The poison, a potent neurotoxin nerve poison , is accidentally ingested by the fishes in their food; such fish can no longer be used for either human or animal consumption. In contrast, lungs represent invaginations of the body surface. Because radicals are very reactive chemically, biological damage, such as attacks on DNA and proteins, results. Rats, however, have only a thin, weak longitudinal muscle which is unstriated where it joins the stomach. This significant extinction event affected the existence of many large animals with the Amphibians being among the worst affected populations. These particulate daughter nuclides are deposited on the respiratory tract when inhaled, the respiratory tract is irradiated by the alpha particles released, and lung cancer can result. However, the olm's skin retains the ability to produce melanin.
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Grassland is another common type of habitat for various snakes and lizards e. Garter Snakes, Fox Snakes. The vegetation in this habitat attracts many insects and rodents, making it easier for the Reptiles to catch prey. Swamps and large water bodies are inhabited by different Reptiles such as crocodiles, alligators, certain turtles and snakes. Animals like the Saltwater Crocodile and Marine Iguana inhabit seaside, travelling in and out of ocean as necessary.
Some species, such as the Sea Snakes and Sea Turtles, live in the ocean. They leave the waters only during the breeding season for laying eggs. These animals typically practice sexual reproduction with some specific species using asexual reproduction. Majority of these animals are amniotes, laying eggs covered with calcareous or leathery shells.
The eggs are generally laid in underground burrows dug by the females. The viviparity and ovoviviparity modes of reproduction are used by many species such as all boas and many vipers. However, the level of viviparity may vary with some species retaining their eggs until shortly before hatching while others nourish the eggs for supplementing the yolks. In some Reptile species, the eggs do not have any yolk with the adults providing all the necessary nourishment through a structure resembling the mammalian placenta.
Six lizard families and one snake family from the Squamata sub-group are known to be capable of agamogenesis or asexual reproduction. In some squamate species, the females are capable of giving birth to unisexual diploid clones of themselves. This type of asexual reproduction is known as parthenogenesis, occurring in various teiid lizards, geckos and lacertid lizards. Komodo dragons have reproduced through parthenogeny in captivitiy.
Like many mammals, birds and Amphibians, their embryonic life consists of an amnion, chorion, as well as an allantois. The incubation period may vary depending on the species and other factors like the temperature of the surroundings. Usually, hatchlings are able to take care of themselves almost immediately after coming out of the eggs.
But, the females of some species are known to protect their eggs and hatchlings. For example, female Pythons coil themselves around the eggs in order to protect them and regulate their temperature. Similarly, crocodiles are known to guard their young after the eggs hatch. TDSD or temperature-dependent sex determination can be observed in many Reptiles. In TDSD, the incubation temperature determines the sex of the offspring.
This characteristic is most commonly seen in crocodiles and turtles, but can also occur in tuataras and lizards. Different food habits can be observed between the four sub-groups. Animals belonging to the Crocodilia, Squamata and Sphenodontia sub-groups are carnivores, feeding on a wide range of prey from vertebrates to fish and insects.
The Testudines are herbivorous in nature with their diet comprising of fruits, shrubs, leaves, grass and marine plant materials like kelp and algae. The populations of many Reptilian species are facing rapid decline due to various factors like deforestation, loss of habitat, hunting for hide and to use them for edible purposes. Various Reptile populations have faced extinction in some specific locations. Due to these reasons, many species are protected by law in most of the countries where they are found.
Many Reptile species, including various lizards and turtles, are very popular all over the world as exotic pets. There is a widespread popularity even for the venomous snakes, especially among keen animal lovers. However, there is a common misconception that these animals do not need as much care as required by mammal pets. The truth is that, Reptiles need to be taken care of properly; otherwise, they cannot survive in captivity.
They should be kept in large tanks or cages where they can move freely. It is not advisable to keep more than one to two animals in a single enclosure. Their tanks should have suitable substrate and the animals should be provided with special heating lamps to allow them to bask and maintain their body temperature.
The temperature of the tanks needs to be monitored with the help of thermostats. Heating pads can also be used for this purpose. Custom made cages can also be used for this purpose as these mimic the natural habitat of a specific species in the best manner possible.
It is advisable to place stones, pieces of wood and small plants in their tanks to provide them with basking spots. Using a fogger to mist the enclosure may be advisable for certain species. When keeping snakes or poisonous lizards as pets, one should keep in mind not to handle them with bare hands.
