Cephalopods are the most highly developed class-type spineless.As a rule, members of this group live in marine waters and prefer tropical or subtropical climate.However, some species live in more temperate conditions, including the polar area.
class Cephalopods: body structure
The body of this group is characterized by bilateral symmetry and clearly divided into two main parts - the head and torso.Leg clams in the course of evolution into a funnel and placed around her tentacles.As for the sink, then the more advanced species, and it is reduced under the skin (may be absent).Primitive representatives are characterized by a large outer shell with a plurality of individual chambers.
skin that covers the body, is composed of a single layer of epithelial and connective tissue layers.By the way, some species have pigment cells, the chromatophores, thanks to which can change the color of the body, becoming virtually invisible against the background of the environment.
on the ventral side of the body is the mantle cavity into which ducts open sexual and excretory systems, as well as the anus.
Cephalopods use a very interesting way to travel.Strong muscle contractions push water from the mantle cavity into the external medium, creating a repulsive force.
Cephalopods: internal structure
digestive system .Exceptionally all members of the class are a group of predators.The main prey are crustaceans, small fish and other shellfish.First, the animal captures its prey using tentacles.It is interesting that in some species the salivary glands produce a poison that seized the animal sacrificed.Next food lends itself to powerful horny jaws, and then enters the throat.The pharyngeal cavity open ducts of the salivary glands, which digest polysaccharides and protein components.Bolus through the esophagus into the stomach where influenced in liver and pancreatic enzymes.Digested food is pushed into the intestine, ending anus.
way, some animals of this class have a special device - the so-called "ink sac", which contains dark matter.When the danger of a secret out of the bag was jetted through the anus, which makes it possible to quickly hide mollusk.
Respiratory system consists of a well-shaped gills, which are placed on the sides, in the mantle cavity.Allocation system consists of 2 - 4 kidneys.
circulatory system is also well developed and consists of the heart, blood vessels, and so-called "gill hearts", which provides a surge of oxygenated blood.Interestingly, as the respiratory pigment found in some members hemocyanin, which contains copper.That is why blood is blue octopus.
It should be noted that this class of animals has the most developed nervous system of all invertebrates.Head ganglia have covered something like a skull.The sense organs - the eyes, the mechanical sensitivity, sense of smell - developed very well.
Cephalopods: the best-known representatives of the class
A representative of cephalopods has its own unique characteristics, amazing tools for hunting and living in the depths of the sea.
example, cuttlefish almost spends all his time buried in the sand at the bottom of the pond.Leave open only the eyes - it helps to quickly detect prey.
Octopus - another famous cephalopod, which prefers to live on the rocky bottom.Here he can perfectly disguise and hide next to the stone.The foot of the animal is divided into several suction tentacles on the inner side.
Another well-known group - squid, which are currently considered the fastest and most active members of the class.
