Macracanthorhynchus hirudinaceus

Geographic Range

Macracanthorhynchus hirudinaceus has a worldwide distribution and is most often associated with domestic swine. (Roberts and Janovy Jr., 1996; Van Cleave, 1953)


Macracanthorhynchus hirudinaceus is an endoparasite of domestic swine. It can also be found in humans and a large number of other mammals. Adults attach to the intestinal wall of the host. Eggs with acanthors (embryonated larvae)are found in the soil near domestic swine and can survive up to three and a half years and withstand subzero temperatures. Acanthors are also found in the gut of the intermediate host. (Roberts and Janovy Jr., 1996; Van Cleave, 1953)

Physical Description

Macracanthorhynchus hirudinaceus is known as the giant thorny-headed worm of the hog. Generally they range from creamy white to yellow orange. The body is flat and gradually becomes smaller from the anterior to the posterior. Females are larger than males. Females can reach 650 mm long by 7 to 8 mm wide. Males range in size from 50 to 90 mm long by 6 to 8 mm wide. Each has a retractile proboscis that is cylindrical in shape and 0.6 to 1.0 mm long and 0.50 to 0.92 mm wide. The proboscis has six backward-curved hooks in each of six spiral rows. The hooks range in size from 0.260 to 0.432 mm. The proboscis in connected to the trunk by the neck. There is a cerebral ganglion i.e. brain. There are flat lemnisci (extensions) that resemble a ribbon and range in size from 20 to 35 mm long. Each lemniscus has approximately 6 giant nuclei. They extend from the base of the neck into the pseudocoelom. The function of the lemnisci is unknown. The testes of the male reside in the front half of the body along with the eight cement glands that are oval in shape. Females have embryos that range in size from 0.092 to 0.100 mm long by 0.051 to 0.056 mm wide. (Crompton and Nickol, 1985; Dunagan and Miller, 1987; Roberts and Janovy Jr., 1996; Van Cleave, 1953)

  • Sexual Dimorphism
  • female larger
  • Range length
    50 to 650 mm
    1.97 to 25.59 in


Macracanthorhynchus hirudinaceus uses an intermediate and definitive host. Intermediate hosts are usually white grubs. Definitive hosts are usually domestic swine but several vertebrates, including humans, are also known to be definitive hosts. Adult females produce a very large number of eggs. The female reproductive system has ovarian balls instead of discrete ovaries. The ovarian balls are within the ligament sac and float freely around. The eggs of M. hirudinaceus are deposited in soil when the feces of the definitive host comes in contact with it. The beetle larvae eat the eggs in the soil. The larva that hatches from the egg is called the acanthor, a resting stage that doesn't develop until an intermediate host is found. Within an hour of being inside the beetle larva, the acanthor hatches from the egg and uses its bladelike hooks to cut through the gut of the beetle larva. It stops in the hemocoel, attaches to the serosa, and begins to feed. The acanthor begins development in approximately 5-20 days. Feeding triggers the developmental stage, the acanthella. At this stage it is a parasite of the beetle larva, feeding and growing. Once the organ system of the acanthocephalan larva is fully developed the acanthella stage terminates and the acanthocephalan is termed a juvenile. A juvenile infective to a definitive host is termed a cystacanth. When the definitve host eats the beetle larva the cystacanth uses its backward-curved hooks to attach to the intestinal wall of the host where it completes development into the adult, becoming infective in 60-90 days. (Crompton and Nickol, 1985; Roberts and Janovy Jr., 1996)


The male everts a copulatory bursa to the female gonopore and transfers sperm to the female. Males secrete a cement plug following copulation. (Brusca and Brusca, 2003)

  • Parental Investment
  • pre-fertilization
    • provisioning
  • pre-hatching/birth
    • provisioning
      • female


