TABLE OF CONTENTS:
1. Classification/Diagnostic characteristics
2. Relationship to humans
3. Habitat and niche
4. Predator avoidance
5. Nutrient acquisition
6. Reproduction and life cycle
7. Growth and development
8. Integument
9. Movement
10. Sensing the environment
11. Gas exchange
12. Waste removal
13. Environmental physiology (temperature, water and salt regulation)
14. Internal circulation
15. Chemical control (i.e. endocrine system)
16. Review Questions
17. Video on the Anatomy of the Squid
18. CITATIONS


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1. Classification/Diagnostic characteristics
- Kingdom: Anamalia
- Phylum: Mollusca
- Class: Cephalopoda
- Order: Teuthida
- Squids have a distinct head, a parrot-like beak, a mantle (body), two gills, eight tentacles with suckers, as well as two other longer tentacles that are used to capture there pray. The eight tentacles with suckers have a double ring of sharp teeth that are used to breakdown and consume there pray. Squids also have two fins located above their mantle that are use to help them navigate the vast ocean. Squids have no bones and thus have a pen “reduced shell” inside its body. Squids have three hearts – a central heart as well as two other gill hearts that pump the blood through their gills.
- Squids have the largest nervous system out of any other organisms in the animal kingdom. This is beneficial since many psychologist researchers have analyzed the system in squids to better understand the nervous system. Further, the giant squid are the largest invertebrates in the world, and their eyes are gigantic!

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2. Relationship to humans
- Squids mainly have only one similar relationship to humans and that relationship is involved between the human and squid eyes. Human and squid eyes are very similar because they both work by refracting the light through a lens to see even though squids are colorblind. However the squid’s eyes are created from their skin during development whereas our eyes are an outgrowth of our brain. Squids are also used as food by humans most commonly referred to as calamari. This fancy food makes squids great targets for hunting and are very expensive; millions of tons of squid are captured every year.
- Additionally, with regards to food, squids' ink is used to color many foods such as black pastas.
- Squid's body mass is also much larger than a humans body mass.
- In new experiments pertaining to the cosmetics industry, the skin of squid, which is usually considered waste and disposed of, is being used as ingredients in lipsticks as natural pigmentation. By successfully isolating chromatophores, which are the reasons behind why squid are iridiscent, scientists can produce pigments with the same color properties.
- Squids have the largest nervous system out of any other organisms in the animal kingdom. This is beneficial since many psychologist researchers have analyzed the system in squids to better understand the nervous system. Further, the giant squid are the largest invertebrates in the world, and their eyes are gigantic!
3. Habitat and niche
- Squids have an extremely large range in terms of where they reside. Each different species of squid has its own habitat. Some squids are found in warm waters whereas others our found in [[#|cooler waters]], but regardless of the temperature, one can find a squid in almost all the large bodies of water. Squids are usually found in depths below 1,000 feet below the surface of water. Smaller squids are usually seen higher up in the depth of the ocean for they have the least competition present.
- Most squids tend to prefer salt water, as most of them live in the oceans, though one can find squids in fresh water as well. All Giant Squids live in salt water.
4. Predator avoidance
- Most squids have two main techniques that they use to avoid predators. Some squids contain cephalopods that are able to change the color of their bodies by controlling these tiny elastic sacs of pigment to change the color of their skins in a way similar to a chameleon by camouflage itself from its surrounding predators. Squids also have an elongated mucus sac that is able to produce ink, which they release into the water when they are trying to escape a predator in an effort to try to confuse the predator.
File:Chtenopteryx sicula2 - from Commons.jpg
File:Chtenopteryx sicula2 - from Commons.jpg
A cephalopad ink sac
5. Nutrient acquisition
- Squids have a parrot-like beak, which they use to absorb nutrients from the water. Squids also use there long tentacles, referred to as feeding tentacles, to consume other organisms such as jellyfish that have a high amount of nutrients in them in an effort to increase their own nutrient levels.
- The tentacles that squids use to grab their food have forceful suction rings on the surface. Squids will use their tongues, which are very sharp, to help break down food. Food then moves down to the throat, into the stomach and finally into the liver where further nutrient and energy acquisition will occur.
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A giant squid uses its feeding tentacles to acquire nutrients from a shark.
6. Reproduction and life cycle
- Squids reproduce in a very weird, yet fascinating way. During the day time, during different times of the year for different species, squids (both male and females) gather around the lower end of the ocean or body of water and the males and the females swim in these circular currents as they try to find a mate. The males during this process try to attract females by continuously changing the color of their skin. - Once a male or a female finds a mate the two begin to mate. The male squid then uses one of its eight short tentacles (the smallest one of those eight) to transport its sperm into the female. This sperm then fertilizes the female’s eggs, which can range from 1,000 up to 70,000 eggs, dependent on the species. Once the eggs our fertilized the female will leave the eggs in a secure area where the eggs will hatch and will make there way to the surface of the water.
- In some squid, mainly those in the North Atlantic Coast, the sperm is placed in a vessicle below the mouth of a female. As the eggs are produced, the spermatophore releases the sperm. The eggs are then attached to seaweed to keep them stationary.
- Squids grow into maturity from 3- years. Since this is not a very long life, the females are sure to release an enormous amount of eggs, up to 11 pounds, to ensure the continuation of their species.
Reproductive Organs of a Female Squid
Reproductive Organs of a Female Squid
7. Growth and development
- A squid starts out as an egg and then overtime grows to mature into an squid as it obtain the right amounts of food and nutrients and after 3 years or so if the conditions are suitable for the squid, the squid can become a giant squid ranging from 40-50 feet in length.
- Females usually create 100,000 eggs about 1 mm in diamater. The larvae that emerge are roughly the same size of the eggs. After a period of growth and development, the larval squid becomes a juvenile about 6 mm in mantle length with adult features.
-Arthropods will grow out of their exoskeleton and go through several periods of molting. Molting is when arthropods shed their exoskeleton to make larger one. Molting is controlled by the endocrine system.
8. Integument
- The skin of the squid is covered with chromatophores, which allow the squid to change the color of its skin, dependent on its environment. The underside of the squid is lighter than its top, for better camouflage from its pray. It was recently discovered that the iridohores, small platelike structures in the skin, are able to change their hue and reflective ability due to electric stimulation of nerves in the skin.
9. Movement
- Squids move throughout the water by sucking water into their mantle captivity and then removing it through the siphon. When they release the water out the siphon the pressure is so great that they move up to 24 mph; they are the fastest invertebrates in the world. They are always moving even during there sleep.
external image Squid_bw.GIF
Squids achieve locomotion through jet propulsion, in which they suck water into their mantle caviy and quickly expel it out of the sihpon to produce a fast jet. The direction of the siphon can be changed according to where the squid wants to travel, allowing them to steer in the water.
10. Sensing the environment
- Squids have two main ways that they sense their environment. One of their main ways that they sense their environment is by using their eyes. Squids have a very similar eye makeup as humans do, however they have no blind spots which makes them able to look at all of there surrounding and react extremely fast when danger is around. Squids also have Statocyst structures, which help them hear their surrounds and helps them find their way around the environment by sensing the soundscape of their environment such as finding their way to the surface of the water and away from the surface of the water.
Interestingly enough, squid can only see in black and white.
11. Gas exchange
- Squids breathe with the help of their gills. Water flows into the mantle of the squid and around its gills, which absorb the oxygen from the water and remove the carbon dioxide. Squids have extremely large gills and even have their own small hearts for each gill, so that it can “scan” a ton of water to obtain sufficient amounts of oxygen for survival.
- The Squid cannot live without oxygen for even a very brief time, and due to their relatively simple and not very effective circulations system, Squids must pass enormous amounts of water continuously through their body to survive. The Squid has evolved to use oxygen carrying proteins with that are able to pick up more oxygen at the gills than other comparably aged species to accommodate for their oxygen needs.
12. Waste removal
- The waste that gathers up in the body of the squid is removed from their anus into the siphon. The waste form the siphon ids then removed from the siphon of the squid when the squid basically removes the “non-oxygenated water” from its mantle.
13. Environmental physiology (temperature, water and salt regulation)
- Each species of squid has a different regulation of water temperature in which it thrives. However, when it comes to the regulation of salt squids don’t really care. Squids can live in both salt rich as well as salt less bodies of water, but they do need water in which there are nutrients present to keep them healthy.
14. Internal circulation
- Squids, like 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. Hemolymph is one of the reasons that a squid can move so fast; it is pumped quickly around the body inside veins, arteries, and capillaries. Squids also have three hearts. One big systemic heart which pumps hemolymph around the body and to the brain, while the two brachial heats, which are located in each of the gills of the squid that helps push hemolymph through the small capillaries located there.
external image internal-anatomy-of-a-squid.png
15.Chemical control (i.e. endocrine system)
- The optic gland in the squid is responsible for controlling the reproductive activity and metabolic processes. The anterior saliva glad is responsible for secreting saliva in the mouth to break down food. The posterior salvia gland on the other hand produces venom that is used to paralyze its prey.
16. Review Questions
1. The chromatophores on the squid change color depending on what factor?
2. How are squid eyes similar to human eyes? How are they different?
3. Describe how male squids attract mates and how squids reproduce once they have found a mate.
4. How does shooting ink help a squid escape from predators?
5. Describe the process of molting in squids, including information on how it is controlled. (Alexander Soloviev)
6. What is the Statocyst structure? What is its function?
17. Video on the Anatomy of the Squid



