October 10 - Microdajus langi

The parasite for today comes from a strange family of ectoparasitic crustaceans called Tantulocarida. There are only a few species within this family and they have a very peculiar development. They are parasitic on a number of deep sea crustaceans, and Microdajus langi itself infects small, shrimp-like crustaceans call tanaids.

Tantulocarids have a very strange life-cycle which is either asexual (which is more common) or sexual (relatively rare). In the asexual cycle, only females larvae are produced. Non-feeding larval stages known as tantulus are released from asexual females which resemble sacs and these larvae can directly attach and infect another host. On the left side of the accompanying photo is an immature female that had just attached onto the host, but once it is attached, it undergoes a strange transformation. On the right side of the photo, you can see a female that has just begun undergoing this development and she eventually develops into a bloated sac filled with eggs.

However, in the sexual cycle both males and females are produced and while males have never been observed alive, they have well-developed swimming legs and sensory organs which allow them to actively seek out and inseminate females. Once fertilised, the female attaches herself onto a crustacean host to start the cycle anew.

Photos from: Boxshall, G.A. and Lincoln, R.J. (1987) The Life Cycle of the Tantulocarida (Crustacea). Philosophical Transactions of the Royal Society of London. Series B 315: 267-303.

Contributed by Tommy Leung.

October 9 - Haemoproteus columbae

Lots of people are a little grossed out by pigeons, jokingly (?) calling them "flying rats". They'd probably be even more grossed out to know that many of those pigeons are hosts to a malaria-like blood parasite called Haemoproteus columbae. These parasites produce large kidney-shaped gametocytes in the red blood cells of doves and pigeons. These infected erythrocytes are ingested by hippoboscid flies (see this post for a similar species) that scamper through the feathers of the birds and feed on their blood for nourishment. H. columbae is the type species for its genus, which was for many years considered to be a large group of morphologically similar parasites that infected not just doves, but other birds, turtles and lizards as well. Molecular data have recently shown, though, that the forms in doves are a distinct lineage, not closely related to the others. This thus also corresponds to the vectors that are used as the parasites in other birds are transmitted by midges, not hippoboscids.

Photo by Jessi Waite.

October 8 - Plasmodium relictum

The beautiful birds of Hawai'i have been battling with an invasive malaria parasite known as Plasmodium relictum, and several - perhaps 10 or more - species have been lost to extinction, due, in part to this novel pathogen. In the early 1800's, the mosquito, Culex quinquefasciatus was brought to Hawai'i, and this vector allowed the parasite to take hold on the islands as well. Because the mosquito does not go much above 4000 meters in elevation, many native lowland species have pushed their ranges up in altitude, but since most of the islands are lower than 5,000 meters, there's just not very far to go. P. relictum has an incredibly wide geographic range and infects a large number of bird species, making it an unusual generalist amongst its kin.

The image is from the USGS Microbiology Image Gallery and was taken by Carter Atkinson.

October 7 - Leucocytozoon simondi

Leucocytozoon simondi is a blood parasite that is common in ducks and other waterfowl in the northern U.S. and Canada. These parasites, part of the same order of parasites as those that cause malaria in humans (Haemosporidia), are transmitted from duck to duck via the bites of blackflies. Their asexual replication occurs in the livers of the birds, followed by appearance of the transmission stages or gametocytes in the blood cells. Because of their large size, deep staining, and propensity to push the nucleus of the red blood cell way up against the cell membrane, these parasites were originally thought to infect white blood cells, not red ones. This species is happy to infect both wild and domestic hosts, but in the latter, they can actually kill the birds through liver damage and anemia.

October 6 - Hymenolepis nana

Hymenolepis nana, or the dwarf tapeworm (only 40 mm long!), is thought to be the most common human cestode on the planet. Unusual amongst tapeworms, H. nana does not require an intermediate host, but can be passed simply from one person (or rodent) to another via the ingestion of eggs that are shed in the feces, and auto-infection occurs in parts of the world where the worms are common. This direct life cycle is thought to be a recent adaptation in this species as the life cycle can be completed via an intermediate such as a flour beetle, much like its cousin, H. microstoma that you met way in the beginning of the year.

