Immortality and Pearl's Survivorship Curve for Hydra

Forrest, Helen

doi:10.2307/1932550

Cited by 6 publications

(1 citation statement)

References 13 publications

(23 reference statements)

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“…Both planula and polyp stages can shrink and rest in low-metabolic-cost states (cysts, dormant hydrorhizae) to survive critical periods, being ready to reactivate cell proliferation and morphogenesis at the onset of favourable seasons . Polyp colonies can last for several years, annually producing large batches of sexually competent medusae, followed by periodic colony shrinkage and recurrent cycles of regenerative processes, without any obvious sign of senescence (Forrest 1963;Müller 1996). This process, also known as renovation, is a type of regeneration.…”

Section: The Complexity Of Hydrozoan Life Cycles and The "Immortal" Jmentioning

confidence: 99%

Reverse development in Cnidaria

Piraino¹,

Vito²,

Schmich³

et al. 2004

Can. J. Zool.

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Cnidarians have long been considered simple animals in spite of the variety of their complex life cycles and developmental patterns. Several cases of developmental conversion are known, leading to the formation of resting stages or to offspring proliferation. Besides their high regenerative and asexual-reproduction potential, a number of cnidarians can undergo ontogeny reversal, or reverse development: one or more stages in the life cycle can reactivate genetic programs specific to earlier stages, leading to back-transformation and morph rejuvenation. The switch is achieved by a variable combination of cellular processes, such as transdifferentiation, programmed cell death, and proliferation of interstitial cells. The potential for ontogeny reversal has limited ecological meaning and is probably just an extreme example of a more general strategy for withstanding unfavourable periods and allowing temporal persistence of species in the environment.Résumé : Depuis longtemps, on considère les cnidaires comme des animaux simples, malgré la variété de leurs cycles biologiques et de leurs patterns de développement complexes. Il existe plusieurs cas de conversions au cours du déve-loppement qui mènent à la formation de stades de repos ou à la prolifération de rejetons. En plus de leur fort potentiel de régénération et de reproduction asexuée, plusieurs cnidaires peuvent subir un renversement de leur ontogenèse ou un développement inversé : un ou plusieurs stades dans le cycle biologique peuvent réactiver des programmes génétiques spécifiques de stades antérieurs, ce qui donne une rétro-transformation et un rajeunissement des morphes. Le revirement est provoqué par une combinaison variable de processus cellulaires, tels que la transdifférentiation, la mort cellulaire programmée et la prolifération de cellules interstitielles. Le potentiel de renversement ontogénique a une signification écologique limitée; il s'agit probablement d'un état extrême d'une stratégie plus générale pour survivre aux périodes défavorables et permettre à l'espèce de se maintenir dans le temps dans son milieu.[Traduit par la Rédaction] Piraino et al. 1754

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Section: The Complexity Of Hydrozoan Life Cycles and The "Immortal" Jmentioning

confidence: 99%

Reverse development in Cnidaria

Piraino¹,

Vito²,

Schmich³

et al. 2004

Can. J. Zool.

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Impairment of regeneration in aging: appropriateness or stochastics?

Хохлов

2013

Biogerontology

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There is a viewpoint that suppression of the proliferative capacity of cells and impairment of the regeneration of tissues and organs in aging are a consequence of specially arisen during evolution mechanisms that reduce the risk of malignant transformation and, thus, protect against cancer. We believe that the restriction of cell proliferation in an aging multicellular organism is not a consequence of implementing a special program of aging. Apparently, such a program does not exist at all and aging is only a "byproduct" of the program of development, implementation of which in higher organisms suggests the need for the emergence of cell populations with very low or even zero proliferative activity, which determines the limited capacity of relevant organs and tissues to regenerate. At the same time, it is the presence of highly differentiated cell populations, barely able or completely unable to reproduce (neurons, cardiomyocytes, hepatocytes), that ensures the normal functioning of the higher animals and humans. Apparently, the impairment of regulatory processes, realized at the neurohumoral level, still plays the main role in the mechanisms of aging of multicellular organisms, not just the accumulation of macromolecular defects in individual cells. It seems that the quality of the cells themselves does not worsen with age as much as reliability of the organism control over cells, organs and tissues, which leads to an increase in the probability of death.

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Ecology

Reisa¹

1973

Biology of Hydra

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Immortality and Pearl's Survivorship Curve for Hydra

Cited by 6 publications

References 13 publications

Reverse development in Cnidaria

Reverse development in Cnidaria

Impairment of regeneration in aging: appropriateness or stochastics?

Ecology

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