Structure and life history of Ascaris Lumbercoides

Structure:

The Structure ofAscaris Lumbricoides determine the external morphology in reference to shape size, colouration, Morphology, Posterior end, Excretory pore, Female Gonopore . the description in short of all these is listed below.

Shape and size:

A body is elongated , cylindrical, and tapering at both end. The female is usually long than male which is 20-25 cm in length.and 47 in diameter, but the male is smaller which is being 10-25 cm in length and 3-5 cm in diameter: Its posterior end is curved while that of female blunt.Its tail is ventrally curved.The cuticle covering the body surface bear minute transverse striations.

Colouration:

They have slightly pink color.The external cuticle is whitish or yellowish but some Ascaris have reddish color due to food ingestion.

Morphology: The anterior end of both the sexes exhibit the same structure. The body is covered with smooth, tough, and smooth cuticle which is straight transversely and give the pseudo segmented appearance to the worm. The cylindrical body has four longitudinal epidermal chords visible externally: the narrow one mid-dorsal, one mid-ventral,and two thick ones are lateral. The dorsal and ventral chords appear white, while the laterals appear brown. The anterior end is pointed bearing mouth which is a triradiate aperture,which is surrounded by three lips which are mid- dorsal and two lateral ventral.The dorsal lips have 2 double sensory papillae and each later-ventrally lip has 1 double sensory papilla.

Posterior region:In female there is no cloaca aperture but there is an anus. In the male, the posterior region is slightly coiled and c-shaped.In male has a cloaca from which two unequal chitinous spicule or penal setae project. In the male,just before the cloaca, there are about 50 pairs of preanal papillae and 5 pairs of post-anal papillae below cloaca These are concerned in copulation.

Excretory pore:A single excretory pore lies mid-ventrally at a distance 2mm.from the anterior end.

Female gonopore:

The genital pore of female lies mid-ventrally at about one three distance from the anterior end. But the genital pore of male opens into the cloaca.

Lifecycle fas Caris Lumbricoid.

The life cycle of Ascaris monogenetic .Lifecycle occurs only in one host,e man. It occurs by 5 different step which is 1,Copulation and fertilization,2, Formation of zygote3, Early development outside the host. 4, Infection to host 5, Lateral development in the new host which is discussed below .

Copulation and fertilization: It

It takes place in the small intestine, usually in the jejunum or ileum of the human beings. The sperm enters into the vagina through penal setae. the sperms come to lie in the seminal receptacle part of uteri.During fertilization, the entire sperm enters the egg. When both male and female worms are present in the intestine , each female worm produces approximately 200,000fertilized ova per day. Fertilization occurs in the oviduct. The fertilized egg passes down, the uterine wall secretes an outer thick , yellow or brown albuminous coat or outer shell having characterized wavy surface and are called as mammilated eggs . After fertilization, the ova undergo second maturation.

Zygote formation:

Unfertilized egg contains globules of glycogen and fat. IImmediately after fertilization, glycogen globules migrate to the surface and form and form a fertilization membrane,which hardens into a thick, clear and chitinous shell. They are small in size about 50 to 75 mm in length and 35to 5 mm in breadth. They are wary and yellow or brown in color. The fertilized egg pass out with the feces: they are unsegmented and they live the host. Eggs fall on the ground and can remain alive for months in the moist soil through complete drying them.Under the suitable condition of temperature, moisture,and oxygen, eggs undergo cleavage and develop into the infective stage. the optimum temperature for development is 85 degreeF.Below 60 degreeF development stops and above 100degreeF the eggs gradually degenerate.

Early development:

The stage of early embryonic development, cleavage or segmentation, etc, starts in the soil. The pattern of cleavage is spiral and determinate. The fertilized egg has undergone two cleavages to form four cells or blastomeres. These four cells are at the first arranged in the shape of 'T' in Ascaris, but the later become arranged in a rhomboid shape, which is the characterized of nematodes. These four cells underwent further cleavage to form smaller blastomeres. In the next cleavage, they all again divided into two each. The fate of various cells resulting so far is fixed.

