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 o ...

l cells of certain

fungi A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...

. It is a characteristic feature of Basidiomycetes fungi. It is created to ensure that each cell, or segment of hypha separated by

septa The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates transit bus, bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people ...

(cross walls), receives a set of differing nuclei, which are obtained through

mating In biology, mating is the pairing of either opposite- sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. '' Copulation'' is the union of the sex organs of two sexually rep ...

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 Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote th ...

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 * Interat ...

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

basidiocarp In fungi, a basidiocarp, basidiome, or basidioma () is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do n ...

s (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 Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial ...

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 Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the International Commission on Stratigraphy, ICS geologic timesca ...

era (298.9–323.2

Mya Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...

). 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 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