Fulbright Update: Primates and Parasites in Amazonian Ecuador

Editor’s Note: Texas Global is pleased to offer a rare field update on the work of a Fulbright U.S. Scholar from the College of Liberal Arts, Professor Anthony Di Fiore, who was featured in a previous story. The author, science writer Kristin Phillips, has written for The University of Texas, the American Natural History Museum, National Audubon Society and other nature- and science-based organizations.  

Separated from a soundscape of cicadas, tamarins and toucans by a thin plate glass window, Anthony Di Fiore hunches over a new white microscope, looking through lenses that illuminate several delicate oval structures.  

Guessing that they are eggs from hookworm that parasitizes the gut of the common woolly monkeys (Lagothrix lagotricha poeppigii), which he studies, Di Fiore shifts the cover slip and suddenly sees something with legs and a cloaca. It looks like a mite, squished on its side. He grabs an old iPhone, holding it against one of the eyepieces to record a short video by manipulating the focus and bringing different parts of the microscopic creature to light. 

“It’s so cool,” he says. “It’s a whole different world, isn’t it?”  

Di Fiore’s excitement is infectious. Students and a colleague hover around for a peek to see what is new. 

For more than 30 years, Di Fiore — a professor in the Department of Anthropology — has been conducting research in the Amazonian or eastern part of Ecuador, working in both Yasuní National Park and at the Tiputini Biodiversity Station (TBS).  

Much of his work has focused on the behavior, ecology and population genetics of atelid primates, the large-bodied woolly, spider and howler monkeys that have prehensile tails, allowing them to grasp and hang from branches high above the rainforest floor. 

But now, at 56, Di Fiore is embarking on a new area of research funded by a Fulbright scholarship: identifying the parasites that infect the wild primates he studies at TBS, as well as those found in the monkeys kept as pets by several indigenous Waorani communities further to the West.  

The latter portion of the research is a collaboration with both community members and Dr. Ciara Wirth, research coordinator for TBS, who has spent the better part of a decade working with Waorani colleagues to detail how these communities interact with and classify the natural world. 

Relatively little is known about the parasites of Amazonian mammals compared to those from other parts of the world, although a scan of academic publications demonstrates a recent uptick in research on this subject.  

The new project aims to document the diversity of species found among Yasuní’s monkeys — some of which may be new species, since many gut parasites evolve with their hosts — as well as to explore whether close contact with wild-born pets in communities could lead to the transfer of parasites into new hosts, such as humans or other domestic animals. 

But in order to catalog primate parasite diversity, you need to follow monkeys. 

Just before dawn, Di Fiore, clothed in an old white dress shirt that saw him through a decade of teaching undergraduates at The University of Texas at Austin, puts on an old red backpack, reinforced in several places with hand stitching and laden with several liters of water, a camera, and sample-collection equipment. He walks past the field station’s open-air dining area and into the forest, at times sliding in his rubber boots on the sticky mud created by the previous night’s rain.  

He is heading to the location where he left the “C” group of woolly monkeys — one of the eight groups studied in the area — at around 5:30 the evening before. After walking quickly on the trail and over a mossy bridge made of two fallen logs, he reaches a Spondias tree, a distant relative of cashews and mangos that is filled with small, ripe yellow fruit, and waits. Within an hour, his breakfast-to-go and thermos of coffee have been consumed. 

The morning is sunny, brightening the canopy of some trees 20-30 meters above, although very little direct light filters to the rainforest floor. Even though the humidity over 90 percent, the temperature is pleasant, birds are calling, and insects are buzzing. The most consistent noise is a low mechanical pulse emanating from the north, the sound of an oil extraction facility near the wide Napo River, about seven kilometers away. 

The morning’s quiet briefly breaks when an adult female woolly monkey, closely followed with a little less skill by her female offspring, jumps into the Spondias from a nearby palm. Woolly monkeys have plush, velvety brown fur from which their black faces, hands, and shiny brown eyes are revealed. After a few minutes of eating fruit, she emits a soft “chirp” contact call that other members of her widely dispersed group respond to. All goes still again; the Group C is still not yet ready to begin their morning. 

“Is today Sunday? Maybe they’ve all gone to church,” Di Fiore quips, constantly looking up and listening for new vocalizations or movement. He walks down into a small stream and up the next ridge — a lovely area with an open understory free of vine tangles — partly for entertainment, partly to not miss potential movement, and partly to thwart the ever-present mosquitoes.  

It takes over two hours before the group begins to move through the canopy, most woollies picking their own path as they forage on new leaves, flowers, and insects. Tropical trees vary in height and openness, and many trees carry a heavy load of vines, moss and epiphytes, which can quickly obscure an individual, although the movement of branches always reveals their location.  

Di Fiore, following different adults in turn, navigates his own path over logs and around understory plants in order to collect scat samples, a noninvasive method to gather DNA for genetic studies. When scat does fall, he spends a few minutes searching for the sample, often cued into an exact location by dung beetles who are invariably sitting on a leaf nearby, antennae waving in anticipation.  

He slings his pack onto the ground, dons purple latex gloves, and uses a stick to isolate one portion of the sample in a small vial with a solution that preserves DNA of both parasites and host, then puts the remainder into a larger vial for day-of screening under the microscope. 

After collecting seven samples, Di Fiore leaves the field early, returning to the project’s treehouse-like laboratory. He opens one parasite sample onto a thin plastic weigh boat, commenting on how stinky it is. After mixing the sample with a solution that allows parasite eggs to float to the surface, he spends five minutes spinning it on a crank-powered centrifuge to help separate the eggs from the undigested plant and insect bits.  

Several processing steps later, he sits down to a prepared slide at the microscope, where he distinguishes five different types of parasites … and makes a mesmerizing video of a larvae wiggling within its egg. 

“All right,” he concludes, opening an unprocessed sample. “This stuff is too cool, but I have to go through another six samples tonight!” 

On returning to Austin, Di Fiore will analyze the DNA samples using metabarcoding to determine the species and diversity of the parasite community infecting the monkeys.