Cleavage of embryonic cell continuous giving rise to blastula at the 16- celled stage which is characterized by having a cavity,the blasters. then gastrula results. Finally, a juvenile has resulted in about 10-14 days.It posses an alimentary canal nerve ring and lateral excretory system. It resembles very much Rhabditis, hence called radiciform larva. This larva molts within the egg shell in about 7 days and becomes second stage juvenile: this stage of the life history of Ascaris is an infection to the host.

Infection to host:

As there is no secondary host of Ascaris of infection to host (man ) occurs when the swelled the infected water . Thus, when the infective eggs reach the small intestine of the host, the eggs are dissolved by the action of hosts' digestive juice and infective second stage juveniles are set free. These are about 0.2 to 0.3 mm long and 13-15 min diameter and have all the structure of the adults except the reproductive organs.

Later development in new host:

They do not develop in the intestine but go on a typical wandering tour of 10 days. The bore through the intestine wall and the enter the mesenteric circulation and pass through the hepatic portal vein ti enter the liver, from where they are carried several times through the body along with the blood stream, then they go through the pulmonary arteries into the lungs.In the lungs juveniles rupture the capillaries and enter the alveoli where they live for some days, here they grow and mount to become 3rd stage larva which mold again to become 4th stage larvae.From here, 4th stage juveniles make their own way through the bronchioles and bronchus into the trachea and them to the throat from where they are swallowed into the esophagus and reach the small intestine for the second time. During 10 day time thIn the intestine 4th and finale juveniles have grown about ten times and 2-3 mm long. In the intestine 4th and final molting take pace, in 60 to 75 days they grow into adult males and female and attain sexual maturity.

Symptoms/pathogen

Infection with Ascaris worm often causes no symptom. Infection with a large number of worms may cause abdomen anal pain intestinal abstraction. Adults feed on the contents of the small intestine and in heavy infection this may compound the problem in malnourished individuals especially children.

Migration of larva may cause localized reaction in various organs . penetration of the larva from capillaries into the lungs and can lead to Loeffler's pneumonia, in which pools of blood and dead epithelial clog air spaces in the lungs. Resulting bacterial infection can be fat.

Treatment/ prevention/ control

Treatment consists of choosing right drugs, therapy, follow-up , and supportive care for each patient. A number of choice of the drug can be used for the treatment of ascariasis. These include Pyrantel,pamoate, mebendazole, albendazole,ivermectin,piperazine citrate and levamisole. Prevention of reinfection poses a substantial problem since Ascaris parasite

Prevention of reinfection poses a substantial problem since Ascaris parasite is absent in soil. Good sanitation to prevent fecal contamination of soil is required.An education program advising against the use of human feces as a fertilizer is also needed in some areas.Soil treatment has been attempted but is generally not practical.Mass treatment with single-dose mebendazole or albendazole for all school age children every three to 4 months have been used in some communities.This serves the dual function of treating the children and reducing the overall worm burden in the community.Vegetable grown in the polluted soil should be

Vegetable grown in the polluted soil should be thoroughly washed and boiled before consumption.

Fingernail should regularly cut to avoid accumulation of egg below them and hand should be properly washed with soap before eating.

If reinfection is completed checked, the worm can be got rid of in 9-12 month even the treatment is not taken.

Reference:

Aggarwal Sarita. A Text Book of Biology,New Delhi.: Madhuban Educational Books, 2011.

Bhamrah, H.S., and Kavita, Juneja. A Text Book of Invertebrates, New Delhi: Anmol Publications Pvt Ltd, 2011.

Jordan E.L. and P. S., Verma. Invertebrate Zoology, New Delhi,: S. Chand and Company Pvt. Ltd., 2011.

Kotpal, R. L., Modern Text Book of Zoology: Invertebrates, New Delhi, India: Rastogi Publications,2011.

http://www.biologydiscussion.com/

http://www.parasitesinhumans.org/

https://web.stanford.edu/class/

https://en.m.wikipedia.org/wiki/Ascaris-lumbercoides