Echinoderms: 6 Curious Things To Know
Echinoderms are invertebrate animals that live exclusively in the sea. The creatures of this group are iconic of the maritime landscape and include, among others, the sea rags, starfish and crinoids.
The name echinoderms literally means “thorny skin”. While not all species possess spines properly, they all have rough skin. Some specimens are also equipped with toxic spines as a defense mechanism.
Erroneously, the idea has spread that echinoderms possess an exoskeleton. The truth is that the structure we observe, which gives the body rigidity and protection, is not external.
The structure consists of calcium carbonate plates, with or without thorns, covered with a thin layer of skin. For this reason we can speak of an endoskeleton, being contained within a layer of living tissue.
These invertebrate complexes enjoy many detective characteristics. In this article, we will discover 6 fascinating things about echinoderms.
6 things to know about echinoderms
1. They have a unique radial symmetry in the animal kingdom
Radial symmetry occurs in echinoderms only in the adult stage. This term indicates a body made up of five equal sections, each with identical internal organs, surrounding a central point.
2. Echinoderms can regenerate their body
These creatures possess the incredible ability to regenerate parts of their body, including external organs such as lost extremities. Thus, in the event of an attack where they lose an extremity, many of them gradually regenerate it after the wound is closed.
Additionally, some species can use regeneration to reproduce, deliberately separating themselves, and causing each piece to transform into an entirely new organism.
3. They don’t even have a drop of blood
Without blood or heart, the echinoderms have a unique mechanism in the animal kingdom: a water-based vascular system to carry oxygen to its vital organs. This hydraulic system is also known as the ambulatory system or the vascular-aquifer system.
In their organism there are grouped channels that carry sea water. These canals are found in the ends of the echinodermis, and are known as ambulatory pedicels, which can end in suckers.
These tips are used for a variety of functions, including feeding, gas exchange, movement, and stimulus detection. The opening to the outside of this vascular system occurs through an opening known as madreporite, joined to the mouth.
4. They breathe from their extremities
As a rule, they breathe when they take sea water through the ambulacral pedicels; the pipes push the hydrogen peroxide through the rest of the body. Through the dermal gills of the epidermis, on the other hand, the exchange of gas with the outside takes place.
5. Some echinoderms feed by expelling their stomachs
The diet varies enormously according to the different groups of echinoderms. Generally, these animals possess mouth, esophagus, stomach and intestines. However, they may or may not have anus. Curiously, sea stars digest their prey by forcefully pushing their stomachs out through their mouths.
Among the echinoderms, there are many species that prefer to feed on molluscs, among them the starfish. In this case, it uses its ambulatory “legs” to grasp and open the shell.
Then, the starfish expels its stomach into the open shell, secretes digestive fluids to dissolve the contents, and returns to swallow its stomach along with the liquefied food.
6. Creatures without eyes or brains
One of the most interesting facts about echinoderms is that they have neither eyes nor brains, but only a rudimentary nerve network. However, many starfish have light-sensitive organs in their extremities. These are simple organs called “eye spots” and which do not provide detailed images, but only help them perceive the different degrees of light. Experts believe that this function allows the starfish to orient itself in its movements.
As you have seen, these creatures are amazing and fundamental to maintaining the ecological and geological balance of the planet. In fact, there are numerous conservative groups that work to preserve the biodiversity of echinoderms.
