Doryteuthis Opalescens
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''Doryteuthis opalescens'', the opalescent inshore squid or market squid, is a small species of
squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...
in the family
Loliginidae Loliginidae, commonly known as pencil squids, is an aquatic family of squid classified in the order Myopsida. Taxonomy The family Loliginidae was formerly classified in the order Teuthida. Taxonomic list The classification below (includi ...
. It is a myopsid squid, a near shore group with
cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...
s over their eyes. The species is found in the eastern Pacific Ocean from
Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...
, Mexico to
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
, United States, and as an inshore squid can be found within a range of off the coast.


Description

Adult ''Doryteuthis opalescens'' can reach a total size of 11 inches (28 cm). Males are typically larger with a mantle length of 5 – 3 1/2 inches (7.5 to 9 cm), while females are 5 –7 inches (13 to 19 cm) 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 ...
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, from Ancient Greek σπέρμα (''spérma''), meaning "seed", and -φόρος (''-phóros''), meaning "bearing", or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especiall ...
transfer during mating. The eyes of ''D. opalescens'' are covered with a non-perforated membrane known as a
cornea The cornea is the transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...
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 cephalopod A cephalopod is any member o ...
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 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 ...
'' from the North Atlantic Coast of North America, and ''
Loligo gahi ''Doryteuthis gahi'', also known as Loligo, the Patagonian longfin squid and Patagonian squid (Spanish: ''calamar patagónico'' or just ''calamar''), is a small-sized squid belonging to the family Loliginidae. It occurs in coastal waters in the s ...
'' from the coast of Chile.


Life history

The life cycle of ''D. opalescens'' has four stages:
eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...
, hatchlings (called
paralarva Coleoidea or Dibranchiata is one of the two subclasses of cephalopod molluscs containing all the various taxa popularly thought of as "soft-bodied" or "shell-less" (i.e. octopus, squid and cuttlefish). Unlike its extant sister group Nautiloidea ...
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. H ...
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 residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
.
Bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
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 pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...
for
fungal A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the tradit ...
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 Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out ...
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. 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 r ...
'' 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 (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...
s and other
plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...
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 ecology, ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is also well ...
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 Califo ...
,
blue shark The blue shark (''Prionace glauca''), also known as the great blue shark, is a species of requiem shark, in the family Carcharhinidae and the only member of its genus which inhabits deep waters in the world's temperate and tropical oceans. Ave ...
, sail fish, striped tuna,
Chinook salmon The Chinook salmon (''Oncorhynchus tshawytscha'') is the largest and most valuable species of Oncorhynchus, Pacific salmon. Its common name is derived from the Chinookan peoples. Other vernacular names for the species include king salmon, quinn ...
,
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 winte ...
, 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 Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethnic ...
in Monterey Bay, California 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, a Romance ethnic group related to or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance languag ...
fishermen A fisherman or fisher 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. Fishermen may be professional or recr ...
had assumed the leading role. After
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
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 are an archipelago in the English Channel, off the French coast of Normandy. They are divided into two Crown Dependencies: the Jersey, Bailiwick of Jersey, which is the largest of the islands; and the Bailiwick of Guernsey, ...
, 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. San Francisco itself is further north along the coast, by about 75 miles (120 km), accessible via California S ...
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, El or el may refer to: Arts and entertainment Fictional entities * El, a character from the manga series ''Shugo Chara!'' by Peach-Pit * Eleven (''Stranger Things'') (El), a fictional character in the TV series ''Stranger Things'' * El, fami ...
. During these warm water and nutrient poor years landings can disappear entirely in certain areas. Between 1998 and 2019, studies found that ''D. opalescens'' populations in more northerly U.S. Pacific Coast waters have increased significantly. This was linked to ocean temperature increases due to climate change.


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 Doryteuthis Western North American coastal fauna Cephalopods described in 1911