Thesis

Temperature acclimation in Embryonic Limax Flavus L. (Mollusca: Gastropoda)

Investigation into the acclimation patterns of Embryonic Limax flavus clearly suggests that heart rate, when measured over a period of time or throughout a temperature range) shows compensatory response patterns similar to those described for oxygen consumption and other rate functions in the adults of this species. The sequence of larval development described by prior workers has been more precisely defined by detailed analysis of phases in the development of two larval organs, the anterior cephalic vesicle and the posterior podocyst. Several unreported relationships were suggested by this analysis. It appears that, at least at lower temperatures, the cephalic vesicle and, to a lesser degree, the podocyst may change pulsation rate or even developmental phase in response to temperature change. These larval organs may play an important adaptive role in the response of the embryo to a varying natural environment. It was determined that the heart begins to beat between day 25 and 30 in most embryos developing at 10°C.. Acclimation studies are reported on over 700 embryos. Compensatory response to higher temperatures was demonstrated within 48 hours. Acclimation patterns at lower temperatures were not so clear and required an additional analysis due to the activity of the larval vesicles and prolonged periods of no observable heartbeat. When the rate -temperature curves of the heart beat are plotted for animals maintained at 6°, 10° 15°, 20° and 25°C and measured acutely at a series of temperatures from 6° to 25°C, translation is demonstrated in which the curve is shifted to the left or up after cold acclimation and to the right or down after warm acclimation. No change in slope or rotation of the rate-temperature curve appears within the normal temperature range. Homeostatic mechanisms do exist in the developing embryos which allow it to make adjustments to a constantly changing natural environment.

Relationships

Items