Venomous Animals

VENOMOUS ANIMALS are characterized by the permanent or periodic presence in their organisms of substances possessing toxic properties with respect to creatures of another species. It is necessary to distinguish strictly venomous animals from accidentally toxic creatures, which, due to various circumstances, may become individual specimens of a harmless species. Examples of true venomous animals include the bee, scorpions, the viper, etc. Individual specimens of sturgeon (such as sevruga, sturgeon, etc.) can also acquire toxic properties; such "accidentally" venomous fish can cause fatal poisoning in humans due to the action of "fish poison." Comparative toxicological experiments provide rich material for judging the relativity of toxic properties, since different animal species may react differently to the same toxic substance. Strychnine is a deadly poison to mammals, whereas the hornbill feeds on Nux vomica seeds; bee stings are very painful to humans, horses, and other animals, while the frog and the European bee-eater readily devour bees. The primary factor determining poisoning by venomous animals is the dose of venom introduced into the organism. Not every viper bite ensures the introduction of the same amount of venom. Here, not only the age of the snake plays a role (a small viper naturally yields less venom than a large one), but even such a fact as the duration of the preceding period of rest of the venom glands. Various states of venomous animals can affect venom production. For example, the spectacled cobra after shedding becomes ten times more venomous than before. An important influence on the outcome of poisoning is exerted by the site of entry of the poison into the organism, i.e., the barrier that the poison encounters. The intact human skin is impermeable to snake venom. When its integrity is broken (snake bite, puncture of a poisoned arrow tip), the poison enters the blood and produces the pharmacological effect characteristic of it. The same poison, when swallowed into the stomach, has no effect because it is neutralized during passage through the liver barrier. But even with typical entry of the poison into the organism, the results can be different. If the poison enters a site poor in blood vessels, its absorption is slower, which is reflected in the general reaction of the organism up to the manifestation of resistance to poisoning, completely unrelated to immune properties. In particular, pigs are resistant to rattlesnake bites, which is explained by the presence under the skin of a thick layer of fat, which is poor in vessels; in the blood of pigs, however, there are no antitoxic principles; at the same time, the blood serum of the mongoose and hedgehog contains substances that bind snake venom in a certain ratio. Among the characteristics of the poisoned organism of a venomous animal, the body size (resp. age) comes to the fore (besides its species properties); therefore, as with other poisons, the venoms of venomous animals are characterized by the value of the toxic or lethal dose calculated per 1 kg of weight of a human or some animal. Individual characteristics of the organism in turn can influence the course and outcome of poisoning by venomous animals. There are cases of idiosyncrasy or, conversely, congenital immunity or acquired non-susceptibility to venom, in particular after successfully surviving poisoning. Such accidental circumstances as the state of intoxication and other moments cannot fail to have an effect on the action of venomous animals. Knowing how venomous animals poison humans is practically important for devising preventive measures against possible poisonings. The toxic properties of many venomous animals are more or less easily discovered under natural conditions. A hornet stings a person; a person eats a poisonous fish, and so on. In both cases, poisoning is the result of ordinary "everyday" relationships, and the toxicity of such animals can be considered overt; at the same time, there are many facts convincing us of the presence of toxic properties that under natural conditions find no overt application by venomous animals in relation to the outside world and are discovered only during experimental research. For example, the blood serum of an eel or skate (Raja) is toxic when injected into various animals. Venomous animals possessing this sort of toxicity are called covertly venomous. Venomous animals either possess special venom apparatuses or various parts of their body (e.g., fish ovaries, blood, etc.) turn out to be toxic. Venomous organs in turn are either modifications of organs normally existing in a given group of animals (e.g., the salivary glands of insects, distinguished by the toxicity of their bite) or they arose in the process of phylogenesis of venomous animals as a "new acquisition" (e.g., the poison glands of scorpions). The venomous organs of animals consist of a poison-producing gland (poison gland) and a piercing (wounding) apparatus by means of which the integrity of the integuments of a human or animal is violated and the poison is introduced into the thickness of the tissues (resp. into the blood); however, many venomous animals possess only poison glands, lacking any wounding "devices" (e.g., ants with poison glands and a reduced sting). In connection with this, one speaks of "armed" and "unarmed" venomous animals. I. Venomous animals with venomous organs. Already some protozoa possess toxic organelles. Thus, in the cortical layer of the protoplasm of various infusoria, columnar formations called trichocysts are embedded. Upon various irritations, the infusorium reflexively "shoots" trichocysts, which pierce attacking predatory infusoria Didinium (Fig. 1) and by their toxic effect can force them to drop their prey. For coelenterates, stinging cells (Fig. 2), embedded in the ectoderm of these animals, are very characteristic. In such a cell there is a capsule with a spiral thread inverted inside. The latter, when the stinging cell operates, is thrown outward (Fig. 3) and pierces the integuments of the organism that has touched the coelenterate. The latter experiences either a sensation of a burn or

