July 31 - Gongylonema peromysci

To a parasite, the vertebrate body is a vast array of habitats waiting to be invaded. And like other animals, most helminths have adapted to a specific niche and are only found in one organ or even one tissue within an organ. Nematodes of the genus Gongylonema live in sinuous tunnels in the wall of the anterior stomach and esophagus of birds and mammals and, when present in large numbers, can cause serious pathology. This spirurid genus is characterized by having wart-like growths on the cuticle of the anterior end. This species uses deer mice as its hosts.

Contributed by Mike Kinsella.

July 30 - Anomalospiza imberbis

This pretty little African bird is commonly called the Cuckoo Finch or Parasitic Weaver and is a member of a family of African birds known as Viduidae, or the indigobirds or whydahs (now there's a good Scrabble word!). These birds are like cuckoos in that they lay their eggs in the nests of other birds and the hosts for Anomalospiza imberbis eggs are usually warblers. The females apparently remove any resident eggs before laying their own and then the little parasitic weavers convince their adoptive parents to feed them for several weeks before heading off to find a mate or join flocks of their own species.

July 29 - Haematopinus quadripertusus

Haematopinus quadripertusus, commonly called the cattle tail louse, get its name because, well, because it lives on the tails of cattle. These lice will actually take their blood meals from both ends of the cow, however, and can also be found on the mouth and in the ears as well as some of the soft bits on the backside. This louse was introduced into the Southern U.S. and is now a major pest of cattle in Florida, where they can cause anemia and weight loss - not something you want if you're trying to fatten up your cattle. Lice can spread from cow to cow when they are in close contact or via rubbing on the same thing such as a post. But, the lice can also colonize completely different herds of cattle by hitching rides on flies!

Image from this site, which has additional information on these parasites.

July 28 - Unnamed zygocercous cercaria (trematode)

Today's parasite is a digenean trematode. And like most other digeneans, it multiplies asexually within its snail first intermediate host (in this case, a marine snail) producing larval stages call cercariae which are then released into the environment to infect the next host in the life-cycle. However, unlike most digeneans where individual cercaria swim off independently, each fending for itself, the cercariae of this species rally in the mantle cavity of the host snail where they hook the ends of their tails together before leaving via the snail's exhalant siphon as a collective. As they leave the snail, they synchronise their swimming motion so that the entire aggregate moves as one.

To an unsuspecting fish, the writhing mass of cercariae resembles a struggling little zooplankton which would make for a tasty mouthful. Instead, as the fish swallows the wriggling ball of cercariae, the parasites get tangled up in the fish's mouth and begin penetrating into the host tissue. Imagine what a nightmarish experience that must be! It would be like you eating a handful of popcorn only to find in mid-chew that the popcorns are drilling their way into your throat!


The scale bar in the photo is 0.5 mm in length and the photo is from this paper:

Beuret, J. and Pearson, J. C. (1994) Description of a new zygocercous cercaria (Opisthorchioidea: Heterophyidae) from prosobranch gastropods collected at Heron Island (Great Barrier Reef, Australia) and a review of zygocercariae. Systematic Parasitology 27:105-12.

Contributed by Tommy Leung.

July 27 - Aspidodera esperanzae

I have to admit that I included this parasite because I found this photo to be so striking. The image is of the sucker that the nematode, Aspidodera esperanzae, uses to attach itself to the intestine of its host. This species was discovered in armadillos in Paraguay in 1995 by a team of Japanese scientists who were part of a collaborative team sent to work on Chagas disease. The species is named after the consul of the Columbian embassy, however.

July 26 - Spongospora subterranea

Given my recent borderline obsession with these fries covered in cheese, bacon and scallions served at the restaruant downstairs from my office, this should have been one of the parasites featured in the week of parasites of plants I love (May 10-17). Spongospora subterranea is a parasite of potatoes that causes a disease with the funny name of "powdery scab." It used to be called a slime mold and grouped with fungi, but is now considered part of the phylum Cercozoa. Free-swimming zoospores invade the roots of the potato and induce galls. There they produce the characteristic lesions that look a lot like scabs, which when they rupture and the spores are shed, look like, well, powdery scabs. Because the spores stay in the soil in enormous numbers, they can be really difficult to eliminate from a field. These parasites can be found throughout Europe, but some believe that they originally came from South America. Spongospora subterranea is the vector for a virus as well. We'll meet that parasite soon.

