What do we know about them - about invertebrates vtorichnopolostnyh animals that combine the type of shellfish?What they have soft, boneless body, some have calcareous shells (like snails), and some it does not exist (as slugs).Some of them lead a peaceful life, eating grass, and some - even dangerous predators and parasites.Someone very slow (eg, snail creeps hour just 12-20 centimeters), while squid, using his "jet engine", can reach speeds of 70 km / h.There are species which are specifically bred for use in food (mussels, oysters) or for pearls, sepia, purple.And there is a very toxic shellfish can cause death just ten of them men.
Among this extremely motley little family there, and cannibals, and even vampires.How did science classifies this type?Mollusks are divided into three classes: bivalves, cephalopods and gastropods.But before talking about the differences between the snail, oysters and squid, let's single out what unites these different in appearance, lifestyle and level of intelligence of animals.All they have no internal skeleton.The shells of some animals they are "home", protected from overheating and predators.Their body consists of a torso, legs and head.In most species, there is a "cloak" - skin fold that covers the heart, liver, kidney.The blood of their yellowish, but some cephalopods - reddish.
Type Shellfish was extremely common in the Jurassic period, when the majority of the Earth's surface was covered with water.There are more than 130,000 species of fossil creatures - almost as many as there are types available today.And among them there are those who thought to be extinct, but they caught alive and unharmed from the depths of the waters.This is what happened with the "fossil" neopilinoy that caught in 1952 in the Pacific Ocean.Therefore we can not say with certainty what kind of disappeared - information about its extinction can be exaggerated.It is believed that during the Jura were giant clams, and this is confirmed by archaeological finds.The largest, found in the southern United States, a copy of cephalopod - a three-meter squid inhabit the sea 325 million. Years ago.However, in 2003 off the coast of Antarctica was caught squid in two and a half meters long.
Class Gastropods is unique in that its representatives have mastered the land, but because it is the most abundant.Unlike bivalves and cephalopods, there are no giants.Some tropical species can reach up to 60 cm, but the majority - are small animals 8-12 cm long.It is called so because of the "legs", which in fact - not of course, but the body itself.Some gastropods have a sink, and some - "naked."They move very slowly, reducing the muscles of the torso and legs;They feed mainly on plant food.In terrestrial snails have a mouth at the bottom of the head, and the top - sensitive tentacles, the tips of which are placed "eyes".The internal organs are under the mantle.
The more interesting group of beings such as the type of shellfish?Some of them (bivalves), live only in water bodies.The largest animals of this class is tridacna: some specimens weighing 300 kg.A characteristic feature of this type are extremely strong muscles which hold shell valves.The biggest pearl extracted from shells, weighing 6 kg.It is interesting that the Black Sea Rapan fell into the Black Sea is only 30 years of the twentieth century, a ship arrived from the Pacific Ocean.Aggressive gluttonous guest in less than 100 years to reduce the population of local mussels and oysters, put them on the brink of extinction.
believed that no gastropods or bivalves have no intelligence.However, such a clam, like an octopus, causing involuntary respect.The representative of cephalopods great to train, recognize the people who feed, distinguish shades of colors weight, transmits information from one individual to another and is the brain, which protects "protocherep" - a special cartilaginous shell.At the same time a huge octopus can squeeze into a gap the thickness of a coin!These molluscs can build homes: from cans or dead shells they collected construction even opens the door!