Figure 1. Paramecium discharging a cloud of trichocysts upon being attacked by a predatory infusorium Didinium.

Figure 2. Stinging cells of Hydra, on the right in a discharged state: 1-cnidocil; 2-capsule; 3-supporting rods; 4-nucleus; 5-spiral thread in protoplasm.

is paralyzed and becomes the prey of the coelenterate. Thus hydra catches small crustaceans, and sea anemones capture small fish. The effect of the "burning" action is especially great upon contact of the human body with siphonophores (Physalia); the human reaction to jellyfish venom can be intensified due to a state of allergy. Sponge divers, due to frequent contact with sea anemones sitting on sponges torn off by hand, sometimes contract an occupational disease consisting of ulceration of the fingers and general intoxication. In stinging cells

Stinging capsules of the Black Sea Actinia equina. Both the secretory part and the wounding apparatus are localized in the same cell. Animals with poison glands and a special wounding apparatus have differently structured venom apparatuses. This category of venomous animals includes: 1) stinging caterpillars of butterflies with twisted chitinous hairs, e.g., fragile barbed hairs of the caterpillars of the brown-tail moth. The cavity of the hairs contains a poisonous secretion (Fig. 4) secreted by special glandular cells of the hypodermis at the base of the hairs.

Figure 4.

FIG. 5.

Figure 4. Diagram of the structure of a venomous hair (1) of an insect: 2-cavity of the hair with secretion; 3-glandular cell; 4-hypodermis; 5-chitin. Figure 5. Venom apparatus of Xylocopa: 1-acid glands; 2-their common duct; 3-alkaline gland; 4-sting; 5-reservoir outlet duct; 6-reservoir. The latter are extremely fragile, easily breaking off even when the caterpillar moves, and are carried away by the wind. When inhaled, they pierce the mucous membranes of the nose and mouth, enter the eyes, and cause various disorders (stomatitis, aphthae, conjunctivitis). When caterpillars are grasped with hands, they pierce the skin and cause the formation of blisters. In dry hairs, venom can persist for over six

Figure 6.

Stingray Trygon pastinaca of seven years (E. Pavlovsky and A. Shtein). Such poisonous caterpillars are also found in the yellow-tail moth (Porthesia similis), and the pine processionary moth (Thaumetopoea processionea) has acquired special renown. 2) Multicellular sacculated glands with a special sting are possessed by scorpions. Their slender postabdomen ("tail") ends in a chitinous vesicle (ampulla) inside of which lie two poison glands opening into a sharp, hard, curved sting (see Scorpions, Fig. 2, B). 3) In Hymenoptera, only females possess venom organs (Fig. 5) because the venom apparatus is a modified part of the female reproductive organs. Its secretory part is represented by two glands—a tubular one (with a reservoir) secreting an "acid" secretion, and a sacculated one producing an alkaline secretion. The proportions in the degree of development of these parts are very diverse, depending on the species. The venom is a mixture of both secretions which mix upon exiting to the exterior. These glands are homologous to the accessory glands of the female reproductive organs. The piercing part is represented by a sting—a complex of chitinous parts that are homologs of the ovipositor. Well-known examples of venomous Hymenoptera are the honeybee, bumblebees, wasps, and others. The lethal dose of bee venom for an adult is considered to be about 500 simultaneous bee stings. Bee venom is characterized by: burning local pain, swelling of the stung place,

Figure 7. Trachinus draco.