18. CITATIONS
http://en.wikipedia.org/wiki/Squid
http://www.squid-world.com/squids-and-humans.html
http://library.thinkquest.org/05aug/01006/squids.htm
http://www.sardineking.com/squid.html
http://www.dfo-mpo.gc.ca/Science/publications/uww-msm/articles/squid-calmar-eng.htm
http://books.google.com/booksid=T2GzCimS2XUC&pg=PA443&lpg=PA443&dq=squid+gas+exchange&source=bl&ots=6oLVxQZhpX&sig=bp8nuxw2AWQcU39IeHvNmWjl9ms&hl=en&sa=X&ei=NOXLUPSOHMLX0QGc-oDoDA&ved=0CFUQ6AEwCA#v=onepage&q=squid%20gas%20exchange&f=false
http://www.squid-world.com/squids-and-humans.html
http://thishya.blogspot.com/2010/12/mrhammerheadshark-and-squid.html
http://www.squid-world.com/squid-feeding.html
http://www.livescience.com/22365-squid-iridescent-rainbow-skin-changes.html
http://www.ucmp.berkeley.edu/protista/slimemolds.html
http://w3.shorecrest.org/~Lisa_Peck/MarineBio/syllabus/ch7invertebrates/Invertwp/2007/patrick/struct.html
http://tolweb.org/treehouses/?treehouse_id=4225
http://www.squid-world.com/squid-habitat.html
http://marine-francine.blogspot.com/2007/11/squid.html
http://articles.economictimes.indiatimes.com/2012-12-03/news/35568799_1_squid-lipstick-food-grade-essence
http://www.carnegiemnh.org/graphics/science/mollusks/tree_lg.jpg
http://ocean.si.edu/sites/default/files/audio/images/Giant_Squid_art_carousel_D1000088.JPG