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Electroreception of the Elasmobranch Thornback Ray, Platyrhinoidis triseriata

Zegwaard, F. (1994) Electroreception of the Elasmobranch Thornback Ray, Platyrhinoidis triseriata. Master's Thesis / Essay, Biology.

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Sharks, skates and rays all have Ampullae of Lorenzini. Nowadays these ampullae are generally accepted as being electroreceptors, with which the animals can sense the (bio)electric fields in their environment. Much biophysical research has been carried out on these electroreceptors, but most of the experiments were conducted under biologically invalid 'in vitro' situations and the properties of the ampullae were therefore greatly influenced. It is important to reevaluate the data obtained to date under biologically more adequate and 'in vivo' conditions. In this report the results of 'in vivo 'experiments on live, anaesthetized thornback rays are described. One of the goals was to perform the experiments on fully submerged animals. The only difficulty we had to overcome was that by submerging the animal, the canal would no longer be insulated and the nerve signals would no longer be measurable. At the present time no solution has been found for this problem. The decision was therefore made to temperarely record the nerve spikes (as a measurement of the activity of the ampulla) without submerging the animal yet. The activity of the nerves to different porepositive, hyperpolarizing stimuli was recorded. With the current set-up we were able to conduct experiments on the animal up to several days, this in contrast to other workers who were only able to make stable recordings up to several hours. We found some differences with the results of previous workers, which could be a result of the differences in the experimental conditions. In our experiments we found a clearly visible reaction of the ampulla to stimuli with a frequency of up to 12 Hz. At higher frequencies the response was less evident. The oscillations we recorded did not respond to any of the stimuli in any way. This is a sharp contrast to what other researchers found and contradicts their explanation of the high sensitivity. They are however physiologically real and are probably more than just artifacts. The way to get answers to these questions is to continue with trying to conduct the experiments under biologically more valid conditions (i.e., by fully submerging the animal) and under more controlled circumstances (i.e., computer controlled amplitude, frequency and time base settings for the stimuli). A program to solve this last problem is already being developed. Another way to get the answers would be with intra-cellular recordings (sofar unsuccesfull).

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:48
Last Modified: 15 Feb 2018 07:48

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