''Doryteuthis opalescens'', the opalescent inshore squid or market squid, is a small

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fittin ...

(

mantle A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...

length (ML) up to 190 mm) in the family Loliginidae. It is a myopsid squid, which is the near shore group and that means that they have

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical ...

s over their eyes. The species lives in the eastern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...

from

Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...

's Baja California peninsula to

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U ...

, United States, and as an inshore squid it can be found with a range of off the coast.

Description

Adult ''Doryteuthis opalescens'' can reach a total size of 11 inches. Males are typically larger with a

length of 5 – 3 1/2 inches , while females are 5 –7 inches in mantle length.Morris, Robert H., Donald P. Abbott, Eugene R. Haderlie. 1980. ''Intertidal Invertebrates of California''. Stanford: Stanford University Press. The mantle of ''D. opalescens'' is not fused to the head and its body is 4 to 5 times longer than it is wide, with fins equal in both length and width. This squid has 8 arms with 2 longer

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s ending in tentacular clubs equipped with suckers at their ends. The tentacular clubs are narrow with 4 rows of suckers and 2 large rows in the center of the tentacular club bordered by outer rows of smaller suckers. The 8

arm In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between th ...

s have only 2 rows of alternating suckers running down their length. In male ''D. opalescens'', the left ventral arm is specialized or “ hectocotylized” for

spermatophore A spermatophore or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. Spermatophore ...

transfer during mating. The eyes of ''D. opalescens'' are covered with a non-perforated membrane known as a

which is a signature of myopsid squid. The color of ''D. opalescens'' can range from white to brown, with the animals able to change their color shades using

chromatophore Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, ...

s depending on mood and for camouflage. They are normally a bluish-white to mottled brown and gold, and they change to dark red or brown when excited, frightened or feeding.

Misidentification

''Doryteuthis opalescens'' is very similar to two other species of squid in the same family: '' Doryteuthis pealeii'' from the North Atlantic Coast of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

, and '' Loligo gahi'' from the coast of

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

Life history

The life cycle of ''D. opalescens'' has four stages:

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

, hatchlings (called

paralarva Paralarvae (singular: ''paralarva'') are young cephalopods in the planktonic stages between hatchling and subadult. This stage differs from the larval stage of animals that undergo true metamorphosis. Paralarvae have been observed only in mem ...

e), juveniles, and adults. Squid live for 6–9 months. ''Doryteuthis opalescens'' eggs are laid on sandy bottom substrates in 10–50 m depth, although there is a report of a shrimp trawler pulling up eggs from 400

fathom A fathom is a unit of length in the imperial and the U.S. customary systems equal to , used especially for measuring the depth of water. The fathom is neither an International Standard (SI) unit, nor an internationally-accepted non-SI unit. ...

s (730 m). Females encapsulate hundreds of eggs in a sheath that is made of many layers of

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

Bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

grow between the layers and may serve as an

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...

for fungal infection. Females insert the egg capsules into the sand with a sticky substance that anchors them in place so that the ocean surge can ventilate them. The presence of eggs on the bottom of tanks stimulates females to lay more eggs. Groups of capsules are placed in masses that can extend into egg beds. Some egg beds can cover acres of the ocean floor. The eggs take 3–8 weeks to hatch with warmer water shortening the incubation time.

Bat star ''Patiria miniata'', the bat star, sea bat, webbed star, or broad-disk star, is a species of sea star (also called a starfish) in the family Asterinidae. It typically has five arms, with the center disk of the animal being much wider than the stu ...

s (''

Asterina miniatus Asterina may refer to: * ''Asterina'' (starfish), a starfish genus in the family Asterinidae * ''Asterina'' (fungus), a fungus genus in the family Asterinaceae {{Genus disambiguation ...

'') are the most prevalent predators of eggs. Fish do not eat them, although they will nip at eggs not covered by the capsule sheath. There is no brooding. Logilo cc

Paralarvae of ''D. opalescens'' hatch from the eggs and immediately begin swimming. Where they go is unknown, but hatchlings of the closely related ''

Loligo pealei The longfin inshore squid (''Doryteuthis pealeii'') is a species of squid of the family Loliginidae. Description This species of squid is often seen with a reddish hue, but like many types of squid can manipulate its color, varying from a deep ...

