Question

Auxospores or rejuvenescent cells are characteristic of which of the following?
A. Diatoms
B. Sporozoans
C. Zooflagellates
D. Dinoflagellates

Answer 1

Hint: Auxospores are the specialized cells that are produced during cell cycle. Auxospores play a very important role to maintain the normal size of the diatoms. In diatoms successive mitotic division can lead to the decrease in the size. They are formed by the fusion of two haploid cells. Rejuvenescent spore of diatom is diploid and auxospore.

Complete answer:
Diatoms produce auxospores to maintain their cell size. Auxospores renewed the cell size by forming two large vegetative cells. They also play an important role in sexual reproduction in diatoms. Auxospores may be formed after haploid gametes fuse to form a diploid zygote. Auxospores can also be produced by diatoms to act as dormant stages, sometimes referred to as resting spores. Auxospores help diatoms to survive unfavorable conditions such as winter or depletion of nutrients. Auxospores are also called as rejuvenescent cells as they form during cell division.
Sporozoans have a complex life cycle. Sporozoans are the infective spores that can reproduce both by sexual and asexual mode. They are formerly placed in the class of sporozoa and also called as apicomplexans. They can also cause diseases such as malaria and cryptosporidiosis.
Zooflagelates are free living parasites. They are unicellular organisms. They can also occur as symbionts. Zooflagellates reproduce through binary fission. They have flagella to move.
Dinoflagellates are single celled eukaryotes. Most of the marine planktons are dinoflagellates. They usually reproduce asexually by the process of simple mitosis or division of cells.
From the above information we can say that auxospores and rejuvenescence is the characteristic of the diatoms.

Therefore, the correct answer is option A.

Note: Auxospores can also form by the process of apomixis, parthenogenesis, or sexual reproduction. To produce two initial thecae auxospores needs to go through two nuclear divisions without cell division. Diatoms require silica uptake to initiate mitotic division. Temperature and light are the important factors for sexual reproduction and auxospore formation.