Morphology and Life Cycles of Some Known Parasites Essay

2158 Words9 Pages
Morphology and Life Cycles of Some Known Parasites Parasite: Dracunculus medinensis Disease: Guinea worm disease (Dracunculiasis) Morphology of Dracunculus medinensis Dracunculus medinens is known to be one of the biggest nematodes existing. The adult females can grow to a maximum length of up to 800 mm long, while the males can only grow to a maximum length of 40 mm. These parasites have a tiny, triangular shaped mouth, with no lips, but it is enveloped by a sclerotized, quadrangular plate. The cephalic papillae are arranged in an outer circle of 4 double papillae at about similar level as the amphids and an inner circle of 2 double papillae, which are unique in that they are dorsally and ventrally located. A huge glandular portion is located at the esophagus and it protrudes and lies at the side of the thin muscular portion. No eggs are produced but there are four larval stages prior to the formation of large adult worms. At the first stage, the larvae appear as thin white tubular stages measuring up to 400µm in length and having a rhabditiform pharynx. At the third stage larvae is much longer, carrying a measurement of up to 600 µm in length, and they possess a filariform pharynx. The adult worms display noticeable sexual dimorphism. The males carry a measurement from 2 - 4 cm in length with unequal spicules, while the cream to white females grow up to 80cm in length by 2mm in width and contain thousands of embryos. In young females, the vulva is located around the midbody but it becomes atrophied and non-functional in adults, as does the intestine due to the high internal pressure generated by the gravid uterus. Although the worms are very long and thin, they are not true filarial worms and are grouped separately. Biology of Dracunculus medinensis High internal pressure is produced by the thousands of embryos in the uteri of a gravid female Dracunculus

More about Morphology and Life Cycles of Some Known Parasites Essay

Open Document