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Tentacle

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Cuttlefish with 2 tentacles and 8 arms
Cuttlefish with 2 tentacles and 8 arms

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 mainly like muscular hydrostats. Most forms of tentacles are used for grasping and feeding. Many are sensory organs, variously receptive to touch, vision, or to the smell or taste of particular foods or threats. Examples of such tentacles are the eyestalks of various kinds of snails. Some kinds of tentacles have both sensory and manipulatory functions.

A tentacle is similar to a cirrus, but a cirrus is an organ that usually lacks the tentacle's strength, size, flexibility, or sensitivity. A nautilus has cirri, but a squid has tentacles.

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Zoology

Zoology

Zoology is the branch of biology that studies the animal kingdom, including the structure, embryology, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. The term is derived from Ancient Greek ζῷον, zōion ('animal'), and λόγος, logos.

Animal

Animal

Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 micrometres (0.00033 in) to 33.6 metres (110 ft). They have complex interactions with each other and their environments, forming intricate food webs. The scientific study of animals is known as zoology.

Invertebrate

Invertebrate

Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column, derived from the notochord. This is a grouping including all animals apart from the chordate subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelids, echinoderms and cnidarians.

Muscular hydrostat

Muscular hydrostat

A muscular hydrostat is a biological structure found in animals. It is used to manipulate items or to move its host about and consists mainly of muscles with no skeletal support. It performs its hydraulic movement without fluid in a separate compartment, as in a hydrostatic skeleton.

Somatosensory system

Somatosensory system

In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch, as well as temperature (thermoception), body position (proprioception), and pain. It is a subset of the sensory nervous system, which also represents visual, auditory, olfactory, and gustatory stimuli.

Visual perception

Visual perception

Visual perception is the ability to interpret the surrounding environment through photopic vision, color vision, scotopic vision, and mesopic vision, using light in the visible spectrum reflected by objects in the environment. This is different from visual acuity, which refers to how clearly a person sees. A person can have problems with visual perceptual processing even if they have 20/20 vision.

Chemoreceptor

Chemoreceptor

A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance to generate a biological signal. This signal may be in the form of an action potential, if the chemoreceptor is a neuron, or in the form of a neurotransmitter that can activate a nerve fiber if the chemoreceptor is a specialized cell, such as taste receptors, or an internal peripheral chemoreceptor, such as the carotid bodies. In physiology, a chemoreceptor detects changes in the normal environment, such as an increase in blood levels of carbon dioxide (hypercapnia) or a decrease in blood levels of oxygen (hypoxia), and transmits that information to the central nervous system which engages body responses to restore homeostasis.

Eyestalk

Eyestalk

In anatomy, an eyestalk is a protrusion that extends an eye away from the body, giving the eye a better field of view. It is a common feature in nature and frequently appears in fiction.

Snail

Snail

A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name snail is also used for most of the members of the molluscan class Gastropoda that have a coiled shell that is large enough for the animal to retract completely into. When the word "snail" is used in this most general sense, it includes not just land snails but also numerous species of sea snails and freshwater snails. Gastropods that naturally lack a shell, or have only an internal shell, are mostly called slugs, and land snails that have only a very small shell are often called semi-slugs.

Cirrus (biology)

Cirrus (biology)

In biology, a cirrus SIRR-əs, plural cirri, SIRR-eye, is a long, thin structure in an animal similar to a tentacle but generally lacking the tentacle's strength, flexibility, thickness, and sensitivity.

Nautilus

Nautilus

The nautilus is a pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina.

Squid

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 fitting these criteria. Like all other cephalopods, squid have a distinct head, bilateral symmetry, and a mantle. They are mainly soft-bodied, like octopuses, but have a small internal skeleton in the form of a rod-like gladius or pen, made of chitin.

Invertebrates

Molluscs

Front view of land snail showing upper and lower sets of tentacles
Front view of land snail showing upper and lower sets of tentacles
Abalone showing pallial tentacles
Abalone showing pallial tentacles

Many molluscs have tentacles of one form or another. The most familiar are those of the pulmonate land snails, which usually have two sets of tentacles on the head: when extended the upper pair have eyes at their tips; the lower pair are chemoreceptors. Both pairs are fully retractable muscular hydrostats, but they are not used for manipulation or prey capture.

