Face first: sampling leaf cutter ants in the Panamanian tropical forest

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Leaf cutter ant Atta cephalotes in Gamboa, Panama. Photo by Alex Wild. 

One of the things that I appreciate the most from being a biologist is that it has allowed me to participate from some pretty interesting (and often quite peculiar) experiences. Travelling to Panama to participate in STRI’s Tropical Biology Field Course meant engaging in more of these experiences. From navigating in the Panama Canal (full cargo ships and all), to watching the forest from the top of a 50m tall crane (more on that soon), this first week of the course has been full of wonderful adventures.

One of these experiences is, at least personally, noteworthy: the sampling of leaf cutter ants (Atta cephalotes). For one of our lectures, we assisted Dr. Ehab Abouheif from McGill University with the sampling of the different castes of this ant. Dr. Abouheif utilizes ant species as models for the study of Evo-Eco-Devo, the study of the relationships of evolution, ecosystem and development and their role in morphological diversity across taxa. For example, A. chephalotes possibly has more than 8 different ant castes (individuals with shared morphological traits and role within the colony), all originating from (more or less) the exact underlying genome since worker ants in the colony are all sisters. He studies how the evolutionary history of this species, alongside environmental factors, have allowed the single genome to produce a surprising amount of morphological and behavioral variation in the species.

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Excavation of A. cephalotes nest. A) Nest entrance identification and clearing. B) Identification and extraction of nest chambers deeper in the soil. Pictures by Angel Rivera-Colon. 

To study this, we had to identify A. cephalotes nests in the forest, excavate to locate the chambers of the nest, and extract individuals. Simple, no? Well, partially. This leaf cutter ant is common in Panama and its nest entrances are not hard to find in the forest. However, to have access to the chambers (and to most of the individuals) you must dig, and dig deep in some occasions. As you do, soldiers (a caste of big ants tasked with the nest’s defense) rushes out of the tunnels. And I mean big ants (soldiers can be 14 mm in length) coming in huge numbers. Armed with forceps, we captured as many as we could, both for sampling purposes, but also to protect ourselves for the nonstop charge of soldiers. Once the chambers were reached, they had to be carefully extracted, as they contain most of the minor workers (smaller ants in charge of other tasks in the nest) and the precious fungal gardens that characterize this group. Here’s the catch, to extract these chambers you must crawl and scoop the chamber out while a barrage of ants is simultaneously trying to protect it. Even when “hey, let me crawl face first into an ant’s nest” is one of those things that doesn’t come into your head often, doing so provides you with an unrivaled vision on how the nest behaves as a dynamic entity. Workers respond to the attack by deploying more soldiers while moving other workers to other parts of the nest. It is also a small trust test between you and the other students. After all, they are the one protecting you from the ants.

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Me, really thinking about what I am about to do. Also, banana for scale.

After sampling, captured ants were measured and classified between size groups. We observed a bimodal distribution in which medium sized minor workers (the smaller workers) and medium sized major workers (like the soldiers) were more common, with extreme and intermediate sized ants being comparatively rare. This appears to be observed in other ants, like the carpenter ant (Camponotus floridanus), and reflect the intricate nest dynamics that have effects on the distributions of castes present in the nest. Within an Evo-Eco-Devo context, these dynamics will also affect the ants’ development and subsequent adaptation to their environment.

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A. cephalotes soldiers being processed for counting and classification process. Picture by Angel Rivera-Colon. 

Overall, I think it was a wonderful experience. Not only did I go face first into a gigantic ant’s nest (and ended up being completely unscathed), the experience provided a really good example of the importance for interdisciplinary research in biology. The integration across many fields is what, in my opinion, makes this project particularly special. You go from doing field work to studying the underlying genetic mechanisms for developmental variation and its evolutionary context. I’m looking forward for other similar opportunities in the next few weeks, and waiting to see what other peculiar things we get to do.

ARC

 

 

 

 

 

 

 

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