disturbances of cardiac activity, nausea, vomiting, and others. When stung by a hornet, massive edemas develop. Bee venom has been tried for the treatment of rheumatism, lumbago, sciatica, gout, dropsy, and others, by subjecting patients to bee stings from one to 50–100 per day (with sequential increases). Such "Bienenstichkuren" yield certain results, but it is necessary to reckon with the side symptoms of the treatment caused by the action of this venom. 4) Some vertebrates possess cutaneous poison glands armed with a stinging apparatus in the form of bony spines or fin rays. Thus, the stingray (Fig. 6) (Trygon pastinaca, Black Sea) has a powerful spine on its tail, serrated on the sides, with two longitudinal grooves filled with highly developed clusters of unicellular skin glands of the deep layers of the epidermis; their secretion gets into the wound inflicted by the tail spine. A more perfect venom apparatus is possessed by some spiny-finned fishes, such as Scor*

Figure 8. Diagram of the structure of the spine of Scorpaena porcus and Trachinus draco (Black Sea) (Fig. 7), Sebastes norwegicus (Murman), Pterois volitans, Synanceia, and others. Among catfish, a similar apparatus is possessed by Plotosus and others. The scheme of the structure of the fish venom apparatus boils down to the following. The sharp spiny fin rays have a pair of longitudinal grooves; in them lie spindle-shaped poison glands formed by a mass of huge glandular cells secreting a serous secretion (Fig. 8). Between them lie flat supporting cells (which are homologs of the indifferent cells of the epidermis). Normally, such glands do not have an excretory duct, as they belong to the type of solid or compact multicellular glands. An excretory duct is formed in them during holocrine secretion when part of the glandular cells disintegrates entirely, and the framework of supporting cells ruptures. The venom enters human tissues when pricked by such a fish. In the weever, besides the fin glands, there is another pair on each fin of powerful poison glands associated with a strong spine of the operculum. 5) In many animals, poison glands are associated with mouthparts that form their wounding part. These are the jaws or hypopharynx of arthropods and the teeth of snakes. There are especially many such poison glands among arthropods (spiders, myriapods, insects). Spiders (Fig. 9) have two tubular poison glands lying in the cephalothorax or in the basal segment of the chelicerae. The latter end in a movable sharp claw, near the apex of which opens the thin excretory duct of the poison gland. Venom is sprayed from the glands under the pressure of their powerful muscular sheath. Spider venom serves to kill prey, which the spider

and then sucks out. There are spiders that are very venomous to humans as well; such are various species of black widows (see) and tropical spiders of Brazil, for example Lycosa raptoria, Fig. 9. Poison Phormictopus and others, causing glands (1) and chelicerae a very severe local reaction (gang- (2) of the black widow. grenous tissue breakdown) and sometimes a fatal outcome. Tarantulas (Trochosa singoriensis, Lycosa tarentula) do not possess the degree of toxicity and danger attributed to them by popular opinion. The largest spiders, Mygale (bird-eating spiders), are apparently not so formidable either. Painfulness of the bite of the spider Cheiracanthium nutrix is noted. The venom of the cross spider (Epeira) has been studied in more detail. Various toxic principles have been found in extracts from the bodies of spiders. Epeiratoxin is contained in spider eggs. Upon injection of extracts into dogs and cats, convulsions, suffocation, and death during a new attack of convulsions begin. Another principle—epeiralysin—is

a hemolytic toxin; it is also contained in spider eggs and is apparently a complex system of various substances. A similar principle from other spiders is called arachnolysin. It is important to bear in mind that epeiratoxin and epeiralysin have nothing to do with the venom of spider poison glands.

