Marine Invertebrates of Bermuda The Common Octopus (Octopus vulgaris) Melissa L. Pierce and James B. Wood (Ed) Abstract Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links

Abstract


      Octopus vulgaris is a prevalent Octopod in most major oceans, but despite its abundance is surprisingly elusive. The diurnal and nocturnal octopus has an average mantle length of twenty five centimeters with arms extending over one meter. They have been found in a wide range of depths from as little as five meters to as deep as two hundred. Although they are solitary organisms, O. vulgaris females will stay and brood their eggs, giving her own life for her unhatched young. Both sexes have a limited life span of twelve to fifteen months. They are both merciless predators of mollusks and crustaceans and prey to larger organisms such as seals and carnivorous fish. Unfortunately, human interest in O. vulgaris does not extend much past their commercial worth and delectability with some cocktail sauce.


Taxonomy


Phylum:Mollusca
  Class:Cephalopoda
    Order:Octopoda
      Family:Octopodidae


Habitat


      Octopus vulgaris lives in tropical and semitropical waters in oceans around the world; from the Atlantic, Indian, Pacific Oceans and the Mediterranean Sea (Quetglas et al. 1998). They inhabit shallow waters and can be seen up to 200 meters (Silva et al. 2002), but the common octopus is generally found in the “near shore zone” (Miesel et al. 2006). Their dispersion range allows for inhabitance of a variety of substrates including rocky, sandy, and reef. Depth has some effect on size and weight, as deeper water O. vulgaris off the coast of Spain were found to be two centimeters shorter and one thousand grams lighter than those caught inshore (Silva et al. 2002). Although they have been found in deep water, the majority of the population is found shallower than 100 meters, specifically between 25 and 50 meters (Silva et al. 2002). Finding O. vulgaris can be difficult, but by searching for ‘middens,’ piles of cleaned shells, their dens can be located.


Ecology


Activity
      It is interesting that O. vulgaris are diurnal and nocturnal since shallow water cephalopods are largely influenced by light cues (Miesel et al. 2006). However, even this can be debated as they are more often day and night active in the Atlantic and Caribbean, while O. vulgaris in the Mediterranean have been speculated to be exclusively nocturnal. However, Meisel et al. (2006) disproved this speculation when they found that even Mediterranean O. vulgaris species showed a preference to daytime activity. In addition, the common octopus does have the ability to switch its activity profile if necessary depending on the changing needs of the organism. It is theorized that one reason for a flexible activity period is as an adaptation to fish predation (Meisel et al. 2006).

Prey
      Octopuses are carnivorous predators and prefer to feed on a variety of live prey species (Fiorito and Gherardi 1999). Although octopuses cannot see colors, they are able to identify their prey by movement, shape, features, and scent (Fiorito and Gherardi 1999). One method they use during hunting is known as ‘groping’ in which they use their arms to feel along rocks, sediment, and in holes for potential food (Fiorito and Gherardi 1999). In another method they use their web for covering prey when pouncing on top of them (Hanlon and Messenger 1996). A third tactic involves the siphon in which they blast sediment with water to reveal buried prey (Hanlon and Messenger 1996). A number of other hunting modes are ambushing, stalking, and luring (Hanlon and Messenger 1996). There are varying studies which report on the amount of time dedicated to feeding by octopuses. In Bermuda specifically, Mather and O’Dor (1991) found that O. vulgaris spent a relatively short amount of time doing this, on average twelve percent of their day. This is a sharp contrast to what is normally seen in octopuses, who are generally known to spend up to sixty five percent of the day foraging (Hanlon and Messenger 1996).
      They are known to feed particularly on crabs, bivalves, and gastropods (Fiorito and Gherardi 1999). O. vulgaris have also been found to feast on polychaetes, other crustaceans, cephalopods, and various species of bony fishes (Hanlon and Messenger 1996). Their radulas are extremely efficient tools for aiding eating of these organisms, especially for penetrating a thick mollusk shell or arthropod skeleton. The octopus will grasp the organism and drill a tiny hole with their radula and using their salivary papilla insert a paralyzing toxin which relaxes the organism allowing their shell or exoskeleton to be penetrated (Fiorito and Gherardi 1999). Bivalve mollusks are pried apart using the octopus’s arms and suckers, but can also be drilled if this fails. However, pulling open bivalves has a much higher energy cost than drilling alone. Once they are done feeding, the mollusk shells are scattered around their den area in piles known as ‘middens’ (Fiorito and Cherardi 1999).

