"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

June 30, 2010

June 30 - Lampea pancerina

Ctenophores are commonly called "comb jellies" because they have rows of cilia that are fused at the base, giving them an appearance like a comb. These organisms are diploblasts like jellyfish (cnidarians) and once were thought to be very closely related to them. Turns out that part of that assumption came from the fact that one genus, Haeckelia, had cnidocytes, stinging cells that jellyfish use to capture prey. Recently, though, it was discovered that Haeckelia was getting their cnidocytes not by developing them, but from stealing them from jellyfish that they were eating. A while ago, we met a parasitic jellyfish and Lampea pancerina is thought to be the only parasitic ctenophore. The young comb jellies live inside tunicates, but not much is known about this relationship.

The image comes from this site.

June 29, 2010

June 29 - Gasterophilus intestinalis

Growing up, I was an avid horseback rider and had both a horse and a pony. Today's parasite was always one of the things I dreaded about summer. Gasterophilus intestinalis, the horse botfly, is an annoying creature to horses and horse owners alike. The females are large and aggressive and pester the horses until they eventually alight and deposit small eggs that stick to the horse's hair like glue, most often on their legs. The eggs itch and so the horse licks and bites at it, eventually swallowing the eggs. The larvae then live out the fall and winter months in the stomach of the horse, which can make the horse lethargic and induce colic. In the spring, they are passed out in the feces, where they pupate and then emerge as new - annoying - flies. We would always try to prevent infection by scraping the eggs of the horses' legs using specially made rough sponge-like things - I spent hours doing that each summer!

The photo shows a very heavy infestation of botfly larvae in the stomach of a horse and comes from this site.

June 28, 2010

June 28 - Parelaphostrongylus tenuis

Parelaphostrongylus tenuis is a parasite of white-tailed deer that lives in the meningeal spaces of a deer's brain and is thus known as "brainworm". Female worms lay eggs that make their way to the lungs via the blood. There, the eggs hatch into first-stage larvae, get coughed up, swallowed, and then passed out. Snails or slugs then come along and are infected by the larvae, which penetrate the foot of the gastropod. Eventually, the nematode makes its way back into a deer, when they are ingested by the browsing deer. The worms penetrate the stomach, make their way to the spinal cord, and then follow this up to the brain to begin the cycle again. As far as we know, the worms don't seem to have a great effect on white-tailed deer, though I suppose they're not known for being particularly smart animals anyway. However, if the worms find themselves in other hosts such as moose, llamas, or goats, the effects can be very severe. In these hosts, the worms cause uncoordination, stumbling and aimlessness, a condition that is very often fatal.

Image comes from this site.

June 27, 2010

June 27 - Stegotricha enterikos

Stegotricha enterikos is a parasite of oysters and has been found infecting them on both coasts of North America. They are quite prevalent and though they live within the body of the oyster and ingest the epithelial cells of the oyster, they don't appear to induce a great deal of pathology in the shellfish.

The image comes from this site.

June 26, 2010

June 26 - Botrytis cinerea

Have you ever enjoyed a glass of sweet dessert wine? It's all thanks to a fungal parasite called Botrytis cinerea, or "grey mould". It is a pathogen which can infect a number of different crop plants including beans, strawberries, cucumbers, tomatoes, and grapes. Unlike many parasites, Botrytis cinerea is not obligately parasitic - it can alternate between living as a parasite, or as detrivore which digests dead organic matter. While this fungi is a cause for headache for most farmers, in vitriculture, it is also known as "noble rot". A late infection by B. cinerea in white grapes lead to drying of the grape berries which increase the sugar concentration without increasing acidity. Maybe a good dessert wine brought to us thanks to the "noble rot" would be a good way to accompany the course of parasites you have been enjoying this week.

June 25, 2010

June 25 - Hydnora africana

Hydnora africana is a parasitic plant that grows on the roots of euphorbs in Africa. For the most part, it grows entirely underground and lacks chlorophyll or leaves. When sufficient rain has fallen, the plant may then poke up a large, but slowly-developing flower that is bright orange. It releases a horrible, putrid odor that attracts dung and carrion beetles, which it traps inside the flower so that they pollinate it. The fruits, known as "jackal fruits" because jackals will readily consume them, are also enjoyed by people, particularly after they have been roasted over a fire. The fruits are also used to treat diarrhea and dysentery and even acne.

