These Are a Few of My Favourite Things (About Evolution): Pt. 1

I recently had a conversation with a friend of mine that had to do with some of the more amazing things we knew from evolutionary theory, which got me thinking about some of the things I’ve learned that have shocked/delighted me the most. I was about to put it all together into one post, but then I thought better of it, and decided to milk this idea for all it’s worth.

Thus, I will be have several posts, that will relate to that theme (read the title if you still don’t know what it is.)

The first crazy thing from evolution that I love is the Lancet Fluke ( or Dicrocoelium dendriticum), and it’s reproductive system (which is pictured above).

From wikipedia (where else…):

Dicrocoelium dendriticum spends its adult life inside the liver of its host (cattle and sheep mostly). After mating, the eggs are excreted in the feces.

The first intermediate host, the terrestrial snail (Cochlicopa lubrica in the United States), eats the feces, and becomes infected by the larvalparasites. The larvae (or miracidium) drill through the wall of the gut and settle in its digestive tract, where they develop into a juvenile stage. The snail tries to defend itself by walling the parasites off in cysts, which it then excretes and leaves behind in the grass.

The second intermediate host, an ant (Formica fusca in the United States), uses the trail of snail slime as a source of moisture. The ant then swallows a cyst loaded with hundreds of juvenile lancet flukes. The parasites enter the gut and then drift through its body. Most of the cercariae encyst in the haemocoel of the ant and mature into metacercariae, but one moves to the sub-esophageal ganglion (a cluster of nerve cells underneath the esophagus). There, the fluke takes control of the ant’s actions by manipulating these nerves. As evening approaches and the air cools, the infected ant is drawn away from other members of the colony and upward to the top of a blade of grass. Once there, it clamps its mandibles onto the top of the blade and stays there until dawn. Afterward, it goes back to its normal activity at the ant colony. If the host ant were to be subjected to the heat of the direct sun, it would die along with the parasite. Night after night, the ant goes back to the top of a blade of grass until a grazing animal comes along and eats the blade, ingesting the ant along with it, thus putting lancet flukes back inside their host. They live out their adult lives inside the animal, reproducing so that the cycle begins again. Infected ants may contain 100 metacercariae, and a high percentage of ants may be infected. Typical infections in cattle may be in the tens of thousands of adult worms.

Yeah, that’s right, that parasite requires 3 different hosts, one of which it TAKES CONTROL OF in order to reproduce and live out its life cycle.

If that doesn’t cause your jaw to drop…well I just don’t know what will.


About dontdontoperate

28 year old originally from Barrie, Ontario, Canada. H.B.Sc. from UofT with a major in chemistry and a double minor in philosophy and math. M.Sc. from UofT in physiology and neuroscience. Finished my Ph.D. in biomedical engineering at McMaster in the fall of 2013.
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2 Responses to These Are a Few of My Favourite Things (About Evolution): Pt. 1

  1. Pingback: These Are a Few of My Favourite Things (About Evolution): Pt. 2: Endogenous Retroviruses | Dontdontoperate's Blog

  2. Pingback: These Are a Few of My Favourite Things (About Evolution): Pt. 3: Endosymbiosis | Dontdontoperate's Blog

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