Married to Symbiodinium and Scleractinia

Zooxanthellae in coral polyps [1]

         Zooxanthellae are endosymbionts that are best known for giving coral reefs their vibrant colors. Coral reefs are calcareous structures that support a wide diversity of marine flora and fauna. It is a “marriage” of convenience for both parties involved: a great example of mutualism. They live exclusively in scleractinian coral species, reef building corals.

Distribution

Warm waters and light limit coral reefs. Thus, the corals are generally found in tropical shallow waters. Coral reefs exist in the Caribbean, the Indian Ocean, and the tropical Pacific. In addition, where one finds corals, one finds zooxanthellae as well. [2] However, some of the zooxanthellae are host specific. 

Coral Life Cycle

[2]

Corals exist as an adult polyp which undergoes sexual reproduction through the release of gametes to form the zygote. The zygote then enters the free swimming state called the planula larva stage, which settle on a substrate and develop into a poly and restarts the cycle. [2] The adult polyp are of a tubular shape with a gastrovascular cavity and a ring of tentacles. An individual polyp secretes a skeleton called corallite and is composed of calcium carbonate in the form of aragonite. [2]

Zooxanthellae  Life Cycle

Zooxanthellae begin as an immature cyst which turns into a mature cyst that divides. After division it evolves into the zoosporangium. After which, the zoosporangium enters a free-swimming form called the zoospore. From here gametes develop and released upon maturation, and the cycle begins again. [3]

A Relationship of Old

Zooxanthellae are a type of dinoflagellate belonging to the genus Symbiodinium while reef building corals belong to the phylum Cnidaria, class Anthazoa, subclass Hexacorallia, and order Scleractinia. Originally scleractinian corals were not reef building corals and preferred the solitary existence. However, about 230 million years ago in the Triassic period a symbiotic relationship was established between zooxanthellae and scleractinian corals. [4] The corals can acquire the zooxanthellae by ingestion in their larval stage. However, they can be acquired by vertical transmission from the parent.

Reasons to Stay Married

[5]

The relationship is that of an obligate mutualism. Without the zooxanthellae corals cannot form reefs. Both parties benefit from the association.  The zooxanthellae provides glycerol, glucose, alanine, and oxygen to the coral polyp. In addition, it facilitates the deposition of calcium carbonate which is needed to from the skeleton, as well as removing carbon dioxide and nitrogenous wastes. Meanwhile the polyp provides nutrients to the zooxanthellae in the form of nitrogen and phosphorous and UV protection. In the polyp the zooxanthellae finds a home and protection from predation. [2]

Drawbacks

Every relationship comes with a few restrictions. The zooxanthellae are the reason for corals being limited to the euphotic zone since zooxanthellae can only live at certain temperatures and light depth. In return the growth of the zooxanthellae is limited within the coral in order to maintain a balance of nutrient flow. When the coral is unable to control the division of zooxanthellae, carbon is diverted to the zooxanthellae instead of the coral, leading to the expulsion of the zooxanthellae. This causes the coral to lose all color, leading to a bleaching effect. [6]

[7]

It’s All About Staying Alive

According to Combes, mutualism is a form of reciprocal slavery and in this case that is very much true. At the end of the day, it comes down to tradeoffs: geographic limitations in exchange for the ability to form reefs, nutrients, and enhanced growth in the case of the coral reef, while zooxanthellae obtains food, shelter, and protection in exchanged for a more limited reproductive rate. In this way, they both enslave the other. At the end of the day, the benefits outnumber the cost of living separate and it becomes a case of “Live together or die alone.”

[1]. http://serc.carleton.edu/images/eslabs/corals/polyp_with_zooxanthellae.jpg

[2] Smith, Alan. “Coral Physiology.” Powerpoint presentation. February 2011.

[3] Steele, R. D. (1975). Stages in the life history of symbiotic zooxanthellae in pellets extruded by its host Aiptasia tagetes (Duch. and Mich.) (Coelenterata, Anthazoa). Biol. Bull. 149:590-600. Retrieved from

http://biostor.org/cache/pdf/0a/fa/8d/0afa8d4a552fb8f7c9bb7564745e3284.pdf

[4]  http://www.reef.edu.au/contents/lt/fr_origins.html

[5] http://www.greenchange.org/img/original/sp%20coral%20reef.jpg

[6]  Woodridge, S. A. (2010). "Is the coral-algae symbiosis really mutually beneficial for the partners?". 

