Hematophagy
Hematophagy ( old Greek αἷμα haima , blood 'and φαγεῖν phagein ,' eat ',' eat ') describes the way some animals feed on blood . These organisms include arthropods , especially blood-sucking insects (e.g. mosquitoes , bed bugs ), arachnids (e.g. ticks , autumn grass mites ), but also intestinal parasites , leeches , fish such as lampreys and mammals such as vampire bats .
Only a few animals are dependent on blood as the exclusive source of food , often this requirement only exists in certain phases of life, for some species a "blood meal" is only mandatory during egg maturation , then it affects the females with fertilized eggs. The mosquitoes only the females suck blood suitable have mouthparts .
Haematophagy is rarely practiced by some primarily herbivorous animal species in order to enrich their diet with high-quality protein or other nutritional components.
Organisms
human
In some cultures the use of blood as a food component or for rites ( blood sacrifices ) is or was necessary. Drinking bovine blood, sometimes mixed with milk, is part of the life and ceremonies of the Maasai . The Eskimos eat seal - and Walrossblut , but also in Europe blood products such as blood sausage accepted as food. Blood sausage is considered to be one of the oldest types of sausage as it is already mentioned in Homer's Odyssey .
In addition, hematophagia is a recurring theme in literature ( Bram Stoker : Dracula , 1897), horror films ( list of vampire films ) and television series ( True Blood ).
Endoparasites
Parasites living in the blood such as plasmodia (the Haemospororida) feed on the blood of their host (reptiles, birds, mammals and humans) with a high host specificity.
Vandelliinae such as Vandellia cirrhosa (from the loach catfish family in the Amazon basin ) swim into the gill openings of larger fish, penetrate the aorta gills , perforate them with their pointed teeth and absorb the blood that escapes without sucking.
Ectoparasites
About 14,000 species of insects from 5 orders are hematophages, as well as many representatives of other tribes and classes , including chordates such as fish, birds and mammals. The evolution of the hematophagous insects ran several times in parallel ( convergent ).
| Tribe / class | Order / group of animals | example | Mouthparts | Anticoagulants in saliva | Pain relievers in saliva | Victim ( host ) |
|---|---|---|---|---|---|---|
| Annelid worms | Leeches | Medical leech | toothed suction mouth | Hirudin | Yes | Mammals , humans |
| Arthropods / Crustaceans | Isopods / Gnathiidae | Paragnathia formica | u. a. Anti- thrombin , three trypsin inhibitors (18 kDa , 21 kDa and 22 kDa) | ? | fishes | |
| Arthropods / arachnids | Mites / ticks | Shield ticks : Common wood tick | Proboscis | Yes | Yes | Birds , mammals, humans |
| Leather ticks | Proboscis | Yes | Yes | |||
| Mites / prostigmata | Autumn grass mite | Proboscis | Yes | Yes | Mammals | |
| Arthropods / insects | Two-winged birds / mosquitoes | Aedes , Anopheles , Stegomyia , black flies , midges , sand flies | Proboscis | Anti- factor X (Xa) (Kazal-type trypsin inhibitor) | ? | Reptiles, birds, mammals, humans |
| Uranotaenia lateralis | Proboscis | probably | ? | Mudskippers | ||
| Two-winged / flies | Brakes , biting flies , tongue fly , tsetse fly , louse flies ( Lipoptena Cervi ), stable flies | Biting tools + proboscis | Yes | ? | Birds, mammals, humans | |
| Fleas | Rat flea , dog flea , cat flea , rabbit flea, human flea | Proboscis | Yes | ? | Mammals, humans | |
| Animal lice (only Anoplura) | Human lice , pubic lice , Seehundlaus, Schweinelaus | Proboscis | Yes | ? | certain mammals, humans | |
| Schnabelkerfe | blood-sucking bugs | Proboscis | Yes | ? | Birds, mammals, humans | |
| Butterflies / Owls | Calyptra | stinging proboscis | ? | ? | Mammals, humans | |
| Chordates / Petromyzontida | Lamprey | Sucker mouth with rasp teeth | Yes | ? | fishes | |
| Chordates / birds | Passerines / tanagers | Vampire finch | beak | probably no | probably no | Blue-footed boobies , Nazca boobies |
| Chordates / Mammals | Bats / leaf noses / vampire bats | Common Vampire ( Desmodus rotundus ) | Toothed mouth, grooved tongue | Desmoteplase as a factor X (Xa) and factor IX inhibitor | Yes | Mammals (esp. Large herbivores), humans |
| Comb-tooth vampire ( Diphylla ecaudata ) | Toothed mouth, grooved tongue | Yes | Yes | Birds |
Blood intake
Mouthparts
Haematophagous animals must be equipped with appropriate mouth tools or tooth formations that enable the host's epidermis to be overcome and vessels to be opened up.
