Crypsis

In ecology, crypsis is the ability of an animal to avoid observation or detection by other animals. It may be a predation strategy or an antipredator adaptation. Methods include camouflage, nocturnality, subterranean lifestyle and mimicry. Crypsis can involve visual, olfactory (with pheromones), or auditory concealment. When it is visual, the term cryptic coloration, effectively a synonym for animal camouflage,[a] is sometimes used, but many different methods of camouflage are employed by animals.

2005-Draco-dussumieri
A Draco lizard showing camouflage methods including background matching, disruptive coloration, reduction of shadow, and cryptic behavior in Bandipur National Park

Overview

There is a strong evolutionary pressure for animals to blend into their environment or conceal their shape, for prey animals to avoid predators and for predators to be able to avoid detection by prey. Exceptions include large herbivores without natural enemies, brilliantly colored birds that rely on flight to escape predators, and venomous or otherwise powerfully armed animals with warning coloration. Cryptic animals include the tawny frogmouth (feather patterning resembles bark), the tuatara (hides in burrows all day; nocturnal), some jellyfish (transparent), the leafy sea dragon, and the flounder (covers itself in sediment).

Methods

Methods of crypsis include (visual) camouflage, nocturnality, and subterranean lifestyle. Camouflage can be achieved by a wide variety of methods, from disruptive coloration to transparency and some forms of mimicry, even in habitats like the open sea where there is no background.[1][2][3]

As a strategy, crypsis is used by predators against prey and by prey against predators.[1]

Crypsis also applies to eggs[4] and pheromone production.[5] Crypsis can in principle involve visual, olfactory, or auditory camouflage.[6]

Visual

Jumping spider with prey
Camouflage allows animals like this disruptively-patterned spider to capture prey more easily.

Many animals have evolved so that they visually resemble their surroundings by using any of the many methods of natural camouflage that may match the color and texture of the surroundings (cryptic coloration) and/or break up the visual outline of the animal itself (disruptive coloration). Such animals may resemble rocks, sand, twigs, leaves, and even bird droppings (mimesis). Other methods including transparency and silvering are widely used by marine animals.[7]

Some animals change color in changing environments seasonally, as in ermine and snowshoe hare, or far more rapidly with chromatophores in their integuments, as in chameleon and cephalopods such as squid.

Countershading, the use of different colors on upper and lower surfaces in graduating tones from a light belly to a darker back, is common in the sea and on land. It is sometimes called Thayer's law, after the American artist Abbott Handerson Thayer, who published a paper on the form in 1896 that explained that countershading paints out shadows to make solid objects appear flat, reversing the way that artists use paint to make flat paintings contain solid objects. Where the background is brighter than is possible even with white pigment, counter-illumination in marine animals, such as squid, can use light to match the background.

Some animals actively camouflage themselves with local materials. The decorator crabs attach plants, animals, small stones, or shell fragments to their carapaces to provide camouflage that matches the local environment. Some species preferentially select stinging animals such as sea anemones or noxious plants, benefiting from aposematism as well as or instead of crypsis.[8]

Olfactory

Some animals, in both terrestrial and aquatic environments, appear to camouflage their odor, which might otherwise attract predators.[9] Numerous arthropods, both insects and spiders, mimic ants, whether to avoid predation, to hunt ants, or (for example in the large blue butterfly caterpillar) to trick the ants into feeding them.[10] Pirate perch (Aphredoderus sayanus) may exhibit chemical crypsis, making them undetectable to frogs and insects colonizing ponds.[11]

Auditory

Some insects, notably some Noctuid moths, (such as the large yellow underwing), and some tiger moths, (such as the garden tiger), were originally theorized to defend themselves against predation by echolocating bats, both by passively absorbing sound with soft, fur-like body coverings and by actively creating sounds to mimic echoes from other locations or objects. The active strategy was described as a "phantom echo" that might therefore represent "auditory crypsis", with alternative theories about interfering with the bats' echolocation ("jamming").[12][13]

