Octopus (Mollusca): Cam Somers


Classification/Diagnostic Characteristics:
- octopus is classified as a cephalopod
- 800 living species of Cepholopods
- appeared in early Cambrian
external image Octopus_bw.GIF&sa=X&ei=-o_KUIPAIdC60AGngYEo&ved=0CAoQ8wc&usg=AFQjCNEmXR5ABbdgIEfFTCzOYbzG3bi33w Link(
Under characteristics, you should add that octopus are known for having 8 large tentacles with [[#|suction cups]] on the undersides of them to help them stick to rocks, a mantle, etc.

All molluscs in general are soft bodied invertabrates with a general top and bottom region. The bottom region being the tentacles in the case of octopi. Some molluscs, like snails, also have shells, but it is not a defining characteristic. (http://www.ucmp.berkeley.edu/taxa/inverts/mollusca/mollusca.php)

Relationship to humans:
- Similar eyes in that they can resolve images
- elaborate courtship behavior similar to humans

Octopus can be pets but aren't very common because of their short life-span (6 months to 5 years), the materials necessary to care for the organism, and their tendency to escape (they are pretty smart after all). People also eat octopus; they can be easily found in your local [[#|fish market]]. Asian countries (ie. Japan and Korea) tend to have them in a lot of their foods. I ate octopus myself before becoming a vegan (personal confirmation that octopus cuisine is common?)
http://justinlp6.weebly.com/humans.html (Bhu)

Some camera companies have adopted the lenses for their cameras from octopus eyes, while other humans have adopted suction cup technology used for a variety of purposes including cardiovascular surgery based on the suction cups of octopuses.

Habitat and Niche:
- Marine/Ocean life
- 800 living species
- The common octopus is a predator; nocturnal hunter that eats mostly crustaceans, bivalves, and fish. They have been known to stockpile food.
Predator avoidance:
- major predator in the open waters
- capture and subdue prey with tentacles
- rapid movement
- Contains a shell that is distasteful or toxic to many species, however most octopus have lost their shells

The octopus will attempt to blend into its environment through camouflage, as it is able to alter its appearance in order to avoid detection by predators. If the octopus is confronted by one of its few predators, such as dolphins, eels, and sharks, it is able to escape by shooting water through its body in order to make a quick getaway. (Colin Gray)
Not only can octopuses shoot water through their body for a quicker escape, but the also have the ability to release an ink that decreases the predators sense of smell, as well as bite predator with a toxic venom. Since octopuses have so many legs, they can also lose a leg if it helps them to escape a predator, for the legs can grow back overtime.-

Nutrient acquisition:

Octopus generally consume scallops, snails, various fish, turtles, small crustaceans, and other octopuses. However, octopuses are characterized as a generalist predator, which catches and consumes whatever prey is encountered and does not have any affinity for a certain type of food. Some octopuses have even been reported to catch and eat birds. If an octopus tends to gravitate towards a certain kind of prey, it is likely because they obtain a worthwhile amount of nutrients in comparison to the effort put in to obtain it. They capture prey with their multiple arms and use their beaks to paralyze their catch with nerve poison, which softens their food and kills it. (
http://marine.alaskapacific.edu/octopus/Research%20energetics.php) [GW]

Reproduction and life cycle:
-Clams release an egg or sperm into the water during the warm months. The egg then fertilizes, and [[#|cellular]] division produces larvae. The larvae then become tiny clams that settle at the bottom of the ocean.
- Sexes are separate in most clams and paired gonads are located in the upper part of the foot region that are mixed with elements of the [[#|digestive system]].


diagram showing stages in development of a clam
diagram showing stages in development of a clam

The simplest molluscan reproductive system relies on external fertilization, but with more complex variations. All produce eggs, from which may emerge trochophorelarvae, more complex veliger larvae, or miniature adults. Two gonads sit next to the coelom, a small cavity that surrounds the heart and sheds ova or sperminto the coloem, from which the nephridia extract them and emit them into the mantle cavity. Molluscs that use such a system [[#|remain]] of one sex all their lives and rely on external fertilization. Some molluscs use internal fertilization and/or are hermaphrodites, functioning as both sexes; both of these methods require more complex reproductive systems. [4]

Growth and development:

Clam growth largely depends on the month and temperature . During April and June, they have the most rapid growth but it slows down in July and August and continues to decrease throughout the fall/winter.

