PLANKTOTROPHY BY THE LECITHOTROPHIC LARVAE OF A NUDIBRANCH,PHESTILLA SIBOGAE(GASTROPODA)

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Abstract
Veliger larvae of the coral-eating nudibranch Phestilla sibogae can metamorphose 3-4 days after hatching in the absence of any external food source. If deprived of a settlement stimulus, starved larvae survived as long as long as 30 days, but had lost metamorphic competence several days before starvation death. Fed larvae survived more than 42 days and retained metamorphic competence for as long as 42 days. Feeding by these potentially lecithotrophic larvae extended the duration of survivorship by at least 28% and the duration of the competent period by as much as 90%. There is evidence from light and electron microscopy for both digestion and uptake of phytoplankton in the larval gut. The ability to extend a brief lecithotrophic larval existence by planktotrophy may explain the wide spread distribution of this species in the tropical Indo-Pacific Ocean.