Subsequent research has provided evidence for only two functions of moth sounds, neither of which involve "auditory crypsis". Tiger moth species appear to cluster into two distinct groups. One type produces sounds as acoustic aposematism, warning the bats that the moths are unpalatable,[14] or at least performing as acoustic mimics of unpalatable moths.[15] The other type uses sonar jamming. In the latter type of moth, detailed analyses failed to support a "phantom echo" mechanism underlying sonar jamming, but instead pointed towards echo interference.[16]

Effects

There is often a self-perpetuating co-evolution, or evolutionary arms race, between the perceptive abilities of animals attempting to detect the cryptic animal and the cryptic characteristics of the hiding species.[17] Different aspects of crypsis and sensory abilities may be more or less pronounced in given predator-prey species pairs.

Zoologists need special methods to study cryptic animals, including biotelemetry techniques such as radio tracking, mark and recapture, and enclosures or exclosures. Cryptic animals tend to be overlooked in studies of biodiversity and ecological risk assessment.

Notes

  1. ^ Military camouflage has multiple purposes, including not only concealment but also esprit de corps and recognition of friend and foe.

References

  1. ^ a b Zuanon, J.; I. Sazima (2006). "The almost invisible league: crypsis and association between minute fishes and shrimps as a possible defence against visually hunting predators". Neotropical Ichthyology. 4 (2): 219–224. doi:10.1590/s1679-62252006000200008.
  2. ^ Allaby, Michael (2014). Crypsis. A Dictionary of Zoology (4th ed.). Oxford University Press.
  3. ^ Allaby, Michael (2015). Crypsis. A Dictionary of Ecology (5th ed.). Oxford University Press.
  4. ^ Nguyen, L. P.; et al. (2007). "Using digital photographs to evaluate the effectiveness of plover egg crypsis". Journal of Wildlife Management. 71 (6): 2084–2089. doi:10.2193/2006-471.
  5. ^ Raffa, K. R.; et al. (2007). "Can chemical communication be cryptic? Adaptations by herbivores to natural enemies exploiting prey semiochemistry". Oecologia. 153 (4): 1009–1019. doi:10.1007/s00442-007-0786-z. PMID 17618465.
  6. ^ "Definition of Crypsis". Amateur Entomologists' Society. Retrieved August 19, 2012.
  7. ^ "All Lives Transform:Adaptation- Mimicry". Morning-earth.org. February 14, 2007. Archived from the original on February 18, 2012. Retrieved January 5, 2012.
  8. ^ Hultgren, Kristin; Stachowicz, Jay in Stevens, M. and Merilaita, S. (2011). "Animal Camouflage" (PDF). Camouflage in decorator crabs: Camouflage in decorator crabs. Cambridge University Press. Retrieved December 13, 2012.CS1 maint: Multiple names: authors list (link)
  9. ^ Michael R. Conover. Predator-Prey Dynamics: the role of olfaction. CRC Press. 2007. ISBN 978-0-8493-9270-2
  10. ^ Donisthorpe, Horace (January 1922). "Mimicry of Ants by Other Arthropods". Transactions of the Royal Entomological Society of London. 69 (3–4): 307–311. doi:10.1111/j.1365-2311.1922.tb02812.x.
  11. ^ Resetarits, Jr., William J.; Binckley, Christopher A. (2013). "Is the pirate really a ghost? Evidence for generalized chemical camouflage in an aquatic predator, pirate perch Aphredoderus sayanus" (PDF). The American Naturalist. 181 (5): 690–699. doi:10.1086/670016. PMID 23594551. Archived from the original (PDF) on June 1, 2013.
  12. ^ Miller, Lee A.; Surlykke, Annemarie (July 2001). "How Some Insects Detect and Avoid Being Eaten by Bats: Tactics and Countertactics of Prey and Predator" (PDF). BioScience. 51 (7): 570–581. doi:10.1641/0006-3568(2001)051[0570:HSIDAA]2.0.CO;2.
  13. ^ Griffin, Donald R. (July 2001). "Full Access Return to the Magic Well: Echolocation Behavior of Bats and Responses of Insect Prey". BioScience. 51 (7): 555–556. doi:10.1641/0006-3568(2001)051[0555:RTTMWE]2.0.CO;2. JSTOR 10.1641/0006-3568%282001%29051%5B0555%3ARTTMWE%5D2.0.CO%3B2.
  14. ^ Hristov, N. I.; Conner, W.E. (2005). "Sound strategy: acoustic aposematism in the bat–tiger moth arms race". Naturwissenschaften. 92 (4): 164–169. doi:10.1007/s00114-005-0611-7. PMID 15772807.
  15. ^ Barber, J. R.; Conner, W. E. (2007). "Acoustic mimicry in a predator–prey interaction". Proceedings of the National Academy of Sciences. 104 (22): 9331–9334. doi:10.1073/pnas.0703627104. PMC 1890494. PMID 17517637.
  16. ^ Corcoran, A.J.; Conner, W.E.; Barber, J.R. (2010). "Anti-bat tiger moth sounds: Form and function". Current Zoology. 56 (3): 358–369.
  17. ^ Franks, D. W.; Noble, J. (2004). "Warning signals and predator-prey coevolution". Proceedings of the Royal Society B: Biological Sciences. 271 (1550): 1859–1865. doi:10.1098/rspb.2004.2795. PMC 1691800. PMID 15315903.

