THE EFFECT OF ALTERNATING TEMPERATURE ON VERTEBRAL COUNT IN THE MEDAKA (ORYZIAS LATIPES)

Abstract

Eggs reared at different sustained temperatures ranging from 20° to 34 °C produced young with vertebral counts progressively lower at higher temperatures. Eggs transferred from 20° to 30° 2 days after fertilization produced significantly fewer vertebrae, and eggs transferred 6 days after fertilization produced significantly more vertebrae than did those reared at either sustained temperature. Eggs subject to temperatures alternating between 22° and 30° every 12 hours throughout development produced intermediate counts, corresponding to those resulting from sustained rearing at 26°, and showed the highest survival and no abnormalities.