An artist's rendition of a Jurassic flea. |
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 things living
on the outside of our beloved reptiles. In doing so, we will also mention a
little about how these creatures probably feasted on the blood of ancient birds
and mammals as well. You will also have the pleasure of reading a bit about
ectoparasite evolution, and how studying these little guys helps us to paint a
more accurate picture of life over a 100 million years ago.
Dino-Lice
Lice are thought to have evolved
over 65 million years ago according to a new study using modern lice DNA. That
time frame places their ancestors in the same place as dinosaurs. One study is even
showing that lice began diversifying on mammals and birds before the dinosaurs
went extinct! (Which means that mammals and birds may have been diversifying at
this time as well?!) How interesting is it that these little guys could be
proxy indicators of bird and mammal radiations preceding what has been
conventionally accepted as post-dinosaurian diversification of these types of
creatures!!?!?!! Here’s an awesome quote
from Dr. Vincent Smith, a researcher who has been working on dino-lice at the
Natural History Museum in London:
Fossilized lice remains from 44 million years ago (left) next to a modern-day louse from an aquatic bird (right). |
“Lice are like living fossils. The
record of our past is written in these parasites, and by reconstructing their
evolutionary history we can use lice as markers to investigate the evolutionary
history of their hosts. …
It was thought that after the dinosaurs
went extinct that's when these birds or mammals diversified into these
different niches, but based on the evidence from lice, the radiation of birds
and mammals was already under way before the dinosaurs went extinct.”
Pretty cool huh? Some researchers
believe that louse-lineages may even go back as far at 115-130 million years
ago! It’s thought that these ancient lice may have fed on feathered dinosaurs
such as China’s Sinornithosaurus. The most recent numbers I could find in the
literature regarding lice stated that the first instances of parasitic lice
occurred between 100 million and 125 million years ago. The same study
suggested that these little guys didn’t become parasites until animals began to
develop fur or feathers. It seems that modern birds may have gotten their
modern louse-burdens from feathered versions of their dino-brethren.
Dino-Fleas
Fossilized flea from the Jurassic period. |
Okay,
so maybe some dinosaurs had lice…but what about another exciting group of ectoparasites…fleas?
There are fossils of fleas that date back to the Jurassic, some 100 million
years ago. They were anywhere from twice to ten times the size of modern fleas
and lack the jumping potential that our familiar forms possess. They also donned
elongated sucking mouthparts that were serrated…presumably for piercing hides
that were much thicker than the hosts’ hides that contemporary fleas must
penetrate. They were dorso-ventrally flattened rather than laterally
compressed. (For those who aren’t biologists, this means that the bodies are
flattened from front to back rather than from the sides. Fish, for example, are
laterally compressed.) They also had spiny bodies and claws that helped them to
cling to prehistoric feathers and fur. It is most likely that these guys fed on
pterosaurs and early rodent-like mammals.
Jurassic flea fossils from China. (Note size compared to the human hand.) |
A
recent examination for fossilized fleas from China found that some fleas
existed 165 million years ago! Two species have been named from these Chinese
fossils. They were given the names Pseudopulex
jurassicus and Pseudopulex magnus
based on compression fossils, which provide much more detail of the fossil’s
anatomy as opposed to impression fossils. P.
jurassicus is smaller in size than P.
magnus. It is believed that these fleas fed on feathered dinosaurs, such as
Epidexipteryx hui and Pedopenna daohugouenis, during the
mid-Jurassic period. I read a few articles that mentioned other types of
dinosaur fleas, but I have yet to uncover the scientific names of those fleas.
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 ectoparasites in the same way that animals like corgis do today.
We think of the astounding size of these animals and about how they ruled the
planet so long ago. As interesting as they are, I think it’s even more fascinating
to know that they were not exempt from the most efficient form of symbiosis
found in any ecosystem. In my head, I can’t help but picture a pissed off velociraptor
rubbing up against a tree to sooth the itch of a group of 2cm long fleas
feasting on his back. (For the record, that’s purely a figment of my imagination,
there’s no evidence to support that fleas actually
fed on velociraptors.) Anyway, the next time you are at a party, you should
throw around the name Pseudopulex
jurrassicus. If this attracts a woman, she’s a keeper. If it doesn’t, then
no woman at that party is worth your time anyway! :p
P - This post is a really nice one. But don't forget mites and ticks, both of which occur on modern "reptiles" and have a very long history (although ticks supposedly blossomed during the Cretaceous and later). And, to my knowledge, nobody is strongly contesting the fossil pentastome material from the Cambrian.
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