One should do extensive research and read appropriate books regarding how to best take care of them before petting any Reptilian animal. These pets can survive as much as mammalian pets of similar size when properly taken care of. The Ringneck Snake is a species of small North American snakes that belong to the harmless colubrid family. The Banded Water Snake also called the southern water snake is a species of aquatic snake widely distributed in parts of the United States.
The Water Monitor is a species of giant monitor lizard found in parts of South and Southeast Asian countries. These semi-aquatic reptiles are common t. The African Fat-tailed Gecko is a species of lizard abundantly spread throughout the western regions of the continent of Africa. Often confused with i. Black caimans found in South America are the fourth largest extant member of the crocodile family.
These robust reptiles were almost hunted to extinct. Dwarf caimans found in South America are the smallest crocodilian belonging to the alligator family. It is one of the two members in its genus, the ot. The Emerald Tree Boa is a non-venomous boa species that is considered to be one of the most beautiful snakes in the world.
They are known for their cr. Common leopard geckos, also known as the spotted fat-tailed gecko, are terrestrial lizards found in Asia. Reproduction in whole or in part without permission is prohibited. Reptile Classification According to the taxonomy, they belong to the kingdom Animalia, phylum Chordata and the clade Amniota.
Olms are gregarious , and usually aggregate either under stones or in fissures. The scarcity of food makes fighting energetically costly, so encounters between males usually only involve display. This is a behavioral adaptation to life underground. Reproduction has only been observed in captivity so far.
No such changes have been observed in the females. The male can start courtship even without the presence of a female. He chases other males away from the chosen area, and may then secrete a female-attracting pheromone.
When the female approaches, he starts to circle around her and fan her with his tail. Then he starts to touch the female's body with his snout, and the female touches his cloaca with her snout. At that point, he starts to move forward with a twitching motion, and the female follows. He then deposits the spermatophore , and the animals keep moving forward until the female hits it with her cloaca, after which she stops and stands still.
The spermatophore sticks to her and the sperm cells swim inside her cloaca where they attempt to fertilize her eggs. The courtship ritual can be repeated several times over a couple of hours. Longevity is estimated at up to 58 years. When compared to the longevity and body mass of other amphibians, olms are outliers , living longer than would be predicted from their size.
Olms from different cave systems differ substantially in body measurements, color and some microscopic characters. Earlier researchers used these differences to support the division into five species, while modern herpetologists understand that external morphology is not reliable for amphibian systematics and can be extremely variable, depending on nourishment, illness, and other factors; even varying among individuals in a single population.
Proteus anguinus is now considered a single species. It has several features separating it from the nominotypical subspecies Proteus a.
These features suggest that the black olm has probably colonized underground habitats more recently and still retains some nontroglomorphic characteristics.
Heavy rains of Slovenia would wash the olms up from their subterranean habitat, giving rise to the folklore belief that great dragons lived beneath the Earth's crust, and the olms were the undeveloped offspring of these mythical beasts. In his book Valvasor compiled the local Slovenian folk stories and pieced together the rich mythology of the creature and documented observations of the olm as "Barely a span long, akin to a lizard, in short, a worm and vermin of which there are many hereabouts".
The first researcher to retrieve a live olm was a physician and researcher from Idrija , Giovanni Antonio Scopoli , who sent dead specimens and drawings to colleagues and collectors. Josephus Nicolaus Laurenti , though, was the first to briefly describe the olm in and give it the scientific name Proteus anguinus. It was not until the end of the century that Carl Franz Anton Ritter von Schreibers from the Naturhistorisches Museum of Vienna started to look into this animal's anatomy.
Soon, the olm started to gain wide recognition and attract significant attention, resulting in thousands of animals being sent to researchers and collectors worldwide. A Dr Edwards was quoted in a book of as believing that " In Marie von Chauvin began the first long-term study of olms in captivity. She learned that they detects prey's motion, panicked when a heavy object was dropped near their habitat, and develop color if exposed to weak light for a few hours a day, but could not cause them to change to a land-dwelling adult form, as she and others had done with axolotl.
