Fissitunicate

Fissitunicate is a term used in mycology to describe a mode of asci dehiscence in some Ascomycota. It refers to asci that have two functional wall layers and release their spores through fissures that split the ascus wall. This fissure-based dehiscence is generally discussed as a form of bitunicate dehiscence, in which the inner and outer walls separate to allow spore discharge, rather than simple rupturing of a single wall.

In structure, fissitunicate asci possess two wall layers that can separate during maturation. The dehiscence occurs via fissures rather than by a single opening mechanism, and the process results in the ejection of ascospores from the now-open ascus. Because fissitunicate asci are part of the broader category of bitunicate asci, they are often studied alongside other two-walled asci that employ distinct dehiscence strategies.

Taxonomically, fissitunicate asci are reported in various lineages within the Ascomycota, particularly among groups that bear bitunicate asci, such as many members of the Dothideomycetes (including orders like Pleosporales and Capnodiales). The occurrence and exact mechanism can vary among taxa, and the term is primarily descriptive of the dehiscence pattern rather than a strict taxonomic rank.

Etymology-wise, fissitunicate derives from Latin fissus meaning split and tunicate meaning covered, reflecting the split-walled nature of the ascus. The concept has been used to distinguish fissure-based dehiscence from other asci-opening modes in mycological literature.

See also: unitunicate asci, bitunicate asci, Ascomycota, fungal dehiscence.