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Author ORCID Identifier
https://orcid.org/0000-0003-0020-8939
Date Available
9-1-2026
Year of Publication
2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
College
Arts and Sciences
Department/School/Program
Biology
Faculty
Nicholas Mario Teets
Faculty
Jeramiah James Smith
Faculty
Jakub Famulski
Abstract
Stress and stress responses are intrinsic parts of life, as the ability to maintain or restore biological functions following periods of environmental challenge is necessary for survival. Extremophiles, organisms adapted to extreme environmental conditions, have pushed these limits by developing strategies for withstanding environmental stress that is lethal for most organisms. Among animals, insects have colonized nearly every habitat on Earth and are tractable models for studying extreme adaptations. The core objective of this dissertation is to identify and describe physiological processes that contribute to extreme adaptations, using Antarctic midges as study models.
In Chapter 2, I compared thermal tolerance limits of the midges Belgica antarctica and Eretmoptera murphyi (Diptera: Chironomidae). Specifically, I measured tolerance to prolonged and acute exposure to thermal stress to test the hypothesis that E. murphyi is pre-adapted to Maritime Antarctica, where B. antarctica occurs. While thermal limits were species-specific, meaning that B. antarctica was generally more tolerant to cold and heat, E. murphyi’s thermal tolerance would be sufficient to survive in several islands where B. antarctica is found. This result suggests that temperature limits are unlikely to restrict E. murphyi from spreading further south than its current range.
In Chapter 3, I identified mechanisms of recovery from freezing in B. antarctica using transcriptomics and macronutrient analysis. Freezing triggered transcriptional changes across multiple stress-response pathways and a short-term metabolic shutdown, however, macronutrient content remained stable. Additionally, development appeared paused for two weeks post-thaw, suggesting that, while freezing is not energetically demanding for this species, it may still incur some degree of fitness cost given Antarctica’s short growing season. The transcriptional analysis allowed me to construct a conceptual model of recovery from freezing and generate a variety of hypotheses about the mechanisms employed by freeze-tolerant insects to survive internal ice formation and help explain why freeze-intolerant species cannot.
In Chapter 4, I tested whether exposure to mild stress improves protection against severe stress (i.e., cross-tolerance) in B. antarctica. All pre-treatments (i.e., freezing, heat, dehydration, submersion in fresh and salt water) improved survival to severe freezing, but this cross-tolerance was non-reciprocal, meaning that pre-exposure to mild freezing did not improve survival to severe levels of any other condition. Additionally, multi-omics analyses showed little evidence for a global mechanism of cross-tolerance to freezing, which suggests cross-tolerance can be achieved via multiple mechanistic routes. Taken together, these results indicate that a highly plastic freeze tolerance may be a critical adaptation for surviving in the world’s most challenging environment.
While abiotic factors pose several constraints to biological systems, the mechanisms that mitigate such challenges are not completely understood. The models and hypotheses generated in this work can be used as framework for future research on how extreme-adapted species mechanistically withstand highly challenging environments.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2026.395
Archival?
Archival
Funding Information
This work was supported by the National Science Foundation Grant (NSFGEO-NERC #1850988) between 2021 and 2024, then by the Department of Biology, University of Kentucky (teaching assistantship, internal) between 2024 and 2026.
Recommended Citation
Lima, Cleverson S., "Adaptations to Extreme Environments in Antarctic Midges" (2026). University of Kentucky Doctoral Dissertations. 861.
https://uknowledge.uky.edu/gradschool_diss/861
Supplementary Dataset C1 - Differentially expressed genes.xlsx (1995 kB)
Supplementary Dataset C2 - Shared biomolecules across treatments.xlsx (425 kB)
Supplementary Dataset C2 - Shared biomolecules across treatments.xlsx (425 kB)
Supplementary Dataset C4 - Metabolite differences between treated and untreated larvae.xlsx (20 kB)
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