External links

Camouflage

Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see (crypsis), or by disguising them as something else (mimesis). Examples include the leopard's spotted coat, the battledress of a modern soldier, and the leaf-mimic katydid's wings. A third approach, motion dazzle, confuses the observer with a conspicuous pattern, making the object visible but momentarily harder to locate. The majority of camouflage methods aim for crypsis, often through a general resemblance to the background, high contrast disruptive coloration, eliminating shadow, and countershading. In the open ocean, where there is no background, the principal methods of camouflage are transparency, silvering, and countershading, while the ability to produce light is among other things used for counter-illumination on the undersides of cephalopods such as squid. Some animals, such as chameleons and octopuses, are capable of actively changing their skin pattern and colours, whether for camouflage or for signalling. It is possible that some plants use camouflage to evade being eaten by herbivores.

Military camouflage was spurred by the increasing range and accuracy of firearms in the 19th century. In particular the replacement of the inaccurate musket with the rifle made personal concealment in battle a survival skill. In the 20th century, military camouflage developed rapidly, especially during the First World War. On land, artists such as André Mare designed camouflage schemes and observation posts disguised as trees. At sea, merchant ships and troop carriers were painted in dazzle patterns that were highly visible, but designed to confuse enemy submarines as to the target's speed, range, and heading. During and after the Second World War, a variety of camouflage schemes were used for aircraft and for ground vehicles in different theatres of war. The use of radar since the mid-20th century has largely made camouflage for fixed-wing military aircraft obsolete.

Non-military use of camouflage includes making cell telephone towers less obtrusive and helping hunters to approach wary game animals. Patterns derived from military camouflage are frequently used in fashion clothing, exploiting their strong designs and sometimes their symbolism. Camouflage themes recur in modern art, and both figuratively and literally in science fiction and works of literature.

Crypsis (disambiguation)

Crypsis has two distinct meanings in biology:

organisms that hide themselves: crypsis

organisms that are difficult to distinguish: crypsis (taxonomy)

Crypsis (genus)

Crypsis is an African and Eurasian plant in the grass family sometimes referred to as pricklegrass.These are annual grasses with short leaves. A few species are invasive weeds outside their native ranges.

