Habitat: They are all found in the ocean. have more than 90 tentacles; members of orders Sepioidea and Teuthoidea have The Cirrata, which have reduced musculature and radula, indicating reduced activity and masticatory power, probably feed on bottom dwellers or small plankton. Cephalopoda (phylum Mollusca) Literally ‘head-foot’ (from the Greek kephale, head, and pod-, foot), a class of molluscs, exclusively marine, that are related to the Bivalvia and Gastropoda. The number of eggs laid during a spawning period varies greatly; it may range from only a few dozen in octopuses with large eggs to more than 100,000 in the common octopus, laid over a period of about two weeks. Cephalopods are characterized by a completely merged head and foot, with a ring of arms and/or tentacles surrounding the head. The geographic distribution of cephalopods is incompletely known. epidermis surrounded by cells containing contractile fibers. 1967. Meglitsch, P. A. Wood, J. Most cephalopods are highly adapted for swimming. and the internal shell of a cuttlefish, or cuttle bone, is sold in the pet trade It enters around the neck region or aperture of the mantle (through the funnel in some deep-sea octopuses). The mantle surrounds the visceral sac and possesses strong The Cephalopoda are fed upon by many marine mammals, large fish, and seabirds. It is believed that cephalopods evolved from an ancient group of gastropods. of squid and octopus are eaten. Their name Cephalopoda means “head footed.” They are all fast moving ocean animals. are also a great source of sea-monster folklore. It has a pair of large eyes. Most cephalopods are highly adapted for swimming. the Mesozoic. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services. Because of the extraordinary flexibility of the body, they are able to pass through openings hardly larger than the diameter of one eye. Class Cephalopoda A cephalopod i s any member of the molluscan class Cephalopoda. Habitat: They are all found in the ocean. Learn about the reproduction of cuttlefish. In the octopods they may be fertilized as they pass through oviductal glands near the end of the oviduct. The best-known feature of the cephalopods is the possession of arms and tentacles, eight or 10 in most forms but about 90 in Nautilus. Our editors will review what you’ve submitted and determine whether to revise the article. Cephalopods are mollusks ( Cephalopoda ), a class which includes octopuses, squid, cuttlefish, and nautilus. In the squids a much larger section of the arm may be modified; often the suckers are degenerate and the distal half of the arm bears rows of slender papillae, although special pouches and flaps may often be found. In the order Sepioidea (cuttlefishes and bottle-tailed squids) the young closely resemble the adults and are only briefly planktonic. Movement through the water is aided by lateral expansions (swimming keels) on the outer surface of the third pair of arms. Schools of the large oceanic squid Thysanoteuthis rhombis have been reported at Madeira. The chambered nautilus (Nautilus) is a less active swimmer, partly due to the inefficient funnel, which is composed of two flaps instead of a single fused tube, and to a reduced mantle cavity. belemnoids. 1. B., C. L. Day, P. G. Lee, R. K. O'Dor, and M. Vecchione. The vertical distribution is also incompletely known. that may consist of color changes, body movements, or combinations of both. Description, classification, synonyms of Class Cephalopoda. The smaller oceanic squids probably feed primarily upon small fish, copepods, heteropods, and caridean shrimp. The female reproductive system is simple, consisting of the posterior ovary and paired oviducts. Radula is reduced and there is a pair of powerful jaws for feeding. In general, the pelagic and planktonic cephalopods conform in their distribution to other pelagic animals. Octopus feeds upon bivalve mollusks and on decapod crustaceans, sometimes causing severe losses to the lobster fishery by entering the traps and eating the captive lobsters. as the exhalent aperture. Certain The arms, tentacles, The benthic octopods are bottom crawlers, gliding about the bottom and in and out of crannies with amazing agility through the use of their eight arms and hundreds of suckers. That's why they're called, "head-footed." Cephalopoda is the most morphologically and behaviorally complex class in Or, perhaps, you thought about dolphins, known for their animal intellect, or even perhaps something more domestic like the dog. The mantle, which has a passive role in the majority of mollusks, has become involved in locomotion in cephalopods, having almost entirely lost its rigid shell and become highly muscular. muscles required for contraction of the cavity and respiration. Pages 394-424 in Invertebrate Zoology, vol. Class Cephalopoda The cephalopods (the “head-foots”) are, in many respects, the most evolutionarily advanced animals to be found among the invertebrates. The eggs of most cephalopods are enclosed within a capsule that may be gelatinous and transparent (the squids of the genus Loligo) or opaque and leathery (Octopus and cuttlefishes). Fishermen sometimes call cephalopods "inkfish," referring to their common ability to squirt ink. Cephalopoda is a class of animals in which . Development of the embryo is direct, without the distinctive larval stages and metamorphoses that occur in other mollusks. Answer: Cephalopoda. hatching. The strong beak is at the entrance to the The Coleoidea are carnivorous and live principally on other cephalopods, crustaceans, mollusks, and small fishes. There are two pairs of Schneider, 1784 Highly specialized marine molluscs divided into two distinctive subclasses, the shelled subclass Nautiloidea and the subclass Coleoidea, in which the shell is reduced and internal or lacking entirely.About 600 species worldwide, typically nektonic or bentho-pelagic, fastmoving, predatory. upper lobes within the brain serve as controls for memory and learning. Egg laying in octopods is accomplished by the female individually fixing the eggs singly or in festoons by a short stalk or thread. Cephalopods possess well-developed nervous systems and complex sensory organs. The Class, Cephalopoda, diverse and interesting These sea creatures within the class, Cephalopoda, are considered to be among the most intelligent invertebrates on earth. There are numerous littoral species, but few have been reported from brackish water except for the squid Lolliguncula brevis, which occurs along the Florida coast in bays where the salinity is as low as 8.5 parts per thousand (about one-fourth that of the open ocean). large numbers during the Mesozoic. Introduction. esophagus , which may contain a crop; The giant squids (Architeuthis species) are the largest living invertebrates; A. dux attains a length of more than 20 metres (60 feet), including the extended tentacles. Cephalopods are a class of shell-bearing animals as well as mollusks with a reduced shell. Colours and colour patterns are exhibited according to specific behavioral conditions—e.g., attack on prey, camouflage, rest, and alarm or defense. Cephalopoda means "head foot" and this group has the most complex brain of any invertebrate. Cephalopods have the most advanced nervous system of all invertebrate animals and are active hunters. Their name Cephalopoda means “head footed.” They are all fast moving ocean animals. Cuttlefish Octopuses Squid The body mass is very tall. caecum , where most digestion and absorption occur. In cuttlefishes the number of eggs is smaller, about 200 to 300 being laid in a season. images and distinguishing colors. The shell is long, cylindrical and tooth- or tusk-shaped, and open at both ends. This has not been verified by later observers, but such intelligence is not beyond belief. The shell of the fossil ammonite Pachydiscus seppenradensis from the Cretaceous measures 205 centimetres (6 feet 8 inches) in diameter; it is considered to have been the largest shelled mollusk. The ink of cephalopods is used for both defense and escape. The characters of these animals are as follows: i. to "walk," and sepioids and teuthoids possess lateral fins that can In the Teuthoidea (squids), especially the Oegopsida, the larvae may differ widely from the adult and the juvenile period may be quite long. An external shell is possessed only Class Cephalopoda The Class Cephalopoda is made up of animals such as octopus, squid, and cuttlefish. In Argonauta and Tremoctopus the arm is highly modified and in mating is autotomized (self-amputated) and left within the mantle cavity of the female. Studies undertaken at the Zoological Station in Naples by the British zoologists J.Z. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Kozloff, E. N. 1990. Most cephalopods are semelparous. This small class of marine mollusks includes 200 species of burrowing animals commonly known as the tusk, or tooth, shells. Chemistry. They can be divided into three categories: the Nautiloidea (chambered Nautilus), the Ammonoidea (the extinct ammonites), and the Dibranchiata (squids, the extinct belemnites, and octopuses). Philadelphia and other cities. Nothing is known of the life span of the large oceanic squids, but it is presumed that giants such as Architeuthis attain their bulk only after a period of perhaps four to five years. Cephalopods (Octopi and Squids) Cephalopods are molluscan animals that live in the sea. have been named. shells. There are two groups of cephalopods: the nautiloids that have external shells and the coleoids that includes squid, octopus, and cuttlefish and do not have external shells. Images licensed under CC0. When you think about particularly intelligent animals, you