Observations on the spawning behaviour of Saccoglossus horsti Brambell & Goodhart, and of other Enteropneusta

Abstract

The genital products of Saccoglossus horsti are discharged within the burrows and expelled after the tide has ebbed. They are not retained in the burrows for any length of time.Fertilization occurs mainly in the overlying surface water, or during the flood.An ‘epidemic’ spawning was observed on three occasions in the field.A rise of temperature to about 160° C. is regarded as the essential factor primarily responsible for initiating the spawning.The females were observed to spawn before the males. Some reciprocal inducement might have occurred.The breeding season in the Solent area is mainly confined to the months of May, June and July, and is seemingly dependent on climatic and tidal conditions during these months.The spawning behaviour of other species of the Enteropneusta is discussed.