In
algal
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular microalgae, s ...
anatomy, a pit connection is a hole in the
septum
In biology, a septum (Latin language, Latin for ''something that encloses''; septa) is a wall, dividing a Body cavity, cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate.
Examples
Hum ...
between two algal cells, and is found only in multicellular
red algae
Red algae, or Rhodophyta (, ; ), make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest Phylum, phyla of algae, containing over 7,000 recognized species within over 900 Genus, genera amidst ongoing taxon ...
− specifically in the subphylum Eurhodophytina, except haploid
Bangiales.
They are often stoppered with proteinaceous "pit plugs". By contrast, many
fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
(only
ascomycetes
Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The de ...
and
basidiomycetes
Basidiomycota () is one of two large division (mycology), 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. Mor ...
, as most other groups lack septa) contain septal pores − an unrelated phenomenon.
Characteristics
A sieve-like membrane may cover the pit in living algae,
[ but in the majority of algae a plug forms, they likely limit the transfer of metabolites between neighbouring cells.]
Formation
Primary pit connections are formed between cells in the same filament, derived from the same parent cell by its division.[ Such connections are always single, and usually circular;][ this is a result of their method of formation. The septum is formed as the walls of a filament grow inwards, dividing the cell; this results in a hole in the middle of the tube where the walls don't quite merge.][ Thus pit connections are visible in the youngest of septa, widening as the septum thickens, until in some cases they may ultimately occupy the entire septum.][
Secondary connections, by contrast, occur between unrelated cells, and serve a role in transferring cell contents and nutrients.]
References
External links
* Transverse SEM images of pit connections in the coralline '' Synarthrophyton'' can be seen in Figs. 54 & 60 in
* (Lower quality) transverse SEM images of pit connections in the coralline '' Phymatolithon'' are available on page 138 at .
{{Protist structures
Red algae