ENVIRONMENTAL CRISIS, ADAPTATIONS AND GENOME IN AMPHIBIANS

Authors
Citation
A. Morescalchi, ENVIRONMENTAL CRISIS, ADAPTATIONS AND GENOME IN AMPHIBIANS, Bollettino di zoologia, 61(4), 1994, pp. 403-407
Citations number
NO
Categorie Soggetti
Zoology
Journal title
ISSN journal
03734137
Volume
61
Issue
4
Year of publication
1994
Pages
403 - 407
Database
ISI
SICI code
0373-4137(1994)61:4<403:ECAAGI>2.0.ZU;2-V
Abstract
Amphibians have proved to be especially useful for monitoring environm ental conditions: in fact, during their life cycle they alternate a do uble array of morpho-functional characters which make larvae fit for f reshwater environments and adults fit for the terrestrial ones. The lo w vagility of amphibian populations and the development of adaptive st rategies more similar to those of invertebrates than to those of tetra pods, allow the exploitation of these organisms as sensitive bioindica tors of the environmental conditions; however these same characters ap pear to expose them to a decline that, in the opinion of some scientis ts, is global, involving areas of our planet which have not yet been a ltered by human action. Among the numerous adaptations that make these amphibians closely dependent on environmental factors there are some cytogenetic characters. It is well-known that these vertebrates exhibi t genome sizes covering the widest range of values in the subphylum. V ariations in their nuclear DNA amount appear to be inversely proportio nal to changes in their cell metabolic rate and parallel the occurrenc e of heterochrony during morphogenesis. In urodeles, the largest genom es are shown by permanently neotenic species or by species involved in wide ontogenetic repatterning by progenesis. In anurans, the range of variability is more restricted; however, the largest genomes are foun d in terrestrial species with direct development, undergoing progeneti c processes. Therefore, in amphibians, adaptation appears to involve a lso their nuclear characters; the rapid environmental changes occurrin g in the last decades may affect also the cytogenetic characters of th ese organisms, and contribute to their global decline.