The Sea Slug Pteraeolidia Ianthina Can Harbour Living Dinoflagellates (Photosynthetic

Multiple Choice

The sea slug Pteraeolidia ianthina can harbour living dinoflagellates (photosynthetic protists) in its skin. These endosymbiotic dinoflagellates reproduce quickly enough to maintain their populations. Low populations do not affect the sea slugs very much, but high populations (> 5 × 105 cells/mg of sea slug protein) can promote sea slug survival.
Percent of sea slug respiratory carbon demand provided by indwelling dinoflagellates.
According to the graph, during which season(s) of the year is the relationship between the sea slug and its dinoflagellates closest to being commensal?

A) winter
B) spring
C) summer
D) spring and summer