DISSECTION: SQUIDS

Pictures found in: Squid

Digestive System: The squid has a flow through digestive system. Food enters their digestive tract through the squid's mouth and is digested into feces which is excreted through the anus.

Circulatory System: The squid has a closed circulatory system with three hearts. H2O and O2 enter the squid's body through its mantle where the respiratory exchange takes place in the gills. CO2 and H2O are then expelled from the body through a siphon.

Nervous System: A squid has a very complex nervous system compared to most invertebrates. Having They have a large brain that coordinates and stores information received around its environment. Also, by using their giant nerve fibers, they can rapidly conduct impulses, which allows them to capture their prey at great velocities.

Excretory System: The excretory system of a squid if also known as a metanephridium, which consists of a ciliated funnel opening into the body cavity and to a duct which opens to its exterior. These ciliated tubes assist in the pumping out waste products.

Reproductive System: The reproduction in squids is external - where the male uses a modified arm to transfer a spermatophore to the female.

Integumentary System: The integumentary system of a squid is enclosed in the mantle, which has two swimming fins along each side. These fins are not the main source of their motility. The skin of the squid is covered in chromatophores, which allows the squid to change color to suit its environment. The underside of the squid is also found to be lighter than the topside, in order to provide camouflage from both prey and predator (countershading).
Under the body are openings to the mantle cavity, which contains the gill and openings to the excretory and reproductive systems. At the front of the mantle cavity lies the siphon, which the squid uses for locomotion through means of jet propulsion. This is done by sucking water into the mantle cavity and quickly expelling it out of the siphon in a fast, strong jet. The direction of the siphon can be changed in order to suit the direction of travel.
Inside the mantle cavity, beyond the siphon, lies the visceral mass of the squid, which is covered in a thin skin. Under this are all the major internal organs of the squid.

Body Plan: The body plan of a squid includes its head and arms, mouth, and eyes.
The head end of the squid bears 8 arms and two tentacles. These tentacles do not grow back if severed.
The mouth of the squid is equipped with a sharp horny beak mainly made of chitin and proteins, and is used to kill and tear prey into manageable pieces.
The eyes of the squid, found on either side of the head, contains a hard lens, which is used much like the lens of a camera or a telescope for focusing; rather than changing shape, like a human eye, it moves mechanically.

Squids live in the ocean - a few, most notably the giant squid and the colossal squid live out in the colder open ocean. Many of the smaller species of squid rely on color changing patterns in order to communicate with each other and to attract prey as well. Squids are considered to be one of the most successful and highly complex of all invertebrates.