|Kohlreuther , 1771|
The scratch worms or scratches (Acanthocephala; from Greek ἄκανθος akanthos = "thorn" and κεφαλή kephale = "head") are a group of intestinal parasites with an obligatory change of host . As intermediate hosts, they attack various aquatic and terrestrial arthropods , especially insects and crustaceans , and as final hosts, fish , amphibians , birds and mammals . Around 1100 species with body lengths between a few millimeters and 70 centimeters have been described to date . The animals are gutless in all stages of development and take their food through the tegument , a canal system in the outer skin. In addition, all known species are separate sexes. It is named after the hooked trunk with which the animals anchor themselves in the host's intestinal wall.
Anatomy of the adult animals
Physique and external anatomy
The scratch worms have a three-part body. The trunk ( metasoma ), which houses all of the internal organs, is the largest section, while the neck and trunk or the scolex (collectively known as the presoma ) only make up a small part of the body's length. A stomach and back side of the scratch worms cannot be determined externally or based on the organ locations; their position was determined on the basis of the organs of the closely related Bdelloida , in which the gonads are always on the ventral side (ventral) and the brain always on the back (dorsal). The number and arrangement of cells during development is typical of the species and stable in most species ( Eutelia ), only the number of germ cells is constantly increasing. In most species, the females are significantly longer and more powerfully built than the males.
The proboscis is equipped with hooks pointing backwards, which serve to attach it to the host's intestine and to which the animals owe their scientific name Acanthocephala . In many species, especially representatives of the Palaeacanthocephala and Eoacanthocephala , there are also hooks or uncurved thorns on the neck, which represents the transition between trunk and trunk, and on the front part of the trunk. The trunk is mostly smooth-walled or wrinkled; in some species, such as Mediorhynchus taeniatus , it only has an externally existing pseudo-segmentation , which gives them the appearance of a segmented worm.
In the very large species, the tegument can be up to two millimeters thick and, like many other tissues in these animals, is formed by a syncytium . In most species, the basis of this cell association is formed by around 6 to 20 individual cells, the adjacent cell membranes of which dissolve and thus form a group-specific tissue with many small or significantly less very large cell nuclei. The cell nuclei enlarge in the course of development and become polyploid through constant mitoses ; in many species they branch out and reach a diameter of up to two millimeters. Especially in large species, the cell nuclei disintegrate into many small fragments without mitotic division. In the epidermis, there are also collagen fibers , which on the outside predominantly run parallel to the direction of the body and in the lower layers in a ring and thus stabilize the epidermis. The outermost area is denser than the inner one, but does not form an armor. This layer is criss-crossed by numerous invaginations, which form a complex lacunae system , which is used for nutrition.
Organ systems and internal anatomy
Below the epidermis there is a circular muscle and a thinner longitudinal muscle layer made of muscles that have a central cavity and whose lumens are connected to one another and to the lacunae system. These muscle tissues also consist of fused cells (syncytium). The so-called hydroskeleton of the animals serves as a counterpart or antagonist to these muscles ; The fluid-filled body cavity creates a counter-pressure for muscle tension and thus causes stretching and expansion in the non-tense parts of the body. The muscles of the trunk sheath, on the other hand, consist of criss-cross muscle fibers. Two cone-like protrusions of the epidermis protrude from the neck into the metasoma and end on the trunk in the front third. These so-called lemnisci are surrounded by muscles that can retract the neck and trunk (neck and trunk retractors ) and thus serve as an antagonist of the trunk muscles . The Lemnisci themselves play a central role in the hydraulics of the trunk, which, with their help, can turn and get caught in the host's intestine.
Within the two-part body cavity there are several cavity systems. In addition to the lacunae system described, there were originally two ligament sacs with a mesodermal coating in the trunk and a separate cavity in the trunk. The ligament sacs are partially separated by a ligament cord, probably a relic of the original intestine. The ligament sacs dissolve in the Palaeacanthocephala in the adult stage, so that the ligament cavities and the body cavity fuse with one another.
The nervous system of the scratchworms is very much reduced due to the endoparasitic way of life and mainly serves to innervate the muscles. They have a central cerebral ganglion on the back of the proboscis sheath, which in most species only consists of 73–86 nerve cells . From this a pair of main nerves pulls into the abdomen into the trunk. The males have another ganglion of around 30 nerve cells in the penile papilla. Only a few tactile senses on the tip of the trunk and on the neck have been identified as sensory organs .
