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The "resident fish doctor and dentist on the reef is the bluestreak cleaner wrasse ". As the bluestreak snacks on the parasites it gently tickles its client.
This seems to bring the larger fish back again for regular servicing. But other parasites find the mucus itself good to eat. So lizardfish visit the cleaner wrasse, which clean the parasites from the skin, gills and mouth. Two small cleaner wrasses servicing a larger fish at a cleaning station The reef lizardfish secretes a mucus coating which reduces drag when they swim. But some parasites find the mucus good to eat. Herbivores[ edit ] Surgeonfish are among the most common of coral reef herbivoresoften feeding in shoals.
This may be a mechanism for overwhelming the highly aggressive defence responses of small territorial damselfishes that vigorously guard small patches of algae on coral reefs. The four largest groups of coral reef fishes that feed on plants are the parrotfishesdamselfishesrabbitfishesand surgeonfishes. All feed primarily on microscopic and macroscopic algae growing on or near coral reefs. Algae can drape reefs in kaleidoscopes of colours and shapes.
Algae are primary producerswhich means they are plants synthesising food directly from solar energy and carbon dioxide and other simple nutrient molecules.
Without algae, everything on the reef would die. One important algal group, the bottom dwelling benthic algae, grows over dead coral and other inert surfaces, and provides grazing fields for herbivores such as parrotfish. They are large herbivores that graze on the algae that grows on hard dead corals. Equipped with two pairs of crushing jaws and their beaks, they pulverize chunks of algae-coated coral, digesting the algae and excreting the coral as fine sand.
They have evolved to find protection by schoolingsometimes with other species like shoaling rabbitfish. Spinefoot rabbitfish are named for their defensive venomous spines, and they are seldom attacked by predators.
Spines are a last-ditch defence.
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It is better to avoid predator detection in the first place, and avoid being thrust into risky spine-to-fang battles.
So rabbitfish have also evolved skilful colour changing abilities. They are small, typically five centimetres two inches long.
Many species are aggressive towards other fishes which also graze on algae, such as surgeonfish. Surgeonfish sometimes use schooling as a countermeasure to defensive attacks by solitary damselfish. Ferocious barracuda prey in schools on parrotfish. Coral rabbitfish have venomous spines which they erect if threatened. Schooling spinefoot rabbitfish are often joined by defenceless parrotfish. Symbiosis[ edit ] A hawkfishsafely perched on Acroporasurveys its surroundings Symbiosis refers to two species that have a close relationship with each other.
The relationship can be mutualisticwhen both species benefit from the relationship, commensalisticwhen one species benefits and the other is unaffected, and parasitisticwhen one species benefits, and the other is harmed.
An example of commensalism occurs between the hawkfish and fire coral. Thanks to their large, skinless pectoral fins, hawkfish can perch on fire corals without harm. Fire corals are not true coralsbut are hydrozoans possessing stinging cells called nematocysts which would normally prevent close contact. The protection fire corals offer hawkfish means the hawkfish has the high ground of the reef, and can safely survey its surroundings like a hawk.
Hawkfish usually stay motionless, but dart out and grab crustaceans and other small invertebrates as they pass by. They are mostly solitary, although some species form pairs and share a head of coral. A more bizarre example of commensalism occurs between the slim, eel-shaped pinhead pearlfish and a particular species of sea cucumber. The pearlfish enters the sea cucumber through its anus, and spends the day safely protected inside the seacucumbers alimentary tract.
At night it emerges the same way and feeds on small crustaceans. The tentacles of sea anemones bristle with tiny harpoons nematocysts primed with toxinsand are an effective deterrent against most predators.
Saddle butterflyfish usually flutter gently rather than swim. But in the presence of their preferred food, sea anemones, this gentleness disappears, and the butterflyfish dash in and out, ripping off the anemone tentacles. Saddle butterflyfish are resistant to the sea anemone toxin.
Yellowtail clownfish with sea anemone Common clownfish guarding their sea anemone home Monogenean parasites of the genus Pseudorhabdosynochus arrows on the gill filament of a grouper. There is a mutualistic relationship between sea anemones and clownfish. This gives the sea anemones a second line of defence. They are guarded by fiercely territorial clownfishwho are also immune to the anemone toxins. To get their meal, butterflyfish must get past these protective clownfish who, although smaller, are not intimidated.