More than twenty years later, the Research Group for functional morphological Studies of the Vertebrates in the Department of Biology Biotechnical Faculty, University of Ljubljana , is one of the leading groups studying the olm under the guidance of Boris Bulog. They were also introduced into the Hermannshöhle Germany and Oliero Italy caves, where they still live today. The olm was used by Charles Darwin in his famous On the Origin of Species as an example for the reduction of structures through disuse: Far from feeling surprise that some of the cave-animals should be very anomalous The olm is extremely vulnerable to changes in its environment, on account of its adaptation to the specific conditions in caves.
Water resources in the karst are extremely sensitive to all kinds of pollution. The reflection of such pollution in the karst underground waters depends on the type and quantity of pollutants, and on the rock structure through which the waters penetrate.
Self-purification processes in the underground waters are not completely understood, but they are quite different from those in surface waters. Among the most serious chemical pollutants are chlorinated hydrocarbon pesticides , fertilizers , polychlorinated biphenyls PCBs , which are or were used in a variety of industrial processes and in the manufacture of many kinds of materials; and metals such as mercury, lead, cadmium, and arsenic.
All of these substances persist in the environment, being slowly, if at all, degraded by natural processes. In addition, all are toxic to life if they accumulate in any appreciable quantity. Slovenian caves became famous for the animals they contained and which could not be found elsewhere.
The olm is illegally taken by collectors. These areas of conservation form the Natura network. Appendix IV further defines "animal and plant species of community interest in need of strict protection". Hunting or keeping a limited number of olm is allowed only under strictly controlled circumstances, determined by local authorities.
The olm was first protected in Slovenia in along with all cave fauna, but the protection was not effective and a substantial black market came into existence. In it was placed on a list of rare and endangered species. This list also had the effect of prohibiting trade of the species.
After joining the European Union , Slovenia had to establish mechanisms for protection of the species included in the EU Habitats Directive. The olm is included in a Slovenian Red list of endangered species. Conservation status in Bosnia and Herzegovina and Montenegro has not yet been defined.
On the IUCN Red List , the olm is listed as vulnerable because of its fragmented and limited distribution and ever-decreasing population. The olm is a symbol of Slovenian natural heritage. The PCBs have been extensively used as a cooling agent in electrical transformers.
It appears that humans are more resistant to the toxicity of these compounds than are some species of laboratory animals, and the main toxic effect observed in humans is chloracne, similar to juvenile acne.
Examples of metal compounds toxic to humans include manganese , lead, cadmium, nickel, and arsenic compounds, beryllium oxide, and the elemental vapours, inorganic salts, and organic compounds of mercury. Mercury can also damage the brain, leading to behavioral changes; however, mercury is also toxic to the peripheral nervous system, causing sensory and motor symptoms. In addition, mercury is toxic to the kidney. Methyl mercury is especially toxic to the developing brain of a fetus.
Lead is probably the most ubiquitous metal poison. Used for numerous purposes, before World War II it was a major constituent in paint, and it has been used in gasoline. Like mercury, lead is toxic to the nervous system and kidney Table 2 , but its toxicity is age-dependent. In children, the blood—brain barrier is not fully developed, and more lead enters the brain. The extent of damage depends on the exposure; at lower levels of exposure, small decreases in intelligence and behavioral changes may result, whereas high levels result in severe brain damage and death.
In adults, lead tends to cause paralysis or weakness, indicative of peripheral nervous system damage. In acute cadmium poisoning by ingestion, irritation of the gastrointestinal tract is the major toxicity, causing nausea, vomiting, diarrhea, and abdominal cramps.
With chronic exposure by inhalation, however, kidneys and lungs are the target organs. Arsenic compounds damage many organs. They cause skin lesions, decrease in heart contractility, blood vessel damage, and injuries of the nervous system, kidney, and liver.
Arsenic compounds also produce skin and lung tumours in humans. Certain nickel and hexavalent chromium compounds, as well as beryllium oxide, are toxic to the lungs and can cause lung cancer. Acids , such as sulfuric and hydrochloric acids, and strongly alkaline compounds, such as sodium hydroxide, and potassium hydroxide are corrosive to tissues on contact and can cause severe tissue injuries Table 2.
Sulfuric acid , sodium hydroxide, and potassium hydroxide are active ingredients in drain cleaners, the ingestion of which can cause severe chemical burns of the mouth and esophagus. Hypochlorites are often used as bleaching agents. In low concentrations, as in household bleaches, hypochlorites have little toxicity but may be irritating to tissues; they can, however, be corrosive at high concentrations. Cyanide ions poison the oxidative metabolic machinery of cells so that insufficient energy is generated.