BioEssays 32 (7): 615–625. Retrieved from http://onlinelibrary.wiley.com/doi/10.1002/bies.200900182/pdf 
[7] http://www.youtube.com/watch?v=u4R0FqkywxE 

Taenia solium: Its Eating Your Brain!

Introduction:

http://www.human-healths.com/wp-content/uploads/2011/08/Taenia-solium4.gif 

Taenia solium, more commonly know as the Pork Tapeworm, is a parasitic worm that uses humans and pigs (go figure) as its major hosts. [1] It is most commonly found in the warm climates regions of the world, and is very similar to Taenia saginata, the Beef Tapeworm. [2] We usually think of adult parasitic worms as tiny organisms with quick generation times, however T. solium can live to be up to a few years old and usually grow to be a dozen feet long. It is spread via human feces (i.e. the pig consumes the feces of the human beings containing the Pork Tapeworm eggs, where the worm eggs develop and move to the muscle tissue, to be ingested by humans). [2] When its larval stage is ingested by a human, it generally develops in their intestines and releases eggs into the feces. Sometimes situations differ, in which case the Pork Tape worm can cause an infection known as Cysticercosis (sis-tis-err-coh-sis), a severe tissue infection. This is one parasitic monster you don't want to mess with. [3]

Symbiont Description:

http://www.dpd.cdc.gov/dpdx/IMAGES/ParasiteImages/S-Z/Taeniasis/Taenia_solium_scolex2.jpg 

Starting from domain and working towards genus, T. solium belongs to Eukarya, Animalia, Platyhelminthes, Cestoda, Cyclophyllidea, Taeniidae, and Taenia. Morphologically, the adult Pork Tapeworm is reminiscent of every other adult tapeworm--consisting of many proglottid segments and a scolex. [1] Each proglottid has a genital opening on one side and on its scolex are four suckers. Its cysticerci (larval form) differs in that the scolex is invaginated. Typically, humans are parasitized by the organism through ingestion of under-cooked pork, however, we have to capability for autoinfection. [2] In this situation, the entire life cycle of the Pork Tapeworm is contained within the human. Instead of the larval stage of the tapeworm migrating from a pig's intestines to its muscle tissue, the larva migrate from the human intestines to other parts of the body; most commonly the brain.

Host Description:

http://www.heron-productions.com/tutorials/tigerpig/pig.jpg 

Generally, the intermediate host is a domesticated pig. Because the pig is domesticated, it is in close contact with humans, the other species needed for completion of the full life cycle. The pig is able to ingest fecal matter of the humans containing the eggs of the Pork Tapeworm. The eggs hatch inside the pig and burrow through its intestinal wall, stopping in the pigs muscle tissue where they can then develop into larvae. [1]

Life Cycle:


The adult T. solium lays its eggs into human feces. When either the eggs or gravid (pregnant) proglottid segments inside the feces are consumed by a pig (or a human in the case of autoinfection), T. solium has reached its intermediate host. Here the Pork Tapeworm eggs will hatch within the pig's intestinal tract and migrate to its muscle tissue where it will develop into its larval stage, called cysticerci. When the pig is killed, processed, and eventually eaten by humans, the infected muscle tissue can further develop in the intestines of said humans (generally only when the meat is under-cooked). The T. solium use their scolex suckers to physically attach themselves to the walls of the intestines, where they can begin to significantly grow in length. After the Pork Tapeworm has developed into a fully grown adult, it will then lay eggs in the person's excrement, starting the process over again. [2]

http://upload.wikimedia.org/wikipedia/commons/8/83/Cysticercosis_by_Taenia_solium_PHIL_3387_lores.jpg 

Ecology:

The distribution of T. solium is very common in urbanized communities where livestock are in close and frequent contact with humans. This is especially so in third world countries where there are few, if any cooking regulations, and under-cooked or unsanitary pork is a commonality. The knowledge of disease causing tapeworms in pigs dates back to Ancient Egypt and is considered the major reason why consumption of pigs are against Jewish and Islamic dietary laws. [4] The effects it has on humans can be fatal, and the prescription medication used to treat it can be costly. The effects of Pork Tapeworm and other parasites like it are a major reason why pork production is so closely scrutinized in the United States.