June 24, 2010

June 24 - Zaops ostreum

How many kind of food can you name comes with its own side dish? Well, the eastern oyster (Crassostrea virginica) should be on that list. This week. we've already seen how a trematode infection can improve the taste of oysters, but it seems that oyster also comes with another gastronomic treat in the form of the pea crab Zaops ostreum. Pea crabs (family Pinnotheridae) are small soft bodied crabs which live inside a variety of marine invertebrates, with most species living in bivalves. Zaops ostreum infect the oyster as a tiny first stage larvae, and grow to maturity within the bivalve's mantle cavity, feeding upon food-laden mucus strings produced by its host's filtering action. It is a true parasite in that it causes harm to its host. Not only does it steal food from the oyster, it also forms an obstruction within the body cavity and erode the gill tissue. From a culinary perspective, there are many serving suggestions available for pea crabs - they can be served raw, deep fried, or sautéed, and can be eaten either as a side dish to oysters, or even on their own (if you can get enough of them to make a meal!).

Photo and contribution by Tommy Leung.

June 23, 2010

June 23 - Bucephalus haimeanus

Do you enjoy seafood? Especially shellfish? Especially raw oysters? Whether you know it or not, the next time you tuck into some raw oysters, there might be a parasite which is responsible for enhancing your gastronomic experience. Usually, having parasites in your shellfish can be seriously bad news. However, apart from the squeamishness factor, the harm caused by your seafood being infected with the asexual stage of a trematode is minimal to neglible.

As we have seen in prior blog entries, the asexual stages of trematode parasites castrate their first intermediate host, utilising it to produce free-living larval stages which are released into the environment. Now if this first host happens to be oysters - which is the case for Bucephalus haimeanus, this has interesting culinary implications. In uninfected oysters, after they spawn they exhaust the all the nutrients and resources they've stored up and become almost tasteless after spawning season is over. However, because infected oysters are castrated, they stay fat and retain their flavor through out the year.

So from a gastronomic point of view, parasitised oysters are a class above their unafflicted brethen!

Contributed by Tommy Leung.

June 22, 2010

June 22 - Ustilago maydis

Ustilago maydis, also known as Corn Smut, is a fungus which infects corn. The fungal infection usually occurs in the plant's ovaries, replacing the corn kernels with enlarged, distorted "galls" which then produce infective spores that are carried away by wind or rain. Like any good parasite, Ustilago feeds off its host, resulting in decreased yield in the infected crop. From an evolutionary biology view point, it is interesting to note that functionally, Ustilago acts rather like a parasitic castrator which reduces or eliminate the host's reproductive capacity, a strategy that has independently evolved in many parasite lineages. Whereas corn smut is considered as a blight on corn in Europe and North Armerica, in Mexico it is considered as a delicacy. Known as huitlacoche, this 'blight' fetch a higher price on the Mexican market than the corn itself. Its taste has been described as being similar to that of truffle - which is perhaps not too surprising as they are both are fungi that grow in association with a plant host. In addition to being a culinary treat, Ustilago maydis is also a useful lab model organism, used in research into plant diseases, as well as other research into cell and molecular biology.

Contributed by Tommy Leung.

June 21, 2010

June 21 - Amoebotaenia lumbrici

The parasite for today plays a central role in a gourmet dish, and that culinary parasite is a tapeworm from the genus Amoebotaenia. Amoebotaenia lumbrici, along with a number of other species from its genus, happens to play a starring role in one of the most prized of French dishes. Host of Amoebotaenia are woodcocks (Scolopax rusticola) and swarms of these tiny tapeworms live inside the bird's intestine. Woodcocks (also known as Bécasse) are popular game birds and gastronomically valued for its strong and unique flavour and taste. The woodcock is usually oven roasted whole with its innards intact. After it has been roasted, the intestine is removed to be chopped up and made into a pâté. The unique flavour of the pâté has apparently been attributed to all those little tapeworms which are packed into the woodcock's gut.

