Doryteuthis opalescens, formerly known as Loligo opalescens, is a small squid that lives within 320 kilometers of shore in the Eastern Pacific Ocean. Commonly known as the market squid, they are endemic to the California current and range from British Columbia, Canada to the tip of the Baja Peninsula in Mexico, though they are most abundant between Punta Eugenia, Mexico, and Monterey Bay, California. They seasonally migrate from British Colombia to Mexico. (NOAA Fisheries Service Contributors, 2012; Stewart, et al., 2011; Zeidberg, 2012)
Doryteuthis opalescens is found in greatest abundance around 15 meters during the day to about 30 meters at night when hunting. These squid live above the continental shelf and have been found at depths up to 500 meters. They make seasonal spawning migrations from British Colombia to Mexico in enormous schools. (NOAA Fisheries Service Contributors, 2012; Zeidberg, 2012)
Male Doryteuthis opalescens average 130 g and females 90 g. An average mantle on a market squid measures 19 cm in males and 17 cm on females. Doryteuthis opalescens has 8 short arms and 2 longer tentacles all equipped with two rows of bowl shaped suckers with blunt teeth in the center. The left ventral arm of the male squid is hectocotolized, so that the last one third of the arm has greatly reduced suckers, modified for reproductive purposes.
This squid has a pair of triangular shaped fins protruding from the head region that stretch from the tip to nearly half way down the mantle. Doryteuthis opalescens, like other squid, possess chromatophores in their skin. These pigment bearing-cells can change color, and are used to confuse predators, attract mates, and communicate with other members of the species. ("The structure, development, food relations, reproduction, and life history of the squid Loligo opalescens Berry", 1965; NOAA Fisheries Service Contributors, 2012; Zeidberg, 2012)
These squid develop quickly and live for about 4 to 9 months. Females lay hundreds of eggs in a sheath made of protein that are coated with bacteria, useful in preventing fungal infection. The eggs are laid in the sand, cemented with a sticky substance to hold them to the ground so the tides and currents don’t sweep them away. The presence of the eggs on the ocean floor encourages other female squid to lay eggs, leading to fields of squid eggs covering large patches of the ocean floor. Eggs hatch within 3 to 5 weeks, warmer water expediting the process. Where the baby squid go once they have hatched is still not known, but it has been documented that within the first 12 hours of life, the baby squid swim to the surface. They will generally feed on copepods and other plankton for the first few months of their lives. ("The structure, development, food relations, reproduction, and life history of the squid Loligo opalescens Berry", 1965; NOAA Fisheries Service Contributors, 2012; Stewart, et al., 2011; Zeidberg, 2012)
Adult squids move to sheltered waters to spawn. During this time, male adult squids change body coloration and use movements to attract females and display red flashes to ward off rival males. The sneaker spawning that D. opalescens is known for occurs when the male squid uses its fifth arm (called the hectocotylus) to grab the female to insert spermatophores. These spermatophores are narrow tubes of chitin, filled partially with a dense mass of sperm. This sneaker spawning lasts from 1-15 seconds. Spermatophores are retained in the female's mantle cavity until the eggs are laid. (Gardiner, 1972; Zeidberg, 2009)
A female Doryteuthis opalescens extracts 100-300 eggs into the sand and covers them with a sticky substance that anchors the eggs and protects them from predators and the natural ocean movements. Eggs present at the bottom of the ocean stimulates other females to lay their eggs. The eggs deposited onto the ocean floor take 3-5 weeks to hatch, depending on temperature. Warmer waters quicken hatch time. At the time of the hatching, this first stage is called a paralarva, and is about 2-3 mm. For the first 12 hours of life, a paralarva immediately starts swimming to the surface. The paralarva then needs to hunt since their protection barrier is now gone. Food includes copepods and other plankton. When D. opalescens reaches 15 mm in length, it is strong enough to swim in groups (shoals). Together these squid swim in search of food generally in groups of 10, and then start to hunt with their tentacles. (Zeidberg, 2012)
Males produce 12 or more spermatophores a day, and store up to 400 of them in a large pouch (Needham’s sac). This spermatophore surrounds the semincal vesicle and enters the female by the opening of the mantle cavity. (Gardiner, 1972)
Athough female D. opalescens die after laying eggs, the timespan to death is not firmly established. Since this lifespan cannot be confirmed, the concept of parental investment is not completely known.