Predators
      Despite their ferocity as invertebrate predators of the oceans, octopuses are preyed upon by numerous dominant carnivores. Pinnipeds in oceans around the world feed on cephalopods; with thirty one of the thirty three species present including them in their diets (Klages 1996). Seals are a threat to the octopus because they are fast swimmers and easily tire octopuses who cannot keep up fast swimming speeds for an extended period of time (Klages 1996). Large predatory fish, such as the Barracuda, are also a threat to O. vulgaris. Eels are also especially dangerous to Octopuses, and are thought to use developed smell senses to locate them (Hanlon and Messenger 1996).
      Octopuses have two types of defense against their predators, primary and secondary (Hanlon and Messenger 1996). Primary defense includes using ‘crypsis,’ also known mainly as camouflage or color changing to match their environment (Hanlon and Messenger 1996). Secondary defenses are only used when the primary response fails, and the octopus is seen by its predator (Hanlon and Messenger 1996). These responses include flight and inking, deimatic behavior, defensive postures, and deflective markings (Hanlon and Messenger 1996).
      The Octopus’s ability to camouflage is nothing short of astounding. It is theorized that this ability was developed as an adaptation for protection from predation due to the evolutionary loss of an external shell (Ferguson and Messenger 1991). Octopuses achieve color change in part by chromatophores, iridophores, and leucophores; all structures of the skin in increasing depth (Froesch and Messenger 1978). Chromatophores are generally known as elastic pigment sacs with muscle fibers attached letting them expand and contract (Ferguson and Messenger 1991). The leucophores are important because they allow for the reflection of white light and consequently allow the skin to reflect wavelengths of light which are prevalent in their habitat and produce disruptive patterns (Froesch and Messenger 1978). The other aspect to cephalopod camouflage is the brain which contains nerves coated in chromatophore fibers, controlling coloration patterning (Froesch 1973).
      Deimatic behavior includes threatening or bluffing actions in order to cause the predator to hesitate (Hanlon and Messenger 1996). Sometimes this behavior will scare away the predator or give the octopus enough time to flee in a jet of ink. Specific deimatic coloration patterns and body postures in O. vulgaris are a paling of the skin, darkening of suckers and area around eyes, arms and web spread widely, and a jetting of water (Hanlon and Messenger 1996). They are also known to threaten the predator by throwing out their arms towards the attacker (Hanlon and Messenger 1996).

Reproduction
      Because of their solitary lifestyle, mating in octopuses does not include long term pairing, monogamy, or intricate courtship (Hanlon and Messenger 1996). O. vulgaris are oviparous, have separate sexes with no sex reversal or hermaphrodites, and females spend extended amounts of time caring for and brooding their eggs. Both the males and females of the species will die after the eggs hatch. Sexual dimorphism is slight, with males having selectively larger suckers on their second and third arms (Hanlon and Messenger 1996). Male and females have an almost equal abundance ratio, with males’ negligibly higher (Silva et al. 2002). The reproductive season runs from February to October, with peak months at April, May, and August (Silva et al. 2002).
      The males produce and maintain sperm in spermatophores and deposit these sacs into the females using an adaptation of the third right arm known as the hectocotylus (Hanlon and Messenger 1996). The specialized arm has a hollowed out groove for the sac to fit into which it uses to deposit the sperm into the female’s oviduct (Hanlon and Messenger 1996). Males usually reach sexually maturity ahead of the females; however they are still able to coordinate reproduction at the same time (Silva et al. 2002). This is possible because the female stores the sperm in her oviducal gland until she is sexually mature and ready to fertilize them (Hanlon and Messenger 1996). If the female wishes she can keep the sperm inside her oviducal gland for up to two thirds of her life (Hanlon and Messenger 1996). This also allows her to collect sperm packets from various partners and use whichever sacs she deems best (Hanlon and Messenger 1996).
      Since courtship is severely reduced or absent, O. vulgaris males and females do not show any form of specific coloration patterning or particular postures (Hanlon and Messenger 1996). At the most, males may show off their large suckers to confirm gender. It is not confirmed exactly how the mating process occurs, but two methods are known. The males either mount the females and deposit their spermatophores or deposit the sperm sacs from a distance alongside the females. Either way, the whole occurrence takes on average an hour, with a sperm sac being deposited every fifteen minutes (Hanlon and Messenger 1996).
      After a successful mating and once the female decides conditions are right for fertilization, she lays her eggs (Hanlon and Messenger 1996). Her eggs are attached to substrate inside the den either in a group or individually, so that she may protect and take care of them. This stage of sexual maturity drastically changes the female’s life processes and activities. Her body will stop growing and she will stop leaving the den to forage for food, discontinuing eating for the rest of her life. All of her time will be consumed with brooding the eggs; making sure they are cleaned and aerated. After hatching both the males and females will die (Hanlon and Messenger 1996).Their entire lifecycle only lasts between twelve and fifteen months (Katsanevakis and Verriopoulos 2005).