SpeciesCrypsis aculeata - from Portugal and Mauritania to Korea

Crypsis acuminata - from Turkey to Kazakhstan

Crypsis alopecuroides - from Portugal and Morocco to Korea; introduced in western North America (British Columbia + western USA)

Crypsis factorovskyi - Caucasus, Turkey, Cyprus, Syria, Lebanon, Palestine, Jordan

Crypsis hadjikyriakou - Cyprus

Crypsis minuartioides - Sharon Plain in northwestern Israel

Crypsis schoenoides - from Britain to China + Pakistan + Mozambique; introduced in North America (western USA, Great Lakes region, Baja California)

Crypsis turkestanica - Central Asia, Caucasus, western Siberia, southern European Russia

Crypsis vaginiflora - Africa; Middle East, India, Pakistan; introduced in North America (Idaho, Oregon, California, Baja California)formerly includedsee Muhlenbergia Munroa Phleum Rhizocephalus Sporobolus Urochondra

Crypsis alopecuroides

Crypsis alopecuroides is a species of grass known by the common name foxtail pricklegrass. It is native to Europe, the Middle East, and North Africa. It is also known in the western United States as a common and widespread introduced species, especially in sandy areas around water, such as lakesides. It has also been collected at shipping points near Philadelphia but has not been seen there in about a century. This is an annual grass producing mostly upright and unbranching stems, often dark in color, up to about 75 centimeters in maximum height. The green leaves are up to 12 centimeters long, sometimes waxy in texture. The inflorescence is a dense cylindrical panicle of tiny green to purple spikelets.

Crypsis schoenoides

Crypsis schoenoides is a species of grass known by the common names swamp pricklegrass, swamp timothy, and cowpond grass. This grass is native to Europe but it is present in most other continents where it was introduced and took hold. This is an annual grass with purple-tinted green stems which forms mats and low clumps near water. It has wide-sheathed leaves and large sheaths that partially cover the inflorescences. The clublike inflorescence may exceed 4 centimeters in length and two in width. It is chunky and purple or purplish-green.

Crypsis vaginiflora

Crypsis vaginiflora is a species of grass known by the common name modest pricklegrass. It is native to North Africa but it can be found in other parts of the world as an introduced species, including the western United States, particularly California, where it is common in wet habitat such as vernal pools. It is an annual grass forming mats of green, prostrate stems not generally exceeding 30 centimeters long. The stems are enveloped in the sheaths of the leaves, the small blades of which break off. The inflorescence is a dense panicle usually no more than 1.5 centimeters long tucked into the sheaths of the uppermost leaves.

Epipleminae

The Epipleminae or epiplemiine moths are a subfamily of the lepidopteran family Uraniidae. The subfamily was first described by George Hampson in 1892. They are the most diverse and widespread uraniid group, occurring mainly throughout the Pantropics but barely reaching into the temperate regions. The Epipleminae are notable for the sexually dimorphic tympanal organ which is unlike any other lepidopteran's in details of its morphology. Some species are also peculiar in being able to roll their wings into a stick-like shape, possibly as a form of crypsis. Such behavior has hitherto only been found in this subfamily and the quite unrelated Ennominae (Sohn & Yen 2005).

Unlike the often colorful Uraniinae, they are smallish and drab species, and have earlier been erroneously placed with the Geometridae or Drepanidae based on phenetic considerations. Only three species have come to note as minor pests of commercial plants:

Leucoplema dohertyi

Epiplema fulvilinea – does not belong into this genus

Dysaethria moza – formerly Epiplema

Frog Skin

Frog Skin is a battledress camouflage pattern with mottle and disruptive coloration to blend into the environment similar to a frog's crypsis skin.

Gloger's rule

Gloger's rule is an ecogeographical rule which states that within a species of endotherms, more heavily pigmented forms tend to be found in more humid environments, e.g. near the equator. It was named after the zoologist Constantin Wilhelm Lambert Gloger, who first remarked upon this phenomenon in 1833 in a review of covariation of climate and avian plumage color. Erwin Stresemann noted that the idea was already expressed by Pallas in Zoographia Rosso-Asiatica (1811). Gloger found that birds in more humid habitats tended to be darker than their relatives from regions with higher aridity. Over 90% of 52 North American bird species studies conform to this rule.One explanation of Gloger's rule in the case of birds appears to be the increased resistance of dark feathers to feather- or hair-degrading bacteria such as Bacillus licheniformis. Feathers in humid environments have a greater bacterial load, and humid environments are more suitable for microbial growth; dark feathers or hair are more difficult to break down. More resilient eumelanins – dark brown to black – are deposited in hot and humid regions, whereas in arid regions, pheomelanins – reddish to sandy color – predominate due to the benefit of crypsis.

