Clathrus archeri

Clathrus archeri (synonyms Lysurus archeri, Anthurus archeri, Pseudocolus archeri), commonly known as octopus stinkhorn or devil's fingers, is a fungus which has a global distribution. This species was first described in 1980 in a collection from Tasmania. The young fungus erupts from a suberumpent egg by forming into four to seven elongated slender arms initially erect and attached at the top. The arms then unfold to reveal a pinkish-red interior covered with a dark-olive spore-containing gleba. In maturity it smells like putrid flesh.

Description
Clathrus archeri grows in 2 distinct stages, first an egg stage followed by the fungal "arms" emerging. During the egg stage, C. archeri forms a white ball-like egg shape, usually 2 - 3 cm in diameter. Next, the thallus emerges from the egg in a starfish-like shape with 4-6 arms on average (up to 8). Each arm can grow up to 10 cm in length and is coated in gleba on the upper surface. Fruiting bodies produce a red-orange color due to the production of carotenoids. Fungal spores are oblong, smooth, and 3.5–6 x 1.5–2 μm in size. As other members of the family Phallaceae, the strong putrid smell of the gleba shows convergent evolution with some angiosperm flowers called sapromyophilous flowers.

In a laboratory setting, C. archeri was found to grow best in 26 C on a compost agar (CA) medium with a pH of 6.0. Under these conditions, the thallus grew an average of 2.9 mm a day over 4 weeks and in a radial shape. C. archeri produces white and fluffy mycelium and eventually turns a pink color. Mycelia strands are 0.5 - 1.5 mm in diameter and branch in a tree-like manner. Fungal Hyphae create irregularly shaped vesicles that contain lipids. On the surface of the hyphae, calcium oxalate crystals are secreted. It is hypothesized that this outer layer of crystals creates a protective hydrophobic layer around the hyphae. C. archeri forms unstable perforate septal pore caps; this may suggest that perforation formation in Phallomycetidae begins later in comparison to similar groups.

Chemistry
Clathrus archeri produces compounds similar to the scent of rotting flesh. This compound production supports evidence of convergent evolution between fungi and angiosperms. This scent is used by the fungus to attract flies to serve as agents for spore dispersal.

Habitat and distribution
Clathrus archeri is commonly found in environments with abundant decaying organic matter. It is most common in leaf litter and mulch, in both woodlands and grasslands. Saprophytes prefer areas with high moisture or water, access to oxygen, neutral pH, and low-medium temperatures.

The species is believed to be endemic to southern Africa, New Zealand and Australia, but has been spreading to other continents and is often invasive. Clathrus archeri now has a global distribution and has been naturalised in Europe and North America. It was first discovered in the UK over a century ago (~1914) and has spread across much of Europe. Clathrus archeri was likely introduced via wool fabric in supplies for WWI. As climate changes drive niche habitat loss, Clathrus archeri is expected to become threatened in Australia but is expected to expand to northeast Europe. The expansion of Clathrus archeri in Europe is further supported by its invasion into 2 new Romanian sites in July 2013. Furthermore, Clathrus archeri has been found in 90 sites in Poland as of 2013, 65% of which are located in forests. Recent modeling studies in Poland expect the alien species to occur in areas with a thick layer of snow, which does not melt in winter, at higher altitudes, where the water deficit is low.

Recently, C. archeri var. alba with white tentacles or arms has been reported from the Shola Forests in the Western Ghats, Kerala, India.

Ecology
Clathrus archeri grows best in environments rich in decaying vegetation. The fungus is a saprotroph. It is most commonly found in leaf litter or mulch below vegetation. The most abundant acid secreted by the fungus is oxalic acid, this acid binds to metal cations and increases the bioavailability of some minerals. Fungal mycelium exhibits calcium pooling which changes soil pH and availability of phosphorus for surrounding flora.

Inedibility
Due to the rotting stench of stinkhorns, there are no common culinary applications.