Chloroplast retention by elphidium excavatum (Terquem). Is it a selective process?

Some foraminifera retain chloroplasts from algae they partly digest. Elphidium excavatum (Terquem) was kept under laboratory cultures for a month and fed monoalgal cultures. The number of chloroplasts retained by this species of foraminifera depended on the algal diet. Higher numbers of chloroplasts were observed when the foraminifera were fed diatom species; the number of chloroplasts retained by each individual was approximately 3.7×104 chloroplasts. Significantly fewer green algal, and dinoflagellate chloroplasts were retained by each individual; the numbers were lower than the starved controls. These results seem to indicate that diatoms are the chloroplast donors for husbandry by E. excavatum.