Effect of Light Wavelength on the Sexual and Asexual Reproduction of the Monogonont Rotifer Brachionus manjavacas

The monogonont rotifer Brachionus manjavacas (Australian strain) showed a steadily increasing population growth and larger number of resting egg production under continuous white light compared to under total darkness when they were batch cultured. By comparing different wavelength of light, such as white (control), 470 (blue), 525 (green) and 660 (red) nm, rotifers showed no significant differences in specific population growth rate, but sexual reproduction showed different patterns associated with light wavelengths. Although there were no significant differences with regard to mixis induction, the resting egg formation actively occurred at 525 nm. We further observed the movement of female rotifers to find the influential factor of different sexual reproduction. There was no significant difference in the mean swimming speed of 10 female rotifers, but the proportion of settling individuals varied with light wavelength. Under 525 nm light, no individuals continuously settled for one minute, while under other light wavelengths the percent of settling females for a minute ranged between 6.1±5.4 and 23.8±6.5%. The higher ratio of swimming females at 525 nm should enhance the male/female encounters, which resulted in higher resting egg formation.