The blood is then absorbed in various ways. Many of the proboscis , especially blood-sucking insects, are very thin tubes ( capillary suckers, solenophages), which take up the blood fluid due to capillary action , without the need for a pump power or a generated negative pressure, e.g. B. Fly (Diptera). Other hematophages actively soak up the blood meal, e.g. B. ticks (Ixodidae) or vampire bats (Desmodontinae).
Arachnids
The common wood tick ( Ixodes ricinus ) has a highly developed lancing and suction apparatus. The mouth area is a part separated from the rest of the body ( gnathosoma or capitulum), which contains the suction tools. These tools are made up of several components. The first part includes the club-shaped pedipalps , they serve as a tactile organ (as in many other arachnids ) to precisely record the structure of the host's skin. Thin skin areas with a warm temperature and high humidity are preferred. A little further inside on the upper side are the two chelicerae . They have several sharp teeth at the tip that the wooden tick can use to cut a hole in the skin. After the hole has been cut, the so-called hypostome is used. It is a pin-like part of the body in the middle of the capitulum, which bears rows of coarse teeth on the underside, while the upper side is flexible and sunk in the middle somewhat like a groove. The telescope-like structures penetrate in about three stages by alternately pushing them independently of one another into the victim's body opening. The hypostome and (in the case of the ticks) cement-like hardening saliva anchors the animal in the skin, the blood is sucked through the pharynx, which acts as a pump, into the food channel and then into the mouth opening at the base of the hypostome.
Two-winged
Mosquitoes (Culicidae) use a biting device, which is formed by combining several mouthparts. Outwardly, two parts can be distinguished: the thin, rigid proboscis and a flexible sheath that serves as a guide during the blood meal. The proboscis is made up of the piercing bristles: upper lip ( labrum ), paired upper jaw ( mandible ) and lower jaw ( maxilla ) as well as pharynx ( hypopharynx ). This bundle combined to form a proboscis can penetrate the skin of the host. Inside it forms two channels. The blood can be absorbed through the hypopharynx by capillary action, and saliva can be injected through the tube formed by other piercing bristles . In the resting position, the proboscis lies protected in a sheath formed by the lower lip ( labium ). When the sting occurs, the lower lip itself does not penetrate the host, it is curved backwards and helps to fix the proboscis at the puncture site without penetrating there itself.
At the end of the labrum (piercing bristle from the upper lip) there are three groups of sensilles, of which the apical and subapical to find the blood-carrying site, the campaniforms are necessary to control blood flow.
The corresponding mouthparts are stunted in the male and only allow the absorption of fluids without puncture and only one sensilla group (campaniform) is developed on their labrum.
Bony fish
The loach catfish Vandellia cirrhosa , which occurs in fresh water, lives above sandbanks, lightly covered with sand and waits for large fish swimming by. Vandellia cirrhosa is a parasite. He can perceive the urea from the metabolic products of large fish exchanged through gill breathing and swims, following the concentration, into the gill openings of the fish. It uses its own gill spines to climb up to the gill aorta and to hold on. It perforates the artery with needle-shaped teeth and takes in the blood of the host fish, which earned it the nickname “Brazilian vampire fish”. However, Vandellia cirrhosa is not a bloodsucker, because the species has no suction organs. The pressure of the blood flowing out of the artery is enough to fill the fish with blood in 30 to 145 seconds. Then he lets go of the host animal.
Mammals
Vampire bats (Desmodontinae) have sickle-shaped incisors and canine teeth for hole-shaped cutting of the skin of their victims, in addition to receding molars without chewing surfaces. The emerging blood is licked with the tongue or sucked up with the tongue folded in through grooves on the underside. A short esophagus and the tubular stomach are further anatomical adaptations to the diet.
saliva
The saliva of haematophagous ectoparasites has less of the task of supporting the swallowing process as it does with other diets, because the blood meal is very rich in water. The primary purpose of the saliva is to facilitate blood uptake by counteracting blood clotting and preventing the victim from noticing the wound during the blood meal. Substances that inhibit blood coagulation and pain-suppressing substances are therefore often released into the wound with the saliva when blood is drawn.