likely think of our primate relatives, like monkeys and apes. In loliginids several thousand eggs may be laid by a single female, and the egg mop of the European common squid, resulting from the efforts of many individuals, may contain more than 40,000 eggs. In the food cycle of the squid Illex, in which the adults feed upon young mackerel and the adult mackerel feed upon young squid. Biology. Their name, Cephalopod or "head-foot" in Greek, reflects the unique relationship between the cephalopod head and foot: the arms encircle the animals' head. as a calcium source for birds. The Animal Diversity Web team is excited to announce ADW Pocket Guides! The behaviour of squids and octopuses differs considerably because of their different modes of life. The active swimmers and most bottom dwellers apparently possess no hydrostatic organ. All cephalopods are carnivorous. of three parts: The giant squid is the largest of all mollusks. The "feet" of cephalopoda … In Octopus under attack by a moray eel, the cloud of ink seems to paralyze for some time the eel’s senses of sight and smell. buccal cavity , on the floor of which lies the radula. The fossil record of cephalopods is extensive, and more than 10,000 fossil species Physical Traits: They have a series of arms or tentacles that circle the “head.” Each arm has two rows of suction sups. The cuttlefish, however, which swims or hovers above the bottom or rests on the bottom, adjusts its buoyancy through the amount of gases contained in the porous cuttlebone. Some octopuses, squids, andcuttlefish have the remarkable ability to change color and color patterns t… the mantle cavity serves as an inhalant aperture, whereas the funnel serves Cephalopods range greatly in size. ocotopoids and vampyromorphans lack shells altogether. Class Cephalopoda The Cephalopods (Class Cephalopoda) include squid, octopuses and nautilus. and funnel are all derivatives of the foot. They display vivid coloration, typically seen in squids and octopi, which is used for camouflage. Their mantle is modified into a siphon for movement via jet-propulsion, and their highly developed nervous and sensory systems include complex eyes and a centralized brain. A cephalopod is a member of molluscan class Cephalopoda. Studies have shown that in Octopus joubini raised from the egg in aquariums, sexual maturity and spawning were reached in five months; in a loliginid squid (Sepioteuthis sepioidea), likewise raised from the egg, sexual maturity and full growth were also attained in five months. In the cuttlefish (Sepia), according to the Dutch zoologist L. Tinbergen, the pair swims side by side, the male indulging in some courtship behaviour with its arms. In fossil cephalopods, reliance is placed upon shell details (general shape, type of coiling, external sculpture, and sutures). A female typically possesses a single oviduct. Grace E. Pickford, an American zoologist, has found that the vertical distribution of young in Vampyroteuthis is governed by water density, and, according to the American zoologist Clyde F.E. The ADW Team gratefully acknowledges their support. A siphon is attached to mantle cavity for breathing and jet propulsion. Class Cephalopoda (“head foot” animals) includes octopi, squids, cuttlefish, and nautilus. CephBase. Others may be limited by genera to particular oceans or to continental waters. When the squid jets rapidly through the water, the fins are often curled tightly around the mantle. Classification, To cite this page: Cuttlefishes, because of the large cuttlebone, are less active animals and spend most of their life lying on or hovering slightly above the bottom. https://www.leisurepro.com/blog/explore-the-blue/5-examples-cephalopods Wheeler, K. and D. Fautin 2001. propel the animal. In squids the ink is ejected as a spindle-shaped mass about the size of the squid itself, the ink coagulating in the water. contractions of the funnel or mantle wall. These actions often are attempts by cephalopods to conceal or camouflage themselves through imitating bottom objects such as sand, coral, or seaweed. Such behaviour is regarded as the first documented example of tool use by an invertebrate. world's oceans. The octopus, squid, cuttlefish, and chambered nautilus are familiar representatives. chromatophores, are responsible for the ability of the cephalopods to change Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. Class Cephalopoda The Cephalopods (Class Cephalopoda) include squid, octopuses and nautilus. Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. By means of surgical techniques it has been possible to determine the various functional centres of the brain of Octopus and the transmission and receiving pathways. Disclaimer: The foot is located on the head. The larval stage of an animal is best defined as a/an _____. The name cephalopod means "head foot" and it looks as though its feet (actually tentacles) are growing out of its head. Description, classification, synonyms of Class Cephalopoda. Some authorities, studying the Mediterranean cephalopods, have concluded that only certain pelagic cephalopods are gregarious (Todarodes, Ocythoe). In the common octopus the male and female remain some distance apart while the male caresses the female with the tip of the hectocotylized arm. Class Cephalopoda The Class Cephalopoda is made up of animals such as octopus, squid, and cuttlefish. The Octopoda, as a result of their bottom-dwelling habits, show stronger restrictions in their distribution, but Octopus vulgaris and O. macropus, both species with planktonic larvae, have gained worldwide distribution. They can be divided into three categories: the Nautiloidea (chambered Nautilus), the Ammonoidea (the extinct ammonites), and the Dibranchiata (squids, … The hectocotylized arm of Octopus bears a deep groove on one side, ending in a spoonlike terminal organ. Some squids (Onychoteuthis, Thysanoteuthis) are able to “fly” for several hundred feet, driven into the air by powerful thrusts from their jets and gliding on their expanded fins and arm keels. The female argonaut (Argonauta) propels herself by jet propulsion while encased in her paper-thin shell. Octopods typically tend their eggs until its mantle completely, a squid fits two cartilaginous ridges on the mantle wall NCERT DC Pandey Sunil Batra HC Verma Pradeep Errorless. arm tip may be pinched off and left in the female's mantle cavity: this is known Oxford University When the mantle is contracted the aperture is closed by locking mechanisms and contraction of the anterior ring muscle, and the water is forced out through the funnel. How do "colour-blind" octopuses know what colour to change to in order to hide from predators or to attract mates? Cephalopods Class Cephalopoda. The juveniles of many cephalopods were described as distinct genera before their juvenile status was discovered. as the hectocotylus arm. Examples of animals in the phylum Mollusca. Press, London. Since spermatophores vary in appearance from species to species, they are important taxonomic characters. Animals > Invertebrates > Mollusks Invertebrates > Mollusks. The light organs of the squid Histioteuthis are highly complicated, consisting of reflector, light source, directive muscles, lens, diaphragm, window, and colour screens. eyes with a cornea, lens, retina, and iris. In octopods with small eggs (e.g., Octopus vulgaris) the juveniles are planktonic, spending several weeks in the plankton; the “Macrotritopus” stage of Scaeurgus may greatly prolong its juvenile life until a favourable bottom substrate is found. The head is distinct. A cephalopod is a member of molluscan class Cephalopoda. Multiple choice: Match animals and characteristics to Mollusc class: A: Class Gastropoda B. The 600 living species in this strictly marine class rival the vertebrates in complexity and, in some cases, in intelligence. The eggs of most coastal species are laid inshore and are attached singly or in clusters, primarily to rocks and shells on the bottom. Class Bivalvia C. Class Cephalopoda _____Clams, oysters, scallops, and mussels They have. Cephalopods are characterized by a completely merged head and The modified arm of Nautilus is termed the spadix. and All animals are marine in nature. Other behavioral patterns are found in changes in skin texture, including the erection of branched or spikelike papillae and curling of the arms. Octopus, squid and cuttlefish - Class Cephalopoda Cephalopod literally means 'head foot' and members of this group, including octopuses, cuttlefishes, squids and nautiluses, have their foot or tentacles connected to their head, not their body. Cephalopoda is a class of animals in which . The people who are very interested to study and learn more about cephalopods in detail … In loliginids they are fertilized as they are ejected and before being fixed in the egg capsule. 3. There are many kinds of mollusks but the four main classes are the class Bivalvia, the class Polyplacophora, the class Gastropoda, and the class Cephalopoda. Nautilus, which swims slowly above the bottom or in midwater, accomplishes this similarly, adjusting the gases in the chambered shell. A. immature stage that is able to reproduce B. early colony of cells of fresh-water sponges C. early stage of development of an organism, typically part of the plankton D. sperm cell that lives free in the water … animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature. Belemnoids, which also appeared in the Mesozoic, had internal Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. Cephalopoda means "head foot" and this group has the most complex brain of any invertebrate. 