Example of:


T. solium exemplifies fecal-oral transmission. In fecal-oral transmission, eggs of the parasite are laid in the fecal matter of the primary host, where they are then consumed by an intermediary host. Because of humans close contact with livestock throughout history, parasitic tapeworms like T. solium adapted long ago to develop a life cycle that utilized fecal-oral transmission and allowed for a high level of reproductive success. [5]

References:


[1] "Taenia solium (Pork Tapeworm)" Standford. http://www.stanford.edu/class/humbio103/ParaSites2001/taeniasis/solium2.html
[2] "Taeniasis" Laboratory Identification of Parasites of Public Health Concern. http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Taeniasis_il.htm
[3] "Cysticercosis" Center For Disease Control and Prevention. http://www.cdc.gov/parasites/cysticercosis/index.html
[4] "Ancient Hebrew Medicine" Health Guidance. http://www.healthguidance.org/entry/6309/1/Ancient-Hebrew-Medicine.html
[5] "Zoonoses and Veterinary Public Health" World Health Organization. http://www.who.int/zoonoses/diseases/taeniasis/en/index.html
Video: http://www.youtube.com/watch?v=sW84z6jP6GA

Haemonchus contortus: A Bite in the Gut

Introduction

          

http://www.nematodes.org/nembase4/species_info.php?species=HCC

         Haemonchus contortus is a strongylid nematode that parasitizes the intestines of primarily sheep and  goats. This parasite, among others, is responsible for the decreased growth and reproduction rates, which greatly affects the goat and sheep industry. “Anemia, low packed cell volume (PCV), diarrhea, dehydration, peripheral, and internal fluid accumulation” are all symptoms of Haemonchosis. This parasitic relationship is particularly problematic in the southeastern part of the United States [1] and in tropical and subtropical regions [2]. Additionally, there is a growing resistance to antihelminth treatments, which makes the parasite difficult to control [1]. Although the data on the epidemiology of the H. contortus is well-gathered in more industrialized countries, data is lacking in underdeveloped countries. This data assists in establishing techniques of avoiding this parasite, due to its high potential to cut into economic profit [2].

Symbiont description

(Genus: Haemonchus; Species: contortus)

http://www.sheep101.info/201/parasite.html 

            Cylindrically shaped nemotode, H. contortus  is sometimes called “barber poles,” particularly the females that have white ovaries and are also red due to the means nutrition – blood [3]. H. contortus has a complete digestive system and survives mostly in wet environments, especially the moist environment of a goat and sheep pasture [1]. More rainfall generally means a greater abundance in such areas. It lives in goat feces, and is therefore spread in that manner [2]. As studied under a microscope, the size of an egg is 70-85 micrometers x 41-48 micrometers. There are many parasites similar to one another that competitively parasitize the same sheep or goat. Therefore, it is useful to take accurate measurements of the egg [4]. The adult parasite (approximately 10-30 mm) has a cuticle layer that allows it to survive in the digestive tract of animals [3].

Host description

Bottlejaw: symtom of presence of H. contortus. http://www.wool.com/Grow_WormBoss_Know-your-worms_Barbers-pole-worm.htm   

         Primarily goats and sheep are the definitive hosts of H. contortus. The life cycle of this parasite does not have any intermediate hosts. Sheep and goats have a chambered stomach similar to cows. This nematode mostly resides in the adult form in the abomasum, the fourth and last chamber of the stomach and are passed through the digestive tract and into the feces. There are several reasons why sheep and goats are susceptible to H. contortus. Firstly, the feces of the host is pelleted, allowing the parasite easy access to the next host as the feces disintegrates. Sheep and goats are often kept in crowded areas, and they tend to graze even in areas of high fecal contamination. Additionally, these animals are flocking ones by nature. Like many illnesses, the old and young hosts are particularly susceptible to infection [5].  

Life cycle

Life cycle of H. contortus. http://pubs.ext.vt.edu/410/410-027/410-027.html   

            As 5,000-10,000 eggs per adult female are passed through the digestive tract, the nearly-hatched egg thrives in the moist environment of the feces and continues to develop in temperature-specific environments (75-85 degrees F). The development of the first stage larvae, called rhabditiform, may take 4-6 days to develop. The second stage larvae, filiariform type, actively climb to the top of the blades of grass to be ingested by the goat or sheep [6]. The third stage larvae then emerges after being ingested into the host, and as the cuticle is cast off, the parasite enters the fourth stage larva. Depending on whether the parasite enters an “arrest period,” the larvae either enters its fifth stage or proceeds to adulthood. Depending on the intensity of the infection, the adult parasite, may remove as much as one fifth of the erythrocyte blood volume per day by feeding on the blood of the inside of the gut [7].

