At the
recommendation of a well-known parasitologist, I began reading about the
parasites that plagued everyone’s favorite prehistoric animals: the dinosaurs.
I found lots of information on various forms of dino-parasites…everything from
protists, to helminths, to insects. I’ve decided to break up this topic into a
series of posts over the next few weeks.
Today, let’s talk about some insidious
little creatures that may have infected dinosaurs…protozoan parasites! These
parasites are single-celled and not something that preserves well in fossils or in amber as
our ectoparasites did. However, they can still be detected in coprolites
(fossilized feces) and by the pathological problems they left evidence of in
the bones of ancient beasts.
Confirmation from
Coprolites
|
Entamoebites antiquus |
In 2006, Dr.
Poinar and his college Dr. Boucot reported the earliest evidence of protozoans
from a Belgian coprolite. This coprolite dated back to the Early Cretaceous,
making this paper the first paper to report intestinal protozoan parasites from
a dinosaur. This protozoan was identified as the cyst from of
Entamoebites antiquus, and is more
similar to our modern day genus
Entamoeba
than to our modern day genus
Endolimax.
Always Check the Amber
As we talked
about last week, there is also a lot of evidence regarding parasitism that can
be found encased in amber. Specifically, we talked about the face that insects
that are known vectors for modern diseases have been found in these little time
capsules. This leads us to believe that they may have been transmitting
diseases back in the days of the dinosaurs as well. Some scientists, such as
Dr. Poinar (co-author or What Bugged the
Dinosaurs?) have claimed to find evidence of protozoans that are similar to
modern-day Leishmania and Haemoproteus parasitic protists.
|
An adorable stuffed-protist
version of Leishmania |
However, some people, such as Dr. David
Grimaldi, (with the Division of Invertebrate Zoology at the American Museum of
Natural History) is skeptical of such claims. In his review of Dr. Poinar’s
book he states, “
Unfortunately, the
vague, dark forms in their light micrographs fail to convince. Since cells
within amber-fossilized insects are well known to have preserved organelles,
identification of the putative pathogens should have been made with electron
microscopy.”
Either way,
finding protozoans in insects that have been preserved in amber can’t be an
easy task. I suppose we will have to wait and see what science and technology
can do in the coming years to either support or debunk claims about the
presence of the tiny, unicellular menaces.
Detection of Protists
Via Paleopathology
|
Depicting the lesions found on "Sue"
a T. rex who suffered from parasitic
protozoan infections. |
In 2009,
another article came out about ancient protozoan parasites that plagued dinosaurs.
By examining lesions in the jaw bones of
Tyrannosaurus
rex skulls, these researchers determined that the lesions were a pathological
result of a transmissible parasitic disease that bears striking resemblance to
a disease that plagues modern-day birds. Because they found the effects of such
disease, and not the actual causative agent, scientist can’t pinpoint the
species to blame. However, there is strong evidence that the parasite to blame
was similar to
Trichomonas gallinae. Paleopathological
evidence of this disease has only been found in the bones of tyrannosaurs, so
far. It seems to have been fairly common among species in some populations and
was probably spread through either consuming infected prey (or cannibalism) or
through nasty bloody battles over
T. rex
turf. Some of the specimens in this study were so heavily infested, that
paleopathologists determined that those specimens most likely died as a direct
result of having that infection. The idea is that these mighty beasts starved
to death because it was too painful too eat when you’ve got your jaws packed
full of protists.
Moral of the Story
When a
conversation turns to dinosaurs, we don’t often think about how these massive
creatures may have played host to unicellular demons. It still astonishes me
that something so small and seemingly insignificant can cause such pathology in
animals as massive and seemingly invincible as a
Tyrannosaurus rex. And those poor guys couldn’t even scratch a jaw
being systematically riddled with holes. Anyway, the next time you are at a
party, you should definitely throw around the name
Entamoebites antiquus. If a dude
introduces himself after hearing you utter such a phrase, you should let him
take you out for coffee. I urge you to accept this offer because he’s either really
awesome for knowing something about ancient parasites, or he reads my blog…which
makes him even more awesome. ;)
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