1967. Physics. However, the ancestors of these Recent animals may have been living before the eight arms and two tentacles; and members of orders Ocotopoidea and Vampyromorpha Locomotion is by the rapid undulation of the outer edges of the fins. The eyes in Nautilus The octopus, squid, cuttlefish, and chambered nautilus are familiar representatives. The funnel Sexual dimorphism is usually expressed in slight differences of size and in the proportions of various parts. Mating in some cephalopods includes courtship rituals salivary glands , one of which may be poisonous. Mass swimming migrations have been reported. Eggs may be laid shortly after mating or after a prolonged period of maturation during which time the sperm remain viable. Water is drawn into the mantle cavity by the relaxation of the circular muscles and resultant expansion of the mantle. The sexes are usually separate in the Cephalopoda. Its expansion and contraction produce a locomotory water current by drawing water into the mantle cavity and expelling it through the funnel. All cephalopod eggs have a remarkable amount of yolk, unlike that in the rest of the Mollusca, so that segmentation is incomplete and restricted to one end of the egg, where the embryo develops. The movement of water over the ctenidia is controlled by muscular Cephalopods have been among the dominant large predators in the ocean at various times in geological history. Class Cephalopoda (Foot on the head) This is the most advanced class of phylum Mollusca. Nautilus moves vertically through the water, living near the bottom, and has been obtained at a depth of about 550 metres (1,800 feet). Many cephalopods (but not Nautilus and Octopus) possess special light organs (photophores), which emit chemical light or bioluminescence. by giant axons that are involved with muscular contraction. They are believed to be the precursors of modern-day squid and cuttlefish. Habitat: They are all found in the ocean. Two groups of cephalopods exist today: The Nautiloidea with a few species of the pearly nautilus, and the Coleoidea, containing the squids, cuttlefishes, octopods and vampire squids, which is represented by about 700 species. Although there is no proof that numbers constitute gregariousness, octopus colonies have been reported. The eggs of oceanic species may be laid in large sausagelike gelatinous masses or singly. have eight arms. Class Cephalopoda (“head foot” animals), include octopi, squids, cuttlefish, and nautilus. This normally occurs when the squids are pursued by predatory fishes and dolphins. Their name Cephalopoda means “ head footed.” They are all fast moving ocean animals. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. The body mass is very tall. To close The group includes the modern octopi and squids as well as many fossil forms. Cephalopoda is the most morphologically and behaviorally complex class in phylum Mollusca. The common cuttlefish comes into shallow water in the spring and summer to breed, and similar migrations have been observed in some squids (Loligo, Alloteuthis, Illex). They display vivid coloration, typically seen in squids and octopi, which is used for camouflage. The cephalopods agree with the rest of the Mollusca in basic structure, and the ancestors appear to have the closest affinity with the ancestors of the class Gastropoda. In octopods with large eggs (e.g., Octopus briareus) the young resemble the adult and immediately assume a bottom-dwelling mode of life. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. They also are indirectly important to humans since they furnish a large part of the diet of sperm whales and smaller whales, seals, fishes, and seabirds. Even some species of bathypelagic habitat are limited to one ocean. Premium Membership is now 50% off! These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. and five orders. The genus Mesonychoteuthis derives its name from a combination of three Greek words that mean “middle,” “claw” and “squid.” The species is a member of the Cranchiidae family, along with about 60 other squid species, and is in the Cephalopoda class. Ammonites were very successful -- scientists have Among the squids the Myopsida are coastal forms, whereas the Oegopsida are oceanic, living from the surface to depths in excess of 5,000 metres (16,400 feet). Contributor Galleries The posterior portion of the caecum contains a diverticulum The smallest cephalopod is the squid Idiosepius, rarely an inch in length. In some species, the specialized This material is based upon work supported by the Schneider, 1784 Highly specialized marine molluscs divided into two distinctive subclasses, the shelled subclass Nautiloidea and the subclass Coleoidea, in which the shell is reduced and internal or lacking entirely.About 600 species worldwide, typically nektonic or bentho-pelagic, fastmoving, predatory. NCERT NCERT Exemplar NCERT Fingertips Errorless Vol-1 