Crucibulum laeve (Brown Bird Nest Fungi)
Scientific name: Crucibulum laeve
Common name: Brown Bird Nest Fungi
Crucibulum is a genus in the Nidulariaceae, a family of fungi whose fruiting bodies resemble tiny egg-filled bird's nests. Often called "splash cups", the fruiting bodies are adapted for spore dispersal by using the kinetic energy of falling drops of rain. The "eggs" inside the bird's nests (technically known as peridioles) are hard waxy shells containing spores, and tend to stick to whatever nearby herbage they land on, thus increasing the odds of being consumed and dispersed by herbivorous animals. Members of this genus are saprobic, obtaining nutrients from dead organic matter, and are typically found growing on decayed wood and wood debris. The three known Crucibulum species (C. laeve, C. parvulum, and C. cyathiforme) are distinguished from other genera of the Nidulariaceae by their relatively simple funiculus – a cord of hyphae that connects the peridiole (the "eggs") to the exterior of the bird's nest.
There are usually 4–6 peridioles (up to 15 have been noted for C. leave that are disc-shaped, whitish in colour, and attached to the endoperidium by a strand called a funicular cord made of mycelia. The funicular cord tends to wither away and disappear as the fruiting body ages. Spores from Crucibulum species typically have an elliptical or roughly spherical shape, and are thick-walled, translucent (hyaline) or light yellow-brown in colour, with dimensions of 5–15 by 5–8 µm. the spores of C. cyathiforme are notably slightly or strongly curved.
Spores are dispersed when a peridiole is dislodged by raindrops or water dripping off an over-hanging leaf. The smooth inner walls of the fruiting body consistently form an angle of 70–75° with the horizontal; it has been demonstrated experimentally that the combined effect of the crucible shape and internal wall angle produce a good splash action. The force of the falling water splashes out the peridiole, uncoiling and snapping the funiculus, the cord that connects it to the fruiting body. As the peridiole continues its flight, the funiculus extends to its full length. The sticky end of the funiculus may adhere to a leaf or a twig some distance away, and the peridiole may end up being wrapped around or hanging down the object to which the funiculus is stuck. The spores can germinate when the thick outer wall of the peridiole wears away, or the peridiole may be eaten by a herbivorous animal, and ultimately passed through its digestive system.
The life cycle of a bird nest fungi
Illustration by Elaine M. Collins, Palomar College; modified from Canadian Journal of Botany 29: 224-234, 1951.
Photo below is a cross section of an inmature fruiting body showing the developing peridioles (eggs)
Photo showing the egg cups and the eggs (peridioles)
One peridiole (egg) has just been distraced from the egg cup.
Young specimens have a thin layer of tissue called an epiphragm that covers the top of the peridium (the cup); it wears off at maturity to expose the peridioles (eggs) within.
The empty cup.