Who Ate the Dinosaurs? Part II: More on Arthropods

       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. Today, let’s continue talking about things living on the outside of our beloved reptiles and make a transition into their upper respiratory tracts for a look at some nifty little arthropods. Then we will discuss some of the possible parasite vectors and their roles in the extinction of dinosaur populations.

Dino-Mites

A piece of Canadian Cretaceous amber with a
preserved feather and associated mite.

            It appears that mites were some of the first animals to walk on land some 400 million years ago. They would later give rise to the group of animals we now call ticks, but that wouldn’t come along until much later. In 1998, eggs from a type of feather mite were found on feathers belonging to a Cretaceous (120 million years ago) dinosaur from modern-day northeast Brazil. Later researchers claimed these eggs to be more similar to mites in the family Cheyletoidea (these guys cause a form of dermatitis known as “walking dandruff” in modern mammals and birds).

T-Rex Ticks?

            Ticks were once thought to have originated about 42 million years ago on the modern continent of South America. However, a recent discovery of a tick stuck in amber from New Jersey pushes tick origins back to about 90 million years ago. This fossilized larval tick was named Carios jerseyi and was a type of soft tick. Unlike most soft ticks, this species had dozens of tiny hairs aligned in two rows along its back. Because this is the only known specimen from this time period so far, its gut contents can not be examined for the blood of dinosaurs. However, because it lived at the same time, and because we know that ticks today feed on everything from birds, to mammals, to lizards and snakes, we can assume that this species probably did feed on dinosaurs. 

Carios jerseyi

Tongue Worms in Dino-Lungs?

           Pentastomids are a group of crustaceans that date back to 500 million years ago! These little guys live in the respiratory tracts of terrestrial vertebrates. Close to 85% of modern pentastomids are found in the lungs of reptiles. Being present so early in the fossil record indicates that these animals have had associations with vertebrates for a very long time. Given what we know about these arthropods, it wouldn’t be too much of a stretch to assume that they may have been present in dinosaurs. From what little bit I’ve read, it seems that many scientists are convinced that dinosaurs played host to tongue worms….however, I have not found any studies confirming this. The problem is that soft-bodied invertebrates, as well as dinosaur lung-tissue, does not preserve well over millions of years. Will we ever know if these guys parasitized dinosaurs for sure? Maybe…we are learning more and more as technology progresses…but for now, suffice it to say that they were probably a common dino-parasite.

A modern-day pentastomid
(Armillifer agkistrodontis)
from a snake.

Insects
            Insect populations exploded during the time of the dinosaurs. We are talking, like dragonflies with two-foot wing spans exploded. This was because the environment was right for them, the world being covered in warm-temperate, subtropical, and tropical biomes. Naturally, many of those species were blood-feeders, such as everyone’s least favorite little blood-sucker, the mosquito.  In addition, there existed many other species of biting flies, and the lice and fleas I mentioned in a previous post. With the arrival of blood-feeding insects, it was only natural that these animals would become choice candidates as vectors for disease transmission.

            Many forms of diseases we know about today are blood-borne. For the sake of brevity, which is as we all know the soul of wit, I will say that the insects that lived with, and probably feed upon, the dinosaurs were probably carrying various infectious agents. These could have been viral, bacterial, or parasitological (as in protists or intestinal worms, perhaps). There have been instances of finding sand flies preserved in amber, which we know to be the vectors of Leishmania today. Dr. Poinar, author of “What Bugged the Dinosaurs?”, has spent much of his time looking at specimens from amber such as the one mentioned above. He was quoted as saying this in an interview I found online: 

“Our research with amber shows that there were evolving, disease-carrying vectors in the Cretaceous, and that at least some of the pathogens they carried infected reptiles.”

            He went on to discuss how big of a role insects played in the gradual downfall and eventual extinction of our archosaurian predecessors as best I could understand from reviews about the book. Needless to say, this one is definitely makings my “must-read-someday” list. Apparently he also co-authored another book called "The Quest for Life in Amber", which may have also made said list.

 Moral of the Story

            When a conversation turns to dinosaurs, we don’t often think about how arthropods may have annoyed them as much as they sometimes annoy us. It is pretty amazing to think of all that we have learned about dino-parasites, but even more amazing is that which we have yet to learn or what information has been lost to evolutionary history. So at the next party you attend, you should casually mention how far back into the fossil record you have to reach to find the presumed origins of arthropods like mites and pentastomes.  Maybe you will start up a vibrant conversation with someone worth talking to. If so, you should most certainly ask them to join you for a cup of coffee sometime and the two of you can contemplate the role of parasitism in the extinction of the dinosaurs. You could make a new friend just because you read my blog. You are welcome. ;)