Zooxantelas: What are, symbiosis, life cycle and function

Zooxantelas are photosynthetic unicellular microalgae living in symbiosis with other organismsin which the host as the guest benefits from each other. Specifically, they are immersed within the tissues of other organisms, which are usually animals.

The majority of zooxantelas belong to the symbiodiniaceae family that are dinoflagellated organisms and much of the genre Symbiodiniumalthough they can also be diatomas or other algae.

In this article we explain what is symbiosis in ecology with examples.

As a base, corals always have a heterotrophic diet where plankton capture through their polyps, as they are animals. But many species also have a symbiosis with zooxantlas, and those who have them obtain most of their energy from these algae. These are Within the tissue of each individual polyp that forms the coral.

What happens in symbiosis is that Algae carry out photosynthesisand certain compounds that are from here are incorporated by the coral, using them mainly to carry out nutrition, but also work for reproduction and calcification. 90% of the carbon requirements of symbiotic corals come from algae. Discover photosynthesis: what is, phases and importance.

In return, the corals They benefit algae with inorganic nutrients For their growth and development, as well as give them a place to live. Both soft and stone corals They can have this association, and that is determined by the species. Pestory corals have greater diversity of zooxantlas, while in soft corals the symbiosis is more stable.

It also influences symbiosis season of the yearbecause they depend on environmental changes. If there are stress conditions, algae can leave the coral with a decrease from 60 to 90% leading to the bleaching of corals, which is the loss of color that was previously given by algae. This can happen both in stone and soft corals. It can occur in patches, because some zooxante the changes better resist, but also It can happen throughout the colony. If adverse conditions pass, algae can return to coral. But if they are constant, as has happened with the warm -up of the oceans for the climate change caused by man, the algae will not return and Corals will die due to vulnerabilityespecially of diseases.

The corals that have zooxante algae are in shallow waters, exposed to sunlight and in areas of the tropical to subtropical strip, as they depend completely from the sun to be able to photosynthesize.

Zooxantelas and other hosts symbiosis

Not only can they be found in corals, but they also establish important symbiotic relationships with other organisms. The relationship and purpose of this symbiosis is similar to that mentioned with corals. Some examples are:

• Aggregator anemone (Elegantissima anthopleura): It is an example of the many anemones that have zooxantlas. In this species it was observed that algae helps to an effect of sunscreen so that the anemone does not burn under the sun, in addition to the other simultaneous nutrition functions mentioned above for all symbiosis with zooxant.
• Inverted jellyfish (Cassiopeia Xamachana): Many jellyfish can have zooxantlas, and this is an example of them. In this case, they serve to obtain carbon, but they also need to capture dams as an external food source.
• Giant marine clam (Gigas tridacna): It is a particular case because it is not a CNIDARY, such as most organisms containing zooxant.

We recommend reading this article about sea anemones: characteristics, types and food.

By asexual reproduction, each unicellular zooxant It divides every 1 to 3 days during the night into two new flagellated cells. They will lose the scourge with the change of photoperiod and transform to the typical coconut morphology of the genre, present when it is in the growth stage and not of division.

There is also a sexual reproduction, because They have been observed tetrads during divisionwhich suggests that there is meiosis. However, there is still no certainty about this because there is no determining evidence indicating meiosis.

Now, zooxantlas They are obtained by the different organisms by intake, absorbed by the ectoderm to be transported to the host endoderm, or transmitted by a mother colony. It is not that organisms are born with zooxantlas, but that they acquire them.

The most important ecosystem function of zooxante the production of calcareous skeletons in stone coralsthat is to say coral reefs. Part of the nutrients that are obtained from the photosynthesis of algae are destined to the development of the coral skeleton, an environment that will give refuge to a huge variety of marine species such as fish, sea sponges, crustaceans, echinoderms, soft corals, jellyfish, mollusks, among other groups. To give an idea of ​​the importance, these reefs are so rich in biodiversity that They house 25% of sea species.

On the other hand, it has been shown that the symbiosis of zooxante with stone and soft corals It contributes to biochemical cycles and global carbon contribution for the exchange of metabolites between host and symbion, being indispensable for the balance of ecosystems.

Now that you know what zooxant, their symbiosis, their life cycle and their function are, do not miss these other ecology articles about gorgonia: characteristics, habitat and food and sea feathers: characteristics, habitat and food.

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