September 30 - Aggregata octopiana

This year, a particular octopus named Paul achieved fame and stardom due to some of his famous shenanigans relating to the World Cup. However, even an invertebrate celebrity such as Paul is not without a parasitic nemesis. Aggregata octopiana is a species of single-celled parasite that infects the common octopus, forming cysts in various parts of the body including the gills, digestive tract, and epidermis. The details of the parasite's life-cycle are currently not clear, though it is known to be a two-host life-cycle involving alternating phases of sexual and asexual reproduction. The sexual phase of this parasite occurs within the octopus where it undergoes a series of differentiation and cell divisions to produce produce infective stages that are shed into the environment. The parasite then infects prawns or other crustaceans that act as the intermediate hosts where asexual phase occurs. The life-cycle starts anew when the infected crustacean is eaten by an octopus.

Contributed by Tommy Leung.

September 29 - Tunga penetrans

Tunga penetrans is a species of flea found in Central and South American and the Caribbean that has a similar life cycle to other fleas, such as Ctenocephalides felis, with one major exception. The females on T. penetrans are not content to hop onto a mammal, drink up some blood and move on - no, instead they move in. Commonly known as chigoe fleas (not to be confused with chiggers, which are larval mites), T. penetrans burrows headfirst into the skin, producing a lesion that is almost always on the foot and is extremely itchy and irritating. The lesion will have a black center, which are the two hindmost legs of the flea and her abdomen. After she feeds on blood from the epidermal capillaries, she will swell up like a little balloon and begin to pump eggs out when her host is walking on sandy soil. In this photo, you can see the familiar head of the flea, but her swollen abdomen has been damaged during the removal from the infected person. A large egg is visible, however.

Image is from the CDC Public Health Image Library.

September 28 - Aphanomyces invadans

Aphanomyces invadans is a highly pathogenic oomycete fungi which infects the Atlantic menhaden Brevoortia tyrannus and many other species of fish from around the world. This water mould has been implicated in massive fish kills in North Carolina, resulting in hundreds of thousands of dead fish. On average, an infection resulting from less than 10 zoospores (the infective stage of this fungi) is enough to kill a fish, and even infection by just a single zoospore can result in ulcerous lesions that can lead to mortality. Fish infected with the fungi develops ulcerous lesions which ultimately lead to extensive tissue necrosis. This fungus develops extremely quicky, doubling its hyphal mass every ten days, and it is also highly invasive, extending its hyphae into various tissues including the liver, kidneys and spinal cord of the fish host. Interestingly, A. invadans outbreaks are associated with high rainfall. This is likely due to the fact that this water mould has a low salinity tolerance and will not grow in higher salinity waters.

Reference:
Kiryu et al. (2003) Infectivity and pathogenicity of the oomycete Aphanomyces invadans in Atlantic menhaden Brevoortia tryannus. Diseases of Aquatic Organisms 54: 135-146.

(Photo from this paper.)

Contributed by Tommy Leung.

September 27 - Odhnerium sp.

Digeneans are flatworms famous for their plastic morphology, that is, the flexibility expressed in their body plan; the variations-on-a-theme, if you will. There are few better examples than Odhnerium species, a genus of accacoeliid worms parasitic in the intestine of the ocean sunfish, Mola mola. Most digeneans have either 0, 1 or 2 suckers, with 2 being the overwhelmingly most common body plan: an oral and a ventral sucker. Then along comes Odhnerium, which lines the anterior dorsal surface with muscular pseudosuckers, in this case at least 9 (they show up as blue waves). What’s a pseudosucker? Good question! It turns out that suckers have a very specific definition: a capsule-bound muscular attachment organ that works by suction. In this case, the suckers are apparently not capsule-bound (i.e. there’s no connective tissue membrane around them) so they only look like suckers – hence “pseudosuckers”. Still, it’s a pretty crazy departure from the normal body plan for digeneans, and it’s hard not to wonder what they’re so important for, since tens of thousands of gut dwelling fluke species do just fine without them. And while we’re at it, check out the ventral sucker, which is up on a sort of stalk called a pedicel, and is more like a pair of muscular flaps forming a clamp, than a typical round sucker.

The blue appearance of the suckers in this particular photo is a trick of the light. The photo was taken during processing to make the specimen into a permanent wholemount. There’s a step in the process when the worm has had all its water replaced by ethanol, and then you gradually replace the ethanol with a clearing agent like eugenol or (in this case) methyl salicylate. As the met-sal penetrated and cleared the tissues, this handsome colour was created for a few seconds, and I snapped the pics because it looked cool.

Contributed by Al Dove.

