BIOLOGY & SCIENCE: Journal : Developmental responses to UV-B radiation in common frog Rana temporaria embryos from along an altitudinal gradient

Monday, April 21, 2008

Journal : Developmental responses to UV-B radiation in common frog Rana temporaria embryos from along an altitudinal gradient

Journal	Population Ecology
Publisher	Springer Japan
ISSN	1438-3896 (Print) 1438-390X (Online)
Issue	Volume 50, Number 2 / April, 2008
Category	Original Article
DOI	10.1007/s10144-007-0071-3
Pages	123-130
Subject Collection	Biomedical and Life Sciences
SpringerLink Date	Tuesday, January 08, 2008

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Olivier Marquis¹, Claude Miaud¹ and Jean-Paul Lena²

(1)	UMR CNRS 5553 Laboratoire d’Ecologie Alpine, Université de Savoie, 73 376 Le Bourget du Lac, France

(2)	UMR CNRS 5023 Laboratoire d’Ecologie des Hydrosystemes Fluviaux, Université Claude Bernard, LYON I, 69622 Villeurbanne Cedex, France

Received: 15 May 2007 Revised: 2 November 2007 Accepted: 4 November 2007 Published online: 9 January 2008

Abstract Solar ultraviolet radiation (UV) is harmful for developing amphibians. As UV increases with altitude and latitude, it is suggested that high altitude and latitude populations have evolved tolerance to high levels of UV. Using laboratory experiments, we tested the hypothesis that Rana temporaria populations from several altitudes (438–2,450 m above sea level) were adapted to UV by assessing the effects of artificial UV on embryos mortality rate, malformations, and body length at hatching. We also tested the protective role of the jelly surrounding the embryos. Without artificial UV exposure, hatching success decreased with altitude of the population. Malformation rates were low for all populations (mean 1.36%), and hatching size increased with altitude. The artificial UV (UV-B, UV-A, and visible) used was similar to the solar spectrum received at high altitude. Exposed embryos had performance similar to that of embryos without exposure: a decreased hatching success with altitude and a low malformation rate (mean 0.85%). However, hatching size did not vary with altitude, and UV-exposed embryos tended to be smaller at hatching than non-exposed embryos. Removal of the protective jelly envelope greatly decreased the performance of UV-exposed embryos: hatching success strongly decreased with altitude and embryos of the highest population (2,450 m asl) did not develop. Malformation reached 4.98%, without population differences, and hatching size of embryos without jelly was smaller than hatching size of non-manipulated embryos with no population effect. This study demonstrates that lowland jellyless embryos were less sensitive (i.e., exhibited a higher survival rate) than highland embryos and, on the other hand, that the jelly envelope was a more efficient protection for embryos in highland than in lowland populations. A trade-off hypothesis is presented to explain this difference in UV tolerance and protection among populations: in a harsh, highland environment (i.e., with a curtailed activity period), embryos have to invest in development and growth and, thus, embryo protection should be a female investment (via the jelly). In a lowland environment, embryonic growth and development are less constrained and embryos are able to invest and use protection or repair mechanisms inherited from their parents.

Keywords Altitude - Amphibian - Embryos - Local adaptation - UV exposure