Tentacle
In
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.
Invertebrates
Molluscs
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. Molluscs have one pair of tentacles close to their mouths that hold close to their captured prey before they can consume it.[1]
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.[2]
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".[3] These tentacles are made of stalks of axial nerve cords that are covered by circular transverse muscle tissue that contract in response to stimuli. There is a layer of helical muscle that helps each tentacle to twist or turn in any direction where the prey is sensed.[1]
The modern convention, however, is to speak of appendages as "tentacles" when they have relatively thin "
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
Many species of the jellyfish-like
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.[5][6]
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.[7]
Trypanorhynch cestodes
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.[2]
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.[2]
Tentillum
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,[9] whereas in the Ctenophora they usually have collocytes.[10][11] Siphonophores are an example of Cnidaria that use tentilla.
References
- ^ PMID 26925401.
- ^ 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.
- ^ Cooke, A. H.; Shipley, Arthur Everett (1895). The Cambridge Natural History. Vol. 34: Molluscs, Trilobites, Brachiopods etc. London, England, U.K.: Macmillan Company.[page needed]
- ^ 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.
- ^ 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.
- ^ 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.
- ISBN 978-0470016176. Archived from the original on 5 June 2013. Retrieved 8 June 2013.)
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ignored (help - ^ 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.
- ^ Harmer, Sir Sidney Frederic; Shipley, Arthur Everett et al. (1906) The Cambridge Natural History Volume 1, Protozoa, Porifera, Coelenterata, Ctenophora, Echinodermata. Macmillan Company.
- (PDF) from the original on 3 March 2016.
External links
- Tentacle Archived 14 May 2013 at the About.com
- Tentacle at the Encyclopædia Britannica
- The dictionary definition of tentacle at Wiktionary