Among mammals, there is a marked tendency in equatorial and tropical regions to have a darker skin color than poleward relatives. In this case, the underlying cause is probably the need to better protect against the more intense solar UV radiation at lower latitudes. However absorption of a certain amount of UV radiation is necessary for the production of certain vitamins, notably vitamin D (see also Osteomalacia).

This principle is also vividly demonstrated among human populations. Populations that evolved in sunnier environments closer to the equator tend to be darker-pigmented than populations originating farther from the equator. There are exceptions, however; among the most well known are the Tibetans and Inuit, who have darker skin than might be expected from their native latitudes. In the first case, this is apparently an adaptation to the extremely high UV irradiation on the Tibetan Plateau, whereas in the second case, the necessity to absorb UV radiation is alleviated by the Inuit's diet naturally rich in vitamin D.

Motion camouflage

Motion camouflage is camouflage which provides a degree of concealment for a moving object, given that motion makes objects easy to detect however well their coloration matches their background or breaks up their outlines. The principal form of motion camouflage, and the type generally meant by the term, involves an attacker's mimicking the optic flow of the background as seen by its target. This enables the attacker to approach the target while appearing to remain stationary from the target's perspective, unlike in classical pursuit. The attacker chooses its flight path so as to remain on the line between the target and some landmark point. The target therefore does not see the attacker move from the landmark point. The only visible evidence that the attacker is moving is its looming, the change in size as the attacker approaches. Motion is also used in a variety of other camouflage strategies, including swaying to mimic plant movements in the wind or ocean currents.

First discovered in hoverflies in 1995, motion camouflage by minimising optic flow has been demonstrated in another insect order, dragonflies, as well as in two groups of vertebrates, falcons and echolocating bats. Since bats hunting at night cannot be using the strategy for camouflage, it has been named, describing its mechanism, as constant absolute target direction. This is an efficient homing strategy, and it has been suggested that anti-aircraft missiles could benefit from similar techniques.

Camouflage is sometimes facilitated by motion, as in the leafy sea dragon and some stick insects. These animals complement their passive camouflage by swaying like plants, either preventing predators from detecting them, or appearing as something other than prey.

Ophidiasteridae

The Ophidiasteridae (Greek ophidia, Οφιδια, "of snakes", diminutive form) are a family of sea stars with about 30 genera. Occurring both in the Indo-Pacific and Atlantic Oceans, ophidiasterids are greatest in diversity in the Indo-Pacific. Many of the genera in this family exhibit brilliant colors and patterns, which sometimes can be attributed to aposematism and crypsis to protect themselves from predators. Some ophidiasterids possess remarkable powers of regeneration, enabling them to either reproduce asexually or to survive serious damage made by predators or forces of nature (an example for this is the genus Linckia). Some species belonging to Linckia, Ophidiaster and Phataria shed single arms that regenerate the disc and the remaining rays to form a complete individual. Some of these also reproduce asexually by parthenogenesis.The name of the family is taken from the genus Ophidiaster, whose limbs are slender, semitubular and serpentine.

Phleum

This page is about the genus of grasses. Phleum is also the name of a Roman site now in Velsen, Netherlands.

Phleum (timothy) is a genus of annual and perennial plants in the grass family. The genus is native to Europe, Asia and north Africa, with one species (P. alpinum) also in North and South America.They are tufted grasses growing to 20–150 cm tall, with cylindrical, spike-like panicles containing many densely packed spikelets.

