Item Details

title

MECHANISMS OF CARBON DIOXIDE DETECTION IN THE EARTHWORM EISENIA HORTENSIS

author

Smith, Emily Jordan

abstract

Carbon dioxide (CO2) is a critical biological signal, which, as a byproduct of respiration, often indicates the presence of other living organisms. The earthworm Eisenia hortensis lives in subterranean burrows containing high levels of CO2 and respires through its skin. Despite the ecological and agricultural importance of earthworms, relatively little is known about how they make decisions in their environment, including their response to elevated levels of CO2. Because we hypothesized that Transient Receptor Potential channel TRPA1 may be involved in CO2 detection in this species, this investigation involved both behavioral assays designed to gauge responses to CO2, and molecular investigations of TRPA1 channels. Because CO2 is noxious at high concentrations, we designed an assay, the exudate assay, to examine CO2 aversion in this species. In the exudate assay, we placed an earthworm in a sealed container and exposed it to varying concentrations of CO2 for one minute, and the amount of exudate secreted in that time was recorded. As earthworms secrete exudate in response to noxious stimuli, we hypothesized that the amount of exudate produced is proportional to the amount of irritation. We repeated these experiments after treatment with several blockers for molecules with potential involvement in CO2 detection, including carbonic anhydrases, guanylate cyclase, TRPA1 channels, acid sensing ion channels, and OTOP channels. Additionally, we attempted sequencing of the TRPA1 gene and utilized qPCR to evaluate the anatomical profile of TRPA1 gene expression in the earthworm. We found that earthworms secreted significantly more exudate in response to CO2 in a dosage-dependent manner, and that this response was muted by the general carbonic anhydrase inhibitor, acetazolamide; the calcium channel blocker, ruthenium red; the sodium channel blocker, amiloride; and ZnCl2. These data provide preliminary evidence of the role of carbonic anhydrase and ASICs in earthworm CO2 detection, and contribute to our understanding of how earthworms detect and react to their environment.

subject

Carbon Dioxide

Carbonic Anhydrase

Chemical Senses

Earthworm

Mucus

TRPA1

contributor

Silver, Wayne L (committee chair)

Johnson, Erik C (committee member)

Saunders, Cecil J (committee member)

date

2021-06-03T08:36:13Z (accessioned)

2021-12-02T09:30:14Z (available)

2021 (issued)

degree

Biology (discipline)

embargo

2021-12-02 (terms)

identifier

http://hdl.handle.net/10339/98823 (uri)

language

en (iso)

publisher

Wake Forest University

type

Thesis