Ecology

Sign of Anemia. http://www.sheep101.info/201/parasite.html    

           This parasitic relationship can be devastating to the agricultural industry, as most goats and sheep bear little resistance to H. contortus and similar parasites. Hosts become extremely weak as they experience anemia and edemia.  When a sheep or goat owner vaccinates his animals, he is vaccinating them for a variety of parasites – not just H. contortus. However, evidence suggests that cross-breeding of certain breeds of sheep may be useful; some sheep seem to bear a natural resistance to some parasitic worms [8].

Example of Aggregated Distribution and Coevolution

Aggregated hosts.  http://www.premier1supplies.com/sheep/species.php   

              The distribution of H. contortus is highly aggregated. Due to internal multiplication, the aggregation of parasites during infective stages, and most importantly, the behavior of the host, the parasite tends to be distributed aggregately. In addition, the relationship demonstrates the coevolution of parasite and host. Although most sheep and goats bear little resistance to H. contortus, the breeds that do bear resistance suggests coevolution. The parasite certainly inflicts virulence upon the host, as the host loses fitness as it succumbs to its parasitic counterparts [9].

References

[1] Lenira Leite-Brownin, M. (2006). Haemonchus contortus (barber pole worm) infestation in goats. Alabama Extension Cooperative System, Retrieved from http://www.aces.edu/pubs/docs/U/UNP-  

[2] Fiaz Qamar, M. Azhar Maqbool, Muhammad Sarwar Khan, Nisar Ahmad, and Muhammad Akram Muneer (2009). Epidemiology of haemonchosis in sheep and goats under different managemental condition. Alabama Extension Cooperative System, 2(11), Retrieved from http://www.veterinaryworld.org/Vol.2 No.11 Full Text/Epidemiology of Haemonchosis in sheep and Goats under differ.pdf

[3] Sendow, J. (2012). Haemonchus contortus. Retrieved from http://animaldiversity.ummz.umich.edu/site/accounts/information/Haemonchus_contortus.html

[4] Sloss, M. and R. Kemp. (1978). Veterinary clinical parasitolgy. (5 ed., p. 45). Ames, Iowa: Iowa State College Press.

[5] Whittier, W. D. (n.d.). Control of internal parasites in sheep. Retrieved from http://pubs.ext.vt.edu/410/410-027/410-027.html

[6] Haemonchus contortus. (n.d.). Retrieved from http://www.goatbiology.com/animations/haem.html

[7] Georgi, J. (1990). Parasitology for veterinarians. (5 ed.). Philedelphia: W.B. Saunders Company.

[8] Correa, J., James G. Floyd, Lisa A. Kriese-Anderson. (1999, October). The use of sheep breeds resistant to internal parasites. Retrieved from http://www.aces.edu/pubs/docs/U/UNP-0006/

[9] Combes, Claude (2001). Parasitism. Chicago: The University of Chicago Press.

Hymenoepimecis argyraphaga: the controller/destroyer of spiders

http://nerdychristie.wordpress.com/category/hymenoepimecis-argyraphaga/

Introduction: 

     The Costa Rican wasp Hymenoepimecis argyraphaga is found in the forests of, you guessed it, Costa Rica! It is a parasitoid that uses the spider Plesiometa argyra as a host. H. argyraphaga  is able to use the spider for food as well as control it to build it a "cocoon web" when necessary. 

Symbiont description: 

     There is an entire family of wasps who use other species to raise their young [1] and H. argyraphaga is a prime example. This Costa Rican wasp has found a way to keep their young protected before they are able to cocoon. Unlike many parasitic wasps which lay hundreds or thousands of eggs into their hosts, this meticulous mom only lays one egg on the host spider's abdomen [1]. Since the larva stage of the wasp is defenseless, the egg is planted on the P. argyra spider where it will hatch. The larva will reside on the spider, virtually free of predation, until it becomes old enough to cocoon into the adult stage. 

Host description: 

     http://listverse.com/2009/07/29/10-fascinating-cases-of-mind-control/

     The spider P. argyra spends most of its day spinning a carefully detailed web to catch the required insects it needs to live. It is often described as an orb--a platform suspended by strong "cables" of spider silk, which resists wind and rain [2]--weaving spider.