So if you ever find yourself in a fancy French restaurant, check if Bécasse pâté is on the menu!

Contributed by Tommy Leung.

June 20, 2010

June 20 - Gyrodactylus turnbulli

Ever wondered what attracted your mom to dear ol' dad? Well, if you mom was a guppy (Poecilia reticulata), it might very well have been his bright flashy colors. Turns out that female guppies can use the brightness of a male's spots to assess whether or not he is infected with a parasite, such as Gyrodactylus turnbulli, a common monogenean trematode. Classic work by Anne Houde and others showed that infected male guppies showed less intense orange spots and that female guppies preferred them less in mate-choice experiments. They may be using these cues as a means of avoiding being parasitized themselves, but they are also probably trying to pick males with good genes so that their offspring might be resistant to parasites, too.

Photo by Marilyn Scott and comes from this website.

June 19, 2010

June 19 - Barsonella lafoni

This species of tapeworm was recently described from African catfish that were collected in Ethiopia and Sudan. The complete life cycle is not currently known, but it has been speculated that they likely use copepods as their first intermediate hosts, which are then consumed by the catfish. The etymology of this species is rather amusing. The genus was also a new one - this was named after Maxwell Barson, who is a fish parasitologist from Zimbabwe. The species name here, though, is in honor of - and I quote from the original species description here - "Dominique Lafon, world-famous winemaker from Meursault, Burgundy, France, who produces one of the most inspiring white wines in the world." I wonder how Lafon feels about this?

June 18, 2010

June 18 - Plasmodium mexicanum

Plasmodium mexicanum is, without a doubt, the best-studied species of lizard malaria parasite, and that is thanks to decades of work by Dr. Joseph Schall and his students. This parasite infects western fence lizards (Sceloporus occidentalis), in northern California and Oregon, but unlike most other Plasmodium species, it doesn't use a mosquito as its vector; it uses a phlebotomine sandfly. Work by Schall and others demonstrated that this parasite does have fitness consequences for its hosts - females lay fewer eggs and males have trouble defending a territory from other males. The parasite also seems to affect the bright coloring on the bellies of these lizards.

Photo by Schall himself.

Happy birthday, Joe.

June 17, 2010

June 17 - Caenocholax fenyesi

Strepsipterans are really, really freaking weird insects. They have sexes that are dimorphic to the extreme, have eyes that are unlike those in any other insect (resembling those of trilobites more), and have been a phylogenetic nightmare, including being one of the textbook cases of long-branch attraction observed in early molecular systematics studies. The life cycle, too, is really, really weird. Let's start with the first-instar larvae - these are the stages that seek out a host. In Caenocholax fenyesi, the males parasitize ants, so they seek out this host, penetrate the cuticle, and grow. Eventually, the male will pupate and emerge as an adult, which looks at least fairly insect-like, but he will only live a few short hours and spend the entire time searching for a female. What about the gals? C. fenyesi females parasitize orthopterans - grasshoppers, crickets, and mantids. When the first instar larvae of a female invades, she remains neotenic and never develops the characteristics of an adult insect. No, she is just an egg-, or rather a larvae-producing blob-like machine. The eggs that she produces hatch inside of her and can freely move about in her hemocoel. Eventually, the larvae will emerge via her brood canal. Females produce phermones to help the males find them and they are inseminated into this same brood canal. Strepsipterans castrate their hosts and the females can make up as much as 90% of the volume of the host insect's abdomen. Males of C. fenyesi were first reported in 1909 and then were subsequently frequently found parasitizing ants throughout the southeast U.S. But, the females remained unknown for 94 years. Finally, in 2003, Jeyaraney Kathirithamby from the University of Oxford and J. Spencer Johnston from Texas A&M found a female that they suspected might be C. fenyesi in a cricket and confirmed the match using DNA sequence data, where the two individuals were 100% identical.

Image is of a male Caenocholax fenyesifrom this site.