'' swim to the surface in the first 12 hours post-hatching. Paralarvae must rapidly learn to hunt, as their yolk is either used up or detached upon escaping from the egg sheath. Through a series of trial and error as these 2–3 mm ML hatchlings learn to eat

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic (inhabiting sea waters), some are benthic (living on the ocean floor), a number of species have ...

s and other

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cruc ...

in the first months of their lives. They are found in the greatest abundance at 15 m depth by night and 30 m depth by day. Thus, they perform a daily vertical migration of 15 meters, no small feat a creature only 3 mm long. This daily migration coupled with the shear zone created by tidal and near-shore currents cause the hatchlings to become entrained within 3 kilometers of shore. That is good for them because in the near-shore environment the plankton is smaller and easier for them to eat. By the time ''D. opalescens'' reaches 15 mm mantle length (about 2 months old) they are strong enough to swim in shoals. These juveniles form groups of tens of individuals and swim over the shelf in search of food. Those that have survived to this point can hunt with the tentacular strike as seen in the adults. At some point between 4–8 months their sexual organs mature and they are now considered adults. Sexually mature animals can be 70–160 mm ML and weigh about 40 grams. Adult ''D. opalescens'' move off the continental shelf by day and can be found to depths of 500 m. Adult shoals return to the surface at night to hunt. At some point these shoals move on shore to spawn where aggregations can reach million of individuals. Originally it was thought that the adults died after spawning, as the egg beds were often littered with dead squid. Now there is debate as to how long adults live after their first egg deposition and whether they can spawn repeatedly over the last weeks or months of their lives.

Predator and prey relationships

''Doryteuthis opalescens'' is a

cannibal Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, bo ...

istic predator that feeds on smaller prey species such as fish, crabs, shrimp, mollusks, and other juvenile squids. It uses its two longer tentacles with tentacular clubs on the end to snare and catch its prey. ''Doryteuthis opalescens'' itself is an important food source for many predators like larger fish, sharks, marine mammals, seabirds, and also humans. Its predators include the

California sea lion The California sea lion (''Zalophus californianus'') is a coastal eared seal native to western North America. It is one of six species of sea lions. Its natural habitat ranges from southeast Alaska to central Mexico, including the Gulf of Ca ...

blue shark The blue shark (''Prionace glauca''), also known as the great blue shark, is a species of requiem shark, in the family Carcharhinidae, which inhabits deep waters in the world's temperate and tropical oceans. Averaging around and preferring ...

, sail fish, striped tuna,

Chinook salmon The Chinook salmon (''Oncorhynchus tshawytscha'') is the largest and most valuable species of Pacific salmon in North America, as well as the largest in the genus '' Oncorhynchus''. Its common name is derived from the Chinookan peoples. Other ...

black-throated diver The black-throated loon (''Gavia arctica''), also known as the Arctic loon and the black-throated diver, is a migratory aquatic bird found in the northern hemisphere, primarily breeding in freshwater lakes in northern Europe and Asia. It winter ...

, and

Brandt's cormorant Brandt's cormorant (''Urile penicillatus'') is a strictly marine bird of the cormorant family of seabirds that inhabits the Pacific coast of North America. It ranges, in the summer, from Alaska to the Gulf of California, but the population north ...

. The fishery for ''D. opalescens'' began with the Chinese in

Monterey Bay, California Monterey Bay is a bay of the Pacific Ocean located on the coast of the U.S. state of California, south of the San Francisco Bay Area and its major city at the south of the bay, San Jose. San Francisco itself is further north along the coast, ...

in 1860. By the turn of the century

Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance language *** Regional Ita ...

fishermen A fisher or fisherman is someone who captures fish and other animals from a body of water, or gathers shellfish. Worldwide, there are about 38 million commercial and subsistence fishers and fish farmers. Fishers may be professional or recreati ...

had assumed the leading role. After

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

there was a resurgence in squid fishing. Since 1981 the fishery, has grown significantly, as effort in Southern California has increased. Now Southern California, mostly areas around the

Channel Islands The Channel Islands ( nrf, Îles d'la Manche; french: îles Anglo-Normandes or ''îles de la Manche'') are an archipelago in the English Channel, off the French coast of Normandy. They include two Crown Dependencies: the Bailiwick of Jersey, ...

, comprises 90% of the squid landings. The fishery in

Monterey Bay Monterey Bay is a bay of the Pacific Ocean located on the coast of the U.S. state of California, south of the San Francisco Bay Area and its major city at the south of the bay, San Jose. San Francisco itself is further north along the coast, by ...

occurs from April to November coinciding with the upwelling season. In Southern California landings begin in November and continue through April correlated with the greater mixing of winter storms. Since 1993 squid has been the #1 fishery in California with landings of 118,000 tons and $41 million in 2000. The population fluctuates greatly with the

El Niño El Niño (; ; ) is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (approximately between the International Date ...

. During these warm water and nutrient poor years landings can disappear entirely in certain areas.

References

* Vecchione, M., E. Shea, S. Bussarawit, F. Anderson, D. Alexeyev, C.-C. Lu, T. Okutani, M. Roeleveld, C. Chotiyaputta, C. Roper, E. Jorgensen & N. Sukramongkol. (2005). ''Phuket Marine Biological Center Research Bulletin'' 66: 23–26.
Opalescent inshore squid
''NOAA FishWatch''. Retrieved 4 November 2012.

External links

Slate.com "Motion in the Ocean"
{{Taxonbar, from=Q13596607 Squid Western North American coastal fauna Molluscs described in 1911