Life cycle: 

     Once the adult female wasp has mated, she will find a suitable P. argyra spider to parasitize. The H. argyraphaga female wasp stings the orchard spider, temporarily paralyzing it so it can lay an egg on the spider's abdomen [3]. The egg will hatch into a larva and it will feast on the spider's hemolymph (the circulatory fluid of invertabrates [4]) through small holes. The larva will continue to grow for about 2-3 weeks while the spider carries on with its normal activities, apparently not noticing it has a larva on its back!

http://livelonger.hubpages.com/hub/parasitic-mind-control-of-insects

     When the larva is ready to pupate, it injects a chemical into the spider [5]. This chemical drastically changes the web-spinning ability of the P. argyra spider. Instead of beautifully patterned webs that it had been spinning, the spider, under the zombie poison of the larva, starts a completely different, sloppy-looking web that is reinforced and will hold a much heavier object--the larva's cocoon [3]. 

http://borne.wordpress.com/2011/02/09/the-spider-and-the-wasp/

     With the platform ready and the spider patiently awaiting his ultimate demise, the larva then freely molts, kills the spider with a toxic poison, and sucks the remains of the juicy insides out before discarding the carcass and building its cocoon [1]. The web allows the larva to cocoon in midair away from other insects/predators that can be found on the ground. The adult wasp will emerge from the cocoon and the cycle will begin again. 

Ecology:

     Spiders are among the most abundant insectivorous predators of terrestrial ecosystems [6]. Thus they can have an ecological impact on the insect population in their habitats. Medical research using spider venom has yielded several chemicals that may be useful to control or treat diseases in humans [7]. Thus P. argyra serves to keep insect populations down and research on its venom could lead to the discovery of treatment for human diseases. The effect of the Costa Rican wasp could potentially alter the population of the P. argyra but keep in mind that H. argyraphaga needs the spider in order for their offspring to survive. Thus, the Costa Rican wasp must find the balance necessary to allow the spider to procreate while also making its own offspring.

An example of manipulation: 

     Manipulation of a host can take many forms but as Combes states "In many other cases, however, the manipulation is done partially or totally at the molecular scale" [8]. H. argyraphaga is an example where the manipulation is done solely by injecting the host with a chemical that alters its behavior. More research needs to be done to fully understand how this chemical is making the spider change its behavior and make a web it has never woven before. H. argyraphaga is also an example of a durable interaction that results in the death of the host--parasitoidism. 

References: 

[1] http://nerdychristie.wordpress.com/category/hymenoepimecis-argyraphaga/

[2] http://books.google.com/books?id=hHpFMh902XEC&pg=PA232&lpg=PA232&dq=pl esiometa+argyra+spider,+orb+spider&source=bl&ots=7ZHff1RJN-&sig=VmGqQVhbCo_Z2elhMCstfuwpO6U&hl=en&sa=X&ei=Ox1VT8KUH4bftgf5xICnDQ&ved=0CGcQ6AEwCA#v=onepage&q=plesiometa%20argyra%20spider%2C%20orb%20spider&f=false

[3] http://livelonger.hubpages.com/hub/parasitic-mind-control-of-insects

[4] http://www.thefreedictionary.com/hemolymph

[5] http://borne.wordpress.com/2011/02/09/the-spider-and-the-wasp/

[6] http://www.conservation.unibas.ch/team/nyffeler/pdf/nyffeler2000bas.pdf

[7] http://insected.arizona.edu/spiderinfo.htm

[8] Combes, Claude. Parasitism. Chicago: The University of Chicago Press. 2001. Print. 

Getting Hooked on Ancylostoma duodenale

                                      http://www.microbeworld.org/images/stories/twip/hookworm.jpg

Introduction to A. duodenale:
The hookworm, Ancylostoma duodenale, is a nematode that mainly parasitizes humans. However, it can also be found in a range of paratenic hosts, including dogs, cats, pigs, and even coyotes [1]. A. duodenale infects humans mainly through direct contact, which usually occurs through the foot [2]. However, it can also be transmitted through the consumption of under-cooked meats such as lamb, beef, and pork. The parasites are released back into the soil through human feces. These hookworms are found mainly in the Mediterranean region and Southeast Asia, but they have also been spotted in regions of South America. Individuals infected by A. duodenale can experience bloody diarrhea and anemia. The severity of the infection is determined by the amount present in the individual [1]. As the amount increases, the host will experience more symptoms including excessive blood loss, iron deficiency anemia, and possibly death [3]. Infants are more vulnerable than adults, and infections in children can lead to permanent growth deficiencies [4].

