nonseptate

Nonseptate describes hyphae that lack cross walls, or septa, resulting in a continuous cytoplasmic mass. In nonseptate hyphae, the cytoplasm and organelles flow through a continuous, unsegmented filament, making the mycelium effectively a single, multinucleate cell (coenocytic). The hyphae tend to be undivided along their length, with nuclei that are often numerous and unevenly distributed. Growth occurs by apical extension and cytoplasmic streaming, enabling rapid colonization of substrates.

Nonseptate hyphae are characteristic of several early-diverging fungal lineages, notably many members of the former Zygomycota (now divided into Mucoromycota and Zoopagomycota) and related groups, as well as some chytrids. In contrast, most higher fungi, such as Ascomycota and Basidiomycota, possess septate hyphae, in which cross-walls subdivide the filament into individual cells connected by septal pores. Some nonfungal organisms, such as certain oomycetes, also form coenocytic hyphae.

The lack of septa can enable rapid cytoplasmic transport and swift expansion of the mycelium, but it can also mean that injury to one region can affect a large portion of the hypha. Reproduction in these organisms typically involves sporangia bearing sporangiospores for asexual reproduction, while sexual reproduction proceeds through zygospores within zygosporangia in many of the coenocytic groups.

See also: septate hyphae.