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Auxospore

 

 
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Auxospore
 
 
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In certain species of diatom
Diatom

Diatoms are a major group of eukaryote algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as Colony in the shape of filaments or ribbons , fans , zigzags , or stellate colonies ....
s, auxospores are specialised cells
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
 that are produced at key stages in their cell cycle
Cell cycle

The cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to its division and duplication . In cells without a nucleus , the cell cycle occurs via a process termed binary fission....
 or life history
Life history theory

Life history theory is an analytical framework widely used in animal and human biology, psychology, and evolutionary anthropology which postulates that many of the physiology traits and behaviors of individuals may be best understood in terms of the key maturational and reproductive characteristics that define the life course....
. Auxospores typically play a role in growth processes, sexual reproduction
Sexual reproduction

Sexual reproduction is characterized by processes that pass a Genetic recombination of Genetics material to offspring, resulting in Genetic diversity....
 or dormancy
Dormancy

Dormancy is a period in an Organism Biological life cycle when growth, development, and physical activity is temporarily suspended. This minimizes metabolism and therefore helps an organism to conserve energy....
.

Auxospores are involved in re-establishing the normal size in diatoms because successive mitotic
Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
 cell division
Cell division

Cell division is a process by which a cell , called the parent cell, divides into two or more cells, called daughter cells. Cell division is usually a small segment of a larger cell cycle....
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
Frustule

A frustule is the hard and porous cell wall or external layer belonging to diatoms. The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance, sometimes pectin, a fiber most commonly found in cell walls of plants....
 (a silica
Silicic acid

Silicic acid is a general name for a family of chemical compounds of the element silicon, hydrogen, and oxygen, with the general formula [SiOx4-2x]n....
 cell wall
Cell wall

A cell wall is a tough, flexible and sometimes fairly rigid layer that surrounds some types of cell . It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism....
), and then grows a smaller valve within it.






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In certain species of diatom
Diatom

Diatoms are a major group of eukaryote algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as Colony in the shape of filaments or ribbons , fans , zigzags , or stellate colonies ....
s, auxospores are specialised cells
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
 that are produced at key stages in their cell cycle
Cell cycle

The cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to its division and duplication . In cells without a nucleus , the cell cycle occurs via a process termed binary fission....
 or life history
Life history theory

Life history theory is an analytical framework widely used in animal and human biology, psychology, and evolutionary anthropology which postulates that many of the physiology traits and behaviors of individuals may be best understood in terms of the key maturational and reproductive characteristics that define the life course....
. Auxospores typically play a role in growth processes, sexual reproduction
Sexual reproduction

Sexual reproduction is characterized by processes that pass a Genetic recombination of Genetics material to offspring, resulting in Genetic diversity....
 or dormancy
Dormancy

Dormancy is a period in an Organism Biological life cycle when growth, development, and physical activity is temporarily suspended. This minimizes metabolism and therefore helps an organism to conserve energy....
.

Auxospores are involved in re-establishing the normal size in diatoms because successive mitotic
Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
 cell division
Cell division

Cell division is a process by which a cell , called the parent cell, divides into two or more cells, called daughter cells. Cell division is usually a small segment of a larger cell cycle....
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
Frustule

A frustule is the hard and porous cell wall or external layer belonging to diatoms. The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance, sometimes pectin, a fiber most commonly found in cell walls of plants....
 (a silica
Silicic acid

Silicic acid is a general name for a family of chemical compounds of the element silicon, hydrogen, and oxygen, with the general formula [SiOx4-2x]n....
 cell wall
Cell wall

A cell wall is a tough, flexible and sometimes fairly rigid layer that surrounds some types of cell . It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism....
), 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 reproduction

Vegetative reproduction is a type of asexual reproduction for plants, and is also called vegetative propagation, vegetative multiplication, or vegetative cloning....
.

Auxospores can also play a role in sexual reproduction in diatoms, and may be formed after haploid gamete
Gamete

A gamete is a Cell that fuses with another gamete during fertilization in organisms that sexual reproduction. In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete?called an ovum ?and a male produces th...
s fuse to form a diploid zygote
Zygote

A zygote is a cell that is the result of fertilization. That is, two ploidy cells—usually an ovum from a female and a sperm cell from a male—merge into a single ploidy cell called the zygote ....
.

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
Oligotrophic

An oligotrophic ecosystem or environment is one that offers little to sustain life. The term is commonly utilised to describe bodies of water or soils with very low nutrient levels....
.