Definition of Asteroidea (starfish)

The different species of starfish make up the same group of invertebrate animals. In the classification of the species or taxonomy these animals are part of the asteroid class.

Organisms that remind us of the stars in the sky

The asteroid name has an explanation logic, Since the appearance of these invertebrates is very similar to that of some stars in the sky. In this sense, it should be noted that the word asteroid was first used by the English astronomer William Herschel to designate celestial bodies that have a resemblance to the stars but not in reality They are.

Fascinating organisms

From the point of view of species classification, starfish are not fish but echinoderms (the sea urchin and the starfish are also part of this classification).

These organisms they lack brain and blood. Although they mostly have five arms, some species can have as many as fifty (for example, the Antarctic starfish). Both his arms and his body can be fully regenerated.

Its arms are born from the central disk of its body and under this structure is the mouth of the star.

These echinoderms have a calcified skin that serves as protection against threat from predators. Likewise, the skin has bright colors in order to scare off potential attackers.

Their body structure has different textures, as some species are smooth and others are spiny or grainy. In any case, they are all covered by overlapping bone plates.

His nervous system is not centralized, so they are able to perceive their environment from anywhere in their body (the sensory cells of your skin allow it to perceive light or the action of currents marine).

Most species measure between 12 and 24 cm in diameter. There are exceptions to this general pattern, as some species are a few millimeters long and others are longer than a meter.

Regarding their distribution, they are present in all the oceans of the planet, both in cold and tropical waters, in coastal areas or thousands of meters from the surface. However, they do not exist in fresh waters.

The radial symmetry of these invertebrate animals is one of their most unique characteristics (the symmetry of the starfish is similar to that of sea urchins in their skeleton).

Regarding your feeding, they eat a carnivorous diet of small invertebrate organisms, such as clams and oysters. To feed on prey, it places its feet on them and later secretes an anesthetic substance that paralyzes its prey.

These marine invertebrates are most active at night. Its movements are possible due to the action of its tube feet that incorporate suction cups adapted to the depths of the marine environment.

Fotolia photos: Liliya / Damedias