Species

formerly includednumerous species now considered better suited to other genera: Aegilops Alopecurus Beckmannia Crypsis Cynodon Cynosurus Digitaria Elytrophorus Ischaemum Mnesithea Muhlenbergia Pennisetum Pentameris Phalaris Polypogon Polytrias Sesleria Tribolium

Raddia

Raddia is a genus of South American plants in the grass family, most of the species found only in Brazil.The genus was named for Italian botanist and herpetologist Giuseppe Raddi, 1770-1829.

SpeciesRaddia angustifolia Soderstr. & Zuloaga - Bahia

Raddia brasiliensis Bertol. - Rio de Janeiro, Bahia, Espírito Santo, Mato Grosso, Paraíba

Raddia distichophylla (Steud. ex Nees) Chase - Bahia

Raddia guianensis (Brongn.) C.L.Hitchc. - Trinidad & Tobago, Pará, French Guiana, Suriname, Venezuela (Carabobo, Yaracuy)

Raddia lancifolia R.P.Oliveira & Longhi-Wagner - Espírito Santo

Raddia megaphylla R.P.Oliveira & Longhi-Wagner - Espírito Santo, Bahia

Raddia portoi Kuhlm. - Bahia

Raddia soderstromii R.P.Oliveira, L.G.Clark & Judz. - Bahia, Rio Grande do Norte, Rio de Janeiro, Sergipe

Raddia stolonifera R.P.Oliveira & Longhi-Wagner - Bahiaformerly includedsee Arberella Crypsis Cryptochloa Piresia Raddiella

Rhizocephalus

Rhizocephalus is a genus of plants in the grass family. The only known species is Rhizocephalus orientalis, native to Afghanistan, Armenia, Georgia, Iran, Iraq, Israel, Jordan, Lebanon, Palestine, Syria, AsiaticTurkey, and Uzbekistan.

Snipe

A snipe is any of about 26 wading bird species in three genera in the family Scolopacidae. They are characterized by a very long, slender bill and crypsis, or camouflage, plumage. The Gallinago snipes have a nearly worldwide distribution, the Lymnocryptes snipe is restricted to Asia and Europe and the Coenocorypha snipes are found only in the outlying islands of New Zealand. The four species of painted snipe are not closely related to the typical snipes, and are placed in their own family, the Rostratulidae.

Spartina

Spartina, commonly known as cordgrass or cord-grass, is a genus of plants in the grass family, frequently found in coastal salt marshes.The genus Spartina has been subsumed into the genus Sporobolus and demoted to the taxonomic status of section after a taxonomic revision in 2014, but it is still common to see Spartina used as the genus.

The word Spartina is derived from σπαρτίνη (spartiné), the Greek word for a cord made from Spanish broom (Spartium junceum). They are native to the coasts of the Atlantic Ocean in western and southern Europe, northwest and southern Africa, the Americas and the southern Atlantic Ocean islands; one or two species also occur on the North American Pacific Ocean coast and in freshwater habitats inland in the Americas. The highest species diversity is on the east coasts of North and South America, particularly Florida.

They form large, often dense colonies, particularly on coastal salt marshes, and grow quickly. The species vary in size from 0.3–2 m tall. Many of the species will produce hybrids if they come into contact.

Species(Species on this list were revised to the genus Sporobolus, section Spartina, in 2014 )

Spartina alterniflora Loisel. – smooth cordgrass – Atlantic coasts of North + South America, West Indies

Spartina anglica C.E.Hubb. – common cordgrass – Great Britain; introduced scattered other places

Spartina arundinacea (Thouars) Carmich – Tristan da Cunha, Amsterdam Island in Indian Ocean

Spartina bakeri Merr. – sand cordgrass – southeastern US

Spartina × caespitosa A.A.Eaton – short cordgrass – eastern US + Canada (PEI to VA)

Spartina ciliata Brongn. – Brazil, Argentina, Uruguay

Spartina cynosuroides (L.) Roth – big cordgrass – eastern US (TX to MA); Tamaulipas, Chihuahua, Bahamas

