Egg-wrapping behaviour protects newt embryos from UV radiation

Oviparous species that do not guard their eggs during development may suffe r significant embryonic mortality. However, the way females lay eggs may he lp prevent this. For example, females of several newt species carefully wra p single eggs into leaves of aquatic vegetation in shallow water. Wrapping behaviour may protect eggs from predators and from mechanical damage. We hy pothesized that egg-wrapping behaviour also protects newt embryos from the negative effects of ultraviolet (UV) radiation. In field experiments, we te sted the effects of ambient levels of UV radiation on marbled newt, Trituru s marmoratus, embryos exposed to sunlight. Of these embryos 95-100% died du ring the first 14 days of exposure. The eggs showed loss of their round sha pe, skin damage, oedemas and fungal infection. In contrast, during the same period, mortality of embryos protected by UV-blocking filters was only 20% . In laboratory experiments, we exposed marbled newt embryos to an artifici ally elevated intensity of UV-B radiation and tested the protective effect of leaves. The mortality of eggs wrapped in leaves and exposed to UV-B radi ation was low and similar to that of unwrapped eggs that were shielded from UV-B radiation with a UV-blocking filter, whereas 119 of 120 unwrapped egg s exposed to UV radiation died within 5 days. (C) 2001 The Association for the Study of Animal Behaviour.