Clamp connection

A clamp connection is a structure formed by growing hyphal cells of certain fungi. It is created to ensure each septum, or segment of hypha separated by crossed walls, receives a set of differing nuclei, which are obtained through mating of hyphae of differing sexual types. It is used to create genetic variation within the hypha much like the mechanisms found in crozier during sexual reproduction.^[1]

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  Figure 1: Cantharellus clamp connection

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  Figure 2: Clamp connections in mushroom hypha

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  Figure 3: Clamp connection formation

Formation

Clamp connections are formed by the terminal hypha during elongation. Before the clamp connection is formed this terminal septa contains two nuclei (depicted as green and orange circles in Figure 3). Once the terminal septa is long enough it begins to form the clamp connection. At the same time each nuclei undergoes mitotic division to produce two daughter cells. As the clamp continues to develop it uptakes one of the daughter (green circle) cells produced and separates it from its sister cell. While this is occurring the remaining nuclei (orange circles) begin to migrate from one another to opposite ends of the cell. Once all these steps have occurred a septum forms, separating each set of nuclei.^[2]

Use in classification

Clamp connections are structures unique to the phylum Basidiomycota. Many fungi from this phylum produce spores in basidiocarps (fruit bodies, that is the mushrooms), above ground. Though clamp connections are exclusive to this phylum, not all species Basidiomycota possess these structures. As such, the presence or absences of clamp connections has been a tool in categorizing genera and species.^[3]

References

1. ^ C.J. Alexopolous, Charles W. Mims, M. Blackwell et al., Introductory Mycology, 4th ed. (John Wiley and Sons, Hoboken NJ, 1996) ISBN 0-471-52229-5
2. ^ http://www.botany.hawaii.edu/faculty/wong/Bot201/Basidiomycota/Clamp_connection_formation.htm
3. ^ Kuo M. "Using a Microscope: Clamp Connections". MushroomExpert.Com. http://www.mushroomexpert.com/microscope_clamps.html. Retrieved 2010-12-15.