An anemone without its clownfish will quickly be eaten by butterflyfish. As a further benefit to the anemone, waste ammonia from the clownfish feed symbiotic algae found in the anemone's tentacles. Parasites of coral reef fish include nematodesPlatyhelminthes cestodesdigeneansand monogeneansleechesparasitic crustaceans such as isopods and copepods   and various microorganisms such as myxosporidia and microsporidia.
Some of these fish parasites have heteroxenous life cycles i. The high biodiversity of coral reefs increases the complexity of the interactions between parasites and their various and numerous hosts.
Numerical estimates of parasite biodiversity have shown that certain coral fish species have up to 30 species of parasites.
Results obtained for the coral reef fish of New Caledonia suggest that extinction of a coral reef fish species of average size would eventually result in the co-extinction of at least ten species of parasites. Toxic fish are fish which contain strong toxins in their bodies. There is a distinction between poisonous fish and venomous fish.
Both types of fish contain strong toxins, but the difference is in the way the toxin is delivered. Venomous fish deliver their toxins called venom by biting, stinging, or stabbing, causing an envenomation.
Venomous fish don't necessarily cause poisoning if they are eaten, since the venom is often destroyed in the digestive system.
Coral reef fish - Wikipedia
By contrast, poisonous fish contain strong toxins which are not destroyed by the digestive system. This makes them poisonous to eat. Venomous fish tend to be either very visible, using flamboyant colours to warn enemies, or skilfully camouflaged and maybe buried in the sand. Apart from the defence or hunting value, venom might have value for bottom dwelling fish by killing the bacteria that try to invade their skin.
Few of these venoms have been studied. They are a yet to be tapped resource for bioprospecting to find drugs with medical uses. It is an ambush predator that sits on the bottom waiting for prey to come close. It does not swim away if disturbed, but erects 13 venomous spines along its back. For defence, it can shoot venom from each or all of these spines. Each spine is like a hypodermic needle, delivering the venom from two sacs attached to the spine. The stonefish has control over whether to shoot its venom, and does so when provoked or frightened.
Despite its formidable defence, the stonefish does have predators.
Uranium Thorium Dating
Some bottom feeding rays and sharks with crushing teeth feed on them, as does the Stokes' seasnake  The most venomous known fish is the reef stonefish. Like many other apex reef fish, the giant moray can cause ciguatera poisoning if eaten.
The stargazer buries itself in sand and can deliver electric shocks as well as venom.
Although not native to the US coast, lionfish have appeared around Florida and have spread up the coast to New York. They are attractive aquarium fish, sometimes used to stock ponds, and may have been washed into the sea during a hurricane. Lionfish can aggressively dart at scuba divers and attempt to puncture the facemask with their venomous spines. The toxin is only dangerous when ingested, so there's no immediate harm to divers.
However, predators as large as nurse sharks can die as a result of eating a trunkfish. Many of the Caribbean groupers and the barracuda for example may contain enough of this toxin to cause severe symptoms in humans who eat them. What makes the situation particularly dangerous is that such species may be toxic only at certain sizes or locations, making it difficult to know whether or when they are or are not safe to eat.
In some locations this leads to many cases of ciguatera poisoning among tropical islanders. It is a delicacy in some cultures the venom is destroyed when it is cookedand can be found for sale in some fish markets with the electric organ removed.
They have been called "the meanest things in creation". Like many other apex reef fish, it is likely to cause ciguatera poisoning if eaten. Coral reefs in the Indo-Pacific are dominated by whitetipblacktip and grey reef shark.
Coral reefs in the western Atlantic Ocean are dominated by the Caribbean reef shark. These sharks are all species of requiem sharkand all have the robust, streamlined bodies that are typical of the requiem shark. They are fast-swimming, agile predators that feed primarily on free-swimming bony fishes and cephalopods.
