<div class="rich-text "> <section class="image-block image-block--float-right "> <div class="image-block__image-wrapper"> <picture> <img alt="An X-ray view of the heads of a worker and a soldier ant and the brains inside their head. The worker is much smaller with the brain filling more of its head." src="/news/~/media/Drexel/Core-Site-Group/News/Images/v2/story-images/2018/July/Eciton-Figure-1_sized.jpg?w=3200&amp;hash=F37EA2DCA9273AC4474763703FDEA203"> </picture> </div> <div class="image-block__caption"> 3-D reconstructions of Eciton burchellii parvispinum heads with the brain and specialized structures highlighted. The head on the left is a worker, and the one on the right is a soldier. Courtesy of Sean O'Donnell. </div> </section> <p style="MARGIN: 0in 0in 0pt">Brains and brawn apparently don’t mix in army ant soldiers, a new study shows.</p> <p style="MARGIN: 0in 0in 0pt">Led by&nbsp;<strong><a style="COLOR: #954f72" href="http://drexel.edu/coas/faculty-research/faculty-directory/odonnell-sean/">Sean O’Donnell, PhD,</a>&nbsp;</strong>a professor in Drexel University’s&nbsp;<a style="COLOR: #954f72" href="http://drexel.edu/coas/">College of Arts and Sciences</a>, a study&nbsp;<a style="COLOR: #954f72" href="https://bmczool.biomedcentral.com/articles/10.1186/s40850-018-0028-3"><span style="COLOR: #954f72">published in&nbsp;</span><em style="COLOR: #954f72">BMC Zoology</em></a>&nbsp;showed that while army ant soldiers have much larger bodies than their worker brethren, their brains are about the same size. Compared to their body size, then, the soldier ants have much smaller brains.</p> <p style="MARGIN: 0in 0in 0pt">Why that occurs might have to do with how much energy it takes to develop and power brain tissue, according to O’Donnell and his co-authors.</p> <p style="MARGIN: 0in 0in 0pt">“The patterns we saw suggested natural selection favors efficient allocation of brain tissue, with the result of reduced investment in the behaviorally specialized soldiers,” O’Donnell said.</p> <p style="MARGIN: 0in 0in 0pt">In many ants, individuals in a colony are divided into different “castes,” meaning group members play different roles to help the colony survive. O’Donnell chose to study ants in the&nbsp;<em>Eciton&nbsp;</em>genus because of the stark body differences between castes; two of the major roles individuals take are workers or soldiers.</p> <p style="MARGIN: 0in 0in 0pt">Soldier ants are larger, stronger and have powerful mandibles that work like pincers to fight off predators threatening the colony. That is effectively their only job.</p> <p style="MARGIN: 0in 0in 0pt">Workers, meanwhile, have smaller bodies and mandibles more suited for grabbing and moving things. Their jobs are more varied, ranging from hunting and collecting food to tending to the young.</p> </div> <div class="rich-text "> <section class="image-block image-block--float-left "> <div class="image-block__image-wrapper"> <picture> <img alt="A bunch of ants moving on the forest floor." src="/news/~/media/Drexel/Core-Site-Group/News/Images/v2/story-images/2018/July/Eciton-Figure-2_sized.jpg?w=3200&amp;hash=6362CE82CA3A739763A8FBA24C62241B"> </picture> </div> </section> <p style="MARGIN: 0in 0in 0pt">As such, it follows that worker ants could have larger brains compared to their body size. With so many different tasks, they need the accompanying brainpower to accomplish them.&nbsp;</p> <p style="MARGIN: 0in 0in 0pt">Moreover, the study found that some specific parts of their brains — including the areas related to learning and smelling — were also comparatively larger in workers than soldiers. The soldiers’ brains could actually be described as a little more “Spartan,” with the special areas more trimmed down.</p> <p style="MARGIN: 0in 0in 0pt">So, does that mean soldier ants are dumber than workers?</p> <p style="MARGIN: 0in 0in 0pt">“I’m not sure I’d say dumber so much as simpler,” O’Donnell said. “That’s our assumption, in a way, not our conclusion. Our idea was that soldiers’ simple behavior might require less brainpower.”</p> <p style="MARGIN: 0in 0in 0pt">In this case, “power” is the important word. Since energy is so precious in ant colonies, they must conserve it to survive. And with brains needing so much energy to power, the researchers theorized that the ants with fewer tasks would be given less of a share of that energy.</p> <p style="MARGIN: 0in 0in 0pt">Basically, the idea is that colonies are favored to spend their limited energy sources as prudently as possible, evolutionarily speaking.</p> <p style="MARGIN: 0in 0in 0pt">“Colony-dwelling animals potentially provide a unique window on how brains and behavior evolve,” O’Donnell said. “An individual animal’s behavior has less relevance to itself, evolutionarily, and more relevance to its colony or group. Natural selection can occur by colony performance, and colony evolution may shape individual animals’ brain investment.”</p> <p style="MARGIN: 0in 0in 0pt">Seeing this in action in&nbsp;<em>Eciton</em>ants provides a glimpse of how things may work for others.</p> <p><span>“This leads to new predictions about patterns of brain investment in social animals,” O’Donnell said.</span><br><br></p> </div> <section class="contact-card-set"> <h2 class="contact-card-set__title">Contact</h2> <div class="contact-card-set__cards"> <div class="contact-card"> <div class="contact-card__name"> <a href="/news/authors/otto-frank"> Frank Otto </a> </div> <div class="contact-card__info"> <a href="mailto:news@drexel.edu" class="icon-link " aria-label="Email news@drexel.edu"> <span class="icon-link__icon"><svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="24" height="24" viewbox="0 0 24 24" role="img" focusable="false"> <g fill-rule="evenodd"> <path d="M20,4 L4,4 C2.9,4 2.01,4.9 2.01,6 L2,18 C2,19.1 2.9,20 4,20 L20,20 C21.1,20 22,19.1 22,18 L22,6 C22,4.9 21.1,4 20,4 L20,4 Z M20,8 L12,13 L4,8 L4,6 L12,11 L20,6 L20,8 L20,8 Z"></path> </g> </svg> </span> <span class="icon-link__text ">news@drexel.edu</span> </a> </div> </div> </div> </section>

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