New research on 100-million-year-old amber with ticks preserved inside indicates these tiny, annoying critters have been around for a long time - and that dinosaurs were among their hosts.
A tick grasping a dinosaur feather inside 99 million-year-old Burmese amber. (Image: Peñalver et al., 2017)
Acquiring ticks is a nasty consequence of doing basically anything outdoors during the warmer months. Whether you're hiking, doing yard work or camping, there's a decent chance you'll need to regularly check yourself (and any canine companions) for the revolting tiny blood-suckers. These globally-ubiquitous parasites can be an unsettling nuisance, but if it's any consolation, we now know they have been a pain in the arse for vertebrate life for aeons. New research on ancient amber with ticks trapped within provides evidence that not only were the arachnids of ill repute around a hundred million years ago, but that dinosaurs were among their targets.
That's right, not only were many (if not basically all) dinosaurs blanketed in feathers like jumbo roosters, but they also probably carried around pendulous clusters of engorged ticks. Apologies to your inner child for further "ruining" dinosaurs.
We don't know a whole lot about the early evolution and lifestyle of ticks. The further back we go, the rarer tick fossils become. We knew that they have been around since some time in the Cretaceous era (between 65 and 145 million years ago), but what they were actually doing during this time has been a mystery. Were these proto-ticks blood feeding? And if so, which animals were they parasitising?
These are questions that a fossil of a lone tick is not well-equipped to answer. Preserved ticks in amber (that is, fossilised tree resin), however, provide a better picture, since other elements of their surroundings can also get gummed up in the resin, giving us some clues about their lifestyle and how they interacted with other organisms. This avenue has produced some palaeontological evidence of ancient ticks and their hosts, but it's limited, and from not that long ago - like 30- to 40-million-year-old amber containing ticks and mammal hair. So, there's been quite a gap between when the first evidence of tick-host relationships appear in the fossil record, and the known earliest origin of ticks.
Hard tick photographed at Cabañeros National Park, Spain. (Image: E. Peñalver)
All of this has changed with the discovery of 99-million-year-old amber containing several ticks - one of which is entangled in a dinosaur feather. The discovery - detailed in new research published today in the journal Nature Communications - doesn't exactly provide the most glamorous vision of the Age of Dinosaurs, but it sheds a light on the fledgling evolution of ticks, giving us a rare snapshot of their world.
Remarkably, the amber also contains a primitive, completely new family of apparently extinct ticks, with one tick swollen with their last blood meal. If your heart is suddenly aflutter over how similar that last bit sounds to that whole Jurassic Park, dino-DNA-in-amber-mosquito situation, crush that dream before it gets too big. There's no chance of resurrecting dinosaurs from this amber. DNA degrades way too fast for that to be a thing. Seriously.
The amber was originally found in Myanmar, Southeast Asia, before eventually being donated to the American Museum of Natural History. To further examine the tiny contents of the amber specimens, a team of researchers based out of Spain and the US used a couple of methods of zooming in to see what was inside. The team used a microscope to identify features of the ticks and feather. They also took special, three-dimensional X-ray images ("micro-CT") of the ticks from the newly-categorised family so they could more accurately see all the external parts.
The tick clinging to the feather was identified as a hard-shelled tick similar to the most common variety of ticks found today, but the feather couldn't be nailed down with that level of accuracy. There's no way to know what species the feather belongs to, but the feather's characteristics are typical for what covered many groups of fuzzy, feathered dinosaurs that were running around in the early Cretaceous. It's unlikely that the feather belongs to any lineages of modern birds, since those don't show up for another 25 million years or so.
The other ticks were so unlike any known tick grouping - extinct or not - that they were assigned to an entirely new family. The ticks were dubbed Deinocroton draculi, and put in the new family Deinocrotonidae. The two-part scientific name literally means "Dracula's terrible tick", which is a fittingly badarse name for a 100-million-year-old vampire.
Modern ticks fall into one of three family groupings: 1) Ixodidae, which are the common "hard ticks", flat with a stiff shell-like covering, 2) Argasidae, "soft ticks", which look like raisins made of velvet, and 3) Nuttalliellidae, which contains a single, rare, primitive species from South Africa that's kind of squishy with dimples all over it like a golf ball. Deinocroton doesn't fit into any of these groups, but seems to have more in common with the South African oddball tick, suggesting it too is an early offshoot.
Deinocroton draculi ticks preserved together, both adult males. Credit: Nature Communications; Peñalver et al.
Neither Deinocroton tick was found next to a dinosaur feather, so direct evidence of their host doesn't exist. Even the individual turgid with blood wouldn't be of much help for ID-ing the host.
"Assessing the composition of the blood meal inside the bloated tick is not feasible because, unfortunately, the tick did not become fully immersed in resin and so its contents were altered by mineral deposition," explained Dr Xavier Delclòs, an author of the study, in a statement.
But indirect evidence suggests these ticks drank from dinosaurs as well. Attached to the ticks are tiny hairs that can be attributed to beetle larvae - specifically skin beetles (dermestids), which we know can be found in bird nests today, eating feathers and skin debris. Given this, it's likely that these ticks were hanging out in a dinosaur nest at some point.
All of this makes one thing quite clear: By 99 million years ago, ticks were already established parasites, plaguing dinosaurs as one of their earliest victims.
The discovery presents an interesting new perspective on the day-to-day lives of dinosaurs. For example, it's possible that ticks transmitted blood-borne diseases between hosts like they do today. This grittier side of palaeoecology is important to consider, because these ancient animals lived in a landscape that had far more going on than just interactions between animals eating other things. Parasites and disease are a huge component of the lives of modern animals, dinosaurs would be no different, and now we have another small insight into how such interactions might have looked.