                                           http://www.youtube.com/watch?v=44aq2A6NkUw

Symbiont Description:
A. duodenale is from the phylum Nematoda, the class Secernentea, the order Strongylida, the family Ancylostomidea, and the genus Ancylostoma. These tiny, s-shaped worms only grow to be roughly 8-13 nm in length. Although it is very small, it still contains a very vicious“bite”. Each hookworm contains two very powerful ventral teeth, along with small pairs of teeth located deeper in its capsule to help it bite and attach itself to its victims [1]. Once inside, the parasite will hook itself onto the intestines and continually drain blood from its host, up to 1 mL blood per individual per day [3].

Host Description: 
The definitive host, or the host where the parasite reaches sexual maturity, is humans. However, A. duodenale also includes paratenic hosts such as lambs, pigs, dogs, and cats. Although the parasite does have paratenic hosts, it can still be described as a holoxenous parasite since it does not need any other hosts to infect the definitive host. The host specificity of A. duodenale helps it to keep selective pressures on just humans, which increases its chances of surviving and reproducing [1].

Life Cycle: 
The life cycle of A. duodenale is relatively simple to follow. First, the eggs are passed through the feces of the human host into the soil where it develops into its first stage, the rhabditiform larvae. Then, the parasite will molt twice in this form before it develops into its infectious stage known as the filariform. In this stage, the parasite will stop growing until it infects a host, either through direct contact or by oral consumption. Once inside the host, the parasite will migrate to the circulatory system until they reach the lungs. From there, they will continue on until they reach their final destination, the small intestines. The hookworms will hook themselves onto the inner wall by biting with their teeth and proceed to start feeding, causing blood loss for the host. From there, the hookworm will mature into adults and reproduce [1]. A single female hookworm can produce roughly 10,000 to 30,000 eggs a day. [3]. The eggs then travel with the host feces, and the cycle starts anew [1].

                 http://dpd.cdc.gov/dpdx/images/ParasiteImages/G-L/Hookworm/Hookworm_LifeCycle.gif

Ecology:
A. duodenale are usually found in warm, moist, and unsanitary conditions, which are prime conditions for the development of eggs and infection of hosts. The consequences of the interaction in nature is not very significant, as the parasites main target is humans, and the average person that is parasitized by these hookworms will only suffer bloody diarrhea for a short period of time. However, if the hookworms remain untreated, and a tremendous amount starts to build up in a single individual, then there is a chance that it could result in the death of the host due to excessive blood loss [3]. A. duodenale can be treated by taking the drugs Mebendazole, Albendazole, and Levamisole, which will generally kill the majority of the hookworms inside the host. Also, taking dietary supplements is helpful to counteract and compensate for the lost nutrients that the parasites takes during the period of infection [1].

An Example of Host Specificity and Parasite Specialization:

The parasite, A. duodenale, is a great example of host specificity and parasite specialization. In the textbook Parasitism, Combes mentions that by specializing in one species of host, the parasite will gain many advantages such as; reduction of pathogenic effect, increasing and maintaining genetic exchange, limiting intraspecific competition, and forcing the selective pressures onto one species of hosts rather than multiple hosts [5]. Since A. duodenale has only one host, it is able to save its resources and decreases the stress involved in having to worry about how to move from one host species to another.

References
 [1] Fetouh, N. "Ancylostoma duodenale." University of Michigan Museum of Zoology Animal Diversity Web. 2003. http://animaldiversity.ummz.umich.edu/site/accounts/information/Ancylostoma_duodenale.html

[2] "Infectious Disease Index Ancylostoma duodenale." MSDS Online. Nov 1999. http://www.msdsonline.com/resources/msds-resources/free-safety-data-sheet-index/ancylostoma-duodenale.aspx

[3] "Ancylostoma duodenale hookworm." Nemaplex. May 2003. http://plpnemweb.ucdavis.edu/nemaplex/Taxadata/Aduodenale.htm

[4] "Ancylostoma duodenale". Right Diagnosis. Feb 2012. http://www.rightdiagnosis.com/a/ancylostoma_duodenale/intro.htm
 
[5] Combes, Claude. Parasitism: The Ecology and Evolution of Intimate Interactions. Chicago: The University of Chicago Press, 2001. 86-89. Print.

Dermatobia hominis: The Human Botfly

•Title
- Dermatobia hominis: The Human Botfly

http://www.bing.com/images/search?q=dermatobia+hominis&view=detail&id=5C732E1539B6FA062CF4274D36D5CB9AEE0ED72F&first=0&FORM=IDFRIR

•Introduction
- Dermatobia hominis is a common forest fly in the regions of Mexico, Central, and South America whose larvae parasitize humans. They are a type of parasite species that needs a warm-blooded host in order to successfully make it through their larval stage. The botfly larvae use the human body (mainly the skin) as a temporary source of food as well as shelter. The morphology of the botfly larvae is almost perfectly adapted for gaining access and retaining settlement in the skin of their hosts. They have also perfected their methods for laying eggs as well as for releasing larvae. This botfly seems to have an almost unstoppable life cycle.


