kleptoplastic

Kleptoplastic is an adjective used to describe organisms that acquire, retain, and utilize functional plastids—chloroplasts or other photosynthetic organelles—from algal prey through kleptoplasty. The phenomenon is most widely documented in sacoglossan sea slugs, but also occurs in some protists such as certain ciliates and dinoflagellates.

In sacoglossan sea slugs, chloroplasts are taken up from their algal diet and housed in specialized tissues, where they can remain photosynthetically active for days to weeks, and in some species for months. The host animal generally does not inherit the plastid’s original nucleus, so maintenance of the stolen plastids rests on host cellular conditions rather than continual genetic support from the alga. Whether algal genes have been transferred to the slug genome to aid plastid maintenance is a topic of ongoing debate.

Other kleptoplastic organisms include the ciliate Mesodinium rubrum, which sequesters plastids from cryptophyte algae and can sustain photosynthesis for several days, and certain dinoflagellates that acquire plastids from prey and use them to supplement their own metabolism.

Kleptoplasty is of interest for studies of endosymbiosis, plastid compatibility, and the ecological and evolutionary implications of transient photosynthetic lifestyles. It highlights how host organisms can exploit foreign organelles to expand their metabolic capabilities, albeit in a temporary and condition-dependent manner.