Some marine snails such as abalone and top snails, Trochidae, have numerous small tentacles around the edge of the mantle. These are known as pallial tentacles.[1]

Among cephalopods, squid have spectacular tentacles. They take the form of highly mobile muscular hydrostats with various appendages such as suction disks and sometimes thorny hooks. Up to the early twentieth century "tentacles" were interchangeably called "arms".[2] The modern convention, however, is to speak of appendages as "tentacles" when they have relatively thin "peduncles" or "stalks" with "clubs" at their tips. In contrast the convention refers to the relatively shorter appendages as "arms". By this definition the eight appendages of octopuses, though quite long, count as arms.[1] It is worth noting, however, that while arms are distinct from tentacles (a definition specific to the limb featuring peduncles), arms do fall within the general definition of "tentacle" as "a flexible, mobile, and elongated organ" and "tentacle" could be used as an umbrella term.

The tentacles of the giant squid and colossal squid have powerful suckers and pointed teeth at the ends. The teeth of the giant squid resemble bottle caps and function like tiny hole saws, while the tentacles of the colossal squid wield two long rows of swiveling, tri-pointed hooks.

Cnidarians and ctenophores

Cnidarians, such as jellyfish, sea anemones, Hydra and coral have numerous hair-like tentacles. Cnidarians have huge numbers of cnidocytes on their tentacles. In medusoid form, the body floats on water so that the tentacles hang down in a ring around the mouth. In polyp form, such as sea anemone and coral, the body is below with the tentacles pointed upwards.

Many species of the jellyfish-like ctenophores have two tentacles, while some have none. Their tentacles have adhesive structures called colloblasts or lasso cells. The colloblasts burst open when prey comes in contact with the tentacle, releasing sticky threads that secure the food.[3]

The tentacles of the Lion's mane jellyfish may be up to 37 m (121 ft) long. They are hollow and are arranged in 8 groups of between 70 and 150. The longer tentacles are equipped with cnidocytes whose venom paralyses and kills prey. The smaller tentacles guide food into the mouth.[4][5]

Bryozoa

Bryozoa (moss animals) are tiny creatures with tentacles around their mouths. The tentacles are almost cylindrical and have bands of cilia which create a water current towards the mouth. The animal extracts edible material from the flow of water.[6]

Trypanorhynch cestodes

A larva of trypanorhynch cestode (only two tentacles shown). Scale-bar: 0.1 mmDetail of one tentacle with its spines. Scale-bar: 0.01 mm.
A larva of trypanorhynch cestode (only two tentacles shown). Scale-bar: 0.1 mm
A larva of trypanorhynch cestode (only two tentacles shown). Scale-bar: 0.1 mmDetail of one tentacle with its spines. Scale-bar: 0.01 mm.
Detail of one tentacle with its spines. Scale-bar: 0.01 mm.

Trypanorhynch cestodes are parasitic in fish. Their scolex shows four tentacles which are covered by spines. These tentacles help the adult cestode to attach to the intestine of the shark or ray that they parasitize. The same tentacles are also present in the larvae.[7]

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Cephalopod limb

Cephalopod limb

All cephalopods possess flexible limbs extending from their heads and surrounding their beaks. These appendages, which function as muscular hydrostats, have been variously termed arms, legs or tentacles.

Chemoreceptor

Chemoreceptor

A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance to generate a biological signal. This signal may be in the form of an action potential, if the chemoreceptor is a neuron, or in the form of a neurotransmitter that can activate a nerve fiber if the chemoreceptor is a specialized cell, such as taste receptors, or an internal peripheral chemoreceptor, such as the carotid bodies. In physiology, a chemoreceptor detects changes in the normal environment, such as an increase in blood levels of carbon dioxide (hypercapnia) or a decrease in blood levels of oxygen (hypoxia), and transmits that information to the central nervous system which engages body responses to restore homeostasis.

Abalone

Abalone

Abalone is a common name for any of a group of small to very large marine gastropod molluscs in the family Haliotidae. Other common names are ear shells, sea ears, and, rarely, muttonfish or muttonshells in parts of Australia, ormer in the UK, perlemoen in South Africa, and paua in New Zealand. Abalones are marine snails. Their taxonomy puts them in the family Haliotidae, which contains only one genus, Haliotis, which once contained six subgenera. These subgenera have become alternative representations of Haliotis. The number of species recognized worldwide ranges between 30 and 130 with over 230 species-level taxa described. The most comprehensive treatment of the family considers 56 species valid, with 18 additional subspecies. The shells of abalones have a low, open spiral structure, and are characterized by several open respiratory pores in a row near the shell's outer edge. The thick inner layer of the shell is composed of nacre (mother-of-pearl), which in many species is highly iridescent, giving rise to a range of strong, changeable colors which make the shells attractive to humans as decorative objects, jewelry, and as a source of colorful mother-of-pearl.

Cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.