The effect is as if there were a lack of oxygen for the cells, even though there is plenty of oxygen in the blood. Hydrogen sulfide and chlorine are highly irritating to the respiratory tract, with pulmonary edema the major toxic effect.
Chronic fluoride poisoning is called fluorosis , which is characterized by tooth mottling and increased bone density. These changes, especially of the bone, are related to a change in body calcium caused by fluoride. Silica and asbestos remain in the lungs for long periods of time, and both produce lung fibrosis Table 2.
In addition, asbestos is a well-known human carcinogen. Sulfur dioxide , an acidic pollutant, irritates the respiratory tract. It causes violent coughing when it irritates the throat, and may result in shortness of breath, lung edema, and pneumonia when it reaches the lungs.
Both ozone and nitrogen oxides are oxidizing pollutants. Like sulfur dioxide, they cause respiratory irritation; ozone and nitrogen oxides, however, tend to be more irritating to the lung than to the upper respiratory tract. Carbon monoxide , an asphyxiating pollutant, binds to hemoglobin more strongly than oxygen does. Such binding produces a hemoglobin molecule that cannot carry its normal load of four oxygen molecules.
In addition, once carbon monoxide is bound, the hemoglobin molecule does not as readily release to the tissues the oxygen molecules already bound to it. Therefore, tissues lack oxygen, resulting in many toxic effects. Because the brain is especially sensitive to the lack of oxygen, most of the symptoms are neurological.
Lack of oxygen is termed asphyxiation, and thus carbon monoxide is an asphyxiant. Poisoning with drugs predominantly involves oral exposures. With drugs, therefore, irritation of the respiratory tract is rare, but anorexia, nausea, and vomiting resulting from gastrointestinal irritation are common. Painkillers analgesics are the most commonly used drugs and account for many poisoning cases.
Examples include aspirin and acetaminophen. Aspirin interferes with the oxidative burning of fuel by cells. To get energy, the cells switch to a less efficient way of burning fuel that does not use oxygen but generates a lot of heat. Increased perspiration develops to counteract a rise in body temperature, leading to dehydration and thirst.
Aspirin also alters the pH in the body, affecting the central nervous system Table 3. The major toxicity of acetaminophen is liver damage. The major toxicity from narcotic analgesics, like morphine , is depression of the central nervous system, especially the brain centre controlling respiration. The cause of death in morphine overdoses is usually respiratory failure.
Benzodiazepines , such as diazepam, clonazepam, and chloridazepoxide, have a wide margin of safety when used at prescribed doses. Their major toxic effect is depression of the central nervous system, which results in muscular incoordination and slurred speech Table 3.
For sleeping pills containing barbiturates , chloral hydrate , paraldehyde, and meprobamate, however, the margin of safety is much narrower, and the major toxicity is severe depression of the central nervous system, leading to respiratory and cardiovascular failure Table 3.
Like benzodiazepines, antipsychotic drugs such as chlorpromazine, perphenazine, and haloperidol have a relatively large therapeutic index, rarely causing fatalities. They occasionally may block the action of the parasympathetic and sympathetic nervous systems and thus produce such undesired effects as dry mouth and blurred vision from the former and a drop in blood pressure upon standing in the latter Table 3.
Nasal decongestants, antihistamines, and cough medicine , which are found in over-the-counter preparations for treating the symptoms of colds, have a low potential to produce toxicity. Nasal decongestants, such as ephedrine , mimic the action of epinephrine by stimulating the sympathetic nervous system, and consequently, an overdose of ephedrine produces symptoms related to stimulation of the sympathetic and central nervous systems Table 3.
Depression of the central nervous system and parasympathetic blockade are two common toxicities of antihistamines such as diphenhydramine Table 3. Depression of the central nervous system is also the major toxicity of dextromethorphan and codeine, both used to suppress coughing. Benzoyl peroxide and parabens applied to the skin may be toxic. Among the most toxic antiseptics are hexachlorophene, benzalkonium, and cetylpyridinium chloride, any of which can cause injuries to internal organs.
Systemic toxicity double vision, drowsiness, tremor, seizures, and death with hexachlorophene is more likely to occur in babies because the relatively thin stratum corneum of their skin is highly permeable. Deficiencies as well as excesses of vitamins are harmful.
