Fish scale

The skin of most fishes is covered with scales, which, in many cases, are animal reflectors or produce animal coloration. Scales vary enormously in size, shape, structure, and extent, ranging from strong and rigid armour plates in fishes such as shrimpfishes and boxfishes, to microscopic or absent in fishes such as eels and anglerfishes. The morphology of a scale can be used to identify the species of fish it came from.

Cartilaginous fishes (sharks and rays) are covered with placoid scales. Most bony fishes are covered with the cycloid scales of salmon and carp, or the ctenoid scales of perch, or the ganoid scales of sturgeons and gars. Some species are covered instead by scutes, and others have no outer covering on the skin.

Fish scales are part of the fish's integumentary system, and are produced from the mesoderm layer of the dermis, which distinguishes them from reptile scales.[1] The same genes involved in tooth and hair development in mammals are also involved in scale development. The placoid scales of cartilaginous fishes are also called dermal denticles and are structurally homologous with vertebrate teeth. It has been suggested that the scales of bony fishes are similar in structure to teeth, but they probably originate from different tissue.[2] Most fish are also covered in a protective layer of mucus (slime).

Fish scales
Cycloid scales cover these teleost fish (rohu)

Placoid scales

Tiger shark
Cartilaginous fishes, like this tiger shark, have placoid scales (dermal denticles)
Denticules cutanés du requin citron Negaprion brevirostris vus au microscope électronique à balayage
Placoid scales as viewed through an electron microscope. Also called dermal denticles, these are structurally homologous with vertebrate teeth.

Placoid scales are found in the cartilaginous fishes: sharks, rays, and chimaeras. They are also called dermal denticles. Placoid scales are structurally homologous with vertebrate teeth ("denticle" translates to "small tooth"), having a central pulp cavity supplied with blood vessels, surrounded by a conical layer of dentine, all of which sits on top of a rectangular basal plate that rests on the dermis. The outermost layer is composed of vitrodentine, a largely inorganic enamel-like substance. Placoid scales cannot grow in size, but rather more scales are added as the fish increases in size.

Similar scales can also be found under the head of the denticle herring. The amount of scale coverage is much less in rays and chimaeras.

Shark skin

Shark skin is almost entirely covered by small placoid scales. The scales are supported by spines, which feel rough when stroked in a backward direction, but when flattened by the forward movement of water, create tiny vortices that reduce hydrodynamic drag, and reduce the turbulence, making swimming both more efficient, and quieter, compared to that of bony fishes.[3] It also serves a role in anti-fouling by exhibiting the lotus effect.[4]

Unlike bony fish, sharks have a complicated dermal corset made of flexible collagenous fibers arranged as a helical network surrounding their body. The corset works as an outer skeleton, providing attachment for their swimming muscles and thus saving energy.[5] Depending on the position of these placoid scales on the body, they can be flexible and can be passively erected, allowing them to change their angle of attack. These scales also have riblets which are aligned in the direction of flow, these riblets reduce the drag force acting on the shark skin by pushing the vortex further away from the skin surface, inhibiting any high-velocity cross-stream flow.[6]

Scale morphology

The general anatomy of the scales varies, but all of them can be divided into three parts: the crown, the neck and the base. The scale pliability is related to the size of the base of the scale. The scales with higher flexibility have a smaller base, and thus are less rigidly attached to the stratum laxum.  On the crown of the fast-swimming sharks there are a series of parallel riblets or ridges which run from an anterior to posterior direction. These riblets serve a major hydrodynamic role and have shown to reduce drag by up to 9% in biomimetic test specimens. The spacing between these riblets and their height has been the subject of numerous experiments and has been a research topic. This spacing and height is consistent in the fast swimming sharks[7]

Drag reduction

The riblets impede the cross-stream translation of the streamwise vortices in the viscous sublayer. The mechanism is complex and not yet understood fully. Basically, the riblets inhibit the vortex formation near the surface because the vortex cannot fit in the valleys formed by the riblets. This pushes the vortex further up from the surface, interacting only with the riblet tips, not causing any high-veloctiy flow in the valleys. Since this high velocity flow now only interacts with the riblet-tip, which is a very small surface area, the momentum transfer which causes drag is now much lower than before, thereby effectively reducing drag. Also, this reduces the cross-stream velocity fluctuations, which aids in momentum transfer too.[7]

The rough, sandpaper-like texture of shark and ray skin, coupled with its toughness, has led it to be valued as a source of rawhide leather, called shagreen. One of the many historical applications of shark shagreen was in making hand-grips for swords. The rough texture of the skin is also used in Japanese cuisine to make graters called oroshiki, by attaching pieces of shark skin to wooden boards. The small size of the scales grates the food very finely.