June 16, 2010

June 16 - Babesia microti

If you suddenly experience symptoms that resemble those of malaria (fever, chills and pains, etc.), but have not traveled to the tropics, but you have traveled to Long Island, Connecticut, or Rhode Island, perhaps you've acquired its relative, Babesia microti. This apicomplexan parasite also infects red blood cells and has a life cycle that is roughly similar to Plasmodium (though without liver or other exo-erythrocytcic stages), but instead of mosquitoes, this parasite uses ticks as its vectors. The normal vertebrate hosts are white-footed mice (Peromyscus leucopus). Because the same species of ticks also transmit Lyme Disease, it is not uncommon for people to become simultaneously infected by both. There seems to be an increase in the number of reported cases recently, due partly to better awareness and diagnosis, but also likely because of greater contact between ticks and people.

June 15, 2010

June 15 - Myxobolus cerebralis

Fishermen are probably familiar with this parasite, which causes whirling disease in trout and salmon. These parasites, which belong to an enigmatic group known as Myxozoa, alternate between tubifex worms and the fish. The parasites in the worm release triactinomyxon spores into the water. These are not passive little cells just waiting to be eaten, though - oh no, these spores are a parasite-injecting machine. They can swim through the water to find a fish host, and then will discharge a coiled filament, which produces a hole in the fish skin and allows the parasite to enter. They will migrate through the fish, eventually coming to reside in the cartilage surrounding the brain. There they cause both skeletal and neurological damage, which frequently results in abnormal movement and behavior - the whirling for which the disease is named. When the fish dies either from predation or other causes, the parasites are released into the water to go find new worm hosts. The origin of this group has been controversial - though single-celled, some morphological and genetic data have placed these parasites as closely related to cnidaria (e.g. jellyfish), while others have suggested that they may actually be bilateria.

June 14, 2010

June 14 - Chlamydophila psittaci

There are many reasons not to keep pet parrots. They're long-lived birds that require years, if not decades, of care. They can be messy and destructive. And, above all, many species are in danger of extinction and quelching the market for them is one helpful thing we can do. But, today's parasite is another reason. Chlamydophila psittaci is a species of bacteria that causes a very serious disease in both birds and mammals, including humans, known as psittacosis. These bacteria have a pretty unusual life cycle - they alternate between being intracellular bacteria in the lungs of their hosts and very resistant stages known as "elementary bodies." When engulfed by phagocytosis and attacked with a lysosome, the elementary bodies say "Ha!" and just begin to replicate instead - even going so far as to use some of the host cell's own organelles. Eventually they kill the host cell and become elementary bodies again, ready to reinfect this host or be spread to another one. In 1929, a major outbreak of psittacosis occurred in the U.S. The result of that was the drafting of more strict regulations concerning the trade of parrots and other pet birds but this epidemic was also partly responsible for the creation of the National Institutes of Health. You can read more about that in this article from The New Yorker that was published last year.

The image comes from this site.

June 13, 2010

June 13 - Marburg virus

In 1967, in the German town of Marburg, 31 people became very ill with a strange new disease - 7 of them died. Many of the people who had become ill were involved with research on polio vaccines and were exposed to monkeys that had been originally imported from Uganda. The culprit was a virus, and it came to be known as Marburg virus, after the town. Marburg was the first filovirus to be discovered and is closely related to Ebola virus. It is transmitted from primate to person or person to person via exposure to infected body fluids such as blood or saliva and can produce rather horrific symptoms, including jaundice, delirium, and liver failure, as well as hemorrhaging. Untreated, it can have a fatality rate of as high as 90%. In 2008, the first case in the U.S. was reported, though the patient acquired the virus in Uganda. Vaccines are currently being developed.

June 12, 2010

June 12 - Paramoeba perniciosa

This amoeba is responsible for causing disease in several species of crabs and lobster. It is a feared parasite amongst crab fishermen and Maryland foodies as epizootics can cause very high mortality of crabs such as blue crabs and gray crabs, by destroying their connective tissue.

Image from micro*scope.

June 11, 2010

June 11 - Bucephalus polymorphus

Bucephalus polymorphus is a species of digenetic trematode (fluke) that alternates between freshwater mollusks and then usually two species of fish as its hosts. The first fish host is mostly a transport vehicle - the parasites encyst under the scales and wait for this fish to be eaten. Heavy infections in the bivalve host can induce castration, which is great for the parasite, as it usually causes the mussel to live longer - and thus allows the parasite to produce more offspring. These parasites are natural "enemies" of zebra mussels in their native ranges, but does not appear to have invaded North America with these bivalves. Although a natural control agent would have its plusses, there is concern that the infection of native fishes by these parasites might be a very unwanted side effect.

