Response of Larvæ of Calyptraea chinensis (L) to Light

Abstract

THE veliger stage of the prosobranch Calyptraea chinensis is passed in capsules fixed to the substratum and guarded under the fore part of the shell of the parent. The young hatch as crawling post-veliger larvæ. During studies on the reproduction of this animal at Plymouth, embryos of all stages were examined at night in sea water in a glass dish lit only by a hooded microscope lamp. Freed veliger larvæ of stages 5 and 5a (unpublished work) were seen to mass in the illuminated part of the dish facing the light. The early and middle larvæ swam well; many of the late veliger larvæ alternately swam and crawled. The later veliger larvæ, which had been ready to hatch, crawled only. When the position of the light was changed, the veligers swam or crawled towards the light. Other newly liberated marine larvæ show a similar response. Larvæ of Lepidochitona cinereus aggregate in regions of low light intensity¹ and larvæ of Spirorbis borealis are photo-positive for up to 2 hr.². The nauplii of barnacles are generally photopositive³ and the cyprids also³. The response to incident light by the early and middle veliger larvæ of Calyptraea is interesting as the larvæ are never free-swimming and are enclosed under the shell where there is little light.