“Chloroplast symbiosis” and the extent to which it occurs in Sacoglossa (Gastropoda: Mollusca)

Abstract

Criteria for defining “chloroplast symbiosis” are outlined. Investigations are described into the presence or absence of chloroplast symbiosis in Limapontia capitata,“pale” and “dark” forms of L. depressa, Alderia modesta and Elysia viridis. Apart from E. viridis, only “pale” forms of L. depressa showed signs of the phenomenon. All sacoglossans hitherto shown definitely to possess “chloroplast symbiosis” have the twin characteristics of being elysioid and having siphonaceous algae as the source of chloroplasts. It is therefore suggested that the phenomenon may not be very widespread in the order, probably occurring in less than half of all species.