September 26 - Carnus hemapterus

Carnus hemapterus is a species of fly where the adults (the imagines, plural of imago), feed on the blood of nestling birds, particularly those of large birds such as owls or falcons. Larvae are birthed by females and feed just on the detritus in the nest, but then the development and emergence of the imagines coincides with the hatching of the birds. Both winged and unwinged flies may be present.

September 25 - Isospora felis

Isospora felis is a coccidian parasite of cats that typically has a direct life cycle, but may also pass through small rodents , which can act as vectors for these parasites. They infect the cells of the small intestine and can produce GI distress in their feline hosts. This genus is quite large, but not much work, particularly molecular work has been done on the group, to tease apart which hosts might be paratenic and which species might be cryptic.

Image by Steve Upton.

September 24 - Acanthochondria cornuta

Acanthochondria cornuta (Müller, 1776) is a chondracanthid copepod that infects the European flounder, Platichthys flesus (Linnaeus, 1758) (Teleostei: Pleuronectidae), in different geographic locations, including, the coast of Portugal. It is a site-specific marine ectoparasite that occurs generally with regularity and in high numbers in the branchial chambers of its flatfish host. As in all other species of chondracanthids, the male is dwarf, being usually found attached to the female in the vicinity of the genital region. In other words, he is not found directly attached to the fish host and is called a “hyperparasite”.

See these papers:
1. Cavaleiro, F. I. & Santos, M. J. (2007) Survey of the metazoan ectoparasites of the European flounder Platichthys flesus (Linnaeus, 1758) along the north-central Portuguese coast. Journal of Parasitology 93, 1218-1222.
2. Cavaleiro, F. I. & Santos, M. J. (2009) Seasonality of metazoan ectoparasites in marine European flounder Platichthys flesus (Teleostei: Pleuronectidae). Parasitology 136, 855-865.

Contributed by Francisca I. Cavaleiro & Maria J. Santos.

September 23 - Diphyllobothrium latum

A common item in Jewish cuisine is gefilte fish, small boiled balls of minced fish meat. Unfortunately, though, the preparation of these little treats typically involved testing the gefilte fish as it cooked, meaning early tastes were of undercooked fish. That habit resulted in lots of Jewish grandmothers becoming infected with a tapeworm called Diphyllobothrium latum. Native to Scandanavia and eastern Russia, these parasites were brought to the U.S. with immigrants who settled in Minnesota, Wisconsin and other northern climes all the way to the Pacific Northwest states and the worms easily adapted to the ecosystem there, infecting native fishes. The life cycle is complex and can involve numerous hosts, beginning with copepods that ingest the eggs and then moving up the food chain to larger and larger fish until they are consumed by a person. Many people do not realize that they are infected as the symptoms may, in fact be mild, even though the tapeworms can be more than 10 meters (i.e. more than 30 feet!) long and pump out a million eggs a day. A common one is a severe vitamin B12 deficiency, however. There are two important components to stopping the spread of this parasite: refraining from defecating in lakes and freezing fish before consuming and cooking it properly. These parasites have likely been associated with humans for a very long time - evidence of these worms has been found in settlements along the coast of South America that may be as old as 10,000 years.

Image from the CDC Public Health Image Library.

Read more about this parasite in Robert Desowitz's wonderful book, "New Guinea Tapeworms and Jewish Grandmothers".

September 22 - Ambylomma americanum

Yeeee haw! Today's parasite is the Lone Star Tick, Ambylomma americanum, though I must confess that although it is sometimes found in Texas, its name comes from the spot on the back of the females of the species. These ticks primarily feed on cattle or deer as adults. This species of tick is not thought to vector Lyme Disease, but they do transmit other parasites to humans, such as granulocytic ehrlichiosis (Ehrlichia ewingii), tularemia (Francisella tularensis), and a close relative of the Lyme disease bacterium, Borrelia lonestari, which produces Southern tick-associated rash illness (STARI). A. americanum also holds the distinction of being the first species of tick that was described from the United States - back before we were the United States - in 1754.

September 21 - Apodinium floodi

Most dinoflagellates are photosynthetic plankton that form the basis of many aquatic food webs or mutualist symbionts, sharing and sharing alike with their hosts. Apodinium floodi is an exception. Unlike its photosynthetic cousins, it is an ectoparasite, and its host is the pelagic sea squirt Oikopleura labradoriensis. Sea squirts, despite their sac-like appearance, actually belongs to a group of animals call the urochordates, which are more closely related to vertebrate animals than all other invertebrates. Apodinium floodi uses a structure call a peduncle to attach itself to the tail of the sea squirt, and penetrate the host's notochord to absorb nutrients from its blood.

It is an evolutionary marvel - a single-celled algae which has evolved to make a living by sucking blood from a pelagic animal!

Contributed by Tommy Leung.