Technical application

There are many examples of biomimetic materials and surfaces based on the structure of aquatic organisms, including sharks. Such applications intend to enable more efficient movement through fluid mediums such as air, water and oil.

Surfaces that mimic the skin of sharks have also been used in order to keep microorganisms and algae from coating the hulls of submarines and ships. One variety is traded as "sharklet".[8][9]

A lot of the new methods for replicating sark skin involve the use of polydimethylsiloxane (PDMS) for creating a mold. Usually the process involves taking a flat piece of shark skin, covering it with the PDMS to form a mold and pouring pdms into that mold again to get a shark skin replica. This method has been used to create a biomimetic surface which has superhydrophobic properties, exhibiting the lotus effect.[8] One study found that these biomimetic surface reduced drag by up to 9%,[6] while with flapping motion drag reduction reached 12.3%.[10]

Leptoid scales

Leptoid scales are found on higher-order bony fish, the teleosts (the more derived clade of ray-finned fishes). As the fish grow, scales are added in concentric layers. The scales are arranged so as to overlap in a head-to-tail configuration, like roof tiles, allowing a smoother flow of water over the body and thereby reducing drag.[11] Leptoid scales come in two forms: cycloid and ctenoid.

Cycloid scales

PSM V35 D074 Scale of common carp
The cycloid scale of a carp has a smooth outer edge
Poropuntius huguenini Bleeker
This Poropuntius huguenini is a carp-like fish with circular cycloid scales that are smooth to the touch

Cycloid (circular) scales have a smooth texture and are uniform, with a smooth outer edge or margin. They are most common on fish with soft fin rays, such as salmon and carp.

Ctenoid scales

PSM V35 D074 Scale of perch
The ctenoid scale of a perch has a toothed outer edge (at top of image)
Manonichthys splendens
This dottyback is a perch-like fish with toothed ctenoid scales that are rough to the touch
Ctenoid Perch Scales
Three ctenoid scales from various locations of a perch were stained. Significant variation can be observed between the medial (middle of the fish), dorsal (top), and caudal (tail end) scales. The ctentii of each of the scales is labeled.

Ctenoid (toothed) scales are like cycloid scales, with small teeth along their outer edges. They are usually found on fishes with spiny fin rays, such as the perch-like fishes. The scales have a rough texture with a toothed outer or posterior edge featuring tiny teeth called ctenii. These scales contain almost no bone, being composed of a surface layer containing hydroxyapatite and calcium carbonate and a deeper layer composed mostly of collagen. The enamel of the other scale types is reduced to superficial ridges and ctenii.

Ctenoid scales, similar to other epidermal structures, originate from placodes and distinctive cellular differentiation makes them exclusive from other structures that arise from the integument.[12] Development starts near the caudal fin, along the lateral line of the fish.[13] The development process begins with an accumulation of fibroblasts between the epidermis and dermis.[12] Collagen fibrils begin to organize themselves in the dermal layer, which leads to the initiation of mineralization.[12] The circumference of the scales grows first, followed by thickness when overlapping layers mineralize together.[12]

Ctenoid scales can be further subdivided into three types:

  • Crenate scales, where the margin of the scale bears indentations and projections.
  • Spinoid scales, where the scale bears spines that are continuous with the scale itself.
  • True ctenoid scales, where the spines on the scale are distinct structures.

Both cycloid and ctenoid scales are overlapping, making them more flexible than cosmoid and ganoid scales. Unlike ganoid scales, they grow in size through additions to the margin. The scales of some species exhibit bands of uneven seasonal growth called annuli (singular annulus). These bands can be used to age the fish. Most ray-finned fishes have ctenoid scales. Some species of flatfishes have ctenoid scales on the eyed side and cycloid scales on the blind side, while other species have ctenoid scales in males and cycloid scales in females.

Ganoid scales

Spotted Gar (Lepisosteus oculatus) (3149758934)
The longnose gar has diamond-shape ganoid scales

Ganoid scales are found in the sturgeons, paddlefishes, gars, bowfin, and bichirs. They are derived from cosmoid scales, with a layer of dentine in the place of cosmine, and a layer of inorganic bone salt called ganoine in place of vitrodentine. Most are diamond-shaped and connected by peg-and-socket joints. They are usually thick and have a minimal amount of overlap as compared to other scales.[14] In sturgeons, the scales are greatly enlarged into armour plates along the sides and back, while in the bowfin the scales are greatly reduced in thickness to resemble cycloid scales (see above).