•Symbiont description
- Dermatobia hominis is commonly known as the Human Botfly. It is normally twice the size of the average housefly and often blue in color. Because of its large size, this botfly has trouble when trying to covertly lay its eggs on potential hosts. Therefore, D. hominis has found a way to get their eggs laid without involving themselves directly. They began by becoming more K selective so that they produce a fewer number of offspring. The mother then works to ensure that the offspring she does produce will survive into the next generation [1]. To make sure her eggs are placed on a host, the female botfly uses an intermediate host to transport the eggs for her. This is why the larval stage of this species is so crucial to its life cycle.

http://www.youtube.com/watch?v=V2Ac6RYSvo8

•Host description
- The preferred host of D. hominis is the human, but it will also parasitize any warm-blooded mammal. The host must be warm-blooded to provide sufficient nutrients and shelter to the larvae, and it also must have its encounter filter open to the intermediate host that carries the botfly’s eggs [2].


•Life Cycle

http://www.parasitesinhumans.org/dermatobia-hominis-human-botfly.html

- The life cycle of botfly typically lasts around three to four months. The cycle begins when the adult D. hominis female becomes ready to lay her eggs. She catches another blood-feeding organism mid-flight (usually a fly or mosquito) and then attaches her eggs with a sort of glue to the abdomen of that host. She then releases the vector to go and continue feeding. When this vector lands on a warm-blooded organism, the eggs of the botfly are released in response to the organism’s warm skin. When the eggs detect a spike in temperature, they begin to hatch and dig their way into the skin of the new host. They can enter at either the point where the host was bitten or dig directly into hair follicles [2]. At this point, a sore surrounding the larva begins to form and an opening is created in the skin for the larva to breathe. The presence of this parasite spurs an immune reaction in the host where white blood cells are sent to the infected area and pus is secreted from the opening. However, this is not enough to destroy the baby botfly. The larva is now an oval-shaped critter with rows of backward-pointing spines surrounding its body and hook-like teeth in its mouth [3]. The larva’s ability to burrow deep into the skin and its adaptation of spines surrounding and covering its body prevents it from being pulled out of the skin. Therefore, the host’s normal response of simply grooming is ineffective and is unable to get rid of the larva. Because of this, the larva can continue to develop for another month or two. Once matured, the larva exits the host either at dawn or at dusk to prevent water loss and increase its chances of survival in a terrestrial setting. Then the larva pupates in the soil on the ground and remains in the pupal stage for another month or so. Lastly, the larva hatches into an adult botfly, where the cycle begins again [4].

CLICK HERE OR COPY AND PASTE THIS URL BECAUSE YOU WILL WANT TO SEE THIS VIDEO!  It provides an explanation of the life cycle along with some very helpful images.  (It is "Monsters Inside Me: Invasion of the Botfly" -- Enjoy!

Monsters Inside Me: Invasion of the Botfly

http://animal.discovery.com/videos/monsters-inside-me-the-botfly.html

•Ecology
- If one botfly larva can cause this much damage, there is a bigger problem when there is an infestation of D. hominis larvae. The larvae are able to benefit from many different regions of the body and do not have one preferred niche. They create painful and strange feeling sores all over the body that secrete pus and can sometimes be fatal. The only treatment currently offered is careful removal of the larvae. Doctors can cover the air hole made in the epidermis with a film (something like nail polish) that will start to suffocate the larva and force it to come out for air. However, improper removal techniques can lead to breaking of the larva body, oftentimes resulting in infection where the larva once was. Because the botfly is able to use more common and conspicuous blood-feeders for its own egg dispersal, its larvae has been found to parasitize many different species of warm-blooded mammals as well as humans. An economic issue with this parasite is that it can also infect domesticated animals and oftentimes infects cattle. This can downgrade the quality of products coming from the livestock ultimately hurting this market[5].

http://trypophobia.net/wp-content/uploads/2011/07/trypophobia_human_bot_fly.jpg

•An example of a Paratenic host
- Dermatobia hominis provides an example of a paratenic host. One intermediate host in the life cycle of this botfly is a biting vector, such as a mosquito, tick, or fly. These biting vectors, however, play no role in the development of the eggs or larvae of the botfly. They simply serve as shuttles to get the eggs where they need to go. However, their function is crucial to the life cycle of the botfly, and without these paratenic hosts, the botfly would not be able to make to the larval stage [6].