Excessive vitamin A retinol, or retinoic acid , known as hypervitaminosis A , can result in skin lesions, edema, and liver damage. Overconsumption by Alaskan natives of polar bear liver, a rich source of vitamin A, has produced acute toxicities, characterized by irresistible sleepiness and severe headaches. Chronic poisoning with vitamin A can cause neurological symptoms, including pain , anorexia, fatigue, and irritability Table 3.
Excess vitamin C can lead to kidney stones. Apart from irritation of the skin and respiratory tract, the most severe toxicity of vitamin K excess is the increased destruction of red blood cells, which leads to anemia and the accumulation of bilirubin, one of the products of hemoglobin degradation Table 3.
Excess bilirubin can result in brain damage in newborns, a condition known as kernicterus. Because the blood—brain barrier is not well developed in newborns, bilirubin enters and damages the brain. Due to the blood—brain barrier, kernicterus is not seen in adults.
Iron , a metal that is necessary for normal health, can also cause poisoning. The toxicity of iron is a result of its corrosive action on the stomach and intestine when present in high concentrations. As a result, intestinal bleeding occurs, which can lead to the development of shock. Among tricyclic antidepressants, amitriptyline and imipramine account for most of the fatal cases of poisoning. These drugs have a number of effects, including blockage of the parasympathetic system and damage to the central nervous system, the latter producing symptoms such as fatigue, weakness, lowered body temperature, seizures, and respiratory depression Table 3.
Death is usually caused by damage to the heart. Lithium salts, used to treat manic depression, have a relatively low therapeutic index. Mind-altering drugs commonly abused include amphetamines, cocaine , phencyclidine, heroin , and methaqualone. These drugs are primarily toxic to the central nervous system; amphetamine and cocaine cause stimulation of the system hallucinations and delirium , and heroin causes the depression of the system depressed respiration and coma.
In contrast, phencyclidine and methaqualone are biphasic, producing first depression drowsiness and then stimulation of the central nervous system delirium and seizures.
Amphetamines also affect the gastrointestinal tract anorexia, nausea, vomiting, diarrhea and stimulate the cardiovascular system increased blood pressure and heart rate, palpitations, and abnormal heart rhythm.
In addition to hallucinations and delirium, cocaine causes euphoria, sexual arousal, confusion, and sympathetic stimulation. Phencyclidine is also known to cause aggression and psychotic behaviour, while methaqualone produces excessive dreaming and amnesia. Digitalis overdose usually begins with gastrointestinal symptoms, such as anorexia, nausea, and vomiting, followed by sensory symptoms, such as pain and visual disturbances Table 3.
There are also effects on the central nervous system, characterized by delirium and hallucinations. The major toxicities of beta blockers e. Sympathetic stimulation relaxes smooth muscles in the tracheobronchial wall and makes the heart beat faster and more forcefully.
Blockage produced by propranolol or metoprolol can cause bronchoconstriction and heart failure Table 3. Drugs for treating asthma, such as theophylline and aminophylline, are structurally similar to caffeine. Like caffeine, which is a stimulant, theophylline and aminophylline also stimulate the central nervous system. Therefore, excitement, delirium, rapid breathing, increased heart rate, and seizures occur with an overdose. With excessive stimulation of the heart, palpitations and irregular heart rhythm arrhythmia can result, leading to sudden death.
Biotoxins can be conveniently grouped into three major categories: The geographic distribution of poisonous organisms varies greatly; poison-producing microorganisms tend to be ubiquitous in their distribution. Poisonous plants and animals are found in greatest abundance and varieties in warm-temperate and tropical regions. Relatively few toxic organisms of any kind are found in polar latitudes. Knowledge of the evolutionary significance and development of most biotoxins is largely speculative and poorly understood.
In some instances they may have developed during the evolution of certain animal species as part of the food procurement mechanism e. Biotoxins may also function as defensive mechanisms, as in some snakes, fishes, arthropods e.
The defense may be quite complex—as in the protection of territorial rights for reproductive purposes—and inhibitory or antibiotic substances may be produced that result in the exclusion of competitive animal or plant species. Certain marine organisms and terrestrial plants may release into the water, air, or soil inhibitory substances that discourage the growth of other organisms; well-known examples include the production of antibiotic substances by microorganisms.