The excretion takes place as the diet almost exclusively through the epidermis, only very large species of the family of Oligacanthorhynchidae arranged have two tufts of simple construction protonephridia with which they excreta from, body cavity filter and the vent run. Besides the sperm, these protonephridia are the only organs of the scratchworms that have kinocilia . The sex organs are located in the back, belly-facing part of the lower ligament sac. The males have one or two pairs of testes and a species-specific number of so-called cement glands - glue glands that are used during copulation . Both open into the copulatrix bursa via the papillae of the penis . The females have no ovaries . These are dissolved into small balls that float freely in the ligament sac and in the case of the palaeacanthocephala in the body cavity. The ovarian balls each consist of two syncitia, the inner one forming the eggs, while the outer one ensures the nutrition of the ball.
The number of chromosomes in scratch worms is very low in all species and is usually around six or eight chromosomes in total. In some species, such as the giant scratcher , there are also different sex chromosomes , so that the heterozygous type XY is present in the male and the homozygous type XX in the female . In many other species, however, there are only uniform sex chromosomes, with them the male lacks an X chromosome and accordingly has the type X0 and has one chromosome less than the female. In Acanthocephalus ranae , chromosome type XY is present in both sexes.
Anatomy of the stages of development
There are three developmental stages of scratch worms (Acanthor, Acanthella and Cystacanthus), which, depending on the source, are viewed as independent larvae or as sub-forms of the subsequent developmental stage. In this context, only the Acanthor is considered to be the clear larva, while the Acanthella and the Cystacanthus are often viewed as subadults.
The Acanthor is the earliest larval form of the scratch worms. It is already fully developed when the adult female is laying eggs and leaves the host's intestine in a multi-layered egg shell. This is only left when the acanthor is in the intestine of the intermediate host, where it drills into the intestinal wall. The egg shell consists of four opaque layers that are separated from one another by intermediate layers. The layers differ in their structure within the scratchworms and represent an important feature for the systematic classification of the species. In all scratchworms, the two outer eggshells contain hardened keratin and are partially connected to one another by keratin braces. Within the Archiacanthocephala, the third layer still contains keratin, while this is missing in the Palaeacanthocephala and Eoacanthocephala. In addition, the innermost egg shell of the Archiacanthocephala and Palaeacanthocephala contains chitin , which the Eoacanthocephala lack. Above all, the outer layers offer the acanthore protection in the digestive tract of the intermediate hosts and swell up and burst due to the influence of digestive enzymes, so that the acanthore is released in the intestine.
In its fully differentiated form, the acanthore essentially consists of three different syncytia , the anterior, central and epidermal syncytium. Like the adult animals, they do not have an intestine; this is not created during embryonic development either. The anterior syncytium ( frontal syncytium ) contains many electron-dense vesicles as well as larger vesicles that contain a mucus-like substance, the purpose of which has not yet been clarified. The central syncytium ( central syncytium ) mainly contains condensed and uncondensed cell nuclei and is often connected to ten subepidermal and two retractor muscle cords, which enable the movement and deformation of the acanthor and are probably formed from the central syncytium. The main part of the body is the epidermal syncytium ( epidermal syncytium ). This forms the epidermal covering of the larva with an interconnected lacunae system and most of the body mass. It also contains cell nuclei and various vesicles, some of which are filled with mucus-like substances. Species-specifically, smaller body spines form on the epidermis in the rear area and stronger hooks in the front area, which are required to penetrate the intestinal wall of the intermediate host.
The contents of the various vesicles in the frontal and epidermal syncytium have so far only been researched very rudimentary. It is believed that they play a central role in penetrating the intestine and in inactivating the immune system in the intermediate host. For example, the Acanthor releases chitinases ( enzymes that break down chitin ).
As soon as the acanthore has left the intestinal lumen and bored into the intestinal wall and later into the body cavity of the intermediate host, the larva begins to reorganize and form an acanthella. All processes of organogenesis up to the formation of the cystacanthus are continuous. With the reorganization, the main axis of the body shifts by 90 ° and the outer covering of the acanthore expands to become the tegument of the acanthella. Filamentous outgrowths grow out of the outer membrane of the tegument and form a sponge-like covering for the larva and can also enclose blood cells ( hemocytes ) of the intermediate host. In the further course it divides into an inner and an outer cover and detaches itself from the epidermis of the larva, creating a space between the two that appears granular under the light microscope and is probably filled with liquid.
