A clamp connection is a hook-like structure formed by growing

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

l cells of certain fungi. It is a characteristic feature of Basidiomycetes fungi. It is created to ensure that each

cell 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 ...

, or segment of hypha separated by septa (cross walls), receives a set of differing nuclei, which are obtained through mating of hyphae of differing sexual types. It is used to maintain

genetic variation Genetic variation is the difference in DNA among individuals or the differences between populations. The multiple sources of genetic variation include mutation and genetic recombination. Mutations are the ultimate sources of genetic variation, b ...

within the hypha much like the mechanisms found in

crozier A crosier or crozier (also known as a paterissa, pastoral staff, or bishop's staff) is a stylized staff that is a symbol of the governing office of a bishop or abbot and is carried by high-ranking prelates of Roman Catholic, Eastern Cathol ...

(hook) during sexual reproduction.

Formation

Clamp connections are formed by the terminal hypha during elongation. Before the clamp connection is formed this terminal segment contains two nuclei. Once the terminal segment is long enough it begins to form the clamp connection. At the same time, each nucleus undergoes mitotic division to produce two daughter nuclei. As the clamp continues to develop it uptakes one of the daughter (green circle) nuclei and separates it from its sister nucleus. 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 In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatr ...

forms, separating each set of nuclei.

Use in classification

Clamp connections are structures unique to the phylum

Basidiomycota Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basi ...

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

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

Fossil record

A fungal mycelium containing abundant clamp connections was found that dated to the Pennsylvanian era (298.9–323.2 Mya). This fossil, classified in the

form genus Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of s ...

'' Palaeancistrus'', has hyphae that compare with extant

saprophytic Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ( ...

basidiomycetes. The oldest known clamp connections exist in hyphae present in the fossil fern '' Botryopteris antiqua'', which predate ''Palaeancistrus'' by about 25 Ma.

References

{{Reflist, refs= {{cite journal , author=Dennis, Robert L. , year=1970 , title=A middle Pennsylvanian basidiomycete mycelium with clamp connections , journal=Mycologia , volume=62 , issue=3 , pages=578–584 , jstor=3757529 , doi=10.2307/3757529 , url=http://www.cybertruffle.org.uk/cyberliber/59350/0062/003/0578.htm {{cite journal , author=Furtado, João S. , year=1966 , title=Significance of the clamp-connection in the basidiomycetes , journal=Persoonia , volume=4 , issue=1 , pages=125–144 , url=http://www.repository.naturalis.nl/document/570025 {{cite journal , author1=Krings, Michael , author2=Dotzler, Nora , author3=Galtier, Jean , author4=Taylor, Thomas N. , year=2011 , title=Oldest fossil basidiomycete clamp connections , journal=Mycoscience , volume=52 , issue=1 , pages=18–23 , doi=10.1007/s10267-010-0065-4, hdl=1808/13681 , hdl-access=free Fungal morphology and anatomy