15 examples of mutualism in nature

Mutualism is a type of symbiosis, where both species that interact benefit from the relationship. Below we present examples of mutualism in biology.

1. The dog and the human being

Probably the mutualistic relationship that we have most at hand is the one that exists between the human being and the dog (Canis lupis familiaris). Human beings have used dogs for centuries for different tasks: herding, hunting, transportation, guidance and company. In exchange, the dog receives food, care and shelter.

The mutualistic relationship between dogs and humans goes back many years.

2. Ants and aphids

One of the most frequent mutualisms in nature occurs between ants (Hymenoptera: Formicidae) and aphids (Hemiptera: Aphididae). In this case, aphids produce a type of honey that attracts ants, and the ants provide protection against enemies and cleanliness by removing the honey.

This mutualism is facultative, ants can survive regardless of the presence or absence of aphids, and vice versa.

Ants use aphids as a food source.

3. Ant and butterflies

The silver blue butterfly (Glaucopsyche lygdamus) in its caterpillar state produces a syrupy liquid that the ant (Formica fusca) uses for food. In return, the ant protects the caterpillar from flies and wasps.

4. Clownfish and anemones

Anemones are marine invertebrate animals that use poison to protect themselves and capture their prey. However, the clownfish has developed protective mechanisms against the poison, allowing it to live and reproduce within the area covered by the anemone’s poisonous tentacles.

The mutualism established between clownfish and certain species of anemones is obligatory, that is, the survival of both species depends on mutual coexistence. The fish is protected from predators while providing the anemone with ammonia for the synthesis of amino acids.

5. Corals and zooxanthella

The beautiful colors that corals present are due to the pigments of zooxanthellae, photosynthetic dinoflagellate algae of the genus Symbiodinium. Corals (genus Acropora sp.) receive carbohydrates in exchange for substrate and nutrients.

6. The cow and cellulose-degrading bacteria

The cow feeds on plants, made up mainly of cellulose. To degrade cellulose, cows and other ruminants harbor bacteria in their stomachs with the ability to digest it.

In this way, the bacteria receive protection and food, while they digest the cellulose, releasing simple sugars that the cows can absorb.

7. Truffles and oaks

Mycorrhizae are mutualistic associations between plant roots and fungi that grow in the soil. For example, truffles are the fruiting bodies of the mushroom genus Tuber sp. that live mycorrhized in the roots of oaks, trees of the genus Quercus.

In this association, the plant provides the carbohydrates it produces thanks to photosynthesis, while the fungus releases inorganic nutrients necessary for the development of the plant.

8. The wasp and the mites

The potter wasp (Allodynerus delphinalis)has pockets on its body where mites hide (Ensliniella parasitica). This mite protects the juvenile stages of the wasp from a parasite, the Melittobia acasta.

The wasp, when it makes its nest, leaves some mites as bodyguards for the eggs and larvae. The mite feeds on the wasp’s lymph, without killing it.

9. The tropical ant and the bullhorn acacia

Thorns of the bullhorn acaciaAcacia cornigera).

The Bush Acacia cornigera It developed hollow spines that looked like bull horns. The tropical ant Pseudomyrmex ferruginea It takes advantage of this characteristic of the plant to create its nests inside the thorns. The ants, for their part, protect the acacia from other competing plants, by removing the leaves of the invasive ones, and also protect it from herbivorous insects and other herbivorous mammals.

10. Legumes and nitrogen-fixing bacteria

The relationship between legumes (beans, alfalfa, peas, chickpeas and soybeans) and nitrogen-fixing bacteria is about 60 million years old. This mutualism is established between the roots of the plant and the bacteria in the soil.

Bacteria, generally of the genera Rhizobium, Ensifer and Bradyrhizobium sp., capture nitrogen from the atmosphere in the nodules that they form on the roots, providing nitrogen to the plants. In exchange, the plant supplies carbohydrates to the bacteria.

11. Aphids and bacteria

The bacteria Buchnera aphidicola is an endosymbiotic (lives inside its host) bacteria of the pea aphid (Acyrtosiphon pisum). This insect feeds on the fluids (poor in nutrients) of plants and needs the vitamins and amino acids produced by the bacteria that live in the animal’s intestine.

This mutualism is obligatory, to the point that bacteria pass from the parent insects to the offspring.

12. The Madagascar orchid and the sphinx moth

A specialized mutualism is that which occurs between Darwin’s orchid (Angraecum sesquipedale) and Morgan’s sphinx moth (Xanthopan morganii praedicta) found on the island of Madagascar. The orchid produces its nectar in a 30 cm appendage that can only be reached by the moth’s long proboscis.

The moth feeds on the nectar of the orchid while pollinating it and transporting its pollen.

13. Lichen

Lichens are obligatory mutualistic associations between fungi and blue-green algae or bacteria. The fungus benefits from the products of photosynthesis and the algae benefit from the moist environment and inorganic nutrients provided by the fungus.

14. Corn and humans

The corn we know today (Zea mays) is a product of artificial selection that humans have carried out over the years. Mutualism occurs because humans feed on the corn cob, while the plant is propagated by the farmers who grow it.

15. The sloth, the moths and the algae

Among sloths, moths and algae, a mutualism is established between three species. The lazy ones (Bradypus variegatus) are slow-moving herbivorous mammals. They live in the treetops, eating exclusively leaves.

The sloth descends from the tree to defecate, carrying the female moth in its hair (Cryptoses sp.) that lays its eggs in the sloth’s feces. The larvae of the moth feed on the sloth’s feces and once adults, they look for the sloth in the treetop. The moth transports nutrients to the algae (Trichophilus sp.) that grow in the sloth’s hair and that also serves as food for the animal.