In certain species of
diatoms, auxospores are specialised
cells
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
that are produced at key stages in their
cell cycle
The cell cycle, or cell-division cycle, is the series of events that take place in a cell that cause it to divide into two daughter cells. These events include the duplication of its DNA ( DNA replication) and some of its organelles, and sub ...
or
life history. Auxospores typically play a role in growth processes,
sexual reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote th ...
or
dormancy
Dormancy is a period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be c ...
.
[Hoek, C. van den, Mann, D. G. and Jahns, H. M. (1995). ]
Algae : An introduction to phycology
', Cambridge University Press, UK.
Auxospores are involved in re-establishing the normal size in diatoms are successive
mitotic
In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...
cell division
Cell division is the process by which a parent cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukaryotes, there ar ...
s leads to a decrease in cell size. This occurs because each daughter cell produced by cell division inherits one of the two valves that make up the
frustule
A frustule is the hard and porous cell wall or external layer of diatoms. The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance, which was referred to in the early literature on ...
(a
silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is o ...
cell wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mec ...
), and then grows a smaller valve within it. Consequently, each division cycle decreases the average size of diatom cells in a population. When its size becomes too small, a dividing diatom cell produces an auxospore to expand its cell size back to that which is normal for
vegetative cells
Vegetative describes vegetation. Vegetative may also refer to:
*Vegetative reproduction, a type of asexual reproduction for plants
*Persistent vegetative state, a condition of people with severe brain damage
*Plant community
A plant community is ...
.
Auxospores can also play a role in sexual reproduction in diatoms, and may be formed after
haploid gamete
A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...
s fuse to form a
diploid
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respecti ...
zygote
A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism.
In multicell ...
.
[Chepurnov, V.A., Mann, D.G., Sabbe, K. and Vyverman, W. (2004). Experimental studies on sexual reproduction in diatoms. ''International Review of Cytology'' 237, 91-154.]
Finally, auxospores can be produced by diatoms to act as dormant stages, sometimes referred to as "resting spores." These are used to survive periods of time that are unfavourable to growth, such as winter or while
nutrients are depleted.
References
Diatom biology
{{Diatom-stub