Ganoid scales Ganoid scales of the Carboniferous fish, Amblypterus striatus. (a) shows the outer surface of four of the scales, and (b) shows the inner surface of two of the scales. Each of the rhomboidal ganoid scales of Amblypterus has a ridge on the inner surface which is produced at one end into a projecting peg which fits into a notch in the next scale, similar to the manner in which tiles are pegged together on the roof of a house.

Elasmoid scales

Coelacanth-PaleozoologicalMuseumOfChina-May23-08
Lobe-finned fishes, like this preserved coelacanth, have elasmoid scales

Elasmoid scales are thin, imbricated scales composed of a layer of dense, lamellar bone called isopedine, above which is a layer of tubercles usually composed of bone, as in Eusthenopteron. The layer of dentine that was present in the first sarcopterygians is usually reduced, as in the extant coelacanth, or entirely absent, as in extant lungfish and in the Devonian Eusthenopteron.[15] Elasmoid scales have appeared several times over the course of fish evolution. They are present in some lobe-finned fishes: coelacanths, all extant and some extinct lungfishes, some tetrapodomorphs like Eusthenopteron, amiids, and teleosts, whose cycloid and ctenoid scales represent the least mineralized elasmoid scales.

Cosmoid scales

Cosmoid scales are found in several ancient lobe-finned fishes, including some of the earliest lungfishes, and were probably derived from a fusion of placoid scales. They are composed of a layer of dense, lamellar bone called isopedine, above which is a layer of spongy bone supplied with blood vessels. The bone layers are covered by a complex dentine layer called cosmine and a superficial outer coating of vitrodentine. Cosmoid scales increase in size through the growth of the lamellar bone layer.

Scutes

A scute is another, less common, type of scale. Scute comes from Latin for shield, and can take the form of:

  • an external shield-like bony plate, or
  • a modified, thickened scale that often is keeled or spiny, or
  • a projecting, modified (rough and strongly ridged) scale, usually associated with the lateral line, or on the caudal peduncle forming caudal keels, or along the ventral profile.

Some fish, such as pineconefish, are completely or partially covered in scutes. River herrings and threadfins have an abdominal row of scutes, which are scales with raised, sharp points that are used for protection. Some jacks have a row of scutes following the lateral line on either side.

Thelodont scales

Thelodont denticles
Left to right: denticles of Paralogania (?), Shielia taiti, Lanarkia horrida

The bony scales of thelodonts, the most abundant form of fossil fish, are well understood. The scales were formed and shed throughout the organisms' lifetimes, and quickly separated after their death.[16]

Bone, a tissue that is both resistant to mechanical damage and relatively prone to fossilization, often preserves internal detail, which allows the histology and growth of the scales to be studied in detail. The scales comprise a non-growing "crown" composed of dentine, with a sometimes-ornamented enameloid upper surface and an aspidine base.[17] Its growing base is made of cell-free bone, which sometimes developed anchorage structures to fix it in the side of the fish.[18] Beyond that, there appear to be five types of bone-growth, which may represent five natural groupings within the thelodonts—or a spectrum ranging between the end members meta- (or ortho-) dentine and mesodentine tissues.[19] Each of the five scale morphs appears to resemble the scales of more derived groupings of fish, suggesting that thelodont groups may have been stem groups to succeeding clades of fish.[18]

However, using scale morphology alone to distinguish species has some pitfalls. Within each organism, scale shape varies hugely according to body area,[20] with intermediate forms appearing between different areas—and to make matters worse, scale morphology may not even be constant within one area. To confuse things further, scale morphologies are not unique to taxa, and may be indistinguishable on the same area of two different species.[21]

The morphology and histology of thelodonts provides the main tool for quantifying their diversity and distinguishing between species, although ultimately using such convergent traits is prone to errors. Nonetheless, a framework comprising three groups has been proposed based upon scale morphology and histology.[19] Comparisons to modern shark species have shown that thelodont scales were functionally similar to those of modern cartilaginous fish, and likewise has allowed an extensive comparison between ecological niches.[22]

Modifications

Scale Common Roach
The cycloid scales of a common roach. The series of lateral line scales is visible in the lower half of the image.

Different groups of fish have evolved a number of modified scales to serve various functions.

Many groups of bony fishes, including pipefishes and seahorses, several families of catfishes, sticklebacks, and poachers, have developed external bony plates, structurally resembling placoid scales, as protective armour. In the boxfishes, the plates are all fused together to form a rigid shell enclosing the entire body. Yet these bony plates are not modified scales, but skin that has been ossified.

