Some animals have an unusual armor called the spine, which is usually hard and prickly — this armor they need for self-defense. These animals will be discussed in this topic.
Sea stars are found in all seas with oceanic salinity. Most species have five arms or arms, but some species may have many more. The rays are connected to a central disc whose diameter is about half their length. Each arm contains gonads and digestive glands, and on its lower surface are rows of ambulacral legs and small tweezers — pedicillaria. The surface of the body is hard and rough, with well-palpable calcareous plates. On the upper side of the disk there is a madrepore plate — a sieve-like entrance to the system of ambulacral canals. The mouth of the starfish is located below. Most species are dioecious. In some, the female carries juveniles in a special chamber under the central disc. Sea stars are predators that eat corals, mollusks, other echinoderms, and carrion. Having found a large prey, the starfish tightly wraps its arms around it, after which it turns its stomach outward, envelops the victim with it and digests it. The economic value of starfish with a minus sign. These are predators that cause damage to underwater farms engaged in artificial breeding of mollusks, trepang or sea urchins. Some starfish can be very damaging to corals. Sea stars are real decorations of the underwater landscape. For humans, they are not dangerous, with the exception of a single species — the crown of thorns.
This graceful medium-sized star with five long rays is common throughout the Indo-Pacific. It can be found at a depth of 5 to 30 m. Long reddish rays are covered with large conical spines.
Sea urchins are spherical echinoderms characterized by a secondary simplification — “loss” of arms. Hedgehogs have a rigid shell of skeletal plates connected to each other, carrying pedicillaria and movable spines, with the help of which some hedgehogs move along the substrate or burrow into the ground. Like stars, hedgehogs also move with the help of ambulacral legs that emerge through the pores in the ambulacral plates on the ventral side of the shell. The mouth is located on the lower (ventral) side of the body, as a rule, in the center and is equipped with a characteristic “gnawing” oral apparatus — the “Aristotelian lantern”, ideally suited for grinding algae and sedentary animals. Indeed, this amazing apparatus, representing a system of movable teeth and muscles, was first described by Aristotle himself. Once a great naturalist was forced to flee from Athens, lived on the Greek islands, walked at low tide, collecting and dissecting marine animals. Unlike stars, some hedgehogs have lost the correct radiality in the body structure and become bilaterally symmetrical: the anus located on the back has shifted back, while the mouth on the ventral side, on the contrary, has shifted forward. Such urchins, in contrast to the “correct” radial, are called “wrong” sea urchins. This happened in connection with the transition to a burrowing lifestyle. Burrowing hedgehogs began to feed on detritus, and therefore the “Aristotelian lantern” was also reduced in them, and food capture is carried out by specialized mucociliary ambulacral legs.
Spiny caterpillars are aggressive eaters, and generally consume everything.
The fish has a round body with small fins, so its speed is low. Its large head and sharp teeth allow it to hunt. In case of danger, the fish can instantly inflate. Some types of fish have spines. But all fish of this species have the poison Tetrodotoxin, which is located mainly in the internal organs and ovaries — the slightest dose of it can be fatal.
Horseshoe crabs are one of the oldest animals on earth. Although they look scary, there is absolutely nothing on their bodies that could hurt us — they have no teeth, their claws are weak and their tail is not venomous or spiky.
Echidnas are small mammals covered in coarse hair and spines. They are also known as spiny anteaters. Although they feed exclusively on ants and termites, they are only distantly related to the true anteaters of the Americas. The echidna got its name from a monster from ancient Greek mythology.
Amazing Australian reptile. The mini dragon grows up to 20 cm long and can live up to 20 years. It can blend in with desert hues, and its thorns serve as a reliable defense against predators. A small thorny devil can eat several thousand ants in one day.