Image from the CDC Public Health Image Library.

October 5 - Petromyzon marinus

The sea lamprey, Petromyzon marinus, is a rather gruesome fish - almost right out of a science fiction movie. Hatched in freshwater rivers, the larvae do not possess these fearsome mouths, but are toothless and live a quiet life, buried in the mud where they simply filter feed. Once they grow to a larger size, however, they metamorphosize into the adult, parasitic form, migrate to the sea, and use their suction-cup shaped mouth to latch onto a fish such as a salmon or other bony fish. There, firmly attached, the razor-like teeth and tongue rasp away at the host's flesh and allow the lamprey to feed on blood and bits of tissue. Host fish often die from the excessive blood loss or infections that ensue in the wounds made by these parasites, which can grow up to three feet in length. Native to the coasts of North America and Europe as well as Lake Champlain, which separates New York from Vermont, the construction of the St. Lawrence Seaway may have allowed these parasites to take up firm residence in the Great Lakes, where they now are considered pests due to their feeding on popular game fish such as lake trout and their disruption of the native ecosystem.

October 4 -Gynaecotyla longiintestinata

Gynaecotyla longiintestinata is a marine trematode from the Aveiro estuary of Potugal. It is in the same family as Maritrema novaezealandensis- the Microphallidae. G. longiintestinata has a typical life-cycle for a trematode from the microphallid family - its uses a snail, in this case the intertidal whelk, Nassarius reticulatus, as a first intermediate host. From there, free-swimming larval stages called cercariae are produced and released into the environment, where they infect the second intermediate host, in this case the crab, Carcinus maenas. They occupy a very specific and peculiar microhabitat within the crab, namely its antennal glands. The definitive hosts of this parasite are shorebirds that feed on crabs.

Photo from:
Russell-Pinto, F. and Bartoli, P. (2002) Cercaria sevillana n. sp., a new cercaria (Digenea: Microphallidae) from Nassarius reticulatus (L.) (Mollusca: Prosobranchia) in Portugal. Systematic Parasitology 53: 175-182.

Contributed by Tommy Leung.

October 3 - Toxocara canis

Toxocara canis is a roundworm (nematode) that occurs worldwide in dogs. In adults, they are generally asymptomatic, but they can be fatal to puppies, particularly if the infection is heavy. Transmission usually occurs via ingestion of the eggs, which are passed in feces. Once swallowed, the larvae hatch and embark on a scenic route - from the intestine to the liver and lungs via the blood stream, where they are coughed up, swallowed again, and eventually mature. Other hosts, including human pet-lovers, can become infected and that characteristic larval wandering can make those humans very sick themselves.

October 2 - Peachia parasitica

Peachia is a genus of anemones, but very different from the big gentle waving sort you see on coral reefs, with happy families of Nemo-like anemone fishes frolicking in them. No, Peachia is a parasite, one of very few parasitic anemones. Who falls victim to a parasitic anemone? Another cnidarian: the jellyfish, Cyanea capillata. I’ve seen them in sea nettles (Chrysaora sp.), too. The few publications of Peachia suggest that it may be a facultative parasite; McDermott et al describe one that lived for 4 years in the lab. Peachia is just another fine example showing how many times parasitism has arisen in the evolutionary history of life on this planet.

McDermott, J.J. et al. (1982) The occurrence of the anemone Peachia parasitica as a symbiont in the scyphozoan Cyanea capillata in the lower Chesapeake Bay. Estuaries 5(4):319-321.

Contributed by Al Dove.

October 1 - Placobdella papillifera

Closely related to a glossiphoniid leech we saw earlier, Placobdella papillifera is a pretty leech distributed in North American freshwater habitats. P. papillifera is a blood-feeder, feeding on turtles (and sometimes alligators!). This leech was found under a rock in Savannah River in South Carolina. There are two pictures shown here, one showing the papillae on the dorsal surface and one showing the smooth ventral region. This leech was large, filling out the entire bottom of a petri dish! (Click on the thumbnail to get a good look at its pretty papillae.)

Contributed by Jessica Light.