Nassula

Nassula
Nassula sp.
Scientific classification
Domain:	Eukaryota
Kingdom:	Chromalveolata
Superphylum:	Alveolata
Phylum:	Ciliophora
Subphylum:	Intramacronucleata
Class:	Nassophorea
Order:	Nassulida
Family:	Nassulidae
Genus:	Nassula Ehrenberg, 1833
Species
Nassula aurea Nassula citrea Nassula ornata Nassula picta

Nassula is a genus of unicellular ciliate protists, belonging to the class Nassophorea. Like other members of the class, Nassula possesses a basket-like feeding apparatus (nasse, or cyrtos) made up of cytopharyngeal rods (nematodesmata), which are themselves composed of closely packed microtubules.^{[1][2] [3]} Nassula use this structure to ingest filamentous cyanobacteria, drawing individual strands of blue-green algae through the cytopharynx and into the body of the cell, where they are digested. As the algae are broken down, they can take on a variety of bright colours, which give Nassula a distinctive, variegated appearance under the microscope.

Appearance and characteristics

The body is ovoid to elongate, and uniformly ciliated, with a single macronucleus and a partial hypostomial frange (synhymenium) running from the left side of the cell to the oral aperture. ^[4] It has been proposed that the elongated species Nassula elegans is actually a form taken by the species Nassula ornata when it is deprived of food.^[5] When food is scarce, members of the genus have the ability to become dormant by forming a microbial cyst. Excystment can be induced by exposure to a medium inoculated with wild bacteria.^[6]

Reproduction

Nassula cell division

Nassula reproduce asexually, by binary fission.^[7] During reproduction, the cell is divided transversally. As in most ciliates (with the exception of the Karyorelictea) the macronucleus splits, during division, and the micronuclei undergo mitosis.

Nassula also reproduce through conjugation, during which compatible mating individuals come together and transfer genetic material across a cytoplasmic link. In conjugation, the micronuclei of each cell undergo meiosis, and haploid micronuclei are then exchanged from one cell to the other.

References

1. ^ http://jcs.biologists.org/content/3/4/493.short
2. ^ http://jcs.biologists.org/content/6/2/385.short
3. ^ http://www.ncbi.nlm.nih.gov/pubmed/10340705
4. ^ Carey, Phillip G., Marine Interstitial Ciliates: An Illustrated Key. Chapman and Hall, 1992, ISBN 978-0-412-40610-2, p. 112
5. ^ http://www.biolbull.org/content/51/4/237.abstract
6. ^ http://onlinelibrary.wiley.com/doi/10.1111/j.1550-7408.1966.tb01874.x/pdf
7. ^ http://jcs.biologists.org/content/2/4/481.full.pdf