The data were collected in order to determine if albino medaka were less tolerant of radiation than were pigmented medaka. The dorsal skin of unexposed albino and pigmented medaka was examined for the presence of a non-melanin photoprotective substance. The dorsal skin of albino and pigmented medaka was also examined for the presence of a photoprotective substance that appears to protect other fish species from UVB radiation. Six unexposed albino and six unexposed pigmented medaka from the culture tanks were killed by cold shock and the skin of each fish in an area behind the head, in front of the dorsal fin, and above the lateral lines was then scraped with a scalpel. The homogenate was centrifuged and the pellet was discarded, yielding a methanol extract.
Photoprotective substance occurs primarily in outer layers of fish skin.
Albino medaka were obtained from the Laboratory of Freshwater Fish Stocks, Bioscience Center, Nagoya University, Japan, and reared to adulthood. Albino medaka had a mean total length of 3.0 cm and a mean wet weight of 0.35 g, while pigmented medaka had a mean total length of 3.2 cm and a mean wet weight of 0.36 g at the time of exposure. Prior to exposure to UVB radiation the fish were held in uncovered culture tanks under the same ambient conditions provided by indirect sunlight from windows and supplemental cool white fluorescent lamps. During this time around one-fourth of the culture tank containing albino medaka was covered so the fish could seek shade from indirect and supplemental light. However, like pigmented medaka, albino medaka were observed to be dispersed throughout the culture tank and were not concentrated under the covered portion.