A poisonous bite is also inflicted by many mites, e.g., the grain itch mite Pediculoides ventricosus (Fig. 10), which sometimes infects grain, straw, and others. During the unloading of grain or when a person sleeps on straw, these mites attack them. The skin reddens and becomes covered with a multitude of nodules, often of an urticarial nature, with a sensation of severe itching and burning. Larvae of chiggers (Trombicula autumnalis) cause the appearance of itchy papules on human skin ("gooseberry disease"). Various flour mites (Tyroglyphidae) when working with flour, dried fruits, and vanilla cause the appearance of a pruriginous rash with the formation of small, intensely itchy nodules. The onion mite (Rhizoglyphus hyacinthi) also exhibits a toxic effect on the skin. It is very probable that the cause of intoxication is the saliva of Pediculoides and Trombicula. Regarding other mites, the possibility of the action of the juices of their crushed body when rubbed into human skin is not excluded. A significant subjective effect on humans is exerted by the bite of chicken mites Dermanyssus gallinae (fam. Gamasidae). Many mites of the superfamily Ixodoidea occasionally attack humans. The bite of some is very painful, while others cause no subjective sensations despite a brightly developed local reaction (Ornithodorus papillipes, Ornithodorus lahorensis, and others). Solifugae (wind scorpions, solpugas) are also classed among venomous animals, but without sufficient grounds. Their bite with powerful chelicerae that crush body integuments is very painful, but solifugae have no poison organs or active principles (E. Pavlovsky and A. Shtein). If there are complications from solifugae bites, it is due to the introduction of a secondary infection into the wound. Some myriapods, specifically centipedes (Chilopoda), have cylindrical poison glands opening at the tips of the movable claw of the maxilliped (Fig. 11). Such are the centipede, the house centipede (Scutigera), which is beneficial by energetically exterminating common flies, and others. The toxicity of myriapods is of no significant importance to humans. Among insects, many species inflict a bite (more precisely, a prick). Such are lice (Pediculus), the bedbug, mosquitoes, fleas, Phlebotomus, Simulium, Culicoides, horseflies, the stable fly, and others. The sensitivity of different people varies. The prick of some bugs (Reduvius) is very painful. The primary reaction of human skin to the bite of various insect groups varies. Upon repeated exposures

Figure 11. Maxilliped (3) of a centipede with poison glands (2); 1—excretory duct.

allergy phenomena become admixed. The effect of a venomous insect bite must be sharply distinguished from the painful consequences after a bite by insects acting as vectors of pathogens of various diseases. — Among vertebrates, the bite of the moray eel (Mediterranean Sea) possesses doubtful toxicity. Unquestionably venomous is the large lizard Gila monster (Mexico, California), which possesses venomous teeth in the lower jaws and submandibular poison glands. Classical venomous animals are snakes (see). Along with such unquestionably venomous species as vipers and proteroglyphous snakes, "po-

So-called "suspiciously venomous" are the opisthoglyphs (Opisthoglypha), because their venomous grooved teeth lie deep in the mouth at the posterior end of the jaws and therefore do not cause a wound during normal opening of the mouth. Examples of rear-fanged snakes are the arrow snake (Tarbometopon lineolatum), the Caucasian cat snake (Tarbophis iberus), and others. The active principles of snake venom are echidnase or echidnin, echidotoxin, and echidnovaccine (Phisalix). They differ in their resistance to heating. Echinotoxin withstands short boiling. It is a paralyzing venom; whereas echidnase causes a local effect (hemorrhagic edema, cytolysis). Echidnovaccine possesses vaccinating properties with respect to snake venom. Animals with venomous glands, but without a wounding apparatus, are found among both vertebrates and invertebrates. The venomous secretion of such animals can act on the integument, mucous membranes, respiratory organs, and olfactory organs. 1) The cutaneous glands of amphibians are the most studied regarding their venom. The glands themselves are simple pouches immersed in the corium (Fig. 12); inside, from the basement membrane, lie ectodermal cells resembling smooth muscle elements; large glandular cells rest upon them. Granular, serous, and mucous cutaneous glands are distinguished. The former are especially large: powerful clusters of them in the form of parotids lie behind the eyes of the toad, salamander, and newt. A milky-looking secretion can be sprayed from them. In the Surinam toad, moreover, glands are located in longitudinal lines along the length of the body on the back and closer to the flanks. The distinction between both sorts of glands is relative, because in the same gland there can be both mucous and granular cells simultaneously. Venomous glands fairly reliably protect some amphibians from enemies. Thus, toads have almost no natural enemies (excluding, of course, man). Toad venom has a bitterly nauseating taste. Various researchers have isolated active principles from it: phrynin, bufidin, bufotoxin. A detailed pharmacological study of toad venom was carried out by N. P. Kravkov. The main toxic properties are inherent in the secretion of the granular glands. Interestingly, toad venom can replace digitalis and cocaine in the nature of its action. Staderini even performed eye operations under toad venom instead of cocaine. This coincides with the use of toads for treating toothache in folk medicine (toads are tied to the gums). However, such treatment sometimes ends in fatal poisoning (Argentina), because mucous membranes, unlike the integument, absorb amphibian venom. The salamander (Salamandra maculosa) was also an object of study of venom, in which samandarin and samandaridin were discovered (Faust). In pharmacological terms, salamander venom belongs to the group of convulsive venoms. The venomousness of salamanders has no practical significance for man, but the venom of certain tailless amphibians, such as the dyeing poison frog (Dendrobates tinctorius), in South America is used by savages for poisoning arrow tips. 2) Among arthropods, various insects possessing strongly smelling, rapidly evaporating liquids have unarmed venomous glands of their kind. The proper toxic properties of these products have not been studied, and the classification of the corresponding animals as venomous is conditional. Such are darkling beetles, e.g., Blaps with scent glands; ground beetles with anal glands, bugs with scent glands, and many others. To the category of animals unarmed with a venom apparatus should also be referred insects possessing the phenomenon of reflex bleeding, when toxic blood is secreted or thrown outward through special openings in the body (e.g., in the joints of the limbs); blister beetles, ladybugs, and others possess such a property. Unarmed