Cetonurus crassiceps scales Cetonurus crassiceps2
The size of the teeth on ctenoid scales can vary with position, as these scales from the rattail Cetonurus crassiceps show
PSM V35 D070 Scale of eel Anguilla japonica 1856
Eels seem scaleless, yet some species are covered with tiny smooth cycloid scales
Arapaima gigas scales 3860

Scales of Arapaima gigas

RhodeusSericeusScales

Scales of European bitterling from the hindflank

See also

References

  1. ^ Sharpe, P. T. (2001). "Fish scale development: Hair today, teeth and scales yesterday?". Current Biology. 11 (18): R751–R752. doi:10.1016/S0960-9822(01)00438-9. PMID 11566120.
  2. ^ Perkins, Sid (16 October 2013). "The First False Teeth". Science. Retrieved 2 March 2018.
  3. ^ Martin, R. Aidan. "Skin of the Teeth". Retrieved 2007-08-28.
  4. ^ Fürstner, Reiner; Barthlott, Wilhelm; Neinhuis, Christoph; Walzel, Peter (2005-02-01). "Wetting and Self-Cleaning Properties of Artificial Superhydrophobic Surfaces". Langmuir. 21 (3): 956–961. doi:10.1021/la0401011. ISSN 0743-7463. PMID 15667174.
  5. ^ Martin, R. Aidan. "The Importance of Being Cartilaginous". ReefQuest Centre for Shark Research. Retrieved 2009-08-29.
  6. ^ a b Hage, W.; Bruse, M.; Bechert, D. W. (2000-05-01). "Experiments with three-dimensional riblets as an idealized model of shark skin". Experiments in Fluids. 28 (5): 403–412. doi:10.1007/s003480050400. ISSN 1432-1114.
  7. ^ a b Motta, Philip; Habegger, Maria Laura; Lang, Amy; Hueter, Robert; Davis, Jessica (2012-10-01). "Scale morphology and flexibility in the shortfin mako Isurus oxyrinchus and the blacktip shark Carcharhinus limbatus". Journal of Morphology. 273 (10): 1096–1110. doi:10.1002/jmor.20047. ISSN 1097-4687. PMID 22730019.
  8. ^ a b Liu, Yunhong; Li, Guangji (2012-12-15). "A new method for producing "Lotus Effect" on a biomimetic shark skin". Journal of Colloid and Interface Science. 388 (1): 235–242. doi:10.1016/j.jcis.2012.08.033. ISSN 0021-9797. PMID 22995249.
  9. ^ "Sharklet Discovery | Sharklet Technologies, Inc". www.sharklet.com. Retrieved 2018-09-26.
  10. ^ Lauder, George V.; Oeffner, Johannes (2012-03-01). "The hydrodynamic function of shark skin and two biomimetic applications". Journal of Experimental Biology. 215 (5): 785–795. doi:10.1242/jeb.063040. ISSN 1477-9145. PMID 22323201.
  11. ^ Ballard, Bonnie; Cheek, Ryan (2 July 2016). Exotic Animal Medicine for the Veterinary Technician. John Wiley & Sons. ISBN 978-1-118-92421-1.
  12. ^ a b c d Kawasaki, Kenta C., "A Genetic Analysis of Cichlid Scale Morphology" (2016). Masters Theses May 2014 - current. 425. http://scholarworks.umass.edu/masters_theses_2/425
  13. ^ Helfman, Gene (2009). The Diversity of Fishes Biology, Evolution, and Ecology. Wiley-Blackwell.
  14. ^ Sherman, Vincent R.; Yaraghi, Nicholas A.; Kisailus, David; Meyers, Marc A. (2016-12-01). "Microstructural and geometric influences in the protective scales of Atractosteus spatula". Journal of the Royal Society Interface. 13 (125): 20160595. doi:10.1098/rsif.2016.0595. ISSN 1742-5689. PMC 5221522. PMID 27974575.
  15. ^ Zylberberg, L., Meunier, F.J., Laurin, M. (2010). A microanatomical and histological study of the postcranial dermal skeleton in the Devonian sarcopterygian Eusthenopteron foordi, Acta Palaeontologica Polonica 55: 459–470.
  16. ^ Turner, S.; Tarling, D. H. (1982). "Thelodont and other agnathan distributions as tests of Lower Paleozoic continental reconstructions". Palaeogeography, Palaeoclimatology, Palaeoecology. 39 (3–4): 295–311. doi:10.1016/0031-0182(82)90027-X.
  17. ^ Märss, T. (2006). "Exoskeletal ultrasculpture of early vertebrates". Journal of Vertebrate Paleontology. 26 (2): 235–252. doi:10.1671/0272-4634(2006)26[235:EUOEV]2.0.CO;2.
  18. ^ a b Janvier, Philippe (1998). "Early vertebrates and their extant relatives". Early Vertebrates. Oxford University Press. pp. 123–127. ISBN 978-0-19-854047-2.
  19. ^ a b Turner, S. (1991). "Monophyly and interrelationships of the Thelodonti". In M. M. Chang, Y. H. Liu & G. R. Zhang. Early Vertebrates and Related Problems of Evolutionary Biology. Science Press, Beijing. pp. 87–119.CS1 maint: Uses editors parameter (link)
  20. ^ Märss, T. (1986). "Squamation of the thelodont agnathan Phlebolepis". Journal of Vertebrate Paleontology. 6 (1): 1–11. doi:10.1080/02724634.1986.10011593.
  21. ^ Botella, H.; J. I. Valenzuela-Rios; P. Carls (2006). "A New Early Devonian thelodont from Celtiberia (Spain), with a revision of Spanish thelodonts". Palaeontology. 49 (1): 141–154. doi:10.1111/j.1475-4983.2005.00534.x.
  22. ^ Ferrón, Humberto G.; Botella, Héctor (2017). "Squamation and ecology of thelodonts". PLoS ONE. 12 (2): e0172781. doi:10.1371/journal.pone.0172781. PMC 5328365. PMID 28241029.

