Ontogeny of UV resistance in a gravel spawning (Phoxinus phoxinus) and a surface spawning (Rutilus rutilus) cyprinid
Kaweewat, K.; Hofer, R.
The vulnerability of early developmental stages of minnow (Phoxinus phoxinus) and roach (Rutilus rutilus) was studied. Despite the different spawning sites, eggs and hatched embryos of both species are sensitive to UV-B radiation, which causes high mortality or malformation. Older free embryos and swim-up larvae, however, develop complete UV resistance. The relative concentration of a substance with maximum absorption at 289-294 nm obtained from methanol extracts of both species was found to increase during larval development and to correlate with increasing UV-B tolerance. As the epidermis lacks any melanin pigmentation it is concluded that this substance is an effective sun screen. UV-B radiation, in addition, leads to a significant dispersion of melanophores in the dermis of the skin.