Warning: if you have a weak stomach, you might not want to watch this.  But this video showing the removal of botfly larvae is pretty awesome!

http://www.youtube.com/watch?v=EqV1MCDLcMM&oref=http%3A%2F%2Fwww.youtube.com%2Fresults%3Fsearch_query%3Dremoval%2Bof%2Bbotfly%2Blarvae%2Bfrom%2Bwomans%2Bhead&has_verified=1&has_verified=1

•References
1.http://animal.discovery.com/invertebrates/monsters-inside-me/human-botfly-dermatobia-hominis/
2.http://www.icb.usp.br/~marcelcp/Dermatobia.htm
3.http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1769786/
4.http://www.parasitesinhumans.org/dermatobia-hominis-human-botfly.html
5.http://animaldiversity.ummz.umich.edu/site/accounts/information/Dermatobia_hominis.html
6.Class notes

Entamoeba histolyica: A Deadly Amoeba

http://entamoebahistolytica.blogspot.com/ (picture)

Introduction:

Entamoeba histolytica has become known as the more serious of the amoeba parasitic infections [1].  Clinically, this parasite causes the disease amoebiasis and the scientific name suggests that this parasite destroys the tissue of its host leaving them with severe diarrhea, also known as dysentery [1], as well as dehydration. In severe cases of infection, E. histolytica burrows through the large intestine and travels through the blood stream to the liver where it feeds and causes abscesses in the liver almost turning it into liquid [3]. It directly infects humans through food and drink that have come into contact with contaminated feces, or it can be spread by direct contact with contaminated feces.  There is no intermediate host for this parasite.  E. histolytica is found worldwide, but it is seen more prominently in tropical regions than elsewhere.  There are some humans who are more susceptible to get this parasite which is, but not limited to, homosexual males, frequent travelers, and institutionalized populations [2].

Symbiont Description:

The genus of this species is Entamoeba, and the species is histolytica.  E. histolytica lives and multiplies as a trophozoite, which is a growing stage in the life cycle of some sporozoan parasites, when they are absorbing nutrients from the host [4].  This oblong trophozoite can only survive within the host and fresh feces, after this stage of transmission the trophozoite becomes a cyst that can survive in soil, water, and on foods until it is consumed by the host. [3]

Host Description:

There is no intermediate host in this parasites life cycle.  E. histolytica only infects humans making it a hologenous parasite.  This parasite has been estimated to infect almost fifty million people worldwide [1].

Life Cycle:

http://en.wikipedia.org/wiki/File:Entamoeba_histolytica_life_cycle-en.svg

Mature cysts pass from the large intestine through the host as feces. Once the host comes into contact orally with contaminated feces, the cysts are ingested and passed through the digestive system. Once in the small intestines, they transform back into trophozoites and migrate to the large intestine. The parasite lives and multiplies, by binary fission, within the large intestine. In severe infections, E. histolytica can break through the large intestine and travel to organs within the body via the blood stream. Once they come into contact with the blood stream, they attach to it and cause abscesses to form. [3]

Ecology:

http://www.youtube.com/watch?v=lkNsFmc9DLs

E. histolytica is not specific to one region, but in industrialized nations they are known to infect immigrants, institutionalized people, and recent travelers [3]. It is easy to cure the minor infections of E. histolytica with two antibiotics: Metronidazole and Tinidazole [1,3]. As long as the symptoms do not become severe, it can be easily treated however if the infection becomes severe one might require surgery to relieve the excess fluid built up around the organ [1].

Example of a Shortened Life Cycle:

E. histolytica has shortened its life cycle compared to most parasites. By having only one host, Entamoeba histolytica does not have as many stages to go through and does not have to rely on certain hosts to reach sexual maturity.  [1]

References:

[1] Entamoeba histolytica info. (2012). Retrieved from http://entamoebahistolytica.org. Accessed February 27, 2012.

[2] Keas, A. (1999). Entamoeba histolytica. Retrieved from https://www.msu.edu/course/zol/316/ehisgeo.htm.

[3] Parasites in humans find the nastiest parasites in humans. (2010). Retrieved from http://www.parasitesinhumans.org/entamoeba-histolytica-amoebiasis.html