Photosynthesis in Copepods

Zooplankton grazers consume appreciable amounts of algae that are not digested. Indigestibility has been considered of adaptive value to the algae and an unqualified disadvantage to the grazer. In Cartesian diver experiments, freshly killed copepods (Acanthocyclops vernalis) produced significant amounts of oxygen when exposed to the light, even after 24 hours of starvation. Also, significant amounts of oxygen were consumed by dead copepods in the dark. These observations suggest that the copepod gut is well suited for photosynthesis by ingested algae.