The central syncytium divides and forms the developmental nuclei of the later organs, which now gradually differentiate. In the late Acanthella, the proboscis forms, which is later often drawn in with the entire front end into the proboscis sheath, giving the larva a cyst-like appearance. The transition to the infectious larva, the cystacanthus, follows.
The cystacanthus is the infectious form of the acanthella, whereby the name refers to the cyst-like form of this stage in the larger types of scratching worms, especially in the giant scratcher . In most scratchworms, however, the infectious stages are curved and thus "sausage-shaped", which means that they correspond to the adult animals with retracted proboscis and are therefore often viewed as subadults. The sex organs are usually very well developed in them, but separated from the massive body wall of the animals by a clear distance. The pores and lacunae of the epidermis are largely closed and no food is ingested, but otherwise there are no anatomical differences to the adults.
Distribution and host range
Scratchworms can be found worldwide in their marine , limnic and terrestrial host animals. There are a number of species that have specialized in individual host organisms and, accordingly, only occur in their area of distribution. For example, there are species that parasitize only in Australian marsupials or in Antarctic seals. Very specific and spatially limited species are still being described anew, including Acanthocephalus reunionensis, which was first described in 2007 in freshwater eels on the island of Réunion in the Indian Ocean, and Pomphorhynchus moyanoi from freshwater fish in central Chile .
However, many species, especially fish parasites, have a relatively unspecific host range and can accordingly be detected in many animal species and in a large area. Individual species parasitize in cosmopolitan livestock such as domestic pigs or farm poultry, or in globally widespread cultural successors such as the brown rat and are accordingly also found worldwide.
Way of life
Anchoring in the host
Within the scratch worms, a parasitological distinction is made between species that anchor themselves only in the mucous membrane of the intestinal lumen and those that penetrate (perforate) the intestine of the ultimate host with their proboscis to anchor themselves.
Non-perforating species usually have a very short proboscis and a correspondingly short proboscis sheath. They get caught within the intestinal villi and do not penetrate the muscular layer of the intestine with their proboscis. As a rule, less than half of their proboscis is surrounded by intestinal tissue from the host. This can be due to the structure of the host's intestines: Trout fish , for example, have a compact layer or perch have a collagen layer, which strengthen the intestinal wall and thus do not allow perforation by species without corresponding collagen-degrading enzymes, but serve as an abutment for the proboscis. These species include the fish scraper Acanthocephalus lucii and Echinorhynchus truttae , which do not penetrate even in smaller fish species without a reinforcing layer, and most of the Archiacanthocephala living in terrestrial vertebrates, including the potential human parasite Moniliformis moniliformis . Some of these species can also detach themselves from the intestinal wall and change their position as well as potentially being transferred from an animal to a larger predator in the adult stage, as has been proven several times for Neoechinorhynchus rutili . When there is a high level of worm infestation in the intestine, even typically perforating species only get caught in the inner layers of the intestine and thus retain the potential to change position.
These types are opposed to perforating types, which have a long neck area and proboscis and usually also develop an eyeball , a blister-like thickening that serves as the final anchorage behind the intestinal wall. As with the Pomphyrhynchus species, this bulb can be located on the tip of the trunk or, as with Eocollis arcanus, at the front end of the trunk. In the case of perforation, the rapid penetration of the toothed proboscis into the intestinal wall can be supported by the protein and collagen-degrading effect of enzymes similar to trypsin , which are released in the area of the proboscis into the intestinal tissue and dissolve it here. Perforating species no longer leave the position where they are hooked and cannot be drifted away with the intestinal current. In species such as Pomphyrhynchus laevi , Eocollis arcanus or Acanthocephalus anguillae , which are typically perforating, in the case of very small parasites or unsuitable hosts it can even happen that the entire body penetrates the intestine and the worms are located outside the intestine in the peritoneum and die there. The perforating scratches also include the giant scratches, which in humans and pigs can also completely penetrate the intestines and subsequently die in the peritoneum.
The food ingestion of the scratchworms takes place exclusively through the epidermis, which means that the worms are dependent on parenteral nutrition from their host. For this purpose there is an extensive lacunae system inside the epidermal syncytium with ring-shaped main canals that are connected by transverse canals. It is connected with the outer invaginations of the epidermis and with the hollow skin muscles below the epidermis, but has no opening into the body cavity. The epidermis is surrounded by a glycocalyx about a micrometer thick , with the help of which nutrients , especially proteins and monosaccharides , are bound from the intestinal contents of the host, absorbed and introduced into the lacunae system. The fluid in the system is kept in motion by the animal's contractions, which ensures that it is distributed throughout the body.
