- Other Geographic Terms
Adults: The roundwormis the largest intestinal nematode infecting humans, with females averaging 30 cm in length (ranging from 20-49 cm) and measuring 3-6 mm in diameter. Males are smaller, ranging from 15-30 cm in length and 2-4 mm in diameter. Both sexes have an elongated, cylindrical body which tapers at both ends; in males the tail curves ventrally. In addition to size, sexes may be differentiated by the vulval opening in females, located ventrally at a point of constriction approximately one third of the body length from the anterior end, and by the papillae in males, grouped pre- and post-anally. Both sexes are cream-colored, sometimes with a pink tinge. The integument of the worm is a chitinous layer of nonnucleated cuticula with circular striations. lacks circular muscles, the only muscle bands being longitudinal, and the worm uses muscular activity to remain in the intestinal lumen of the host. This roundworm also lacks a circulatory system and its digestive, excretory, nervous and reproductive systems are all suspended within the pseudocoelom.
There are three forms of eggs: fertilized, decorticate and unfertilized. Fertilized eggs are golden brown in color and ovoid in shape, measuring 30-40 μm by 50-60 μm. The egg is termed decorticate if the thick, external mamillated layer is absent. Unfertilized eggs are larger (reaching 90 μm in length) and more elongated in shape, have a thinner shell and are poorly organized internally, being a mass of variably sized granules. (Chong, 2003; Khuroo, 1996)
- Sexual Dimorphism
- female larger
- sexes shaped differently
- Range length
- 20 to 49 cm
- 7.87 to 19.29 in
Male nematodes use chemotaxis to locate females. They have no visual abilities, and instead are attracted to specific sex pheromones which females release. Once the male has located a mate, it uses copulatory accessories such as papillae, spicules and its curved tail to direct sperm and stabilize the female during mating. There is no evidence of post-copulatory behaviors such as mate-guarding, although males of other species of nematode have been observed to secrete copulatory plugs into the vulva to prevent other males from fertilizing the same female. However, no information was found regarding the specific mating systems of (Gaugler, et al., 2004).
- Key Reproductive Features
- year-round breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Range number of offspring
- 234,000 eggs laid daily (high)
- Average number of offspring
- 200,000 eggs laid daily
- Range age at sexual or reproductive maturity (female)
- 8 to 12 weeks
- Range age at sexual or reproductive maturity (male)
- 8 to 12 weeks
- Parental Investment
- no parental involvement
- Range lifespan
- 6 to 18 months
- Range lifespan
Communication and Perception
Nematodes have limited visual abilities, instead relying on chemosensory interactions to find mates and food and to orient themselves inside the host. Specifically, the females release sex pheromones to attract males. Roundworms also possess papillae, used for tactile sensation and particularly employed in copulation. However, no specific information is known regarding communication and perception in (Gaugler, et al., 2004).
- Other Communication Modes
- Primary Diet
- eats body fluids
- Animal Foods
- body fluids
- Ecosystem Impact
- Humans, Homo sapiens
Economic Importance for Humans: Positive
No information was found regarding benefits to humans provided by, but as an intestinal parasite it is unlikely that there are any.
Economic Importance for Humans: Negative
- Negative Impacts
- injures humans
Karen Guy (author), University of Michigan-Ann Arbor, Heidi Liere (editor), University of Michigan-Ann Arbor, John Marino (editor), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor, Renee Mulcrone (editor), Special Projects.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
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.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
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 disease in humans
an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).
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.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
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
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
- oceanic islands
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
found in the oriental region of the world. In other words, India and southeast Asia.
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
chemicals released into air or water that are detected by and responded to by other animals of the same species
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.
living in cities and large towns, landscapes dominated by human structures and activity.
- year-round breeding
breeding takes place throughout the year
Baron, S., G. Castro, D. Wakelin, J. Cross. 1996. Medical Microbiology. Galveston, Texas: The University of Texas Medical Branch of Galveston. Accessed March 19, 2011 at http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mmed&part=Section4.bxml.
Bethony, J., S. Brooker, M. Albonico, S. Geiger, A. Loukas, D. Diemert, P. Hotez. 2006. Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm. The Lancet, 367 (9521): 1521-1532. Accessed March 19, 2011 at http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(06)68653-4/fulltext.
Brown, H., W. Cort. 1927. The Egg Production of Ascaris lumbricoides. The Journal of Parasitology, Volume 14 Issue 2: 88-90.
Chong, Y. 2003. "Ascaris lumbricoides" (On-line). Web Atlas of Medical Parasitology. Accessed March 19, 2011 at http://www.atlas.or.kr/atlas/alphabet_view.php?my_codeName=Ascaris%20lumbricoides.
Crompton, D. 1988. The prevalence of ascariasis. Parasitology Today, Volume 4 Issue 6: 162-169.
Dora-Laskey, A., U. Ezenkwele, E. Weiss. 2009. "Ascaris lumbricoides" (On-line). eMedicine - Medscape. Accessed March 19, 2011 at http://emedicine.medscape.com/article/788398-overview.
Gaugler, R., A. Bilgrami, R. Huettel. 2004. Nematode Behavior. Trowbridge, UK: CABI. Accessed April 06, 2011 at http://books.google.com/books?hl=en&lr=&id=gr10r8veZ9gC&oi=fnd&pg=PA127&dq=Ascaris+lumbricoides+reproductive+behavior&ots=5f1xK5jhAe&sig=R1VA6-5wjwsEr6NxzOdaGnPAlv0#v=onepage&q=&f=false.
Khuroo, M. 1996. Ascariasis. Gastroenterology Clinics, 25 (3): 553-577.
Sprent, J. 1952. On the migratory behavior of the larvae of various Ascaris species in white mice: I. Distribution in tissues. The Journal of Infectious Diseases, 90 (2): 165-176.