Symbiotic relationships


Symbiotic relationships

In nature Symbiotic relationships may take various forms. Parasitism, Commensalism, Amensalism and Mutualism. I am not going to discuss amensalism in any great detail because it is a very rare form. However the three most common types of symbiotic relationships are: Parasitism, Commensalism, Mutualism

  • Parasitism

    This is one of the most common of the symbiotic relationships. With the parasitism, one of the organisms (the parasite)benefits from the interaction, whilst the other organism (the host)is usually affected negatively.

  • Commensalism

    Commensalism is a positive interaction or relationship between two organisms in which only one partner benefits and the other is not harmed. This is usually associated with a feeding scenario, and describes where one species benefit and the other is not affected. A common form is Cattle Egrets following Buffalo, feeding off the insects that are disturbed.

  • Metabiosis – Where one species uses something made by a second species. Usually after its death, a hermit crab using a Gastropod shell to live in.
  • Inquilism – The second organism is used directly for housing, protection or structural support. Animals using holes in trees to live in. Male Paper Nautilus  lives in female shell, Hornbills.
  • Phorsey – One species using another for transportation to get to a desired area. Mites using dung beetles to get to dung to feed on fly eggs and larvae.
  • Amensalism

    This is a rare form of the symbiotic relationships, where one species is not affected (it does not benefit or suffer) while the other suffers.It usually occurs when one species releases chemical compounds as part of its normal metabolic functions.  These compounds have a detrimental affect on other organisms. There are basically two types of Amenssalism, competition and antibiosis.

  • Competition – In competition, a larger or more powerful organism excludes another organism from its source of shelter or food.
  • Antibiosis – during antibiosis, one organism secretes a chemical that kills the other organism, while the one that secreted the chemical is unharmed. One species releases chemical compounds as part of its normal metabolic functions and these have a detrimental affect on other organisms. Two examples of antibiosis amensalism are provided by the bread mold Penicillium and black walnut trees.
  • The bread mold Penicillium commonly grows on any bread that has passed its shelf life.  This mold is capable of producing penicillin, which destroys many of the forms of bacteria that would also like to grow on this bread. It is this understanding of the bacteria-killing properties of penicillin that led to the use of it as an antibiotic medicine. The Penicillium (spelled correctly) does not benefit from the death of the other bacteria, making this an example of antibiosis amensalism
  • Black walnut trees.Walnut roots exude juglone which is toxic to other plants, stopping their seeds from germinating or preventing them from actually growing well.
  • Mutualism

    Mutualism is also a positive interaction or relationship between two organisms where both organisms benefit from the interaction.This is an account of mutualism and parasitism within the bio diverse Fernkloof Reserve in Hermanus. The symbiotic relationship in this case, involves two types of symbiosis – mutualism and parasitism. Mutualism is between the tree Kiggelaria africana commonly known as the Wild peach, and the Klaas’s cuckoo.

    Brood parasitism occurs when the Klaas’s cuckoo lays up to 24 eggs in one breeding season and chooses a host bird from a selection of 16 species to incubate and rear their young. The Kiggelaria africana is the host tree to the acraea horta butterfly and her caterpillars on which the cuckoo feeds.


  16 host bird species used by Klaas’s cuckoo.


The tree and the bird – symbiotic relationships

Klaas’s cuckoo (Chrysococcyx klaas ) and the Wild Peach ( Kiggelaria Africana)

The tree produces hydrocyanic acid which has been isolated from various parts of the tree, especially the leaves. Hydrocyanic acid is extremely poisonous and, because of this, herbivores avoid browsing from this tree. The leaves are, however, eaten by the caterpillar of the Acraea horta or the Garden Acraea (a butterfly of the Nymphalidae family). Their caterpillars sometimes eat the tree bare, but this is part of a natural process and the Kiggelaria trees always rapidly re-grow their foliage see more on Wikipedia

The bird, the butterfly and brood parasitism – symbiotic relationships

The caterpillars of the Garden Acraea butterfly (Acraea horta) feed on the Kiggelaria Africana and the Klaas’s cuckoo feeds on the caterpillars, therefore limiting the damage to the tree. The Klaas’s cuckoo has been seen beating the caterpillars against branches to knock off their spines,  before eating them.

This cuckoo masterfully manipulates local ‘host’ birds into raising its young. The male cuckoo harasses the host bird encouraging it to leave its nest and chase the cuckoo. That’s when the female cuckoo quickly lays her egg in the host’s nest. The cuckoo’s eggs are a lot smaller than other birds of a similar size which helps to disguise it among the host’s eggs; the female also evicts 1 egg from the host nest before laying her egg to keep the numbers correct.

Klaas’s cuckoo 

The Klaas’s cuckoo chicks usually hatch after an incubation period of 11-12 days which is shorter than its host species with a much longer incubation period of anything from 14 to 21 days. The cuckoo chick’s feet are much bigger than those of the host species and it often tramples the other chicks. They may also physically evict any host chicks or eggs from the nest. The cuckoo chick stays in the nest for about 19-21 days, after which it remains with the host bird for up to 25 days.

This is a classic example of a food web, illustrating the system of interwoven and interdependent food chains within this biome. A symbiotic relationship between a tree, a bird and a caterpillar which is both mutual and parasitic. Wild peach Kiggelaria Africana

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