The lacunae system of the trunk and that of the trunk are separate from each other. Corresponding food intake also takes place in the proboscis sheath. This is where cells and fluids collect, which are released when the parasite has wounded the intestines. In this way, the scratch mainly absorbs lipids in the form of triglycerides and vitamin A , which are stored in the intestinal wall of many fish and birds. For this lipid uptake, the apical organ at the tip of the proboscis or in the proboscis sheath plays an important role that has not yet been fully explained.
Reproduction and development
All scratch worms are sexually separate, so there are male and female animals. A parthenogenesis as with the closely related Bdelloida or asexual reproduction does not occur to them. During copulation, the male grasps the rear end of the female with the bursa copulatrix and then inverts it, as a result of which the female rear end with the genital opening is pulled into the bursa. Then it presses the penis papilla located in the bursa into the female's vagina and releases the sperm into it. These are thread-like (filiform) with a length of 20 to 80 micrometers and free-swimming, they have neither mitochondria nor an acrosome . They actively move to the ovarian balls of the females and there fertilize the eggs that are still in the balls.
The fertilized egg cell ( zygote ) begins after the fusion of the cell nuclei of the sperm and the egg with a furrow of two forming and fusing polar bodies , which begins like a spiral furrow with a division into micromers and macromers . A fertilization membrane forms around the early zygote. The cell membranes of the emerging cells dissolve very early and thus form the syncytia that make up the later body of the acanthore. In the course of embryonic development, the egg becomes spindle-shaped and, starting from a simple covering, several eggshells are deposited around the embryo and harden. During this development, the egg leaves the ovarian ball and now floats freely in the mother's ligament sac.
The fully developed eggs are sorted out from the body fluid and deposited using a sorting mechanism on the uterine bell. To do this, the uterine bell, which is located at the entrance of the uterus in the ventral ligament sac, sucks in all the eggs and pushes them into a sorting device, in which the thin, spindle-shaped eggs are pressed into the uterus and the plump, not yet fully developed eggs, into the dorsal ones Ligament sac are returned. This pumping function brings the liquid in the ligament sacs into a permanent flow through which the eggs move from the rear part of the dorsal sac to the anterior body and then back into the ventral sac. The eggs in the uterus are released into the host's intestine and are released into the open with its faeces. As parasites, the scratchworms lay a very large number of eggs. The giant scraper involves around 80,000 eggs a day to make up for the losses that inevitably arise in later development.
Some of the eggs are taken up by the intermediate hosts in the open water or in the ground, whereby the eggshells of many scratch worms contain sugar or other substances that increase their attractiveness. In the intestine of the intermediate host, the acanthor leaves the egg shell after it has swollen and become brittle due to the influence of digestive enzymes and bores into the intestinal wall and a few weeks later into the body cavity of the animals. The intermediate host's immune system responds to the intruder by causing the hemocytes to form a thin cyst shell around the larva. Within the cyst, the acanthor develops into acanthella and forms the evertable proboscis and other anatomical features of the animal. The acanthella finally becomes the permanent stage, the infectious larva or cystacanthus, which remains infectious for a long period of time.
Only when a definitive host takes in the intermediate host and with it the infectious Cystacanthus, the development can be brought to a conclusion. In the intestine of the new host, the cystacanthus frees itself from the cyst shell and attaches itself to the intestinal wall with the help of its hooked trunk. If it is not the final host, but a missing or waiting host, the cystacanthus burrows again through the intestine and encysts there again. In the final host, however, it develops into a fully formed adult worm and remains in the intestine, where it feeds and forms offspring.
Evolution and systematics
Since the scratchworms live as endoparasites in other animals and also have no fossilizable hard parts, they have not been identified as fossils . There is also no fossil record for the closely related taxa, so that one can only speculate about the evolutionary age of these groups.
There is a very high probability that the scratchworms form a natural group, a so-called monophylum , which comes from a common ancestor and does not contain any other animal groups. Various molecular biological investigations and morphological comparisons have plausibly proven that their closest relatives are the also free-living Bdelloida , which in the classic system are classified as rotifers .
This thesis is supported anatomically. The reason for the assignment is mainly due to the cell constancy ( eutelia ) occurring in both groups , the syncytial structure of the epidermis with depressions typical for both groups, the lemniski, which are only found in scratchworms and various rotifers, the ultrastructural fine structure of the trunk retractor and the structure and Course of the ligament cord, which corresponds to the regressed intestine of various rotifers.