Giant squid

Giant squid

The giant squid is a species of deep-ocean dwelling squid in the family Architeuthidae. It can grow to a tremendous size, offering an example of abyssal gigantism: recent estimates put the maximum size at around 12–13 m (39–43 ft) for females and 10 m (33 ft) for males, from the posterior fins to the tip of the two long tentacles. The mantle of the giant squid is about 2 m long, and the length of the squid excluding its tentacles rarely exceeds 5 m (16 ft). Claims of specimens measuring 20 m (66 ft) or more have not been scientifically documented.

Colossal squid

Colossal squid

The colossal squid is part of the family Cranchiidae. It is sometimes called the Antarctic squid or giant cranch squid and is believed to be the largest squid species in terms of mass. It is the only recognized member of the genus Mesonychoteuthis and is known from only a small number of specimens. The species is confirmed to reach a mass of at least 495 kilograms (1,091 lb), though the largest specimens—known only from beaks found in sperm whale stomachs—may perhaps weigh as much as 600–700 kilograms (1,300–1,500 lb), making it the largest known invertebrate. Maximum total length has been estimated at 9–10 metres (30–33 ft). The colossal squid has the largest eyes of any known creature ever to exist, with an estimated diameter of 30–40 cm (12–16 in).

Crown cork

Crown cork

The crown cork, the first form of bottle cap, was invented by William Painter in 1892 in Baltimore. The company making it was originally called the Bottle Seal Company, but it changed its name with the almost immediate success of the crown cork to the Crown Cork and Seal Company. It still informally goes by that name, but is officially Crown Holdings.

Hole saw

Hole saw

A hole saw, also known as a hole cutter, is a saw blade of annular (ring) shape, whose annular kerf creates a hole in the workpiece without having to cut up the core material. It is used in a drill. Hole saws typically have a pilot drill bit (arbor) at their center to keep the saw teeth from walking. The fact that a hole saw creates the hole without needing to cut up the core often makes it preferable to twist drills or spade drills for relatively large holes. The same hole can be made faster and using less power.

Jellyfish

Jellyfish

Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle; the medusa is normally the sexual phase, which produces planula larvae that disperse widely and enter a sedentary polyp phase before reaching sexual maturity.

Hydra (genus)

Hydra (genus)

Hydra is a genus of small freshwater organisms of the phylum Cnidaria and class Hydrozoa. They are native to the temperate and tropical regions. The genus was named by Linnaeus in 1758 after the Hydra, which was the many-headed beast defeated by Heracles, as when the animal had a part severed, it would regenerate much like the hydra’s heads. Biologists are especially interested in Hydra because of their regenerative ability; they do not appear to die of old age, or to age at all.

Coral

Coral

Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.

Cnidocyte

Cnidocyte

A cnidocyte is an explosive cell containing one large secretory organelle called a cnidocyst that can deliver a sting to other organisms. The presence of this cell defines the phylum Cnidaria. Cnidae are used to capture prey and as a defense against predators. A cnidocyte fires a structure that contains a toxin within the cnidocyst; this is responsible for the stings delivered by a cnidarian.

Vertebrates

Amphibians

The legless amphibians called caecilians have two short tentacles, one on each side of the head, between their eyes and nostrils. The current opinion is that these tentacles supplement the normal sense of smell, possibly for navigation and to locate prey underground.[1]

Mammals

The star-nosed mole, Condylura cristata, of North America, has 22 short but conspicuous tentacles around its nose. They are mobile and extremely sensitive, helping the animal to find its way about the burrow and detect prey. They are about 1–4 mm long and hold about 25,000 touch receptors called Eimer's organs, perhaps giving this mole the most delicate sense of touch among mammals.[1]

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Amphibian

Amphibian

Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this.

Caecilian

Caecilian

Caecilians ; ) are a group of limbless, vermiform (worm-shaped) or serpentine (snake-shaped) amphibians. They mostly live hidden in soil or in streambeds, and this cryptic lifestyle renders caecilians among the least familiar amphibians. Modern caecilians live in the tropics of South and Central America, Africa, and southern Asia. Caecilians feed on small subterranean creatures such as earthworms. The body is cylindrical and often darkly coloured, and the skull is bullet-shaped and strongly built. Caecilian heads have several unique adaptations, including fused cranial and jaw bones, a two-part system of jaw muscles, and a chemosensory tentacle in front of the eye. The skin is slimy and bears ringlike markings or grooves, which may contain tiny scales.