Figure 12. Cross-section of frog skin with alveolar glands: 1 - epidermis; 2 - oxyphilic glandular cells; 3 - mucous glandular cells; 4 - excretory duct.

scent glands are also present in some myriapods (e.g., Fontaria gracilis). Unarmed venomous glands are also called defensive, and the bright coloration of the body of their possessor, which is interpreted as "warning" or "cautionary," is often associated with them. However, in many cases, possessors of such coloration nevertheless fall prey to other animals, so the indicated interpretation is not firmly substantiated (Heikertinger). II. Animals without special venom apparatuses that possess toxic properties due to the venomousness of some of their organs, tissues, or excretory products. 1) Some animals are venomous when consumed as food or generally when ingested per os. Such are, for example, venomous fishes causing poisoning called ciguatera (not to be confused with fish poison poisoning). Plectognaths, puffers, tetrodons, four-toothed puffers: Tetrodon (Spheroides) pardalis (Fig. 13), Tetrodon porphyreus, Tetrodon inermis, and many others enjoy the greatest renown in this regard. They live in tropical seas, and there are many of them in Japan. Near Vladivostok, Tetrodon vermicularis and others are encountered. The meat of these fishes is edible, but their ovaries and roe are very venomous. Over 22 years in Japan, 3,106 cases of puffer poisoning with 2090 fatal outcomes were recorded. Tetrodon venom (or fugu) acts on the central nervous system, paralyzing the respiratory or vasomotor centers with parallel paralysis of the peripheral endings of motor nerves. Tahara isolated tetrodonin and tetrodotoxin (=tetrodotoxic acid) from the roe of fresh puffers. Tetrototoxin is the toxic principle. Ostracion, or the trunkfish, is also considered venomous in Japan. From other teleost fishes

Figure 13. Spheroides chrysops.

various species of the Central Asian marinka (Schizothorax) (Fig. 14) are venomous. Their meat is tasty, but the roe (ovaries) and supposedly the black peritoneal lining possess toxic properties and cause vomiting, diarrhea, severe exhaustion, and other phenomena. It is necessary to note the absence in the medical literature of detailed descriptions of cases of human poisoning by marinka. Kushelevsky notes that its roe does not lose its venomous properties from salting and cooking. The barbel (Barbus) (Fig. 15), widespread in central and southern Europe, is venomous predominantly during the mating period. Eating its roe causes a cholera-like disease (barbencholera). Among tropical fishes, Clupea (Meletta) venenosa and Clupea (Meletta) trissa are considered very venomous, and cases of fatal poisoning after ingesting them as food have been noted in the literature. Regarding cyclostome fishes, there are indications of cases of severe poisoning after eating soup from brook lampreys (Lampetra planeri). It is believed that the venom is localized in the secretion of unicellular cutaneous glands, therefore for safety purposes it is recommended to salt fresh lampreys and wash off thoroughly with water the mucous secretion abundantly released during this process. In some southern coastal localities, sea urchins, specifically their gonads, are eaten. It has long been noticed that during the reproductive period, the ovaries of Toxopneustes lividus become venomous. 2) When certain insects are used per os (e.g., when ingested internally as an aphrodisiac, blister beetles—Lytta, Mylabris, and others), severe poisoning develops with kidney damage (action of cantharidin). 3) Such insects as beetles of the genus Paederus (fam. Staphylinidae) possess tissue venomousness; their blood and internal genitalia contain a toxic principle and cause serious vesicular dermatitis on the skin, not identical to the action of Spanish flies. For the action to manifest, the beetle must be crushed on the skin and its juices must get into scratches in the epidermis. Even more consequences are observed when these

