Cyanophyta is a class of blue-green algae also known as cyanobacteria. They usually reproduce through asexual mechanisms. The asexual reproduction in Cyanophyta is through methods such as binary fission, fragmentation, and hormogonia formation.
Asexual Reproduction in Cyanophyta
Binary Fission
Binary fission happens to be the most common method of asexual reproduction in cyanobacteria. In this process, a single cell of the algae divides into two identical daughter cells. Binary fission begins with DNA replication followed by the elongation of the cell.
Finally, the cell wall is formed to divide the replicated DNA into two cells. These daughter cells are then separated from the mother cell. Each of these cells grows into an individual organism.
Fragmentation
Fragmentation is another common method of asexual reproduction in cyanobacteria. It is usually seen in filamentous forms of blue-green algae. Here, the filamentous body of the algae breaks into smaller fragments.
Each fragment grows into an independent organism. When the filaments are fragmented they may get dispersed giving way to their colonization in different environmental conditions and habitats.
Hormogonia Formation
Hormogonia are specialized cells of some types of cyanobacteria for their asexual reproduction. These hormogonia are motile and have a filament-like structure that gets detached from the parent filament or colony.
The detached filaments move independently by propelling themselves through gliding or twitching movements, or by secreting mucilage. Once they settle in a favorable environment they grow into new filaments or colonies.
Endospores
The non-motile Dermocarpa produces endospores formed by the enlargement of one or two cells. These enlarged cells will have their protoplast divided into multiple spores. These spores on dispersal can grow into individual organisms.
Exospores
In cyanobacteria called Chaemosiphon, the dorsal part of the protoplast gets separated to form exospores that are capable of growing into a new individual.
Akinetes
Akinetes are resting spores with thick walls, found next to heterocysts. They can withstand unfavorable conditions and develop into a new individual when conditions are favorable. Eg. Anabaena.
Nannocytes
Cells of some filamentous cyanobacteria such as Microcystis can undergo multiple divisions without affecting the shape of the organism. These newly formed cells have naked protoplast. They do not disperse but grow in situ to form new organisms.
Conclusion
While asexual reproduction is the predominant method of reproduction in cyanobacteria. Sexual reproduction in Cyanophyta is almost non-existent. However, some of the members can undergo sexual reproduction under certain conditions. Here, the exchange of genetic material happens leading to the formation of a new individual. But, it is rare when compared to asexual reproduction in Cyanophyta.