Star-nosed mole

Star-nosed mole

The star-nosed mole is a small semiaquatic mole found in moist, low elevation areas in the northern parts of North America. It is the only extant member of the tribe Condylurini and genus Condylura, and it has more than 25,000 minute sensory receptors in touch organs, known as Eimer's organs, with which this hamster-sized mole feels its way around. With the help of its Eimer's organs, it may be perfectly poised to detect seismic wave vibrations.

North America

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 the Caribbean Sea, and to the west and south by the Pacific Ocean. Because it is on the North American Tectonic Plate, Greenland is included as a part of North America geographically.

Somatosensory system

Somatosensory system

In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch, as well as temperature (thermoception), body position (proprioception), and pain. It is a subset of the sensory nervous system, which also represents visual, auditory, olfactory, and gustatory stimuli.

Eimer's organ

Eimer's organ

Eimer's organs are sensory organs in which the epidermis is modified to form bulbous papillae. First isolated by Theodor Eimer from the European mole in 1871, these organs are present in many moles, and are particularly common in the star-nosed mole, which bears 25,000 of them on its unique tentacled snout. The organs are formed from a stack of epidermal cells, which is innervated by nerve processes from myelinated fibers in the dermis, which form terminal swellings just below the outer keratinized layer of epidermis. They contain a Merkel cell-neurite complex in the epidermis and a lamellated corpuscle in the dermal connective tissue.

Tentillum

Deep-sea ctenophore trailing tentacles studded with tentilla
Deep-sea ctenophore trailing tentacles studded with tentilla

The word tentillum (pl. tentilla) literally means "little tentacle". However, irrespective of size, it usually refers to a side branch of a larger tentacle. In some cases such tentilla are specialised for particular functions; for example, in the Cnidaria tentilla usually bear cnidocytes,[8] whereas in the Ctenophora they usually have collocytes.[9][10] Siphonophores are an example of Cnidaria that use tentilla.

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Source: "Tentacle", Wikipedia, Wikimedia Foundation, (2023, February 6th), https://en.wikipedia.org/wiki/Tentacle.

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References
  1. ^ a b c d Boumis R (2013). "Animals With Tentacles". Pawnation. AOL Inc. Archived from the original on 3 December 2013. Retrieved 8 June 2013.
  2. ^ Cooke, A. H.; Shipley, Arthur Everett et al. (1895). The Cambridge Natural History Volume 34: Molluscs, Trilobites, Brachiopods etc. Macmillan Company.
  3. ^ Bird J (5 June 2007). "CNIDARIANS: SIMPLE ANIMALS WITH A STING!". oceanicresearch.org. Oceanic Research Group. Archived from the original on 7 July 2013. Retrieved 8 June 2013.
  4. ^ Kosner AW (10 July 2012). "Lion's Mane Jellyfish Image: This Is (Literally) How Things Blow Up On The Internet!". Forbes. Archived from the original on 25 June 2013. Retrieved 8 June 2013.
  5. ^ Wild Facts (29 November 2011). "Wild Fact #419 – One Large Jelly – Lion's Mane Jellyfish". wild-facts.com. Archived from the original on 19 December 2012. Retrieved 8 June 2013.
  6. ^ Claus N (May 2013). Bryozoa (Ectoprocta: 'Moss' Animals). els.net. eLS. John Wiley & Sons Ltd. doi:10.1002/9780470015902.a0001613.pub2. ISBN 978-0470016176. Archived from the original on 5 June 2013. Retrieved 8 June 2013.
  7. ^ Beveridge, Ian; Bray, Rodney A.; Cribb, Thomas H.; Justine, Jean-Lou (2014). "Diversity of trypanorhynch metacestodes in teleost fishes from coral reefs off eastern Australia and New Caledonia". Parasite. 21: 60. doi:10.1051/parasite/2014060. ISSN 1776-1042. PMC 4234045. PMID 25402635. Archived from the original on 9 January 2018. open access
  8. ^ Marine Species Identification Portal : Zooplankton of the South Atlantic Ocean : Glossary : tentilla Archived 2 December 2013 at the Wayback Machine. Species-identification.org. Retrieved on 2013-05-02.
  9. ^ Harmer, Sir Sidney Frederic; Shipley, Arthur Everett et al. (1906) The Cambridge Natural History Volume 1, Protozoa, Porifera, Coelenterata, Ctenophora, Echinodermata. Macmillan Company.
  10. ^ Mackie G.O.; Mills C.E.; Singla C.L. (1988). "Structure and function of the prehensile tentilla of Euplokamis (Ctenophora, Cydippida)" (PDF). Zoomorphology. 107 (6): 319. doi:10.1007/BF00312216. S2CID 317017. Archived (PDF) from the original on 3 March 2016.
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