Further reading

  • Helfman, G.S., B.B. Collette and D.E. Facey (1997). The Diversity of Fishes. Blackwell Science. pp. 33–36. ISBN 978-0-86542-256-8.CS1 maint: Multiple names: authors list (link)

External links

  • Hydrodynamic aspects of shark scales [1]
  • Fish scales and flow manipulation [2]
Bolinao, Pangasinan

Bolinao, officially the Municipality of Bolinao, (Pangasinan: Baley na Bolinao; Ilokano: Ili ti Bolinao; Tagalog: Bayan ng Bolinao), is a 1st class municipality in the province of Pangasinan, Philippines. According to the 2015 census, it has a population of 82,084 people.Sea urchins are regularly harvested at Isla Silaki, Bolinao. The town, aside from being a fishing domain, is also a heritage site in the Philippines, possessing an olden church surrounded by heritage houses. The town is also the location of the cave where the gold-teeth Bolinao Skulls with fish scale designs were found. Scholars have been pushing for the town's cultural landscape into the UNESCO World Heritage List.

Comoran fish scale gecko

The Comoran fish scale gecko (Geckolepis humbloti) is a species of lizard in the family Gekkonidae. It is endemic to Grande Comore in the Comoros. It is sometimes considered a subspecies of Geckolepis maculata, however Hawlitschek et. al. (2015) resurrected humbloti when it was determined to be paraphyletic based on DNA data.

Donald T. Campbell

Donald Thomas Campbell (November 20, 1916 – May 5, 1996) was an American social scientist. He is noted for his work in methodology. He coined the term "evolutionary epistemology" and developed a selectionist theory of human creativity. A Review of General Psychology survey, published in 2002, ranked Campbell as the 33rd most cited psychologist of the 20th century.

Fish scale (disambiguation)

Fish scale may refer to:

The rigid plates on the skin of a fish

Fishscale, an album by Ghostface Killah

A slang term for high-quality cocaine

Fish Scales, a rapper

A fish scale, a type of often hand-held hanging spring scale with a fisherman hangs a caught fish on to measure its weight.

Geckolepis

Geckolepis is a genus of geckos, commonly referred to as fish scale geckos, which are endemic to Madagascar and the Comoro Islands. They are nocturnal, arboreal, insectivorous lizards, found in primary and secondary forest, as well as degraded habitats. They are best known for their ability to lose their skin and scales when grasped by a predator.

Geckolepis maculata

Geckolepis maculata is a species of gecko that is commonly found in Madagascar. The gecko has large scales, large legs, and is chestnut-cream with black bands. Its common names are Peters's spotted gecko and fish-scale gecko.

Immanuel Episcopal Church (Bellows Falls, Vermont)

The present Immanuel Episcopal Church was finished in Bellows Falls in Vermont in 1869 and was designed by the renowned Gothic revival architect Richard M. Upjohn. The building's Gothic style would have been typical of 14th-century France. The multi-colored fish scale slate roof is typical of the Victorian Gothic style of architecture.One of the building's notable features is the buttressed and pinnacled bell tower that has an octagonal "lantern"-styled top. There is a Paul Revere bell hanging in the tower that hung in the original 1817 church that was on the same site.One famous interment in the cemetery next door is Hetty Green, the "Witch of Wall Street", who was the wealthiest woman in the world during her time.

