The effect of the rate and onset of temperature increase on spawning of the periwinkle, Littorina littorea (L.)

Abstract

Littorina littorea (L.) from a rocky shore on Pendleton Island, New Brunswick, Canada were experimentally manipulated to determine the effect of temperature on spawning as a possible means of explaining the differential timing of settlement observed in two consecutive years. Variation in the rate or onset of temperature increase influenced the duration of spawning. Under conditions simulating shore temperature, spawning continued for 17–21 wk. An accelerated rate of temperature increase reduced spawning to a period of 8–14 wk. When the rate of temperature increase was normal but the onset of temperature increase was delayed, spawning was extended to 21–24 wk. The number of embryos released from individual females increased in direct proportion to the spire height. The number of embryos released in the accelerated and delayed treatments depended on the spire height of the female. For smaller females (spire height <17 mm) there was no effect of temperature manipulation. However, for the larger, more fecund, females significant differences from the control were observed in the number of embryos released under conditions of accelerated temperature. No significant differences were evident between the control and the delayed temperature increase experiment. In L. Littorea the rate of temperature increase as opposed to the timing of the increase has a more pronounced effect on the reproductive output.