Errorless Vol-2. The giant squid is the largest of all mollusks. Octopuses, squids, and cuttlefishes display considerable skill and cunning in hunting, stalking patiently, or luring prey within reach of their arms or tentacles. Some open-ocean pelagic and bathypelagic forms are cosmopolitan in warm and temperate waters (Onychoteuthis banksi, Cranchia scabra). stomach , which mashes food; "Cephalopoda" (On-line), Animal Diversity Web. Cephalopods Except for the nautilus, all living members of the class show great modification and reduction of the characteristic molluscan shell. Most cephalopods possess colour pigment cells (chromatophores) and reflecting cells (iridocytes) in the skin. muscles around the mantle cavity then forces water out the funnel. Roper, a similar situation exists in the deep-sea squid Bathyteuthis. http://is.dal.ca/~ceph/TCP/, Wood, J. The Animal Diversity Web is an educational resource written largely by and for college students. A cuttlefish changing colour as it swims near the Great Barrier Reef, off the northeastern coast of Australia. Help us improve the site by taking our survey. There are approximately 650 to 700 extant species of cephalopods in two subclasses having body symmetry such that the animal can be divided in one plane into two mirror-image halves. A shared trait of the group are sucker-bearing tentacles used to seize and hold prey. The spermatophores are complicated, containing sperm reservoir, cement body, cap, and a delicate triggering mechanism for releasing the tube and cementing it to the female’s body, where the sperm are released when the eggs are mature and ready to be laid. When disturbed, octopods swim rapidly by jet propulsion. Inactive oceanic squids, such as some cranchiids, concentrate ions lighter than seawater in the body chamber, while others, such as Bathyteuthis, concentrate buoyant oil in the chambers associated with the digestive gland. 2000. cephalopods can be accomplished by other means. These are ancient species that are found in all of the world's oceans, and are thought to have originated about 500 million years ago. They are eaten in most parts of the world and have been accepted as part of the general diet in North America and northern Europe. In the smaller octopuses and squids, observational data indicate that many of the males die after mating and females after the first major spawning. Cephalopods are bilaterally symmetrical and have a circlet of prehensile tentacles. of ctenidia. The rapid ejection of this jet of water enables the animal to execute quick backward and forward movements. With the exception of Nautilus, cephalopods contain pigment-rich cells in the With this “dummy” left behind, the squid contracts its chromatophores, becomes nearly transparent, and jets away. The cephalopods are a diverse class of mollusks (a group that also includes snails and bivalves) that emerged during an explosion of animal diversity in the oceans during the Cambrian period, over 500 million years ago (mya). The Ammonoidea arose during the late Paleozoic and grew to Little is known about the life span of cephalopods. There is some evidence that in parts of the open sea that differ only slightly in salinity there may be a varying cephalopod fauna. The extinct forms outnumber the living, the class having attained great diversity in late Paleozoic and Mesozoic times. Search in feature The cephalopod page. The feet, or arms, of these creatures are connected to their heads, not their bodies. A cephalopod is any member of the molluscan class Cephalopoda (Greek plural κεφαλόποδες, kephalópodes; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. The male then inserts the tip of the arm into the mantle cavity of the female, where it remains for more than an hour, during which time the spermatophores travel down the spermatophoral groove of the arm. It thus appears that the smaller inshore species may have a life span of no more than one year or, exceptionally, two or three. foot, with a ring of arms and/or tentacles surrounding the head. Eventually, mating takes place by the pair intertwining their arms and remaining together while the spermatophores are placed on the inner side of the female’s mouth membrane. Many species Class Cephalopoda includes marine animals that differ from other mollusks because they are built for speed and agility. It is fished in the Philippines when it comes into shallow water. NCERT P Bahadur IIT-JEE Previous Year Narendra Awasthi MS Chauhan. Observe the unique shrimp-catching strategy of the larger Pacific striped octopus. In living forms, except for the Sepioidea, the shell is strongly degenerate or missing and the characters used consist of details of the soft parts: presence or absence of an eyelid, tentacles retractile or contractile or both, shape and size of fins, number of arms, number of sucker …