There is male-male competition among numerous species of acanthocephalans. This male-male competition produces sexual size dimorphism. In most invertebrates sexual dimorphism favors females being larger. Males are favored to be larger with strong male-male competition. Acanthocephalans exhibit strong male-male competition. Acanthocephalans do not have bigger testes as a result of the strong male-male competition. Relative testis volume decreases as male body volume relative to female volume increases. Males have a cement gland that produces a copulatory plug soon after mating. Since they are virtually insured of their success there is no need for a greater amount of sperm to be produced to out compete other males. (Moore, 1984; Poulin and Morand, 2000)

Communication and Perception

The nervous system is reduced. Simple sensory receptors are on the proboscis, probably for tactile stimulation. Males have sense organs in the genital area. (Brusca and Brusca, 2003)

Food Habits

Macracanthorhynchus hirudinaceus lacks any trace of a gut. Feeding takes place by assimilating nutrients from the intestinal contents of the host i.e. it feeds on what the host has digested. The tegument of M. hirudinaceus is a site of both absorption and digestion. Among nutrients absorbed are sugars, amino acids, nucleotides, and triglycerides. (Crompton and Nickol, 1985; Roberts and Janovy Jr., 1996)

  • Animal Foods
  • body fluids


Although this species may not be preyed on directly, mortality of the young is likely high since most do not reach a suitable host.

Ecosystem Roles

Macracanthorhynchus hirudinaceus is an endoparasite of domestic swine. It can also be found in humans and a large number of other mammals. Adults attach to the intestinal wall of the host. Eggs with acanthors (embryonated larvae)are found in the soil near domestic swine and can survive up to three and a half years and withstand subzero temperatures. Acanthors are also found in the gut of the intermediate host, such as beetles.

Species Used as Host

Economic Importance for Humans: Positive

There are no positive aspects associated with humans.

Economic Importance for Humans: Negative

Epizootics are infrequent but are always possible among domestic swine. The chances of an epizootic wiping out an entire farm of domestic swine and negatively affecting revenue for the farmers are very small. If the acanthocephalan completely perforated the gut of the domestic swine the pig could die from secondary infections. There are cases of humans being infected with Macracanthorhynchus hirudinaceus but they do not pose any major threat. This is mostly due to the nature of the intermediate host. (Crompton and Nickol, 1985)

Conservation Status


  • IUCN Red List [Link]
    Not Evaluated

Other Comments

In another species of Archiacanthocephala, Moniliformis moniliformis, the cockroach Periplaneta americana, an intermediate host, was negatively affected by the parasite. The infected cockroach was attracted to light and more hyperactive. These cockroaches are more likely to be eaten by a rat, which is a definitive host. The beetle larva intermediate host of Macracanthorhynchus hirudinaceous could possibly be affected the same way. (Moore, 1984)


Renee Sherman Mulcrone (editor).

Adam Barron (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.



Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

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living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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living in the southern part of the New World. In other words, Central and South America.

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living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal


Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.


uses smells or other chemicals to communicate


having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body


having the capacity to move from one place to another.


found in the oriental region of the world. In other words, India and southeast Asia.

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reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


living in residential areas on the outskirts of large cities or towns.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..

Crompton, D., B. Nickol. 1985. Biology of the Acanthocephala. Cambridge: Cambridge University Press.

Dunagan, T., D. Miller. 1987. A model of the cerebral ganglion in Macracanthorhynchus hirudinaceus. Journal of Parasitology, 73: 853-855.

Moore, J. 1984. Parasites that change the behavior of their host. Scientific American, 250: 108-114.

Poulin, R., S. Morand. 2000. Testes size, body size and male-male competition in Acanthocephalan parasites. Journal of Zoology, 250: 551-558.

Roberts, L., J. Janovy Jr.. 1996. Foundations of Parasitology,sixth edition. Boston: Mcgraw-Hill Companies,Inc..

Van Cleave, H. 1953. Acanthocephala of North American mammals. University of Illinois Press, Urbana: Illinois Biological Monographs.