Berg.)

beetles get into the eye and are crushed in it [conjunctivitis, inflammation of the thickness of the eyelid, inflammation of the cornea and iris, and others (E. Andresen)]. The larvae of the beetle Diamphidia locusta (tropical Africa) contain a very potent venom in their juices, which Bushmen use to poison arrow tips. The adult beetle, however, is completely harmless. 4) The toxic properties of various endoparasites must be considered separately. Inhabiting the host's body, they cause its chronic intoxication. The nature of their active principles varies. Some are exotoxins, i.e., they are released during the parasite's life from its body as a secretion of special glands (e.g., in ancylostomids; the equine nematode Sclerostomum secretes in the secretion of its head glands sclerotoxin, which possesses hemolytic properties and dissolves the cells of the intestinal mucous membrane) or in the form of excretory products. Other active principles are released only

Figure 15. Barbus barbus. (After Berg.)

upon the destruction of the parasite's body itself (endotoxins). An example of parasite toxins is the trypanotoxin of various mammalian trypanosomes. Extracts of dried trypanosomes, when injected into mice, cause convulsions and even death. Various parasitic worms are also unquestionably toxic. The broad tapeworm can cause malignant anemia; severe intoxication occurs in ancylostomiasis; ascarids possess toxicity. The toxicity of parasitic worms is clearly revealed in experiments with isolated organs. In experiments by Pavlovsky and Dunaeva, an extract from the broad tapeworm (Diphyllobothrium latum) at a dilution of 1 : 5,000 to 1 : 100,000,000 caused, in the overwhelming majority of cases, depression of the isolated heart's function of a vagotropic nature (Fig. 16). Their experiments with the action of Taenia saginata extracts on the isolated rabbit heart showed a biphasic action—initially short-term excitation, followed by prolonged depression of cardiac activity. The unarmed tapeworm toxin should be considered muscular and vagotropic. Experiments

Figure 16. Action of extract from the broad tapeworm on the isolated heart: A—normal; B—action of extract (washing according to E. Pavlovsky and V. Dunaeva). F. Talyzin with the action of extract from the broad tapeworm on smooth-muscle organs showed an inhibitory effect

Figure 17. Action of extract

from the broad tapeworm at a dose of 1 : 1,000 on the rabbit intestine. (According to Talyzin.) of the toxin on the motor function of the isolated intestine (Fig. 17). III. Accidentally venomous animals may become such either during their lifetime or after death. Some edible mollusks become poisonous during their lifetime. It is pointed out that when inhabiting polluted sea water, e.g., in an inner harbor, edible mollusks—mussels (Mytilus edulis) (Fig. 18)—become poisonous and cause poisoning after being eaten, even ending in death. Brieger considers mytilotoxin (which causes curare-like paralysis) and mytilocongestin (Richet), which produces anaphylaxis phenomena, to be the poisonous principle of mussels. When the mollusks are transferred to clean water, they lose their toxic properties over time. Some animals can become poisonous when they feed on insects that are harmless to themselves but poisonous to others. For example, frogs that devour blister beetles become poisonous to humans (when eaten). The category of accidental animal toxicity includes the bees' deposition of so-called "drunken honey." Eating it causes intoxication, vomiting, loss of consciousness for up to a day, etc. The cause of honey's toxicity has not been precisely established. It is possible that the collection of honey by bees from rhododendron flowers plays a role here (containing

Fig. 18. Mussel—Mytilus edulis: 1—edge of the mantle; 2—byssus; 3—foot. (According to Lang.) the glycoside andromedotoxin), or its toxicity depends on careless honey collection when bees get into it and are crushed there. Finally, accidentally poisonous animals include fish possessing "fish poison." The latter is an exogenous body in relation to the fish and depends on the vital activity of bacteria (see Botulism).—Treatment of poisoning by animal venoms is specific when antitoxic serums are available, or it is symptomatic in nature.