Littleton-upon-Severn

Littleton-upon-Severn is a village and civil parish in South Gloucestershire near the mouth of the River Severn and is located to the west of Thornbury. Historically it belonged to the Hundred of Langley and Swinehead. In 1831 it had a population of 179 people.A church was first mentioned as being in the village when the Abbott of Malmuesbury held a Court Leet here each year under a licence from King Edward the Martyr (975-979), and in the Domesday Book, it was listed as being in the Langley hundred, and having a priest and thirty acres of pasture. In the twelfth century, the wooden church was replaced with a stone building, and the font and piscine are also twelfth century.The present parish church of St Mary's of Malmesbury is a Grade II* listed building, having been registered on 30 March 1960. It dates from the fourteenth century but was largely rebuilt in 1878. It is built out of rubble stone in the Decorated style, with a roof of fish-scale tiles. The plan consists of a nave, south porch and aisle, chancel, north vestry, and tower at the west end.The village contains a popular 17th Century pub called The White Hart. In 2015 it as reported that locals were distressed with the prospect of a developer wanting to built a refugee centre for some 1000 migrants in the village.Littleton Brick Pits are an artificial lagoon, once the site of clay extraction for brick making, where the Avon Wildlife Trust have reintroduced reedbeds close to the Severn Estuary, as a feeding and resting place for migrating birds.

Mackerel sky

A mackerel sky is a common term for a sky with rows of cirrocumulus or altocumulus clouds displaying an undulating, rippling pattern similar in appearance to fish scales; this is caused by high altitude atmospheric waves.Cirrocumulus appears almost exclusively with cirrus some way ahead of a warm front and is a reliable forecaster that the weather is about to change. When these high clouds progressively invade the sky and the barometric pressure begins to fall, precipitation associated with the disturbance is likely about 6 to 12 hours away. A thickening and lowering of cirrocumulus into middle-étage altostratus or altocumulus is a good sign the warm front or low has moved closer and it may start raining within less than six hours. The old rhymes "Mackerel sky, not twenty-four hours dry" and "Mares' tails and mackerel scales make lofty ships to carry low sails" both refer to this long-recognized phenomenon.

Other phrases in weather lore take mackerel skies as a sign of changeable weather. Examples include "Mackerel sky, mackerel sky. Never long wet and never long dry", and "A dappled sky, like a painted woman, soon changes its face".It is sometimes known as a buttermilk sky, particularly when in the early cirrocumulus stage, in reference to the clouds' "curdled" appearance. In France it is sometimes called a ciel moutonné (fleecy sky); and in Spain a cielo empedrado (cobbled sky); in Germany it is known as Schäfchenwolken (sheep clouds), and in Italy the clouds are known as a pecorelle (little sheep).

Nickel (Canadian coin)

The Canadian five-cent coin, commonly called a nickel, is a coin worth five cents or one-twentieth of a Canadian dollar. It was patterned on the corresponding coin in the neighbouring United States. It became the smallest-valued coin in the currency upon the discontinuation of the penny in 2013. Due to inflation, the purchasing power of the nickel continues to drop and currently the coin represents less than 0.5% of the country's lowest minimum hourly wage.

The denomination (i.e., the Canadian five-cent piece) had been introduced in 1858 as a small, thin sterling silver coin, that was colloquially known as a "fish scale," not a nickel. The larger base metal version made of nickel, and called a "nickel," was introduced as a Canadian coin in 1922, originally as 99.9% nickel metal. These coins were magnetic, due to the high nickel content. Versions during World War II were minted in copper-zinc, then chrome and nickel-plated steel, and finally returned again to nickel, at the end of the war. A plated steel version was again made 1951–54 during the Korean War. Rising nickel prices eventually caused another switch to cupronickel in 1982 (an alloy similar to the US nickel), but more recently, Canadian nickels are minted in nickel-plated steel, containing a small amount of copper. Due to the aforementioned rise in nickel prices, since 1982, five cent pieces composed of 99.9% nickel, have been slowly removed from circulation to be melted by the Royal Canadian Mint, only cupronickel and modern multi-ply plated steel five cent pieces are considered "Circulation Coins." As a result, pre-1982 five cent pieces are often sought by collectors.

From 1942 to 1963, Canadian five-cent coins were produced in a distinctive 12-sided shape, evocative of the British threepence coin. Originally this was done to distinguish the copper-coloured tombac (copper-zinc alloy) coins, from pennies. However, the characteristic shape was retained for another nineteen years after 1944 when this coin was later produced in 99.9% nickel and chrome-plated steel.

The coin is produced by the Royal Canadian Mint at its facility in Winnipeg.

