Thursday, October 14, 2010

Hymenolepis nana - The Tapeworm

I. Introduction

Kingdom: Animalia
Phylum: Platyhelminthes
Class: Cestoda
Order: Cyclophyllidea
Family: Hymenolepididae
Genius: Hymenolepis
Species: Nana

The species, Hymenolepis nana, which I chose to do my project on, is in the phylum Platyhelminthes. Like all Platyhelminthes, H nana if acoelomate, triplobastic, protostomic, and lacks a respiratory, circulatory, and skeletal systems.
H nana is completely parasitic and has to rely on its host for nearly everything. Over the course of their lifespan, tapeworms tend to have more than one host. However, an adult H nana will typically spend its life in the intestine of its host. If infected with a tapeworm, the host could suffer and lose weight quickly. The lifespan of a tapeworm can be up to twenty years! I chose H nana because it is the most common tapeworm found in humans, especially small children. Its main habitat is in temperate zones and it can be found in nearly all cosmopolitan areas. In fact it is named by some scientists as the cosmopolitan tape worm.

II. Anatomy

The anatomy for H. nana is rather simple. H. nana has no external cilia or any other kind of locomotive organ. The head of the tapeworm is called the ‘scolex’ and it contains six hooks to attach itself to the host’s inner intestine. Behind the head are multiple reproductive organs. The scolex of the tapeworm has no eyes or mouth because it does not need to see or eat.

III. Form and Function

H. nana lacks a digestive system. Instead the tapeworm directly absorbs food and nutrients from the host. On the surface of the tapeworm are a multitude of tiny wrinkles which greatly increases the surface area of the tapeworm and therefore allows more food to enter.
The excretory function of H. nana is like other Platyhelminthes. Metabolic waste is mostly diffused through the body wall.
The reproductive units found behind the scolex are called ‘proglottids’. Tapeworms are hermaphrodites because the proglottids have both female and male reproductive organs. H. nana can reproduce sexually or asexually. Once a proglottid is fertilized it releases from the body. The proglottid is full of tiny zygotes. The proglottid then leaves the body through the feces. The larva bursts from the proglottid and infect an intermediary host. The larva grow in the intermediary host and are then transferred the primary host through consumption. Because the majority of the tapeworm’s life cycle is spent inside a host’s body, tapeworms do not have any defense mechanism against predators.

IV. Impact on the World and Humanity

Tapeworms are always found in third world countries where cleanliness and hygene are not as prevalent. Tapeworms can be found in multiple climates all around the world. However H. nana is most commonly found in dry and arid areas such as the Indian subcontinent, South America, and the Mediterranean. H. nana is also the most common tapeworm found in the United States. The symptoms are usually very vague and most of the time there are no symptoms at all. If symptoms do occur, they are usually weight loss and abdominal pain. If not treated tapeworm infections can be fatal. A tapeworm infection in a child is much more serious than one in an adult. The best way to eradicate H. nana in an area is to remove exposure of human fecal matter and any other kind of fecal matter for other tapeworms.

V. Journal Article Review

This article is about a woman who discovered she had a tapeworm. She is originally from England but went to southern Africa for a trip. She spent nearly eight months there and had a blast. Unfortunately for her though she brought home a friend. The story is about how she found and cured herself of the tapeworm.

Video >>>

Works Cited
"Cestodes." Innvista Home. Web. 14 Oct. 2010. .
"Chapter 4. The Cestodes (Tapeworms)." Public Health Information and Resources - Home Page. Web. 14 Oct. 2010. .
"Introduction: Cestodes (Tapeworms): Merck Manual Professional." Merck & Co., Inc. - We Believe the Most Important Condition Is the Human One. Web. 14 Oct. 2010. .
"Tapeworm Time!" Douchebaggery Abounds. Web. 14 Oct. 2010. .
"Tapeworm Time!" Douchebaggery Abounds. Web. 14 Oct. 2010. .
"Your Health: Hi Mum, I've Got an 8ft Worm in My Tum! Love Zoe Xxx; Zoe Young, 29, Will Never Forget Her Dream Holiday to Africa - Especially When Zoe Found out She'd Brought Home More Than Just a Lovely Suntan!" Questia Online Library. Web. 14 Oct. 2010. .

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