On the basis of these results, the rotifers do not represent a natural grouping in the classic combination and would have to be supplemented by the scratch worms. In this case, the current classification of both groups as a stem in the classical taxonomy is no longer justifiable, it is no longer used in more recent publications. The common group of scratchworms and rotifers is often called Syndermata as a taxon.
Main article: Systematics of scratch worms
A number of common features, so-called apomorphies , can be named as indicators for the monophyly of the scratchworms . These include, among other things, the very specific epidermis with the lacunae system for feeding the animals, which only exists in the scratching worms, the evertable trunk with the hooks, the ligament sacs and the very special design of the female genital organs with the specialized uterine bell .
The scratchworms contain three taxa classified as classes, which differ mainly in their size and host range as well as some morphological features. The design of the ligament sac, the position of the main ducts of the lacunae system and the number of cement glands in males play an important role; the structure of the eggshells, the characteristics of the life cycle (intermediate and final hosts) and molecular biological characteristics are also used as a basis for the classification . All of these characteristics suggest that the three classes are monophyletic groups :
Importance to humans
As a parasite of humans
As a parasite for humans, the scratch worms only play a very insignificant role. In principle, humans are the ultimate hosts for the giant scraper and for some smaller species, but the infection is extremely unlikely and therefore very rare. The normal way to get infected with the cystacanthus of the giant scratcher would be to eat an infected beetle larva. In 2007, for example, the case of a toddler from Iran was infected with the moniliformis moniliformis scratch after putting dirt and a cockroach in its mouth.
According to Mehlhorn & Piekarski 2002, in countries where insects are used as food, infections with giant scratches can be very high regionally. In some regions of China, for example, there are said to be more intestinal operations to remove giant scratches than to treat appendicitis .
Economic importance as a domestic and farm animal parasite
The Macracanthorhynchose of the domestic pig is mainly found in countries and regions in which pigs are kept in open pasture. In most regions of Central Europe, in which pig farming is now practiced as intensive stables, it does not occur. Internationally, macracanthorhynchosis is a relatively common parasitosis.
Acanthocephaloses, on the other hand, play a very important role in water fowl breeding and fish farming, as well as fishing, as scratch worms can be very common in these animals. Individual ducks can be infested with up to 150 worms; Such an infestation leads to severe injuries to the intestinal mucosa and results in diarrhea and massive intestinal bleeding.
In fish farming, a heavy attack with scratches leads to growth disorders and other complaints for the breeding animals. Scratchworms with a proboscis that penetrate far into the muscle layer can already be recognized on the outside of the intestine through the connective tissue capsules. In the case of severe infestation, the eyes protrude in some fish, especially trout fish with severe infestation with Echinorhynchis truttae . In the case of acute peritonitis, treatment is no longer possible.
In zoos , especially in the 1960s to 1980s, primates were very often infected by scratchworms, especially Moniliformis moniliformis and Prosthenorchis elegans . The transmission route via cockroaches, which can be found very often in the animal enclosures, played a major role. Due to stricter hygiene regulations, this accumulation has fallen sharply since the 1990s, but even today primates regularly die of peritonitis caused by scratches .
Treatment and prevention
Targeted treatment with chemical preparations for giant scratches is hardly established and, as a rule, is also not necessary, as this has neither economic nor veterinary consequences. In the event of severe infestation in young pigs, various active ingredients can be used, including multiple treatments with macrocyclic lactones such as ivermectin , which has been shown to remove 86 to 100% of scratchworms for a seven-day treatment. The main preventive measures that can be named are the reduction of intermediate farmers and the shift from grazing to barns; Both have led to the fact that the infestation with the giant scraper has decreased significantly in Central Europe and is now regarded as non-existent.
In poultry, agents such as fenbendazole are classified as effective, which are also primarily intended to remove the scratches. Stable housing and controlled watering are also effective prevention here.
The diagnosis of acanthocephalosis in the fish is usually only carried out after a thorough inspection of the intestines after they have been killed. In the case of mass infestation in pond farming , especially in trout farming, medication is mixed into the dry food to drive out the scratching worms. This is di-n-butyltin oxide, which is given in the feed over several days. Infested fish can be fished as a preventive measure to reduce parasite infestation. In addition, very heavily infested waters are drained and limed in order to kill the intermediate hosts and thus the larvae of the parasites.
