copyright © Cambridge University Press 1976, Diapause of the southwestern corn borer, Diatraea grandiosella Dyar (Lepidoptera, Pyralidae): effects of a juvenile hormone mimic: G. M. Chippendalea1 and C.-M. Yina1a1, Department of Entomology, University of Missouri, Columbia, Missouri 65201, U.S.A.
- ^ Tadic, M. (1957). The Biology of the Codling Moth as the Basis for Its Control. Univerzitet U Beogradu.
- ISSN0013-8738.
- ^
Scholl PJ (1991). "Gonotrophic Development in the Rodent Bot Fly Cuterebra fontinella (Diptera: Oestridae)". Journal of Medical Entomology. 28 (3): 474–476. PMID 1875379.
- ^ a b c Huffaker, C.B. and Gutierrez, A.P., Eds. 1999. Ecological Entomology. John Wiley & Sons, Inc.
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