Photo from Wikipedia

June 10, 2010

June 10 -Syphacia obvelata

This pinworm is commonly found in laboratory rodents such as mice and hamsters, as well as wild rodents. Because they are easy to maintain in these lab animals, they are often used as model organisms to study the biology of pinworms and to test anti-nematode compounds. This species, like some other pinworms, are capable of "retroinfection" - if the host's feces aren't moving quickly enough out, the eggs can hatch, mature, and just migrate back up the intestine to join their parents in churning out more eggs. Typically, though, the eggs are accidentally consumed by a rodent when it is grooming and go through the life cycle the normal way.. Ah, phew- that's comforting.

Image comes from this page.

June 9, 2010

June 9 - Orthohalarachne attenuata

Back in 1984, a 35-year old guy started feeling a pain in his eye and went to his doctor. The doctor looked under his eyelid and saw nothing. The next day, the pain was worse so he went back and asked the doctor to examine him again. During that visit, the doctor found - and removed - a single mite of the species Orthohalarachne attenuata. Ok, weird, but not that weird, right? Wrong. Orthohalarachne attenuata is a species of mite that normally is found in the nasal passages of fur seals, sea lions, and walruses. In seals, the mites can be both prevalent (as in almost every single seal has them) and abundant (as in more than 1000 mites per seal and in a few cases in one study, more than 2000!). These incredibly high infestations can cause problems for the seal's breathing, but can also do damage in the lungs and leave the seals susceptible to other infections, too. Transmission between seals occurs by -- sneezing on each other, of course. So, how did this young guy in California get a nasal mite in his eye? Turns out that two days before his first doctor's visit, he had visited Sea World - where he stood too close to some walruses and got sneezed on.

Photo contributed by Mike Kinsella. Documentation of the human case in this paper.

June 8, 2010

June 8 - Plasmodium floridense

In January, you read about Plasmodium minuoviride, a malaria parasite of lizards, and learned that over 100 malaria parasites use lizard hosts. Today’s parasite – Plasmodium floridense – is another of these lizard parasites. As you might have guessed from its species name, it was first described in Florida, but its distribution includes the southern United States, most of the Caribbean, as well as parts of Central America. It is known from roughly 30 lizard species (a high host number for this kind of parasite), with most of these belonging to the lizard genus Anolis.

Prevalence (the percentage of animals infected) of P. floridense varies greatly among these hosts, ranging 5 to 50%. The cause of this variation is unknown. Differences in host ecology might affect prevalence, because – for example – some lizard species occur in open areas and infected lizards might use heat from the sun to raise their body temperature (i.e., a “behavioral fever”). Likewise, a vector species may encounter some lizard species more frequently than others, based on differences in these lizards’ roosting preferences, thereby skewing the rates of infection. These and several other potential factors could be causing the variation in prevalence of P. floridense.

Anolis lizards make good subjects in which evaluate the factors affecting parasite prevalence. They have undergone a repeated pattern of adaptive evolution in the Greater Antilles, and based on their behavior, morphology, and ecology, these lizards can be categorized into one of several “ecomorph” types. The pattern on each island is very similar, as near to a replicated experimental design as an evolutionary biologist could hope. Preliminary research on Hispaniola has shown that P. floridense infections are found primarily in lizards of one ecomorph type, and ongoing work will determine if this pattern is consistent across other islands (Falk et al., unpublished).

Contributed by Bryan Falk.

June 7, 2010

June 7 - Diplozoon paradoxum

We normally think of parasites as rather despicable creatures - out for food and shelter and not caring who suffers in their quest. But today's parasite, the monogenean Diplozoon paradoxum, has at least one redeeming quality - it just might be the most monogamous organism on the planet. A young D. paradoxum, called a diplora, settles down on the gills of a fish and waits for a mate. If another one never comes along, then the single parasite will simply die (of loneliness?). However, if another comes along, the two worms actually fuse their bodies completely together and become adults, with one producing testes and the other producing ovaries allowing them to continually cross-fertilize. And that is how they will stay - forever.

