Discovering New Groundwater Invertebrates in Central Texas

New species of animals evolve through speciation, a process whereby a lineage diverges into a new species. When these new species are first discovered, they are undescribed, meaning they have not been given a formal scientific name, and it may not be known how they are related to other species. These new species may also be “cryptic.” A cryptic species looks identical to a described species, but genetically is very different. Describing species and identifying cryptic species usually requires genetic analysis.

In FRI (Freshman Research Initiative) Biodiversity Discovery, groups of undergraduate researchers work together to discover and describe new, cryptic species. In our group, we are looking at amphipods and isopods (both crustaceans) collected from the Edwards Aquifer.

The image shows an amphipod and an isopod we collected. Our goal for our research is to identify any undescribed amphipod species from the Edwards Aquifer and to look for cryptic species that are remaining undiscovered due to their similarities to known species. To do this, we use DNA sequencing to determine the exact sequence of base pairs in a gene for each specimen collected. The particular gene we are sequencing is cytochrome c​ oxidase subunit 1, or CO1. CO1 is found in the mitochondria of cells; it codes for a protein that is essential for cellular respiration, and is the ideal gene for our analysis. This gene is ideal because the DNA sequence for CO1 does not vary much within a species, but it varies greatly between species. So, all of our Stygobromus russelli​ should have similar or identical CO1 DNA sequences, and if one of our specimens has a different sequence, then we may have found a cryptic species. 

While collecting amphipods, there weren’t any specimens that appeared, physically, to be an undescribed species. They all looked like known amphipod species, so really our only chances of having an undescribed species is to find a cryptic amphipod through our DNA sequencing of CO1. However, one of our specimens, collected from the North Fork of the San Gabriel River in Georgetown, Texas, is a potentially important find. This specimen appears to be a Stygobromus balconis​, a species that has never been found north of Austin. If we can confirm through DNA sequencing that this specimen really is S. balconis, then it can mean big things for amphipod researchers regarding the distribution of this species. If this specimen is not S. balconis​​, then we may have a new cryptic species that could play an important role in understanding the evolutionary history of amphipoda. 

FRI Biodiversity Discovery is dedicated to exploring the diversity of all species using DNA analysis, morphometrics,and phylogenies. When trying to understand the tree of life, no organism is unimportant, even a 12mm long crustacean.