Other species of reef sharks include the Galapagos sharkthe tawny nurse shark and hammerheads. The whitetip reef shark is a small shark usually less than 1. It is associated almost exclusively with coral reefs where it can be encountered around coral heads and ledges with high vertical relief, or over sandy flats, in lagoonsor near drop-offs to deeper water.
Unlike other requiem sharks, which usually rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gills and lie still on the bottom.
Coral reef fish
They have slender, lithe body, which allows them to wriggle into crevices and holes and extract prey inaccessible to other reef sharks. On the other hand, they are rather clumsy when attempting to take food suspended in open water. The whitetip reef shark does not frequent very shallow water like the blacktip reef shark, nor the outer reef like the grey reef shark.
An individual shark may use the same cave for months to years. The daytime home range of a whitetip reef shark is limited to about 0. Applications of U-series geochronology The U-series chronometers can be used to date a wide variety of igneous, marine, terrestrial, and skeletal materials.
A detailed discussion of every application is beyond the scope of this introduction, so we focus here on just the most common ones.Corals And Fins
For instance, U-series dating of coral skeletons that grew in a specific environment and depth range relative to sea level can be used to reconstruct the history of sea level changes.
Fossil corals can exhibit some open-system behavior as they age, depending in part on the conditions they are in, such as diagenesis of coralline aragonite to calcite by meteoric water. Various methods have been proposed to mathematically correct or adjust for non-closed system behavior in corals to deduce an age.
Although these methods are not universally accepted as robust, they do provide indications about relative ages and likely age assignments to important paleoclimate horizons, such as glacial and interglacial epochs. In a similar fashion to corals, calcium carbonate cave deposits formed slowly over time by precipitation from ground water can be dated to reconstruct sea level changes e.
Unlike coralline aragonite, dense calcite cave formations are not as susceptible to diagenesis and have greater potential for preservation through time. Here we use Th as a normalizing isotope for U and Th in Th-U dating and, because there is no longer-lived Ra isotope, we use chemically analogous Ba as a normalizer of Th and Ra in Ra-Th dating. While such ages are often used to infer when an eruption occurred, the event that is actually being dated is not the eruption per se, but the formation of minerals in a cooling magma, which happened sometime earlier.
A modification of the internal isochron approach uses Ra-Th dating of minerals in historical eruptions to deduce the timescale over which the minerals themselves grew by comparing their ages to the known eruption age. Another volcanic rock dating method using these isotopes looks at variations in daughter-parent isotope ratios between the whole-rock compositions of volcanic units of different ages at one volcano, and through a series of assumptions deduces the relative time between eruptions.
This method is particularly useful for dating submarine lavas, where traditional radiocarbon methods dating of eruption—related charcoal is not possible. In addition, there are important volcanic applications of shorter lived U-series isotopes Pb 22 year half-life and Po day half-lifeexpressed as the RaPb and PbPo systems that are very useful for determining recent eruption chronologies and rapid mineral formation rates, based for instance on volatility differences between Po and Pb, and chemical differences between Ra and Pb as well as the volatility of very short-lived isotopes between Ra and Pb such as Rn.
The PbPo method was used for instance, to produce the very first eruption ages of suspected recent submarine eruptions on mid-ocean ridges, providing the final evidence for new crust generation there, as predicted by plate tectonic theory a half century before. Contact details of some of the laboratories offering U-series geochronology in the US and elsewhere are listed below.
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Andrea Dutton, University of Florida Prof. Ken Sims, University of Wyoming Prof. Gideon Henderson, University of Oxford Prof. Mary Reid, Northern Arizona Univ. Yusuke Yokoyama, University of Tokyo Prof. Earth and Planetary Science Letters, U-Th dating of corals to calibrate the C timescale. Fossil corals from Barbados dated by alpha-counting to test Milankovitch hypothesis.
U-Th dating of deep sea corals. Geochimica et Cosmochimica Acta, Pioneering work using mass spectrometry to date fossil corals. Protactinium dating of carbonates. Describes open-system U-series geochemical arrays in Barbados fossil corals. Dating of aragonitic sediments on the Bahamas Bank. U-series dating of cave deposits and continental carbonates Paired U-Th and C dating to resolve atmospheric C concentration.