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Altitudinal adaptations of earthworms

Perry, Iain 2020. Altitudinal adaptations of earthworms. PhD Thesis, Cardiff University.
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Abstract

To date few have looked into how earthworms have adapted or acclimatised to the harsh and dynamic environment of high altitude. In this work, I explore the terrestrial invertebrates, earthworms that were found at high altitude on the volcanic island of Pico in the Azores (Portugal) and at Les Deux Alpes in the French Alps. I initially identify species presence along an altitudinal transect compare species diversity and lineage, before investigating gene regulatory control and genomic adaptation between high and low altitude populations to identify if high altitude populations have acquired a genetic advantage to their low altitude cousin or if all worms have it within them to survive if given time to acclimatise. Altitudinal transects of two temperate-zone mountains were conducted, at Les Deux Alpes and Pico, to identify presence and abundance of species. The two most abundant species, Lumbricus terrestris and Aporrectodea caliginosa, were investigated to identify diversity and species lineage to determine which species better allowed for adaption and acclimatisation investigations, that are not heavily influenced by deeply rooted species diversity. Having identified A. caliginosa in Pico as the most suitable candidate for investigating adaption and acclimatisation with its low population diversity, an de novo genome assembly was developed and annotated. Live individuals of A. caliginosa from a high and a low altitude site on Pico were acclimatised to standard laboratory conditions for six months prior to experimental exposure to conditions simulating six climatic conditions for two weeks with temperature and oxygen as variables. RNAseq was performed on the RNA taken from a body transect (including muscular, nerve and gut tissues) of the exposed experimental worms, and differential gene expression was calculated and explored between the high and low altitude populations. Despite both populations normalising in identical soils for 6 months, high altitude individuals had a lower response in gene expression than the Low altitude individuals and suggested an element of epigenetic conditioning or adaption allowing a more plastic response to the changes in conditions. In particular, HMGB1, a gene that is known for its roles in regulating environmental responses, had a comparatively lower expression in the high altitude population than the low altitude population when exposed to simulated high altitude climatic stressors. SNP analysis from transcriptomic sequences revealed the high altitude individuals had SNPs associated with genes that linked to directly to this gene indicating a level of adaption through SNPs and acclimatisation through potential epigenetic priming within the high altitude population.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Biosciences
Subjects: Q Science > Q Science (General)
Date of First Compliant Deposit: 12 January 2021
Last Modified: 13 Jan 2021 10:16
URI: http://orca-mwe.cf.ac.uk/id/eprint/137601

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