Similar chemical-warfare mechanisms are used in battles for territorial rights among the inhabitants of a coral reef , a field, or a forest. Thus biotoxins play important roles in the regulation of natural populations. Of increasing interest has been the discovery that certain substances, which may be toxic to one group of organisms, may serve a vital function in the life processes of the source organism.
Venom-producing animals and stinging and dermatogenic i. Biotoxic agents may produce their injurious effects by becoming involved in the food supply; ingestion of a poisonous microbial organism, plant, or marine animal or one of their toxic by-products may cause intoxication. An example is that of the shore fishes of many tropical islands; otherwise valuable food fishes are frequently contaminated by a poison called ciguatoxin.
The poison, a potent neurotoxin nerve poison , is accidentally ingested by the fishes in their food; such fish can no longer be used for either human or animal consumption. Some of the effects produced by biotoxins on humans are of an acute nature, and the injuries they cause are readily discernible.
The effects of some of the mycotoxins poisons produced by fungi and poisons produced by plants, however, are long-term and chronic; they result in the development of cancerous growths and other chronic degenerative changes that are sometimes difficult to detect.
Microbial poisons are produced by the Monera bacteria and blue-green algae and Protista algae, protozoa, and others , and the Fungi. Various classifications have been proposed for the microbial poisons, but none is entirely satisfactory. The problems encountered when dealing with these organisms result from a lack of precise knowledge concerning their biological nature and their phylogenetic relationships; in addition, their poisons show great diversity and chemical complexity.
The following outline, however, is useful in dealing with this subject. The main differences in these toxins lie in their chemical structure. Poisonous proteins from bacteria are sometimes referred to as bacterial exotoxins. The exotoxins are generally produced by gram-positive organisms i. The exotoxins usually do not contain any nonprotein substances, and most are antigenic ; i. The exotoxins may appear in the culture medium in which the bacteria are growing during the declining phases of growth; in some cases they are released at the time of normal destruction of the cells after death autolysis.
The exotoxins are less stable to heat than are the endotoxins, and they may be detoxified by agents that do not affect endotoxins. They are more toxic than endotoxins, and each exotoxin exerts specific effects which are collectively known as pharmacological properties. Exotoxins are neutralized by homologous antibodies— i. Endotoxins are antigens composed of complexes of proteins, polysaccharides large molecules built up of numerous sugars , and lipids fats.
The protein part determines the antigenicity, or quality of being reacted against as a foreign substance in a living organism. The polysaccharide part determines the immunological specificity, or limitations on the types of antibodies that can react with the endotoxin molecule and neutralize it the immunological reaction.
Some of the lipids possibly determine the toxicity. Endotoxins are derived from the bacterial cell wall and, when cells are grown in culture , are released only on autolysis. Endotoxins are not neutralized by homologous antibodies and are relatively stable to heat; all of them have the same pharmacological properties.
The Cyanobacteria, or blue-green algae , are among the most primitive and widely distributed of all organisms.
They have extreme temperature tolerances. Some strains of a species are toxic; other strains of the same species are not. Water blooms of blue-green algae have been responsible for the death of fishes, waterfowl, cattle, horses, swine, and other animals. Blue-green algae have also been implicated as causes of human intoxications. Fungi are plantlike members of the kingdom Fungi Mycota that do not contain chlorophyll. A significant number are known to produce poisons of various types.
Toxic fungi can be roughly divided into two main categories on the basis of their size: The toxic microfungi are members of one of two classes: Ascomycetes , or the sac fungi, and the Deuteromycetes , or the imperfect fungi i. The large toxic mushrooms, or toadstools, are mostly members of the class Basidiomycetes , although some Ascomycetes, such as the poisonous false morel Gyromitra esculenta , may attain a size as large as some of the mushrooms.
The ability of certain fungi, such as ergot Claviceps purpurea and some mushrooms, to produce intoxication has long been known. During the 19th century it was recognized that molds are responsible for such diseases as yellow-rice toxicoses in Japan and alimentary toxic aleukia in Russia.
The eruption of so-called turkey X disease in England in and the resulting discovery of the substance known as aflatoxin see Table 4 stimulated study of the subject of mycotoxicology. Poisonous mushrooms , or toadstools as they are commonly called, are the widely distributed members of the class Basidiomycetes, although only a few are known to be poisonous when eaten see Table 5 ; some of the poisons, however, are deadly.