Endoparasites do not need these mechanisms; they focus on preventing an immune response, but not as salivary components.
Local anesthesia
The saliva of many haematophagous ectoparasites contains pain-numbing substances. These components are usually released early during the wounding process to prevent the victim from noticing the bite . This is mainly necessary for ectoparasites that have to stay longer to eat blood. Fast attacks with a short dwell time are an alternative strategy, another is to colonize areas of the body that are poorly controlled by the victim himself.
The saliva of vampire bats also contains locally anesthetic components, they lick the area of their victim before they remove hair or feathers and then bite a hole.
Anticoagulants
Anticoagulant substances were found in the saliva of almost all hematophagous animal groups. Only for hematophagous butterflies and birds are no anticoagulant substances known in the saliva.
The importance of anticoagulant substances must be high for haematophagous ectoparasites, because according to the multiple parallel evolution of such animal groups, also within the insects, the anticoagulants in their saliva also developed in parallel each time. This reveals an imperative due to this diet that requires an explanation. It could be sought in the fact that haematophages cannot afford to clog their fine tubular mouthparts with clots. It is also obvious that the bleeding during the meal should not stop due to clotting. In particular, removal due to the capillary action of the proboscis would be hindered by coagulation processes. Experiments have shown that hematophagous predatory bugs can ingest blood even after their salivary glands have been removed, but they then need much more time, even for smaller amounts. This is explained with difficulty probing for a blood vessel. The insect can only effectively search for a vessel with its mouthparts as long as the blood flow is not interrupted. Without the release of anticoagulant saliva, only the small amount of initial bleeding can be used that occurred when the tissue was opened accidentally, right up to the rapid onset of clotting. The insect has to repeatedly place a new attachment point until it happens to come across a productive container.
The saliva of vampire bats also contains anticoagulants, while the common vampire ( Desmodus rotundus ) contains the protein Desmoteplase . As a factor X (Xa) and factor IX inhibitor, it prevents blood clotting for up to eight hours after the bite.
The anticoagulant mechanisms are varied, some are directed against certain coagulation factors, others against platelet aggregation.
These anticoagulants are also being investigated by pharmaceutical research as they could help prevent and dissolve thrombi and blood clots to help prevent thrombosis and embolism .
Blood processing
digestion
Blood contains a relatively large amount of water and protein , but few fats and carbohydrates . Correspondingly, many proteases are required for digestion .
Some of the ectoparasites harbor endosymbiotes , for example Aeromonas veronii biovar sobria lives in the intestine of the leech ( Hirudo medicinalis ), presumably supporting its blood digestion.
Excretion and egg maturation
Water ballast is a particular challenge for flying ectoparasites, as the blood uptake can exceed their actual body weight and severely impair their ability to fly. This applies to both insects and, for example, bats. Vampire bats often return to the same victim repeatedly within one night in order to continue their meal after they have digested their blood meal of around 20 to 30 milliliters and excreted most of the water , because the flight powers of the animals would be well over 30 milliliters (about 30 grams) Overstrain with a weight of 15 to 50 grams. Therefore, after the blood meal is diuresis hormonally strongly encouraged to much of the amount of water very quickly about their urinary organ excrete. The need for water excretion is unknown for non-hematophagous animals, on the contrary, much of the kidney work and water absorption in the digestive tract of land animals, especially flying animals, is aimed at minimizing water excretion.
As with other animals, there is a need for haematophagous organisms to excrete superfluous metabolic products. Because of the high uptake of oxygen transport molecules from the blood, iron from porphyrin compounds (such as heme ) and nitrogen compounds from proteins (such as hemoglobin and albumin ) are particularly abundant.
The need for nitrogen excretion affects almost all animals. Guanine is the nitrogen-containing main excretion product of the leather tick ( Argas arboreus ) with a share of 59.2–97.3% of the excretion mass, it contains 70–100% of the excreted nitrogen.