Spartina densiflora Brongn. – denseflower cordgrass – Venezuela, Brazil, Argentina, Uruguay, Chile

Spartina foliosa Trin. – California cordgrass – California, Baja California, Baja California Sur

Spartina gracilis Trin. – alkali cordgrass – western Canada, western + central US, Chihuahua, Jalisco, Michoacán

Spartina longispica Hauman & Parodi ex St.-Yves – Argentina, Uruguay

Spartina maritima (Curtis) Fernald – small cordgrass – Great Britain, Netherlands, Belgium, France, Spain, Portugal, Italy, Croatia, Morocco, Mauritania, Namibia, South Africa

Spartina patens (Aiton) Muhl – saltmeadow cordgrass – east coast of North America from Labrador to Tamaulipas; West Indies

Spartina pectinata Bosc ex Link – prairie cordgrass from Northwest Territories to Texas + Newfoundland

Spartina spartinae (Trin.) Merr. ex Hitchc. – Gulf cordgrass – Atlantic coast of North America from Florida to Argentina, incl Caribbean + Gulf of Mexico

Spartina × townsendii H.Groves & J.Groves (S. alterniflora × S. maritima) – Townsend's cordgrass – western Europe

Spartina versicolor Fabre – Mediterranean, AzoresFormerly includedsee Bouteloua Crypsis Dactylis Digitaria

Species complex

In biology, a species complex is a group of closely related organisms that are very similar in appearance to the point that the boundaries between them are often unclear. Terms sometimes used synonymously but with more precise meanings are: cryptic species for two or more species hidden under one species name, sibling species for two cryptic species that are each other's closest relative, and species flock for a group of closely related species living in the same habitat. As informal taxonomic ranks, species group, species aggregate, and superspecies are also in use.

Two or more taxa once considered conspecific (of the same species) may later be subdivided into infraspecific taxa (taxa within a species, such as bacterial strains or plant varieties), but this is not a species complex.

A species complex is in most cases a monophyletic group with a common ancestor, although there are exceptions. It may represent an early stage after speciation, but may also have been separated for a long time period without evolving morphological differences. Hybrid speciation can be a component in the evolution of a species complex.

Species complexes exist in all groups of organisms. They are identified by the rigorous study of differences between individual species, making use of minute morphological details, tests of reproductive isolation, or DNA-based methods such as molecular phylogenetics or DNA barcoding. The existence of extremely similar species may cause local and global species diversity to be underestimated. Recognizing similar but distinct species is important for disease and pest control, and in conservation biology, although drawing dividing lines between species can be inherently difficult.

Underwater camouflage

Underwater camouflage is the set of methods of achieving crypsis—avoidance of observation—that allows otherwise visible aquatic organisms to remain unnoticed by other organisms such as predators or prey.

Camouflage in large bodies of water differs markedly from camouflage on land. The environment is essentially the same on all sides. Light always falls from above, and there is generally no variable background to compare with trees and bushes. Three main camouflage methods predominate in water: transparency, reflection, and counter-illumination. Transparency and reflectivity are most important in the top 100 metres of the ocean; counter-illumination is the main method from 100 metres down to 1000 metres; while camouflage becomes less important in the dark waters below 1000 metres.

Camouflage in relatively shallow waters is more like terrestrial camouflage, where additional methods are used by many animals. For example, self-decoration is employed by decorator crabs; mimesis by animals such as the leafy sea dragon; countershading by many fish including sharks; distraction with eyespots by many fish; active camouflage through ability to change colour rapidly in fish such as the flounder, and cephalopods including octopus, cuttlefish, and squid.

Urochondra

Urochondra is a genus of plants in the grass family. The only known species is Urochondra setulosa, native to northeastern Africa (Djibouti, Eritrea, Sudan, Somalia, Socotra) and southwestern Asia (Saudi Arabia, Oman, Yemen, northwestern India, and Sindh Province in Pakistan). The species grows in coastal sand dunes, salt marshes and estuaries.

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