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Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "chromatophores." The chromatophores are contained within vesicles of the host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that gave rise to the chloroplasts of algae and plants.
The closest living relative of P. chromatophora is the heterotroph P. ovalis. P. ovalis uses threadlike pseudopods to capture its prey, which it digests internally. Which of the following, if observed, would be the best reason for relabeling P. chromatophora as a mixotroph instead of an autotroph?
A) a pigmented central vacuole, surrounded by a nucleomorph
B) a vacuole with food inside
C) a secretory vesicle
D) a contractile vacuole

Question

Quizplus · Accepted Answer

If P. chromatophora was observed with a vacuole containing food, it would indicate that it is also capable of heterotrophic nutrition in addition to its autotrophic capabilities. This would make it a mixotroph rather than purely autotrophic. None of the other options listed would indicate a shift towards heterotrophy.

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