While iron is a limiting factor for many organisms , it is in abundance for hematophagous organisms, so it must be excreted. On the other hand, iron is also an essential substance for many haematophages , especially for the maturation of blood-sucking insects , which is why in mosquitoes, for example, only females suck blood during egg maturation. About 87% of the iron uptake from heme is excreted by the yellow fever mosquito ( Aedes aegypti ) after the meal, about 7% is used for egg maturation and about 6% is stored in body tissue. When iron was absorbed from transferrin, about 8% of it was excreted, about 77% benefited egg development and about 15% was stored in body tissue. Since transferrin is significantly less present in food, about 98% of the iron content of eggs comes from heme. 1.2–8.6% of the excretion of Argas arboreus takes place in the form of hematin , which in addition to iron also contains 0.23–1, Contains 45% of the absorbed nitrogen. The hematin content gives the excrement of many hematophages a black color.
Secondary transfer
Many ectoparasites with frequent host changes , especially haematophagous, are popular vectors for other parasites or pathogenic microorganisms , which serve to transport and spread them . For example, a hematophagous ectoparasite such as B. the anopheles mosquito transmit the hematophagous endoparasite Plasmodium (malaria pathogen). Borrelia in particular emerge as transmitted pathogens among bacteria .
The elucidation of Chagas disease around 1910 was not achieved by identifying the pathogen in sick people, but by identifying a previously unknown flagellate ( Trypanosoma cruzi ) in predatory bugs (Reduviidae).
For example, if leeches have not been pretreated with antibiotics , about 20% of the medicinal use of leeches result in Aeromonas infections , because they harbor the dreaded "hospital pathogens" as endosymbiotes. Introduced directly into the blood, the bacteria can cause blood poisoning ( sepsis ).
Strategies of victims
Dealing with endoparasites
One strategy of the hosts is to continuously improve the immune protection against endoparasites in the course of evolution.
A possible infestation by endoparasites can often be prevented by hygiene measures , vaccination protection or preventive medication . However, there are hardly any effective vaccinations available against most haematophagous endoparasites.
Actual infestation can often be reduced or cured by therapeutic measures ( surgery or drugs).
Avoidance of ectoparasites
The threatened hosts use a variety of strategies to avoid haematophagous ectoparasites. This includes, for example, good mobility, especially manual (primates) or other body parts (cow's tail, cat's tongue), firm body covering (arthropods, thick clothing), body cleaning (elephants, humans), social grooming (bats), inter-species body care ( partner shrimp , Maggot chopper ), rubbing (many mammals), sensitivity of the body surface , lack of hair (humans), use of repellants and biocides ( pyrethrum ). Another possibility is to hide behind mosquito nets (humans), to submerge, to cover with a layer of mud ( water buffalo ) or to conceal one's own heat radiation ( this is why reindeer sometimes flee on snow surfaces in summer).
Therapeutic measures
The primary therapy is the removal of the parasite through personal hygiene. In the case of stronger infestation, washing additives are useful (louse remedies). In stubborn cases, surgical removal is necessary.
As a result of the saliva being released into the wound by the ectoparasite, proteins or other allergens are usually transferred on the one hand, and pathogens on the other . The allergens trigger an immune reaction with local release of histamine and inflammation of the bite site , which can be irritating to painful. In rare cases, an allergic reaction can also occur that requires medical attention.
The consequences of haematophagous by human parasites transmitted infection and their drug treatment sometimes pose a serious and long-term medical challenge.
Other: blood smell
It has not been described whether blood odor (the perception of odor originating from or similar to blood) attracts hematophagous organisms. For some scavengers and carnivores, however, the scent of blood is known:
Predatory fish like sharks are known to be attracted by bleeding bait. A species of catfish in Amazonia, Cetopsis candiru , belonging to the whale catfish ( Cetopsidae ), feeds on dead or dying larger fish and on the carcasses of mammals floating in the water by eating a hole in the abdominal wall and eating the animals from the inside. They follow the smell of carrion and blood and are suspected of being responsible for attacks on women bathing, especially during menstruation.
The volatile substance trans-4,5-epoxy- (E) -2-decenal from the blood is particularly treacherous for predators .
Web links
literature
Lexicon of Biology . 7th volume. Spektrum Akademischer Verlag, Heidelberg 2004, ISBN 3-8274-0332-4 .
Individual evidence
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