The expected lifespan in the wild is on average 4 to 9 months. (Zeidberg, 2012)
Doryteuthis opalescens can be cannibalistic. They feed on smaller prey species such as fish, crabs and shrimp, mollusks, and other juvenile squid, which would in turn also affect the lifespan of the squid. These squid swim in groups after reaching 15 mm, and migrate to the surface at night to feed. (Morris, 2008; Zeidberg, 2012)
Doryteuthis opalescens is predominantly a visual communicator. This species, like all cephalopods, has extremely well developed eyes and a complex nervous system with a central brain. Connected to the brain by radial muscles are specialized organs called chromatophores. These sacs in the skin contain red, brown, orange and yellow pigment and are under direct control of the central nervous system, giving the squid the ability to change color within milliseconds without disrupting its other physical movements. Different colors and patterns are the result of different combinations of chromatophores being expanded at different times and for various durations. This enables the squid to display a variety of body patterns which can be held, repeated, changed instantaneously, or graded in intensity of expression. When the animal is undisturbed, it appears pale with a blue/green opalescence as a result of iridophores, iridescent chromatophores also located in the skin. Chromatic signals are most commonly observed during predation and mating events. Color undulates over the body when prey is caught, and the body turns dark during ingestion. When mating, the head and arms of the male turn bright red, with no signal in the females. Defensive situations also elicit chromatic signals, as do unfamiliar surroundings. Chromatic signals can be combined with certain postural and locomotor signals during intraspecific encounters and are thus termed “displays".
The most prominent perception channel in D. opalescens are photoreceptors, or the eyes. The eyes are extremely developed and play a vital role in visual communication. Despite having highly developed eyes, there is no evidence that D. opalescens responds directly to color change, but instead to intensity and brightness of the signals. Though they are thought to be colorblind, cephalopods are quick learners and can distinguish between black and white, horizontal and vertical, and circles and other shapes.
Mechanoreceptors in the form of statocysts are also very important. Statocysts are paired organs in cephalopods with functions similar to those of the inner ear of humans. They transmit information about gravity, position, and acceleration to the brain which helps the squid maintain equilibrium in the water column, as well as directs head, eye and body movement. This species also uses tactile perception through it’s arms and tentacles. ("The structure, development, food relations, reproduction, and life history of the squid Loligo opalescens Berry", 1965; Hanlon and Messenger, 1996; Nixon and Young, 2003)
Doryteuthis opalescens is carnivorous. Diet of adults consists mostly of smaller crustaceans (euphausiids, shrimp, and amphipods) fish, and other squids. This species is fast and agile and has been observed taunting its prey before capture. The speed of the squid and the immediate extension of its tentacles allow it to capture prey larger than itself. Complex eye structures also help detect prey. Feeding is presumed to occur throughout the day, but is typically witnessed at night under the lighted areas of docks or boats. ("The structure, development, food relations, reproduction, and life history of the squid Loligo opalescens Berry", 1965; Hanlon and Messenger, 1996)
Doryteuthis opalescens has many predators, and thus possesses many tactics of self defense. Crypsis and visual displays using chromatophores and iridophores can be used to confuse, threaten, or deceive its predators. Squid are extremely fast swimmers, which aids in predator avoidance. They also possess ink sacs, which release ink to further confuse predators. Despite these adaptations, these squid are important consumers in the oceanic food web and are vital to the survival of many species of the eastern Pacific ocean. (NOAA Fisheries Service Contributors, 2012)
Doryteuthis opalescens play important roles as both predators and prey in the oceanic trophic pyramid. ("The structure, development, food relations, reproduction, and life history of the squid Loligo opalescens Berry", 1965)
Doryteuthis opalescens provides enormous economic importance for humans. This species, commonly referred to as the market squid, is an important source of protein for humans worldwide. It is rich in selenium, riboflavin, and vitamin B12. As of 2000, market squid fishery has become the most valuable fishery in the state of California. In 2010, over 253.4 million pounds of squid were harvested from California waters, most of which were frozen and exported throughout the world. This species is ideal to withstand commercial fishing pressure due to the shortness of its lifespan and the efficiency of reproduction. An entire population can nearly replace itself annually. Currently, there is no commercial aquaculture for market squid. Fishing for D. opalescens is monitored by the California Department of Fish and Game, which set strict guidelines in 2004. Guidelines established include permit requirements as well as seasonal catch limits. Fishing methods include attracting the squid to the surface with bright lights, then dropping shortened seines or scoop nets. This reduces bycatch and minimizes disruption of benthic habitats. (NOAA Fisheries Service Contributors, 2012)
There are no known adverse effects of Doryteuthis opalescens on humans.
