1. Squid Dissection

2. Locomotion  Squid are among the fastest invertebrates on earth speeding through the water at up to 40 km/h (24 mph).  When escaping predators, some squid can even jump 3m (about 12ft) out of the water and glide like a flying fish.  They can move fast because they are naturally jet propelled.  The outside body of the squid is called the mantle which fits like a hat over the real body and organs of the squid.

3.  By opening up the mantle around the head, squid suck water inside the mantle.  They then squish the mantle closed.  The water is let out in only one place, the funnel.  Like a jet fighter engine nozzle, the squid can open, close, twist, and turn the funnel to go where they want.

4. Breathing/Respiration  Squid live in the ocean, therefore they need some type of gill(s) in order to get oxygen from the water.  Oxygen needs to pass from the water into the blood.

5.  Squid do this by putting the blood next to the water with only a thin wall, one cell thick, between water and blood in a feathery structure called the CTENIDIUM (two are called CTENIDIA).

6.  The ctenidia are found on either side of the siphon.  Oxygen-rich water is continually pushed past the ctenidia by contraction of the mantle.  Some rare, deep-water squid that swim using webbed arms don't have gills, the webs are so thin that they work as gills.

7. Eating  Squid are very successful predators.  They feed on fish, shrimp, just about anything swimming that's smaller than them.  Squid have eight arms and two tentacles, unlike octopus which only have eight arms.  They rip-apart prey and stuff it into the mouth in the center of them.  The tentacles are much longer and have suckers only at the ends.

8.  Squid get close to prey, then shoot out the extra-long tentacles to capture it and pull it in.  The squid takes bites out of the prey with a beak made out of the same stuff as human fingernails (chiten).  The meat is ripped apart even more by the radula, a conveyor belt of tiny teeth that nearly all mollusks have.

9.  Food is swallowed and travels through the esophagus into the small muscular stomach where digetive juices from the liver and pancreas help break it down.  The mushy food is then passed into the big cecum where it is absorbed into the squid's hemolymph (blood) and spread through the body.  Wastes are passed out the rectum, through the funnel, and into the water as the squid squirts away.

10. Reproduction  Most squid live only a short time, one to three years.  A male squid makes sperm with a single testis and then wraps it into a packet of sperm called a spermatophore with a gland called Needham’s sac.  He hands it off like a football to the female using his long tentacles.  The spermatophore is stuck to the inside wall of the female's mantle so she can use it to fertilize her eggs when she lays them.

12.  Often the female doesn't wait for the male to remove his tentacle and she rips it off during her escape.  The male dies after mating.  Female Loligo sp. squid lay from 1000 to 5000 eggs in strings or 'fingers' stuck to the bottom of the ocean.  She has two glands called nidamental glands, that make a hard, bad-tasting covering for the egg finger so that other animals won't eat the eggs.

13.  After laying her eggs, the female usually dies.  After several weeks baby squid, about the size of a rice grain, hatch out and head to deep water to feed for one or two years before returning to mate and die.

14. Circulation  Most mollusks (clams, oysters, scallops, snails, and slugs) have an open circulatory system, meaning that the organs slosh around in a single pool of bluish 'blood' called HEMOLYMPH.  The fast paced life of a squid is possible partly because its hemolymph is pumped quickly around the body inside veins, arteries, and capillaries; a closed circulatory system like humans have.  Earth squid have three hearts: One big systemic heart pumps hemolymph around the body and to the brain, while one branchial heart on each gill helps push hemolymph through the little capillaries there.

15. Nervous System  Squid have a fairly large brain between their big eyes.  The largest parts of the brain are the parts related to vision.  Since squid have a soft body (not protected by shells like its relatives clams, oysters, and snails) the brain is protected by a rubbery box almost like a skull made out of cartilage.

16.  Humans studied squid brains and nerves for a long time because squid nerve cells are some of the largest on the planet, much bigger than human nerve cells.  Two really big ones called Stellagate Ganglia control the quick squeezing of the mantle.  They are so big that humans were able to figure out how nerves work by changing the chemicals and electrical impulses in these nerves.  This research led people to develop ways to fight some human diseases like muscular dystrophy, muscular sclerosis, and Alzheimer's.

17.  Research indicates that squid cannot smell, and they have no noses.  They can feel different textures, but cannot tell one shape from another.  They 'hear' by sensing vibrations in the water.

18.  Squid eyes are very similar to fish eyes.  Squid use their eyes to find and capture prey.  They have no eyelid, but control the amount of light coming into the eye by opening and closing their slitted pupil.  They focus on something by moving a hard, clear LENS back and forth within the eye.  Some species of squid may be able to see color.

19. Changing Color  The color of a dead squid is very different from the changing colors of a live squid.  Color cells, called CHROMATOPHORES, in the squid's skin contract and expand to produce different colors and patterns.  Sometimes squid use this ability to hide, but most times their color reflects their moods.  Squid can turn dark, squeeze ink out of their ink sac, then turn light or clear to confuse a predator and escape.

20.  Squid ink is made out of melanin (the same stuff that produces human tans) and mucous.  Chemicals in the ink also confuse fish noses to help squid get away.  Some squid can even glow in the dark, called bioluminescence.  Glowing squid use photophores to produce more or less light.

21. 1. Place the squid with the dorsal (back) side up in the dissecting pan. This means put the side with the funnel down and the fin side up. Make sure the tentacles and arms are towards you. 2. Locate the head, eyes, beaks (mouth), arms (8), two longer feeding tentacles, fins, mantle, and skin.