Mutualisms between fungi and animals
The entomologists focusing on these fascinating social insects have long considered the symbiotic relationship between the Macrotermitinae. Insect-Fungus Symbiosis: Nutrition, Mutualism, and C mensalism between fungi and insects. The chapters interplay between beetle and fungus that allows their joint sur association (helotism?) with scale insects is ignored completely. There are more species of animals than any other group of organisms, so it is not surprising that fungi have come to form mutualistic relationships with many of.
When we hear of fungi-insect symbiosis we might think of the relationship only as a parasitic one where the fungi attack and usually kill the insect. However, this is not the only type of relation these organisms have established.
Entomologists, who study insects, have found that about 4, species of insects cultivate fungi as their primary source of food. In return, fungi have their spores dispersed by the insects.
This sounds like a fair deal to me! Insects that cultivate fungi, or so called fungivorous insects, have developed adaptations that allow them to exploit this abundant resource. For example, the winged female ant of the genus Atta, carries spores in a small pocket in her mouth. When a suitable nest is found, she starts growing fungi and, she begins laying eggs once the fungal colony is established.
Termites and Termitomyces In civilization, termites are one of the worst pests that we can imagine. However, in nature they play an important role in the decomposition of plant material. Termites have bacteria in their gut that allow them to digest cellulose and thereby recycling plant material.
In additional because of their large biomass, they also serve as a food source for a number of other species of animals. Where the ants that cultivate fungi are in the new-world tropics, the termites that cultivate fungi are native to the old-world tropic. These termites belong to the subfamily Macrotermitinae which include approximately twelve genera that are distributed in Africa, Madagascar, India and much of south-east Asia.
The start of new colonies is similar to that of the Attine ants. The colony begins with a winged male and female rather than a winged female that has already been impregnated. The two termites will wall themselves in an underground "royal chamber" from which they will never leave.
When mature, the queen will be quite large, relative to the other termites. The abdomen containing the eggs make up most of the large size of the queen, which may be up to 10 centimeters long in Macrotermes bellicosus. The queen then begins laying eggs, and the workers that result bring food to the couple, take new eggs away for incubation and add further to the nest. The workers continue to build the fungus garden around the royal chamber. Above the royal chamber, the workers build mounds that may be as much as six meters tall and three meters across at the base.
Click here to see a large termite mound. The mound have air shafts that leads to the fungus garden, which by this time, may be a large central structure that is 50 cm 20 in in diameter and weighing as much as 25 kg 55 lbs or may be made up of a number of smaller chambers.
Colonies may contain as many as a million termites that forage for plant debris, mostly in the form of wood. Unlike the Attine ants, the termites will eat the plant material where they find it and upon returning to the colony will place their fecal droppings in the fungus garden. The fungus garden is sponge-like in appearance and on the surface arise spherical structures that are composed of clustered conidiophore and conidia.
While tending the garden, the workers will nibble on the fungus. The cellulolytic enzymes, that are in the mycelium, remain active in the gut of the workers. The king, queen, soldiers and nymphs do not eat the fungus directly, and live on the salivary secretion of the workers.
The fungi that are in these termite mounts, unlike those in the Attine ant colonies, are well known since they fruit readily in nature. The mushrooms formed have been observed to be connected to the fungus gardens of the termites. Click here to see picture of the connection.
These mushrooms have been identified as Termitomyces, a genus known only from the termite mounds. There are thirty species in this genus.
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In some species, a member of the Ascomycota, a species of Xylaria, may also be found growing with the mushrooms. The Macrotermitinae are major pests of tropical agriculture and cause damage to wooden structures.
They take nutrients underground to their mounds where they remain locked up and unavailable for years. However, they are part of the food chain, serve as food for many animals, and the Termitomyces species have become highly prized, edible mushrooms, in the tropics, and attempts are underway to cultivate these species.
Fungi and Insects: A Love Story
Ambrosia Fungi Some scolytid beetles are wood inhabiting insects, and form tunnels in trees that are diseased or have been cut. The tunnels have narrow openings to the outside which widen into a number of cave like chambers where the eggs and larvae will develop.
The tunnels and chambers are lined with the ambrosia fungus and is usually a source of food for the adult and is the sole source of food for the larvae. This is a very highly evolved relationship with only certain beetles and fungi occurring together.
Neither the fungus nor the beetle species are found free-living in nature. This relationship has also proven to be harmful to a number of economic plants.
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You can read here about the economic damage that is caused, by the symbiosis between these two organism, on the plants that they live. The Asian Ambrosia Beetle is a common species on the mainland that has causes disease in trees. Some pictures of the beetles, its larvae and the damage that it can cause can be seen here.
The adult female beetle carries the fungus with them during their migration and when they are hibernating for the winter.
There is a specialized sac, the mycangia, that occur in various locations of the body in different species of insects. When the female finds a suitable plant on which to live, she bores a small hole by which she will have access, which will eventually form a series or gallery of tunnels.
It is along the gallery walls that the fungus garden is started. The mycangia produce secretions that prevent the spores from drying and also provides nutrients needed for the germination of the spores. When new tunnels are bored, the beetles prepare a mixture of feces and wood fragments which they smear on the tunnel wall as a substrate for the fungus to grow.
As in the case of the colonial insect, there is only one fungus growing on the tunnel walls. This fungus is used as food for both the new larvae that may be borne along the gallery or in special chambers called cradles, and it is responsible for the damage that is done to the tree. However, it is not known how the beetles maintain pure cultures of the ambrosia fungi.
When the tunnels are abandoned, contaminating fungi develop abundantly, and grow over the ambrosia fungi. Fungi that are cultivated by scolytid beetles, in tunnels or galleries, dug in trees. Many of the fungi cultivated are plant pathogens harmful to the tree on which they are growing.
Swollen tips of the mycelium on which the leaf-cutting ants feed. They are so called because they cut leaves into smaller pieces that can more readily be carried by a single ant. These ants are native mostly to Central and South America that gather plant material to cultivate a fungus garden that they use for food. The gathering of plant material is often devastating to the vegetation in the area.
Termites that build large termites mounds that shelter the termite colony. Unlike termites with which we are familiar, termites in this group do not contain the protozoan symbiont in their gut that allows them to digest wood. Thus, they do not eat wood, but rather use the wood that they gathered to feed the fungus garden that they cultivate. It is the fungus that is utilized by the termite for food. Specialized body part that female scolytid beetles carry the fungus that they will cultivate when they find a suitable tree host.
Used here to indicate that the fungi that cultivate mushrooms for food are able to grow only the species that they utilize for food rather than having a mixture of many species of fungi.
Wood boring beetles that cultivate ambrosia fungi, in the galleries that they dig in the trees. A genus of Basidiomycota that forms colonies on top of plants that have scale insects. The photos below could be a variety of different options, but unfortunately I did not dig down to uncover what it was attached to, so I am unable to complete the identification.
I saw this while hiking at Boyce Mayview Park. An unknown fungus attacking a Harvestman An unknown fungus attacking a Harvestman Two other species were found in Ohio during a group hike in the Mohican-Memorial State Forest. They were very similar but their hosts were different. Cordyceps militaris is attached to a butterfly pupae and Cordyceps cardinalis is attached to a butterfly larvae.
See Cordyceps militaris photos below: I took these photos in Western Pennsylvania Example 1: Some mushrooms are bioluminescent and they glow at night.