Macroparasites and their megamammal hosts: Pleistocene-Holocene sloths

Macroparasites of megamammals: The case of a Pleistocene-Holocene extinct ground sloth from northwestern Patagonia, Argentina

by: María Ornela Beltrame, Victoria Cañal, Carina Llano, Ramiro Barberena

Summarized by Ariel Telesford, a geology major with a minor in G.I.S at the University of South Florida and is currently a senior. He plans to work within the structural geology field, whether it be in mining, construction or the oil and gas industry. He plans to complete his master’s degree in London, England in the near future. Outside of academics, he is an avid gym-goer and plays multiple sports, mainly soccer and volleyball. 

What data were used? Feces extracted from a cave in Patagonia, Argentina was examined for parasites and other variables to determine environmental factors and diet of these sloths. The samples of feces used for this study were a part of a stratigraphic unit that dated between 16,600 and 13,600 calendar years before present (B.P.). This falls within the Pleistocene Epoch that spans from 2.58 million years ago to 11,700 years ago. 

Methods: Optical microscopy at 100x and 400x was utilized to identify and study the parasites found in the feces, as well as the diet of the sloth. Pollen analysis of the feces was conducted to determine environmental factors during that time, as the types of pollen present can inform researchers about a number of environmental factors, like temperature or moisture in the area. Pollen found within these species were compared to the known pollen record.

Results: The pollen analysis revealed that the climate was generally colder than what it is today and were found to belong to a specific shrub steppe. This supports what we already know concerning a cooler climate during the Pleistocene. The microscopic work done revealed that the sloths’ diet consisted mainly of shrub and grass, due to woody fragments and herbaceous matter found. This was consistent with the type of parasites (Nematoda family, also known as roundworms) that were found within the feces, since these worms usually inhabit grassy environments. These parasites also had researchers considering the various health impacts that parasites could have had on these sloths. The species of parasites found in the feces were also found in modern-day herbivores, indicating that co-extinction did not occur along with the extinction of these sloths during the mega-mammal extinction event of the Pleistocene. These results led researchers to hypothesize that host-switching (i.e., finding a new host) likely occurred for these parasites to survive.

Figure showing the parasitic eggs found in 8 out of the 21 samples of feces. Most of these eggs belong to the nematode (roundworm) family, specifically Strongylida species.

Why is this study important? When looking at extinction events throughout geological time, a lot of focus is placed on the organisms that are directly impacted by the event. However, we know that nature is super connected and intertwined and thus we must consider the effects these extinction events have on the organisms that are extremely dependent on those that were wiped out. 

The big picture:  The research done here shows the importance of considering even the smallest organisms when we try to understand the ecology of prehistoric times. This study should improve our understanding of the relationship that organisms have with each other (parasite-host in this case). Further work in paleoparasitological studies will help us understand host-switching, co-extinction, and the domino effect of extinction events on dependent species, especially when trying to recreate prehistoric environments. 

Citation: María Ornela Beltrame, Victoria Cañal, Carina Llano, Ramiro Barberena. Macroparasites of megamammals: The case of a Pleistocene-Holocene extinct ground sloth from northwestern Patagonia, Argentina, Quaternary International, Volume 568, 2020. Pages 36-42. ISSN 1040-6182. Retrieved from (