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.


Egypt­ian starfish.


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.

See also
The most unusual skyscrapers


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 urchin


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.

See also
The best beaches of Crete


spiny spi­ders



spiny cater­pil­lars


Spiny cater­pil­lars are aggres­sive eaters, and gen­er­al­ly con­sume every­thing.



hedge­hog fish

NOAA Ocean Explorer: Islands in the Stream 2002

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


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.

horseshoe crab

spiny echid­nas


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.


Thorny Dev­il


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.