Radiolarians, whose representatives we will consider in our article, are the simplest animals. Despite the primitive structure, they are the champions in the number of chromosomes among all living organisms.
Radiolarians: representatives and habitat
These organisms are part of plankton. The body of radiolarians consists of one cell. Most often they can be found in the warm waters of the ocean. Plankton is not capable of independent movement. It consists of small organisms that drift in the water column.
In nature, about 8 thousand species are known. Many representatives of the radiolarian type are found exclusively in the fossil state. Their second name is beamers. It is explained by the structure of the skeleton. Its rays, which strengthen the pseudopodia from the inside, determine the bizarre body shape of radiolarians. These are animals with radial symmetry.
Pseudopodia, or radiolarian prolegs, come in various types. Some of them are derivatives of the internal capsule. They are shaped like rays and are called axopodia. This type of prepodia determines the motor activity of these unicellular organisms.
If in the formation of organellessurface cytoplasm takes part in the movement, pseudopodia acquire a filamentous shape. They are called phyllopodia. They perform the function of capturing food particles.
Skeleton structure
Living radiolarians have an intracellular skeleton. Its formation takes place in several stages. First, the central cytoplasm forms a skeletal capsule, then radial needles depart from it.
Representatives of the class Radiolarians are combined into several subclasses. This classification is based on several features. This is the structure and chemical composition of the skeleton, as well as the structure of axopodia - the organelles of the movement of radiolarians. In representatives of the subclass Acantharia, the skeleton includes up to 20 needles. All of them are formed by strontium sulfate. The skeleton of the protozoa of the subclass Polycystinia is entirely composed of silicon sulfate. The most deep-sea radiolarians are Feodarii. The basis of their skeleton is a combination of organic matter and silica.
Life processes
Since radiolarians are representatives of protozoa, all the features of the physiology of this subkingdom are also characteristic of them. Digestion takes place in special vacuoles. Radiolarians reproduce in two ways. This may be cell division in half or sporulation. Radiolarians breathe through the cell membrane.
In some species, the cytoplasm contains single-celled algae that absorb carbon dioxide for photosynthesis. At the same time, they highlightextra oxygen. Radiolarians use it for respiration and the oxidation of organic matter. At the same time, algae need the cytoplasm of radiolarians as a habitat. This mutually beneficial existence is called symbiosis. It is observed only in radiolarians, which live in the zone of water illuminated by the sun.
Representatives of radiolarians and sunflowers: main differences
The simplest organisms are very diverse. Sometimes radiolarians are compared with their "relatives" - sunflowers. The latter also belong to the Sarcode class, have a spherical cell shape. But sunflowers prefer to live in fresh water. Their cytoplasm lacks a central capsule.
Unlike representatives of radiolarians, they do not have an internal skeleton. It is located outside the round cell. But in terms of chemical composition, the skeletons of radiolarians and sunflowers are similar. These are mainly silicon compounds.
Their axopodia, similar to rays, move away from the cage. These structures contain stinging organelles, with the help of which sunflowers capture prey. They prey on bacteria, unicellular algae, invertebrate larvae, ciliates and euglena.
Unique Traits
Despite the fact that radiolarians are representatives of the most primitive animals, many of their features remain a mystery to scientists. Just imagine, their genetic apparatus consists of 1600 chromosomes! For comparison, a person has only 46 of them.
Whenlooking at the photo of radiolarians, it may seem that their cell is inside the skeleton. In fact, this is not at all the case. Living radiolarians have an internal skeleton. And it becomes visible after the death of cellular structures.
Meaning in nature
Radiolarian skeletons are the basis of many rocks. These are quite ancient organisms. Their first fossil remains were found in the Precambrian beds. Therefore, radiolarians are often used in geology when it is necessary to determine the age of rocks.
Dying away, the skeletons of these protozoa initially settle to the bottom in the form of radiolarian silt. Over time, it turns into sedimentary rocks. These include radiolarites, flasks, silica, and quartz. Silt can also turn into special minerals. This is jasper and opal. They are widely used in the jewelry industry in the form of gemstones.
So, radiolarians are representatives of the subkingdom Unicellular animals, the Sarcodidae group. They have an internal skeleton, which may consist of silicon dioxide, strontium s alts, or organic matter. Radiolarians are part of plankton and are found in warm tropical seas. These are very ancient organisms, among which many fossil species come across. Therefore, in geology they are used to determine the age of rocks. Skeletons of radiolarians are part of many sedimentary rocks and minerals: silica, opok, radiolarites, quartz, opal.
