Does jelly envelope protect the common frog Rana temporaria embryos from UV-B radiation?

Abstract

Animals have evolved a number of ways to protect themselves from the harmful effects of ultraviolet-B (UV-B) radiation, but little is known about the relative importance of different mechanisms protecting amphibian embryos from UV-B radiation. Using enzymatic removal of gelatinous coats (jelly envelope) surrounding the eggs of Rana temporaria, we tested the hypothesis that the jelly envelope acts as a sunscreen that protects embryos from harmful effects of UV-B radiation. We conducted two independent factorial laboratory experiments employing three different UV-B (no UV-B, normal, and enhanced) levels and jelly removal (control, modified, and completely removed) treatments. We found no UV-B X jelly removed treatment interactions in survival rates or in frequency of abnormal individuals, suggesting that jelly removal did not increase susceptibility of embryos to UV-B radiation. These results support the contention that the jelly envelope is not the most important means of protecting B. temporaria embryos from UV-B radiation. Other factors (e.g., melanin pigments, other sunscreen compounds, effective DNA-repair mechanisms) must be responsible for the high UV-B radiation tolerance of embryos.