Light, temperature and the breeding of Balanus balanoides

Abstract

Variations in the breeding habits of cirripedes are discussed.The effect of temperature and light during various stages of gonad development has been determined for B. balanoides.Constant illumination inhibits breeding, the inhibition relating to the later stages of gonad development.There is a critical temperature above which breeding will not take place, the level of which may possibly be raised by decreased periods of illumination. A period of 4–6 weeks at less than 12 h of light per day and below the critical temperature is required for maturation of the gametes. It is difficult to advance the date at which egg-masses are laid down by more than a few weeks.The results are discussed in relation to the animal's ecology. There is a very close adaptation to boreo-arctic conditions; the north-south gradient in the time at which the eggs are fertilized is related to the temperature gradient but the constancy from year to year of this date in any one locality under the same micro-environment cannot be explained on the basis of temperatures. Light periodicity is probably involved.