The king of the sea: the Octopus
We would love to write in today’s blog a few words about Common Octopus. During our dives in Costa del Sol we see them always, minimum two, three on each dive. In the waters of Alboran Sea while diving with Black Frog Divers you will see from small, baby octopuses (5cm ) to large adults (25cm).
The common octopus inhabited the eastern Atlantic, Mediterranean Sea, southern coast of England, Senegal in Africa, Azores, Canary Islands, and Cape Verde Islands.
The species is also common in the Western Atlantic.
Few Characteristics of common octopus: they grow up to 25 cm in mantle length with arms up to 1 m long. Males have larger suckers on their second and third arms.
Octopus hunts at dusk. During hunting they use their arms to feel along rocks, sediment, and in holes for potential food, or use their web for covering prey when pouncing on top of them. Another tactic involves the siphon in which they blast sediment with water to reveal buried prey or ambushing, stalking and luring.
The octopus will eat almost anything it can catch, but crabs, crayfish and bivalve mollusks are preferred. It is able to change color to blend in with its surroundings, and is able to jump upon any unwary prey that strays across its path. The prey is paralyzed by a nerve poison, which the octopus secretes in its saliva, is able to grasp its prey using its powerful arms . If the victim is a shelled mollusk, the octopus uses its beak to punch a hole in the shell before sucking out the contents.
Common octopus can distinguish the brightness, size, shape and horizontal or vertical orientation of objects. They are intelligent enough to learn how to unscrew a jar. Common Octopus is the only invertebrate animal protected by the Animals Act 1986 in the UK, because of its high intelligence.
Habitat of the common octopus: typically found in tropical waters throughout the world, such as the Mediterranean Sea and East Atlantic. They prefer the floor of relatively shallow, rocky, coastal waters, often no deeper than 200 meters. Their preferred temperature ranges from about 15 °C to 16 °C. In warm seasons, the octopus can often be found deeper than usual in order to escape the warmer water.
Octopus situates itself in a shelter where a minimal amount of its body is presented to the external water. It move most of the time along the ocean or sea floor, the octopus does sometimes swim throughout the water, in doing so, the octopus uses a jet mechanism that involves creating a much higher pressure in their mantle cavity that allows them to propel themselves through the water. The common octopus heart and gills are located within their mantle.
Respiration: the octopus uses gills as its respiratory surface. The structure of the octopus’ gills allows for a high amount of oxygen uptake. Also the thin skin of the octopus accounts for a large portion of oxygen uptake, estimates around 41% of all oxygen absorption is through the skin when at rest. This number is affected by the activity of the animal – the oxygen uptake increases when the octopus is exercising due to its entire body being constantly exposed to water, but the total amount of oxygen absorption through skin is actually decreased to 33% as a result of the metabolic cost of swimming. When the animal is curled up after eating, its absorption through its skin can drop to 3% of its total oxygen uptake.
Circulation: Octopuses use hemocyanin as their respiratory pigment, which binds oxygen through copper rather than the iron used by our own hemoglobin.
Octopus has three hearts, one main two-chambered heart charged with sending oxygenated blood to the body and two smaller bronchial hearts, one next to each set of gills. The circulatory circuit sends oxygenated blood from the gills to the atrium of the systemic heart, then to its ventricle which pumps this blood to the rest of the body. Deoxygenated blood from the body goes to the bronchial hearts which pumps the blood across the gills to oxygenate it, and then the blood flows back to the systemic atrium for the process to begin again.
Predators of the Common Octopus: seals are a threat to the octopus because they are fast swimmers and easily tire octopuses also Barracuda and Eels are dangerous to Octopuses.
Octopuses have two types of defense against their predators, primary includes using camouflage or color changing to match their environment secondary are only used when the primary response fails, and the octopus is seen by its predator these include flight and inking, defensive postures, and deflective markings. Octopus use threatening or bluffing actions in order to cause the predator to hesitate . Sometimes this behavior will scare away the predator or give the octopus enough time to flee in a jet of ink. Specific coloration patterns and body postures, paling of the skin, darkening of suckers and area around eyes, arms and web spread widely, and a jetting of water or throwing out their arms towards the attacker are used to threaten the predator.
The Octopus ability to camouflage is astounding. This ability was developed as an adaptation for protection due to the evolutionary loss of an external shell. Octopuses achieve color change in structures of the skin. Elastic pigment sacs with muscle fibers attached letting them expand and contract.
Reproduction of Common Octopus: because of their solitary lifestyle, mating does not include long term pairing or monogamy. Both the males and females of the species will die after the eggs hatch. The reproductive season is from February to October.
The males produce and maintain sperm in spermatophores and deposit these sacs into the females using the third right arm. Female stores the sperm in her oviducal gland until she is sexually mature and ready to fertilize. She can keep the sperm inside her for up to two thirds of her life. She can collect sperm packets from various partners and use whichever sacs she deems best.
After a successful mating, lasting about 1h, and once the female decides conditions are right for fertilization, she lays her eggs. This stage, drastically changes the females life. Her body will stop growing and she will stop leaving the den to hunt for food, discontinuing eating for the rest of her life. All of her time will be consumed with brooding the eggs. After hatching both the males and females will die. Their entire lifecycle only lasts between twelve and fifteen months.
We hope that you like this short article and if you have never seen an Octopus or you really like them and want to see them, come to Spain and dive with Black Frog Divers and we will make sure that you come back with plenty of photographs of that amazing sea creature.