Thesis

Developmental timing and genetic architecture of external taste expansion in the blind Mexican cavefish, Astyanax mexicanus

Berning, D.

Record Number:
5960
Year:
2022
Pages:
75 pages
URL:
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1659518960425867
Abstract:
Extreme environments can have profound impacts on the evolution of sensory traits. Cave systems frequently include the complete or near absence of light, which is associated with the regression or expansion of different senses. Expanded senses likely assist in aiding survival, particularly to compensate for the loss of vision. Taste, for instance, is crucial for detecting and differentiating beneficial food items from those that pose a risk to organismal health. The Mexican tetra, Astyanax mexicanus, is ideal for investigating the genetic and developmental basis of sensory expansion owing to its two drastically different morphotypes, the surface and cave morphs, that have evolved unusual adaptations to their respective environments. For decades we have known that the cave morphotype has a radically increased number and area of coverage of external taste buds compared to their surface counterpart, however the timing of this external expansion and the genetic architecture has not been comprehensively interrogated. We used immunofluorescent histochemistry to examine the timing (and differences) in dorsal and ventral spatial expansion of external taste buds between the surface morphotype and two distinct cave populations of A. mexicanus. Calretinin-positive staining revealed that the distance of the expansion of the most caudal external taste bud in both cave populations reaches significance around nine-months post-fertilization. Quantitative trait loci analyses performed on a surface x cave F2 pedigree linked numerous external gustatory-related phenotypes to two main genetic regions. Interestingly, these genetic regions seem to be associated with different spatial regions of expansion, with both chromosomes 7 and 15 being linked to dorsal and lateral expansions and chromosome 15 primarily being associated with the ventral expansion of taste buds, consistent with work performed in other systems. Together, this work sheds light on both the developmental timing and genetic architecture of extraoral taste buds, an important but poorly understood example of constructive evolution.
Institution:
MS, University of Cincinnati, Arts and Sciences: Biological Sciences
Times Cited:
1
Relevent Species:
Astyanax jordani (Hubbs and Innes 1936) Buckup 2003