Bdelloid rotifer

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Classification

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Domain: Eukaryota

Kingdom: Animalia

Phylum: Rotifera

Superclass: Eurotaria


Class

Bdelloid morphology.jpg

Bdelloidea are a class of rotifers. There are over 450 species of bdelloid rotifers distinguished by their morphology. This includes species such as Adineta ricciae, Rotaria rotatoria, and Philodina acuticornis. Bdelloidea's species concept is based on molecular and morphological data due to their asexual nature.

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Description and Significance

Appearance:
Bdelloid rotifers are microscopic worm-like organisms that are usually between 150 to 750 µm long. Their bodies are made up of three main regions: head, trunk, and foot. Bdelloids have a well developed corona that is divided into two parts on a retractable head. Bdelloid rotifers can only be identified by eye while they are alive in order to see how they feed and crawl, which are their defining characteristics for classification. Through a weak hand lens, bdelloid rotifers appear as tiny white dots.

Habitat:
Bdelloidea can be found in fresh and brackish water all over the world. They can also be found in moss, lichen, and soil while also being able to survive dry, harsh environments through desiccation-induced dormancy, also known as anhydrobiosis. Bdelloid rotifers are considered to be cosmopolitan.

Significance:
Bdelloid rotifers are the oldest and most diverse asexuals to be discovered, surviving for over 80 millions years. Besides reproducing asexually, bdelloid rotifers are all female therefore reproducing through parthenogenesis. Bdelloidea defy biologist's ideas surrounding the centrality of sex by creating genetic diversity asexually. Daughter bdelloids inherit both copies of each gene from their mother, but these genes never intermix. This allows the genes to remain distinct and evolve to take on new roles regardless of their partner gene's destiny. Researcher's believe that these two-for-one gene helps bdelloids compensate for the loss of diversity that typically occurs without sex.


Genome Structure

Bdelloid rotifers are found to have colinear chromosomes, with a mitochondrial genome sequence of 15,319 bp for R. rotatoria.

Horizontal gene transfer is rare in multi-cellular eukaryotes, but it has been found that bdelloid rotifers contain a high proportion of horizontally transferred, non-metazoan genes. The bdelloid rotifer incorporates foreign DNA from fungi, plants, and bacteria. The foreign DNA is incorporated when repairing their chromosomes from double strand breaks. The efficient repairing of double strand breaks allows the bdelloid rotifers to be resistant from ionization radiation. HGT is higher in species that desiccate more frequently in order to repair the double strand breaks in their chromosomes.

strong>Interesting Features:

Cell Structure, Metabolism and Life Cycle

Interesting features of cell structure; how it gains energy; what important molecules it produces.


Ecology and Pathogenesis

Habitat; symbiosis; biogeochemical significance; contributions to environment.
If relevant, how does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Author

Page authored by Larynn Hall, student of Prof. Jay Lennon at IndianaUniversity.