Recent Research


      There are many aspects and angles of cephalopod research which could be done. A large amount of recent research for O. vulgaris has to do with either color patterning or impacts of fisheries. The impact of trawling on the common octopus population could be potentially detrimental, especially with the octopus’s reduced life span. Katsanevakis and Verriopoulos (2005) recorded population densities in a well known trawl area in the eastern Mediterranean off the coasts of Greece. Because of increasing catch landings and popularity of octopus as a cuisine option, the impacts of harvesting on populations is important to consider.
      In a country such as Greece where few restrictions on trawling are set and even less are enforced, O. vulgaris populations are in need of a checkup (Katsanevakis and Verriopoulos 2005). Such studies are also important because if trawling and fishing coincides with breeding season, the populations have the potential to be almost completely decimated.


Commercial Importance


      O. vulgaris is the common labeling for commercial octopuses caught by fisheries around the world. They are a large part of the market and industry, with 20,000 to 100,000 tons caught on average per year (Garcia and Castro 1998). However, species catch commonly exceeded 100,000 (Hernandez-Lopez and Castro-Hernandez 2001). The common octopus accounts for about fifty percent of total world octopus catch (Hernandez-Lopez and Castro-Hernandez 2001).
      The method for capture is usually otter trawls, but in rocky areas octopus pots are used (Quetglas et al. 1998). Octopus pots are responsible for a significant percentage of annual catch, averaging thirty-six percent along the Spanish Mediterranean coast (Quetglas et al. 1998). In the same area, O. vulgaris make up twenty to forty percent of the entire trawl catch for the year (Quetglas et al. 1998). Fisheries use knowledge such as breeding grounds of O. vulgaris to increase trawl yields (Quetglas et al. 1998). The locations of these grounds are beneficial to fisheries because O. vulgaris will migrate inshore to shallower water for reproduction, and trawling is not allowed deeper than fifty meters (Quetglas et al. 1998). In the Canary Islands, iron traps are used to catch O. vulgaris, and can be found at depths up to two hundred meters (Garcia and Castro 1998). Other methods used for capture include lures, spears, hook-and-lines, and set-nets (Katsanevakis and Verriopoulos 2005).
      Octopus is a favorite dish in restaurants around the world, particularly in countries whose diets comprise largely of food fished from the sea. In Japan and Greece especially it is eaten raw, fried, smoked, and in a variety of other preparations (Nagai and Suzuki 2002). Because of demand, the common octopus is a target species for many fisheries (Garcia and Castro 1998). In Northwestern African alone it is the number one target species for fisheries (Hernandez-Lopez and Castro-Hernandez 2001). There are many repercussions of the large scale fishing of O. vulgaris for human consumption, many which the full effects of which are unknown, such as population dynamics and species distribution (Katsanevakis and Verriopoulos 2005).


Bermuda Laws


      Bermuda laws pertaining to MPAs and no collection zones help to protect the habitats of O. vulgaris and the organisms themselves. In 2000, Bermuda passed the Customs Tariff Amendment (No 2) Act in which they stated that all mollusk species in any form meant for human consumption are subject to a tax of ten percent per kilogram.