Photo is from this page.

July 25 - Orobranche californica

Some parasites are quite pretty - particularly parasitic plants, like Orobranche californica, California broomrape. These plants do not have leaves or chlorophyll and take their nutrients from their hosts, in this case, goldenrods and sagebrushes. This species grows all along the west coast of North America. It is currently divided into several subspecies based on habitat and host preferences.

July 24 - Lepeophtheirus salmonis

Here's another species of parasitic copepod, but this one's not going to fish eyes - just feeding off the skin, mucus, and blood of its hosts. Lepeophtheirus salmonis is the salmon louse, which, as the name suggests, infects salmon and marine species of trout. These parasites can cause a great deal of morbidity in their fish hosts and may have severe consequences for both wild and farmed fish populations as very heavy infections of these parasites can kill the hosts. You can read more about these parasites on this site, which is also the source of the image.

July 23 - Ribeiroia ondatrae

Meet Ribeiroia ondatrae, a nasty and evil (if you ask a tadpole) digenetic trematode. R. ondatrae has quite the complex life cycle requiring three different hosts. Briefly, R. ondatrae uses an aquatic snail as the first intermediate host, tadpoles as the second intermediate hosts and finally, an aquatic bird as the definitive host. R. ondatrae has gained world wide attention as a possible ecological driver behind amphibian declines due to the severe and grotesque limb/body malformations caused by infection, as the cercariae typically encyst as metacercariae within the developing hind limbs of a tadpole. Over the past decade or so, the consequences of this parasite for its tadpole intermediate host have been intensively investigated, especially in the context of additional stressors such as environmental contaminates. However, much more work is required in order to determine the specific mechanisms behind how this parasite actually messes up normal limb patterning and development.

Contributed by Dorina Szuroczki.

July 22 - Ommatokoita elongata

If you find the idea of having something lodged in your eye distressing (ok let's face it, who doesn't?), then today's parasite is probably your worst nightmare. Fortunately for you, it is not a human parasite. The hosts for today's parasite are Greenland sharks (Somniosus microcephalus) and Pacific sleeper sharks (Somniosus pacificus) - both large deep water sharks. Ommatokoita elongata is a parasitic copepod, approximately 5 cm in length (almost 2 inches) with a very specific and truly cringe-worthy preference about where it attaches on to the host.The adult female copepod attaches herself to the shark's eye with an anchoring structure call the bulba, and grazes on the surface of the cornea (see photo, black arrow indicates attachment point), hanging off the eyes of the shark like a grotesque tassle

There are two possible reasons for the copepod's attachment site. Shark skin is covered in microscopic, teeth-like structures call denticles which can make it difficult for parasites to attach themselves to skin (though some species of parasitic copepods
manage). Secondly the eye is considered to be a "immunologically benign environment" for parasites, thus such an attachment is less likely to illicit an immune response.

While the parasite can cause significant damage to the cornea and result in blindness for the host, most sharks seem unaffected by the presence of the parasite and many sharks have the copepod in both eyes, strangely enough. This goes to show when considering the virulence (harmfulness of a parasite to its host) of a parasite, it is worth taking into account the perspective of the host involved - what may seem debilitating to us may not necessarily be the case for the actual organism in question.


Photo source: Borucinska, J.D., Benz, G.W. and Whiteley, H.E. (1998) Ocular lesions associated with attachment of the parasitic copepod Ommatokoita elongata (Grant) to corneas of Greenland sharks, Somniosus microcephalus (Bloch & Schneider) Journal of Fish Diseases, 21:415-422

Also some good photos of live Greenland sharks with the parasite can be seen in Caloyianis, N. "Greenland Sharks." National Geographic 194, no. 3 (1998): 60–71.

Contributed by Tommy Leung.