Student discovers 18 new species of aquatic beetle in South America

JUNE 22, 2020

by Brendan M. Lynch, University of Kansas

It would be striking for a seasoned entomologist with decades of fieldwork to discover such a large number of species unknown to science. But for University of Kansas student Rachel Smith, an undergraduate majoring in ecology & evolutionary biology, the find is extraordinary: Smith recently published a description of 18 new species of aquatic water beetle from the genus Chasmogenus in the peer-reviewed journal ZooKeys.

"The average size of these beetles, I would say, is about the size of a capital 'O' in a 12-point font," said Smith of the collection of new species. "They spend a lot of their life in forest streams and pools. They're aquatic, so they're all great swimmers—and they can fly."

The research involved Smith traveling to Suriname to perform fieldwork as well as passing countless hours in the lab of Andrew Short, associate professor of ecology & evolutionary biology and associate curator with KU's Biodiversity Institute, who co-wrote the new paper.

Smith said many of the aquatic beetle species are virtually indistinguishable simply by looking at them, even under a microscope.

"Something unique and fascinating about this genus, particularly the ones I worked on, is that many look almost exactly the same," she said. "Even to my trained eye, it's hard to tell them apart just based on external morphology. Their uniqueness is in there but kind of hidden in this very uniform external morphology."

To identify the new species, Smith compared DNA evidence from the aquatic beetles with a few external morphological differences that could be observed. But this was not enough: Much of Smith's work also hinged on dissecting these tiny specimens collected in northeastern South America to spot key differences in their internal anatomy.

"Because it's difficult to tell them apart from external morphology, you kind of have to go inside," she said. "I ended up doing over 100 dissections of these beetles to extract the male genitalia and look at it under a microscope. That really was the true way to tell them apart. Ultimately, it came down to male genitalia and genetic divergence that I used to delimit many of these species."

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