Personal Interest


      It’s difficult to pinpoint exactly when I became interested (a more subtle term than obsessed) in cephalopods. Maybe it was a due to numerous family ‘outings’ to various nature reserves and habitats throughout Northern California. Or perhaps it was because of our family membership to the Monterey Bay Aquarium where I would spend the whole day staring at the hovering cuttlefish if my mom had let me. When in my junior year of high school I had the opportunity to take a combination astronomy/marine biology course I was thrilled. Although the class was merely a one semester overview of the basic organisms known in marine science, I loved every minute of it. Despite the fact that for my Rocky Intertidal Project I had to wake up at 4am to drive to Santa Cruz so that I could be there in time for low tide. Any chance I had to learn about or see cephalopods, I was there.
      I guess my “interest” was pretty apparent because it wasn’t long before my friends caught on and were calling me whenever they were standing in front of the Cephalopod exhibit at the aquarium or telling me about a neat special on the Discovery Channel. To this day I still get frequent calls and messages from my friends at home asking me such common questions as “How are the cephalopods doing?” or “Did you kiss an octopus yet?” It followed me to college where I have earned nicknames and even a personal mantra, “peace, love, fish, and Melissa!”
      There is no real reason why I fell in love with these beautiful creatures. When I came to BIOS I knew that this was the perfect place for me to learn more about cephalopods. When I found out about the prevalence of octopuses in Whalebone Bay, located nearby to the station, I was excited to see them. The opportunity to do an entire report on them was just what I wanted. This is the reason why I have chosen Octopus vulgaris as my species.


References

Ferguson, G.P. and J.B. Messenger (1991). “A countershading reflex in cephalopods.” Proc. Royal Soc. Lond. 243: 63-67.

Fiorito, G. and F. Gherardi (1998). “Prey-handling behavior of Octopus vulgaris (Mollusca, Cephalopoda) on Bivalve preys.” Behavioural Processes 46: 75-88.

Froesch, D. (1973). “Projection of Chromatophore Nerves on the Body Surface of Octopus vulgaris.” Mar. Biol. 19: 153-155.

Froesch, D. and J.B. Messenger (1978). “On leucophores and the chromatic unit of Octopus vulgaris.” J. Zool., Lond. 186:163-173.

Hanlon, R.T. and J.B. Messenger. Cephalopod Behavior. Cambridge: Cambridge University Press, 1996.

Hernandez-Garcia, V., J.L. Hernandez-Lopez, J.J. Castro (1998). “The octopes (Octopus vulgaris) in the small-scale trap fishery off the Canary Islands (Central-East Atlantic).” Fisheries Research 35: 183-189.

Hernandez-Lopez, J.L., J.J. Castro-Hernandez, V. Hernandez-Garcia (2001). “Age Determination from the daily deposition of concentric rings on common octopus (Octopus vulgaris) beaks.” Fish. Bull. 99: 679-684.

Katsanevakis, S. and G. Verriopoulos (2005). “Seasonal population dynamics of Octopus vulgaris in the eastern Mediterranean.” ICUS J. Mar. Sci. 63: 151-160.

Klages, N.T.W. (1996). “Cephalopods as Prey. II. Seals.” Phil. Trans. R. Soc. Lond. 351: 1045-1052.

Meisel, D.V., R.A. Byrne, M. Kuba, J. Mather, W. Ploberger, E. Reschenhofer (2006). “Contrasting Activity Patterns of Two Related Octopus Species, Octopus macropus and Octopus vulgaris.” J of Comparative Psych. 120: 191-197.

Nagai, T. and S. Nobutaka (2002). “Preperation and partial characterization of collagen from paper nautilus (Argonauta argo, Linnaeus) outer skin.” Food Chemistry 76: 149-153.

Quetglas, A., F. Alemany, A. Carbonell, P. Merella, and P. Sanchez (1998). “Biology and fishery of Octopus vulgaris Cuvier, 1797, caught by trawlers in Mallorca (Balearic Sea, Western Mediterranean).” Fisheries Research 36: 237-249.

Silva, L., I. Sobrino, and F. Ramos (2002). “Reproductive Biology of the Common Octopus, Octopus vulgaris Cuvier, Cuvier 1797(Cephalopoda: Octopodidae) in the Gulf of Cadiz (SW Spain).” Bull. Mar. Sci. 71(2): 837-850.

Links

The Cephalopod Page
Octopus macropus escaping through a 1 inch hole
CephBase
Monterey Bay Aquarium
Octopus Camouflage Video
Bermuda Law Database