Diplozoon is the official symbol of the Meguro Parasitological Museum in Japan - if you visit, you can even buy jewelry featuring the conjoined parasites.

The image comes from this site.

June 6, 2010

June 6 - Dermanyssus gallinae

Dermanyssus gallinae, or the red mite, is an ectoparasite of birds. They do not live on birds, but rather hop on them to feed on their blood at night, while they are sleeping. They can be major pests for chicken and other poultry farmers. They will occasionally take blood meals from mammals, even humans, if they work with or live near birds.

June 5, 2010

June 5 - Macracanthorhynchus hirudinaceus

Today's parasite has quite a handle of a Latin name - perhaps you'll prefer the common name - "Giant Thorny-Headed Worm of Swine." As that moniker suggests, this is an acanthocephalan, and like its relatives has a life cycle that alternates between an invertebrate and a vertebrate. The eggs of this parasites are eaten by beetles where they will develop into juveniles or cytacanths. These insects then get eaten by pigs (or occasionally dogs or even humans in very rare cases). The adults attach themselves to the small intestinal wall and can get quite large - up to 65 centimeters. The eggs pass out with the pig's feces and interestingly, if a bird accidentally eats them if they are on something that they're gobbling up, they pass right through unharmed to wait for the right (beetle) host.

June 4, 2010

June 4 - Lernaeocera branchialis

Life is about dealing with changes, but for Lernaeocera branchialis, some of those changes are pretty profound. This parasitic copepod starts out as a free-swimming nauplius, like other crustaceans. Then, it turns into a copepodid and seeks out an intermediate host, something slow and easy to find, like a flounder. It mates with an opposite-sex copepodid on this host and then sets off to find its final host, usually a cod or haddock. It then completely metamorphosizes into a large (4 cm), red, worm-like thing with a big egg sac and "antlers". Its head remains inserted into the gills of the fish where it feeds from the blood and pumps out new eggs.

The photo is from this site.

June 3, 2010

June 3 - Boschniakia hookeri

If you're hiking in western North America and look down and spot a pine cone sitting on its end, take a closer look - it might be Boschniakia hookeri, known as groundcone. These are species of broomrapes, holoparasitic plants with no chlorophyll that depend on plants like alders or huckleberries for water and nutrients. The part that looks like a pinecone can be brown or purple, yellow or red and this is the inflorescence. Native Americans/Canadians sometimes ate the stems of these plants as a snack.

June 2, 2010

June 2 - Rhinosporidium seeberi

Rhinosporidium seeberi is a bit of a mystery. It is found primarily in India and Sri Lanka and causes a disease known simply as rhinosporidiosis, which is an infection in the mucosal tissues of the nose, pharynx, and sometimes the eyes. The organism is a member of the group Mesomycetozoea, which are single-celled organisms thought to predate the split between animals and fungi. The natural history of these parasites is also not very well known - they are thought to occur in water and possibly soil and infect people when tissues are exposed when they bathe in common ponds. The image come from this website - if you're brave, open that link for some pictures of the infection in people.

June 1, 2010

June 1 - Compsilura concinnata

Gypsy moths are a notorious invasive species in the eastern U.S., causing massive damage to hardwood trees like oaks, aspens and apples. These moths were originally imported in the late 1860's by a biologist to try to breed disease-free silk-spinning caterpillars that then escaped and spread like crazy. (I remember being a kid when they first reached my hometown in northern New York - it was like a plague had descended on us!) In an effort to control them, a parasitoid fly, Compsilura concinnata, was introduced from Europe. Although the flies do help to some degree, they may have caused more damage than good because they also prey on native caterpillars. Part of this is because the gypsy moth is univoltine, that is it just undergoes one generation per year, but the flies are multivoltine. The flies use gypsy moth caterpillars for their first generation in the spring, but then when the gypsy moths are gone, the flies turn to other caterpillars for the rest of the warm months. The beautiful Luna Moths have been hard hit by these "control" agents.

The image is from this site and read more about the effect on luna moths here.