ascaris

File:Ascaris female 200x section.jpg

File:Ascaris esophagus (cropped).jpg

• Adult: cylindrical shape, creamy white or pinkish in color
• Male: average {{Convert|15–30|cm}}; more slender than the female
• Female: average {{Convert|20–35|cm}}

The body is long, cylindrical, and fusiform (pointed at both the ends). The body wall is composed of cuticle, epidermis and musculature. There is a pseudocoelom. The digestive tract is complete with prominent muscular pharynx. Respiration is by simple diffusion across body wall. The nervous system consists of a nerve ring and many longitudinal nerve cord. They are dioecious and have separate reproductive systems consisting of thread like gonads and genital ducts that open outside by apertures. Fertilization is internal and development is mostly indirect. Sexual dimorphism is well marked. Externally, males are much shorter than females and males also have a curved posterior end, unlike females. Internally, in males, all the digestive, reproductive systems open in a common chamber- cloaca whereas in females, there is a separate anus for digestive tract and female genital pore for female reproductive system.

As part of the parasite defense strategy, Ascaris roundworms secrete a series of inhibitors to target digestive and immune-related host proteases, which include pepsin, trypsin, chymotrypsin/elastase, cathepsins, and metallocarboxypeptidases (MCPs).

Ascaris species inhibit MCPs by releasing an enzyme known as Ascaris carboxypeptidase inhibitor (ACI). This enzyme binds to the active site of MCP and blocks the cleavage of its own proteins by the host MCP.{{cite journal |last1=Sanglas |first1=Laura |last2=Aviles |first2=Francesc X. |last3=Huber |first3=Robert |last4=Gomis-Rüth |first4=F. Xavier |last5=Arolas |first5=Joan L. |title=Mammalian metallopeptidase inhibition at the defense barrier of Ascaris parasite |journal=Proceedings of the National Academy of Sciences |date=2009 |volume=106 |issue=6 |pages=1743–1747 | pmc=2644108 | doi=10.1073/pnas.0812623106 |pmid=19179285 |bibcode=2009PNAS..106.1743S |doi-access=free }} Similarly, they inhibit trypsin by releasing the protein Ascaris Trypsin Inhibitor ([https://www.rcsb.org/structure/1ATA pdb 1ATA]).{{cite journal |last1=Grasberger |first1=Bruce L |last2=Clore |first2=G.Marius |last3=Gronenborn |first3=Angela M |title=High-resolution structure of Ascaris trypsin inhibitor in solution: direct evidence for a pH-induced conformational transition in the reactive site |journal=Structure |date=1994 |volume=2 |issue=7 |pages=669–678 |doi=10.1016/s0969-2126(00)00067-8 |pmid=7922043|doi-access=free }}

Ascaris has been present in humans for at least several thousand years, as evidenced by Ascaris eggs found in paleofeces and in the intestines of mummified humans.{{cite journal|vauthors=Leles D, Gardner SL, Reinhard K, Iniguez A, Araujo A|date=2012|title=Are Ascaris lumbricoides and Ascaris suum a single species?|journal=Parasites & Vectors|volume=5|issue=42|pages=42|doi=10.1186/1756-3305-5-42|pmc=3293767|pmid=22348306 |doi-access=free }}

A. lumbricoides was originally called Lumbricus teres and was first described in detail by Edward Tyson in 1683.{{cite book|title=Parasitic Diseases |edition=6 |vauthors=Despommier DD, Griffin DO, Gwadz RW, Hotez PJ, Knirsch CA |date=2017 |publisher=Parasites Without Borders |isbn=978-0-9978400-1-8}} The genus Ascaris was originally described as the genus for Ascaris lumbricoides by Carl Linnaeus in 1758.{{cite journal|title=Are Ascaris lumbricoides and Ascaris suum a single species? |vauthors=Leles D, Gardner SL, Reinhard K, Iniguez A, Araujo A |journal=Parasites & Vectors |date=2012 |volume=5 |issue=42 |pages=42 |doi=10.1186/1756-3305-5-42|pmid=22348306 |pmc=3293767 |doi-access=free }} The morphologically similar Ascaris suum was described from pigs by Johann August Ephraim Goeze in 1782.

• List of parasites of humans

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Category:Ascaridomorpha

Category:Chromadorea genera

Category:Taxa named by Carl Linnaeus