Lead indicator in the water
Due to their parasitic way of life in fish , scratchworms and other endoparasites of limnic and marine fish, especially heavy metals, accumulate much more intensely than their hosts. For this reason, the scratchworms living in the fish are examined primarily as an indicator of the lead content in water.
Most of the information in this article has been taken from the sources given under literature; the following sources are also cited:
- The entire section is based primarily on Lorenzen 1996 and the article Acanthocephala in Mehlhorn 2001
- after Mehlhorn & Piekarski 2002
- The entire section is mainly based on the article Acanthor in Mehlhorn 2001
- The entire section is mainly based on the article Acanthella in Mehlhorn 2001
- The entire section is mainly based on the article Cystacanth in Mehlhorn 2001
- LR Smales, P. Sasal, H. Taraschewski: Acanthocephalus reunionensis n sp (Acanthocephala: Echinorhynchidae), a parasite of Anguilla species (Anguillidae) from Reunion Island. Parasite 14 (2), 2007: pp. 131-134 ( abstract )
- VL: Olmos, EM Habit: A new species of Pomphorhynchus (Acanthocephala: Palaeacanthocephala) in freshwater fishes from central Chile. Journal of Parasitology 93 (1), 2007: pp. 179-183 ( abstract )
- James R. Garey, Thomas J. Near, Michael R. Nonnemacher1, Steven A. Nadler: Molecular evidence for Acanthocephala as a subtaxon of Rotifera. Journal of Molecular Evolution 43 (3), 1996; P. 287–292 ( doi: 10.1007 / BF02338837 )
- Martín García-Varela, Gerardo Pérez-Ponce de León, Patricia de la Torre, Michael P. Cummings, SSS Sarma, Juan P. Laclette: Phylogenetic Relationships of Acanthocephala Based on Analysis of 18S Ribosomal RNA Gene Sequences. Journal of Molecular Evolution 50 (6), 2000; P. 532–540 ( doi: 10.1007 / s002390010056 )
- Thomas J. Near: Acanthocephalan Phylogeny and the Evolution of Parasitism. Integrative and Comparative Biology 42, 2002; Pp. 668-677. ( Full text ; PDF; 236 kB)
- Phylogenetic Relationships of the Acanthocephala Inferred from 18S Ribosomal DNA Sequences. Molecular Phylogenetics and Evolution 10 (3), 1998; Pp. 287-298. ( Full text ( memento of the original from April 23, 2015 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this note. )
- F. Berenji, A. Fata, Z. Hosseininejad: A case of Moniliformis moniliformis (Acanthocephala) infection in Iran. Korean Journal of Parasitology 45 (2), 2007: pp. 145–148 ( abstract )
- Experimental Studies on Lead Accumulation in the Eel-Specific Endoparasites Anguillicola crassus (Nematoda) and Paratenuisentis ambiguus (Acanthocephala) as Compared with their Host, Anguilla anguilla. Archives of Environmental Contamination and Toxicology 37 (2), 1999; Pp. 190–195 ( doi: 10.1007 / s002449900505 )
- Holger Herlyn: On the ultrastructure, morphology and phylogeny of the Acanthocephala , Logos Verlag, Berlin 2000, ISBN 3-89722-439-9 .
- Sievert Lorenzen: Acanthocephala, scratches in: Wilfried Westheide , Reinhard Rieger : Special Zoology. Part 1: Protozoa and invertebrates. Gustav Fischer Verlag, Stuttgart and Jena 1996; Pp. 723-728, ISBN 3-437-20515-3 .
- Heinz Mehlhorn : Outline of the parasite science spectrum Akademischer Verlag, Berlin, Heidelberg 2002; Pp. 277-284, ISBN 3-8274-1158-0 .
- Article Acanthocephala , Acanthella , Acanthor and Cystacanth in: Heinz Mehlhorn : Encyclopedic Reference of Parasitology. Biology, Structure, Function Springer Verlag, Berlin, Heidelberg, New York 2001, ISBN 3-540-66239-1 .
- Article Acanthocephalacidal Drugs and Acanthocephalan Infections in: Heinz Mehlhorn: Encyclopedic Reference of Parasitology. Diseases, Treatment, Therapy Springer Verlag, Berlin, Heidelberg, New York 2001; Pp. 1-13, ISBN 3-540-66239-1 .
- Warwick L. Nicholas: The Biology of Acanthocephala. Advances in Parasitology 11, 1973; Pp. 671-706.
- Horst Taraschewski: Host-Parasite Interactions in Acanthocephala: a Morphological Approach. Advances in Parasitology 46, 2000; Pp. 1-179.