Despite having a short lifespan and the ability regenerate nearly an entire population annually, Doryteuthis opalescens is still currently considered at a level of Moderate Conservation Concern by the Monterey Aquarium Seafood Watch. This labels the species as a "good alternative" for consumption based on five criteria: inherent vulnerability, status of stocks, nature of bycatch, habitat and ecosystem effects, and management effectiveness. Conservation status is updated as needed based on yearly statistics. (NOAA Fisheries Service Contributors, 2012; Stewart, et al., 2011)
Mandie Armstrong (author), San Diego Mesa College, Hollis Buchanan (author), San Diego Mesa College, Jillian Davidson (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Renee Mulcrone (editor), Special Projects.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
active at dawn and dusk
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
fertilization takes place within the female's body
makes seasonal movements between breeding and wintering grounds
eats mollusks, members of Phylum Mollusca
Having one mate at a time.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
generates and uses light to communicate
an animal that mainly eats fish
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.
uses touch to communicate
uses sight to communicate
California Department of Fish and Game. The structure, development, food relations, reproduction, and life history of the squid Loligo opalescens Berry. Fish Bulletin 131. California: State of California Department of Fish and Game. 1965.
Gardiner, M. 1972. The biology of invertebrates. New York: Mc Graw-Hill Book Co.
Hanlon, R., J. Messenger. 1996. Cephalopod behavior. Cambridge, UK: Cambridge University Press.
Morris, R. 2008. Intertidal invertebrates of California. Stanford: Stanford University Press.
Moynihan, M. 1985. Communication and noncommunication By cephalopods. Bloomington, Indiana: Indiana University Press.
NOAA Fisheries Service Contributors, 2012. "FishWatch: Loligo opalescens" (On-line). NOAA National Marine Fisheries Service. Accessed August 12, 2012 at http://www.nmfs.noaa.gov/fishwatch/species/market_squid.htm.
Nixon, M., J. Young. 2003. The brains and lives of cephalopods. New York: Oxford University Press.
Snyderman, M. 1998. California marine life. Niwot, Colorado: Robert Rinehart Publishers.
Stewart, J., S. Port-Minner, R. Mazurek. 2011. "California Market Squid Seafood Watch Report" (On-line). Monterey Bay Aquarium Seafood Watch. Accessed August 12, 2012 at http://www.montereybayaquarium.org/cr/SeafoodWatch/web/sfw_factsheet.aspx?fid=287.
Zeidberg, L. 2009. First observations of ‘sneaker mating’ in the California market squid, Doryteuthis opalescens, (Cephalopoda: Myopsida). Marine Biodiversity Records, 2: e6. Accessed August 17, 2012 at http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=3462396.
Zeidberg, L. 2012. "The Cephalopod Page" (On-line). Loligo opalescens, California Market squid. Accessed August 12, 2012 at www.thecephalopodpage.org/Lopal.php.