Rotifers: What are, characteristics, types and examples

The rotifers are microscopic organisms of the rotipa edgewhich inhabit aquatic freshwater environments. Its size varies between 200 and 500 micrometers, which makes them difficult to observe with the naked eye. In addition, rotifers are important in ecology and evolution studies, since Its presence is indicative of water quality In aquatic ecosystems. Despite its small size and soft body, fossils have been found, such as Habrotrocha angusticollisin turba deposits of the Pleistocene, which suggests its presence on Earth for at least 6000 years.

• Size: microscopic, generally less than 2 mm; More than 1000 species described.
• Cellular structure: body formed by a constant number of cells; Brachionus species have about 1000 cells.
• Segmented body: Divided into three parts: head, trunk and foot.
• Crown: region ciliated at the apical end, responsible for locomotion.
• MASTAX: Oral structure with chitine jaws to crush food.
• Lorica: Dense layer of protein similar to keratin, which varies in form and rigidity.
• Pseudocele: Body cavity full of liquid that suspends the digestive system.
• Adherence: Foot with the cement gland to fix surfaces.

The rotator edge is classified into three main types or classes:

Sixth Class

It is characterized by rotifers that inhabit the crustacean gills of the genus Nebalia. A distinctive feature of this class is that males and females have similar sizeswhich is rare in other rotifers. In addition, they have an elongated body and a reduced crown. Its muscle structure is comparable to that of other rotifers, with longitudinal and striated muscles.

BDELLOIDEA CLASS

Known for their parthenogenetic reproduction capacity and their Resilience to adverse conditionslike drought. These species can enter a state of lethargy, which allows them to survive in unfavorable environments. Its evolutionary history dates back to more than 25 million years.

Monogononta class

Includes rotifers that can be Both swimmers and sessilewith a gonada and a reduced crown. This class is distinguished by seasonal reproduction, where males are generally smaller than females. Some females can reproduce by partnogenesis, although this is uncommon.

The rotifers inhabit mainly in fresh water environmentsincluding wet soils, stagnant and currents. They are considered cosmopolitan organismspresent in fresh, brackish and marine waters worldwide, except in Antarctica. Many species are planktonic and can be found in water films on lichens and mosses, as well as in puddles and rain gutters.

Some species are sesile or colonial, while others are endemic to specific regions. The members of the Sensonidea order have been found exclusively in marine environments, living in crustacean bodies. In addition, rotifers can inhabit artificial habitats and in the interstitial water of soils, contributing to the cycle of nutrients in these ecosystems.

Rotifers are mainly detritivorous, feeding on bacteria, algae and protozoa in decomposition. Their size allows them to consume particles of up to 10 micrometers, thus contributing to the recycling of nutrients in aquatic ecosystems. Used in aquaculturefish and fish farms are added to improve water quality. In this article you can learn more about aquaculture: what is, advantages and disadvantages.

The food mechanism of rotifers is based on The crown actioncovered with cilia that generate a vortex of water, attracting food towards their mouths. The particles are sifted and passed through their digestive system. Filtrating species have well developed and mastox cilia, which crushes food. Some rotifers are predators, using similar jaws to tweezers to grab dams, while others have funnel -shaped crowns with bristles that catch organisms. In addition, some rotifers They form symbiotic relationships with other organismssuch as crustaceans and algae, expanding its food diversity and its role in the ecosystem.

The reproduction of the rotifers has a remarkable diversity between the different classes.

• SIXONIDE CLASS: Reproduction is bisexual, with functional males and females in equal proportion. Gametogenesis is carried out by meiosis, resulting in the production of gametes.
• BDELLOIDEA CLASS: They reproduce exclusively by partenogenesis, which means that there are only females in these populations. This form of asexual reproduction allows them to adapt to adverse environmental conditions.
• Monogononta class: Males are less common and generally smaller. They have a testicle that produces sperm, which are injected into the female pseudoceloma through an evertible penis. Most females have only one ovary and a vitlecery that produces vitellus.

SIXONIDEA CLASS (two species)

• Six Nebaliae
• SIXON ANNULATUS

Monogononta class (around 1800 species)

• Brachionus Nilsoni
• Adriuma Colurella
• Angusta Aspelta
• Dicranophorus artamus
• Ascomorpha Ecaudis
• Lecane Bulla
• Cephalodella Apocolea

Bdelloidea class (around 360 species)

• Collaris Hattroch
• Elusa Vegeta Hencing
• SCEPANOTROCHA CORNICULATA
• Dinkotrocha aculeata
• Plate Laticeps
• Mniobia obtusicornis
• Philodine Acticornis

Now that you know what the rotifers are, you may be interested in this article about microfauna: what is and examples.

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