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Home: Welcome

We use the Mexican tetra, Astyanax mexicanus, to study genetic changes that drive morphological and physiological evolution 

Cave-dwelling populations of Astyanax mexicanus evolved in a very different environment compared to their river-dwelling ancestors. Over 200,000 years ago, the fish invaded perpetually dark underground limestone caves in the Sierras of Northeastern Mexico. They adapted to a diet of bat droppings and flood debris while surface counterparts consumed plants and insects in abundance.  


Cavefish have a very different appearance compared to surface fish although they are the same species. Most apparent, they have reduced pigment and lack eyes. They evolved an insatiable appetite and modified their metabolism to store more fat than surface fish. Some of their adaptations, like insulin resistance, are deadly in humans. Our lab is currently focused on how cavefish have altered their digestive system to maximize energy assimilation.

The Mexican tetra has emerged as a model system in part due to the growing number of methods and resources for analyzing gene function. We have used quantitative trait loci (QTL) mapping to identify genomic regions linked to altered nutrient accumulation and gut morphology. To uncover the types and locations of genetic changes responsible for cavefish adaptations we combine comparative genomics, transcriptomics, and gene editing.

Image by CDC
Home: Research

Current projects are aimed at uncovering how evolution has modified

  • Plasticity of intestinal homeostasis in response to the environment

  • Development and function of the enteric nervous system 

  • Nutrient absorption and metabolism

  • Microbiome composition

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Home: Our Team


Assistant Professor



Postdoctoral Fellow

I am a postdoctoral fellow with experience in germ cells and models of male infertility. I'm interested in understanding the developmental biology and genetics of gonadal sex differentiation in teleosts, particularly zebrafish and Astyanax mexicanus




Graduate Student in Ecology, Evolution, and Conservation Biology

David is an international Ph.D. student in the ECCB program at UNR. A graduate of the Autonomous University of State with a Bachelor in Biology and a Master's in Science from Midwestern State University, his research experience focused on morphological plasticity in response to prey and the developmental effects of hypoxia in squamates. Now in the Riddle Lab, David is researching the genetics of carotenoid and retinoid storage and transport and their role in the early development of Astyanax mexicanus in a low nutrient environment. His main interest is evolutionary development and phenotypic plasticity influenced by extreme environmental pressures.




Graduate Student in Molecular Biosciences

Pavani is an international student pursuing her Ph.D. in cell and molecular biology at UNR. She earned her B.Sc (hon) in Zoology with a first class at the University of Colombo, Sri Lanka. As an undergraduate, Pavani became passionate about studying cave ecosystems and the adaptive plasticity of vertebrates in extreme environments.  Now, as a graduate student in the Riddle Lab, Pavani studies the evolutionary development of the enteric nervous system using the unique model system, Mexican cavefish (Astyanax mexicanus).


LinkedIn: /in/pavani-perera

Twitter: @/pavi_dilsh 



Aquatics Technician

Heather has a lifelong passion for aquatic life and fishkeeping and is thrilled to manage the care of the Riddle laboratory’s cavefish facility. When she is not wrangling Astyanax mexicanus, she writes about the intersections of music, bioacoustics, and artistic relationships with environmental concerns. Heather holds a MPhil (2021) and PhD (2023) in Ethnomusicology from New York University.


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Graduate Student in Neuroscience

Bethany Ponte is a current 2nd year Ph.D. student in the Integrative Neuroscience Program. She has a BS degree in Psychology with an Emphasis in Biology from UC Davis and turned to graduate school to learn more about the biological side of neuroscience and do research. In Dr. Riddle’s lab, she is investigating the homeostasis of the A. mexicanus gastrointestinal tract. She is particularly interested in how the two morphs can regulate their digestive tract to adapt to the varying diets and times of starvation they experience in the wild. The broader implications of this research are twofold. It will provide information about the regulation of insulin and cell division and their relationship to the development of diabetes and intestinal cancers.




Graduate Student in Molecular Biosciences

Maeve received her BS in Biology from University of California, Santa Cruz in 2020, and continued as a research assistant in the COVID Molecular Diagnostic Lab there at UCSC post grad. She then went on to working for the Miura lab here at UNR in late 2021 studying 3’UTR effects on glutamatergic neurons differentiation while she applied to grad school, and was accepted into the Riddle lab for the Fall of 2022. She is particularly excited to explore the microbiome of A. mexicanus and its effect on gut homeostasis.



Our lab is committed to allyship for marginalized and underrepresented communities


Some of the ways we are working to create an anti-racist environment in our group and promote diversity, inclusion, and equitable access to STEM education are:

  • Educating ourselves about racial injustice and systemic discrimination

  • Listening to and uplifting voices from marginalized communities

  • Speaking out and pushing for change when we see microaggressions or institutional policies that disadvantage marginalized communities, both within the lab and within the larger campus community

  • Making space and time for lab members to heal, take care of their communities, or fight for justice, and continuing to provide financial, career, and other support while they do so

  • Donating to or volunteering for organizations that promote the success and well-being of marginalized communities in STEM

  • Highlighting the contributions of underrepresented communities to STEM

  • Regularly discussing how to promote diversity in STEM during lab meetings

  • Acknowledging that the UNR is situated on the traditional homelands of the Numu (Northern Paiute), Wasiw (Washoe), Newe (western Shoshone), and Nuwu (Southern Paiute) peoples. These lands continue to be a gathering place for Indigenous Peoples, and we recognize their deep connections to these places. We extend our appreciation to live and learn on their territory.

  • Staying up to date on the initiatives, resources, and events organized by UNR office of Diversity and Inclusion

  • Coordinating our efforts with the EECB student Justice, Equity, Diversity, and Inclusion Committee (JEDI)

Image and some text adapted from Sammy Katta and EECB JEDI

Home: About
Image by Roman Kraft


Home: Publications
group photo at bucce ball.jpg


September 02, 2022

We had our first in-person group lab meeting on 2 September 2022. We discussed what actions we could take to become a green lab and the broad goals of the lab. And in the afternoon, we headed to Bundox Bocce in Reno to play some Bocce ball with Pizza and drinks! We celebrated Bethany’s Birthday with the extended team. Happy birthday Bethany!!

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