Ski wax

Ski wax is a material applied to the bottom of snow runners, including skis, snowboards, and toboggans, to improve their coefficient of friction performance under varying snow conditions. The two main types of wax used on skis are glide waxes and grip waxes. They address kinetic friction—to be minimized with a glide wax—and static friction—to be achieved with a grip wax. Both types of wax are designed to be matched with the varying properties of snow, including crystal type and size, and moisture content of the snow surface, which vary with temperature and the temperature history of the snow. Glide wax is selected to minimize sliding friction for both alpine and cross-country skiing. Grip wax (also called "kick wax") provides on-snow traction for cross-country skiers, as they stride forward using classic technique.

Modern plastic materials (e.g. high-modulus polyethylene and Teflon), used on ski bases, have excellent gliding properties on snow, which in many circumstances diminish the added value of a glide wax. Likewise, uni-directional textures (e.g. fish scale or micro-scale hairs) underfoot on cross-country skis can offer a practical substitute for grip wax for those skiers, using the classic technique.

St. Dominic's Catholic Church

St. Dominic's Catholic Church is a historic church on Main Street in Springfield, Kentucky. The Romanesque building was constructed in 1890 and added to the National Register of Historic Places in 1989.It has a pyramidal roofed tower shingled with red fish scale slate. It is the second building of the church; it replaced an 1843 structure.

Thorpe Hall (Peterborough)

Thorpe Hall at Longthorpe in the city of Peterborough, Cambridgeshire, is a Grade I listed building, built by Peter Mills between 1653 and 1656, for the Lord Chief Justice, Oliver St John. The house is unusual in being one of the very few mansions built during the Commonwealth period. After a period as a hospital, it is currently used as a Sue Ryder Care hospice.

While Parliamentary soldiers were in Peterborough in 1643 during the civil war, they ransacked the cathedral. Parliament disposed of Church property to raise money for the army and navy and the parliamentarian Oliver St John bought the lease to the manor of Longthorpe and built Thorpe Hall. In 1654 it was described by the author John Evelyn as "a stately place...built out of the ruins of the Bishop's Palace and cloisters."A symmetrical composition in ashlar, rusticated quoins, with square, groups of rusticated chimney shafts; the north and south elevations are identical, three dormers, casements under pediments, the centre one semi-circular. A stone slate roof overhangs on modillions. There are seven windows, with plain stone surrounds to top and ground floors. The porch with Tuscan columns supports a balcony. The balcony window on the first floor has a segmental pediment and shouldered architrave. The windows of the second and sixth bays have pediments, while the others have frieze and moulded cornice. A band marks first floor height. There is a flight of eight steps with balustrade supporting two urns. The interior is complete, except for library panelling now at Leeds Castle. Principal rooms have richly decorated fireplaces and plaster ceilings by Peter Mills. The principal staircase has heavily carved foliated open panels to broad balustrade. A stone screen on the landing was added in 1850 by Francis Ruddle of Peterborough.Thorpe Hall is situated in a Grade II listed garden that is open to members of the public throughout the year. The curved walls forming the entrance courtyard, gatepiers and entrance gates, former stables to the right, and a shouldered stone architrave gateway flanked by vertically halved pilasters with volutes are also Grade I listed buildings. The late nineteenth century lodge, octagonal summerhouse in red brick with fish scale slate roof, and a free-standing archway resembling a Venetian window in design are Grade II listed buildings.

A maternity hospital from 1943 to 1970, it was transferred to the National Health Service in 1948, coming under No. 12 Group (Peterborough and Stamford Hospitals Management Committee) of the East Anglian Regional Hospitals Board. In 1986 it was acquired by the Sue Ryder Foundation and is currently in use as a hospice.

Triparanol

Triparanol (INN, BAN) (brand and developmental code names MER/29, as well as many other brand names), patented in 1959 and introduced in the United States in 1960, was the first synthetic cholesterol-lowering drug. It was withdrawn in 1962 due to severe adverse effects such as nausea and vomiting, vision loss due to irreversible cataracts, alopecia, skin disorders (e.g., dryness, itching, peeling, and "fish-scale" texture), and accelerated atherosclerosis and is now considered to be obsolete.The drug acts by inhibiting 24-dehydrocholesterol reductase, which catalyzes the final step of cholesterol biosynthesis, the conversion of desmosterol into cholesterol. This results in tissue accumulation of desmosterol, which in turn is responsible for the side effects of triparanol. Unlike statins, triparanol does not inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis, and in contrast to triparanol, statins can significantly lower cholesterol levels without resulting in accumulation of intermediates like desmosterol. The developmental code name of triparanol, MER/29, became so well known that it became the registered trade name of the drug.Estrogen is known to lower cholesterol levels, but produces side effects like gynecomastia and decreased libido in men. It was hoped that a drug could be developed that lacked overt estrogenic effects but still lowered cholesterol levels. Triparanol is a triphenylethanol and was derived from chlorotrianisene (TACE), a nonsteroidal triphenylethylene estrogen, and the nonsteroidal triphenylethanol antiestrogen ethamoxytriphetol (MER-25) is a derivative of triparanol. The selective estrogen receptor modulator clomifene is also structurally related to triparanol. The developers of triparanol jokingly referred to it as a "non-estrogenic estrogen".

