Seasonal effects of photoperiod and temperature on the ovary of the three-spined stickleback, Gasterosteus aculeatus L.

Publisher Website
Google Scholar
Abstract
Seasonal effects of photoperiod (16 h light (L): 8 h dark (D) and 8 h L: 16 h D) and temperature (18 and 8–9 °C) were studied on the ovary of the three-spined stickleback at 2-month intervals throughout the year. At the higher temperature, advanced oocyte development took place only in 16 h L: 8 h D in November and January, while in March and May an increasing proportion of the females matured also in 8 h L: 16 h D. Many fish in 8 h L: 16 h D, 18 °C, in November–May showed a marked regression of the ovaries and large numbers of atretic eggs. At the lower temperature in November–May the ovaries developed slowly, or showed little change compared with the initial controls. No consistent effect of photoperiod was found at the lower temperature in any season. The ovaries regressed in July, fastest at the higher temperature. No photoperiodic effects could, however, be detected. At the commencement of the September experiment the ovaries were in a regressed state and no advanced oocyte development was reached in any group.