Clams have growth lines on their shells which usually show age, similar to growth rings on trees.

Octopi are one of the few organisms that never stop growing. In fact, as they grow larger, their growth rate increases. One can determine the age of an octopus by counting the number of layers of sting tissue, a sting being a body part located in the octopus’s head. Each layer marks a year of life. (http://cagelessthinking.com/the-octopus-growing-great-ideas-with-surprise-and-misdirection/)


Octopi uses jet propulsion. The mantle cavity takes in water and then forces the water out through the [[#|siphon]]. The water leaving the body of the octopi then propels the octopi to move forward. [2]

Octopus are capable of several modes of movement; they are capable of bi-pedal locomotion, walking on 2 legs, along the ocean floor, or crawling along the ocean floor. Jet propulsion is the fastest form of movement, but crawling is typically used to inconspicuously avoid predators. (GC)

A video demonstrating octopus movement. Pretty sneaky. (BHu)

Octopus shoots water out of siphon to move forward quickly
Octopus shoots water out of siphon to move forward quickly


- chambered external shell divided by paritions and tubes
- head is closely related with a large branched foot that bears tentacles and a siphon
- protection from predators by being very distasteful or having toxins - rapidly moving and very active
- reason for rapid movement is jet propulsion coming from the siphon and the water being propelled through the cavity

Clams are bivalves, meaning that they have shells consisting of two halves, or valves. The two halves of the shell are joined at the top (dorsal) section by a ligamentous hinge and held shut by a pair of strong adductor muscles on each side. The hinge allows for the opening and closing of the shell. In close proximity to the hinge is the umbo, commonly known as the "beak." The umbo is the oldest section of the shell with subsequent shell growth radiating out from it. When the clam is active and feeding, the shell continues to grow. If the adductor muscles are relaxed, the shell is pulled open by ligaments located on each side of the umbo. The shell is made of calcium carbonate and is secreted by the mantle (soft body wall). The mantle is a soft, retractable organ attached to both sections of the inside of a clam's shell and is directly responsible for creating and growing the clam's shell. The mantle processes the calcium deposits that it has stored over weeks or months. The clam opens its shell and extends its mantle to the edges of both sides. The mantle releases the glue-like calcium compounds along the edges of the shell.
Taken from the website:

Sensing the environment:
- complex sensory organs- eyes that have ability to resolve images
- large muscular mantle for an external supporting structure
Gas exchange:
- chambered external shell
- divided by partitions penetrated by tubes through which gases and liquids can be moved to control the animals buoyancy
Waste Removal:
- cone of feces and mucus called prostyle at rear of stomach
- mucus with waste particles becomes less sticky due to acidic conditions, thereby releasing the waste
The digestive track is ciliated with a mouth, anus, and complex stomach. Food is taken up by the cells that line the digestive glands, and then passed into the blood. The undigested material is compressed, packaged, and discharged through the anus into the mantle cavity and carried away from the animal through the water currents. The packaging of wastes in solid material prevents the fouling of water passing through the gills. (3)


Environment Physiology:
- excurrent siphon is modified to allow the animal to control the water content of the mantle cavity
- water is forcibly ejected from the cavity through the siphon
- gills hang on mantle cavity

Internal Circulation:
- open circulatory system- retain vestiges of an enclosed coelm around major organs
- blood chamber which fluid from an open circulatory system bathes the internal organs before returning to the blood vessels

Chemical Control:

Brief video describing the movement and gas exchange of the species Enteroctopus dofleini//, commonly known as the Giant Pacific Octopus (Alexander Soloviev)

(I think we have the page severely mixed up.)

Review Questions

1. Describe how an octopus is able to avoid detection by predators.
2. Is there any resemblance between the endocrine system of humans and of octupi? (evan)
3. The octopus excretes this to try to avoid certain predators and uses this to rapidly escape its predator?
4. How many living species of octopuses are there?
5. Describe the reproductive capabilities of the octopus, and contrast it with humans. (Prashant)

1. Hillis, David M., David Sadava, H. C. Heller, and Mary V. Price. Principles of Life High School Edition. Sudnerland, MA: Sinauer Associates, 2012. Print.
2. Miller, Kenneth R., Joseph S. Levine. Biology. Upper Saddle River, NJ: Prentice Hall, 2004. Print.


Chisholm, Hugh, ed. (1911). "Molluscoida". Encyclopædia Britannica (11th ed.). Cambridge University Press.