Weyto language

Weyto is a speculative extinct language thought to have been spoken in the Lake Tana region of Ethiopia by the Weyto, a small group of hippopotamus hunters who now speak Amharic.

The Weyto language was first mentioned by the Scottish traveler James Bruce, who spoke Amharic, passed through the area about 1770 and reported that "the Wayto speak a language radically different from any of those in Abyssinia," but was unable to obtain any "certain information" on it, despite prevailing upon the king to send for two Weyto men for him to ask questions, which they would "neither answer nor understand" even when threatened with hanging. The next European to report on them, Eugen Mittwoch, described them as uniformly speaking a dialect of Amharic (Mittwoch 1907). This report was confirmed by Marcel Griaule when he passed through in 1928, although he added that at one point a Weyto sang an unrecorded song "in the dead language of the Wohitos" whose meaning the singer himself did not understand, except for a handful of words for hippopotamus body parts which, he says, had remained in use.

This Amharic dialect is described by Marcel Cohen (1939) as featuring a fair number of words derived from Amharic roots but twisted in sound or meaning in order to confuse outsiders, making it a sort of argot; in addition to these, it had a small number of Cushitic loanwords not found in standard Amharic, and a large number of Arabic loanwords mainly related to Islam. Of the substantial wordlist collected by Griaule, Cohen only considered six terms to be etymologically obscure: šəlkərít "fish-scale", qəntat "wing", čəgəmbit "mosquito", annessa "shoulder", ənkies "hippopotamus thigh", wazəməs "hippopotamus spine." By 1965, the visiting anthropologist Frederick Gamst found "no surviving native words, not even relating to their hunting and fishing work tasks." (Gamst 1965.)

The paucity of the data available has not prevented speculation on the classification of their original language; Cohen suggested that it might have been either an Agaw language or a non-Amharic Semitic language, while Dimmendaal (1989) says it "probably belonged to Cushitic" (as does Agaw), and Gamst (1965) says "...it can be assumed that if the Wäyto did not speak Amharic 200 years ago, their language must have been Agäw..." According to the Ethnologue, Bender et al. (1976) saw it as Cushitic, while Bender 1983 saw it as either Eastern Sudanic or Awngi. It thus effectively remains unclassified, largely for lack of data, but possibly related to Agaw.

Wisteria Lodge (Reading, Massachusetts)

Wisteria Lodge is a historic house at 146 Summer Avenue in Reading, Massachusetts. The ​2 1⁄2-story Second Empire wood-frame house was built in 1850 by Oscar Foote, a local real estate developer entrepreneur who attempted to market bottled mineral water from nearby springs. The house has a mansard roof with fish scale slate shingles, bracketed eaves, an elaborate porte cochere, and styled window surrounds with triangular pediments. The porches ahd porte cochere are supported by square columns set on paneled piers, with arched molding between.The house was listed on the National Register of Historic Places in 1984.

Yale Avenue Historic District

The Yale Avenue Historic District is a residential historic district near the center of Wakefield, Massachusetts. It encompasses eight residential properties, all but one of which were developed in the 1860s and 1870s, after the arrival of the railroad in town. These properties were built primarily for Boston businessmen, and mark the start of Wakefield's transition to a suburb.The district, which was listed on the National Register of Historic Places in 1989, consists of five houses (16-24) on the south side of Yale Street, and three (21-25) directly opposite on the north side. Five are Italianate in style, one is Second Empire, one is Queen Anne, and the newest house in the district, 22 Yale Avenue, was built c. 1896 in the Colonial Revival Style. All are 2-1/2 stories in height, and of wood frame construction, with clapboards and/or shingles on their exteriors, and most have porches.Although the houses are nominally in one style, most exhibit features that are reminiscent of a different style. The house at 20 Yale Avenue, for instance, follows a somewhat typical Italianate L-shaped plan, but its porch is more elaborately decorated with what might be considered Queen Anne features. The house at 23 Yale Avenue, built c. 1863, marks a shift from the Italianate to the Second Empire with the addition of a mansard-style roof with fish scale shingles. 24 Yale Avenue is one of t Wakefield's few surviving Stick style houses, and 22 Yale Avenue is an early and modest example of the Colonial Revival.

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