11.Most of them feed on detritus or are scavengers. Some are predators that prey on small crustaceans and worms.
Using special hooks placed on their limbs, they filter out plankton. Every species has its own preferred diet, but many feeds on more than one food source. The feeding preferences may change over a lifetime.
12.The nervous system of brittle stars has a simple structure.
As its most important elements are the nervous ring around the mouth and the radial nerves that run in the animal arms.
13.They use chemoreceptors in search of food.
14.For locomotion, brittle stars use their arms.
Arms are elastic and allow the brittle star to move relatively fast. Four of five arms are used for locomotion with an extra arm being the symmetry axis. Contrary to starfish, brittle stars use tube feet for transporting food to mouth, respiration and sensing, not to locomotion as they are not equipped with suction cups.
15.The respiratory system is made of respiratory pockets and tube feet.
Respiratory pockets are located at the base of the arms. Their walls are equipped with muscles that contract and loosen to force water circulation.
16.They can regenerate lost arms as long as they have at least one of them.
They can shed an arm anytime, like octopuses. This mechanism is used to distract the potential predator and gives brittle star an opportunity to edge away from danger.
17.Most brittle stars reproduce sexually.
Gametes are being produced inside the central disc and released to the external environment when fully developed. There, fertilization takes place. From the zygote, a larva develops which, contrary to adult individuals has bicubic symmetry. There is a high probability of different larvae forms among other brittle star species, but as only 2% were examined, discoveries are yet to come.
18.Larvae are tiny and are a part of the plankton.
Either way, the larva must undergo transformation to become an adult, bottom-dwelling individual with radial symmetry.
19.There are species with no larval stage at all.
Amphipholis squamata, common in all parts of the British Isles is one of them.
20.Some species, however, are hermaphroditic or protandric.
Protandric animals produce male and female gametes at different times. Hermaphroditism is the occurrence of male and female reproductive glands in the body of one individual at the same time or the presence of a hermaphroditic gland in its body.