I keep having ideas for “picture gallery” posts, involving different papers’ illustrations of the same sort of thing. So far I’ve only done one (the cockroach feeding apparati) as they turn out to be a lot of work and you can never tell which papers are going to have illustrations and which ones aren’t.
In searching for pictures of encapsulated roundworm larvae in various organs of various animals, I determined that they all look sort of the same. And it’s not that interesting to compare, say, a picture of mouse muscle to a picture of raccoon or porcupine muscle. It’s all muscle. Also it may not be a good idea to extend this blog into worms and other complicated parasite species. Malaria is a parasite and also an infectious disease. But what about worms? So in the area of parasitology, I may want to stick to protozoans.
Leucocytozoons are single-celled organisms that infect birds, and are transmitted by the bugs known as blackflies. They were first observed in the 19th century in owl blood, by a zoologist named Danilewsky working in Kharkov, Ukraine. Danilewsky named them for their resemblance to white blood cells, though the exact genus “Leucocytozoon” was not applied until 1904, as detailed in this historical report by Lithuanian pedant and protozoan expert Gediminas Valkiūnas.
They seem to have life cycles similar to malaria, being fellow members of the phylum Apicomplexa. They go through many stages of life. Sporozoites are generated in the gut of an insect, and migrate to the salivary glands. The insect injects them into the blood of a vertebrate, and they go through several more stages, first in the liver and then in red blood cells. Then an insect takes a blood meal, the parasites end up in the insect’s gut, and they eventually make more sporozoites. It seems that Leucocytozoons are not as specific as malaria parasites, as they often infect white blood cells as well as RBCs, and the sporozoites of some species thrive in places other than the liver.
* * *
This figure shows the “macrogametocyte” stage (macro-gamete-ocyte) of the parasite life cycle. The macrogametocytes grow inside red blood cells, eventually filling and distorting the cells. This may be a pretty standard illustration. But it brought something else to mind.
From Fallis AM, Desser SS, and Khan RA (1974), On species of Leucytozoon. Advances in Parasitology 12:1-67 : (available from the publisher, subscription required, or available in partial form from Google Books)
As rendered by the Canadian authors of the paper linked above, these jaunty, big-eyed, dancing blobs are quite evocative. The genus ranges from L. vandenbrandeni (#2), which looks like a baleful ocean sunfish and lives inside the similarly aquatic birds called cormorants, to L. bonasae (#19), which infects grouse and appears to be wearing one of those baggy vinyl baseball caps from the golden age of breakdancing.
The Leucocytozoons bring to mind another type of sinister creature on a more macroscopic scale, from one of my favorite children’s books.
Yes, the Vermicious Knids, which menace visitors to the Space Hotel in Roald Dahl’s Chocolate Factory sequel, Charlie and the Great Glass Elevator. Described initially as resembling eggs with no features other than eyes, they then show that they could change shape.
The macrogametocytes of Leucytozoons look especially similar to Vermicious Knids when the latter are only displaying one eye, as in the above message to humanity, or in these creative illustrations by comics artist Isaac Cates.
* * *
As you’d expect, most useful photos of these organisms are in color and therefore don’t look much like these ink drawings.
But here’s some beautiful drawings, in color, of red blood cells containing a similar parasite, Haemoproteus syrnii. Just like the first Leucocytozoons ever observed, this organism infects owls. What are they trying to say? Are they communicating by Braille or some other pattern-based system? Or by spelling out letters? They seem only capable of “C” and “O”.
From Karadjian G et al. (2013), Haemoproteus syrnii in Strix aluco from France: Morphology, stages of sporogony in a hippoboscid fly, molecular characterization and discussion on the identification of Haemoproteus species. Parasite 20:32 (11 pages) :