These cephalopods have eight "normal arms," along with a pair of retractile arms with clubbed suckers on the ends. Their torpedo-shaped, stream-lined bodies with terminal fins often appear somewhat blunter and wider as their depth increases, and enclose a thin membraneous internal shell. The two fins comprise a length of approximately two-thirds of the organism's body and produce a diamond-shape when seen from the dorsal view. These squid have well-developed heads with large eyes that are useful in predation. These squid possess colors and stripes; colors change during the escape mechanisms to a pink, red, or brown hue. ("Squids, cuttlefishes, octopuses", 1967; Banister and Campbell, 1985; Wilson, 1999)
The yolky eggs undergo direct development without the presence of a true larval stage. The eggs are laid in large colorless capsules during the night. The swollen capsules shrink as the embryos develop and, after approximately thirty days of embryonic development, the young hatch, resembling miniature adults, about 5 to 7mm in length. The young maintain a vertical body structure for a period of time, floating and drifting submissively through the water. Growth occurs rapidly for the young during the summer, and the species is sexually mature between the months of June and October. After 1 to 1.5 years, the adults die, completing the life cycle. (Grzimek, 1972)
Reproductive behavior and specific mating rituals are limited to the act of congregating on the bottom of the sea before fertilization. For reproduction, members of Loligo have fused, unpaired gonads located at the posterior ends of their bodies. Specialized glands of the female provide substances for egg coverings and open into the mantle cavity. This species collects in large numbers on the ocean bottom and produces huge masses of gelatinous spawn. The spawn are attached to solid objects on the ocean bottom.
Male squid gather sperm into a spermatophore carried on a specialized tentacle, called a hectocotylus. This tentacle is used to transfer the spermatophore to the female's mantle cavity, and is possibly broken off there. The anterior portion of the spermatophore has a gelatinous substance that discharges explosively upon contact with the female glandular stucture. The sperm are then released into the mantle cavity to pursue the rather large, yolky eggs. ("Squids, cuttlefishes, octopuses", 1967; Banister and Campbell, 1985; Grzimek, 1972)
Females lay up to 100,000 eggs attached to sea floor substrates. Sexual maturity is reached about one year after hatching. Although it is possible for squid to reproduce more than once, they most often don't because of their limited lifespan.
Females provide their eggs richly with yolk. There is no further parental investment.
The long-finned squid lives approximately 1-2 years in or out of captivity, three years at the most. Natural causes are the common cause of death; adults usually die after a mere year and a half. It is very common for squid to be eaten by predators, explaining why numbers in schools of squid are dramatically reduced during and after migration, falling prey to their predators. Cannibalism is also a very common cause of death of individuals. The large number of eggs produced more than compensates for the high mortality rate. (Wilson 2001, Grzimek 1972)
Little is known of communication among (Nichols and Cooke, 1971), yet the most predominate communication and perception channel is visual, using their large, well-developed eyes to recognize sexes for mating, prey for eating, and so forth.
Long-finned squids have a muscular bag behind the head which contains the organism's gills that provide rapid jet-propulsion used to escape predators. When the squid retracts backwards by use of the jet-propulsion, the body quickly changes to a much lighter color, and a bag of pigment opens into the mantle cavity that emits a large black cloud, confusing the predator. (Berg, et al., 1999; Nichols and Cooke, 1971)
Squid are important as a food base for oceanic predators, as well as being important predators of smaller marine vertebrates and invertebrates.
Aside from the obvious use of squid as food, research, and education, an unusual use of these squid is for jewelry: many primitive tribes use the hooked rings of the species' suction cups for rings. (Grzimek, 1972)is also used as fish bait and fish-meal production in the Mediterranean.
This species is very common during specific times of the year in nearshore waters and may prey on small fish and herring important to nearshore fisheries. However, squid are also economically important to humans. (Grzimek, 1972; Nichols and Cooke, 1971)
is abundant and is not threatened.
Tanya Dewey (editor), Animal Diversity Web.
Rae Taylor (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
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
the nearshore aquatic habitats near a coast, or shoreline.
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
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
makes seasonal movements between breeding and wintering grounds
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.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
an animal that mainly eats fish
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
1998-2001. "CephBase" (On-line). Accessed September 14, 2001 at http://www.cephbase.utmb.edu/spdb/speciesc.cfm?CephID=229.
1967. Squids, cuttlefishes, octopuses. Pp. 93-94 in The Larousse Encyclopedia of Animal Life. London: McGraw-Hill Book Company.
Banister, K., A. Campbell. 1985. Mollusks. Pp. 255-270 in The Encyclopedia of Aquatic Life. New York, NY: Facts of File Publications.
Berg, L., D. Martin, E. Solomon. 1999. Biology. Orlando, FL: Harcourt Brace College Publishers.
Grzimek, B. 1972. Mollusks. Grzimek's Animal Life Encyclopedia, Vol. 3: Mollusks & Echinoderms. New York, NY: Van Nostrand Reinhold Company.
Nichols, D., J. Cooke. 1971. The Oxford Book of Invertebrates. Oxford: Oxford University Press.
Wilson, E. 1999. "MarLIN: The Marine Life Information Network for Britain & Ireland" (On-line). Accessed September 14, 2001 at http://www.marlin.ac.uk/species/Loligoforbesii.htm.