Title

Kinetic and Taxic Responses of the Infective Larva of Ancylostoma braziliense to Environmental Stimuli

Date of Award

1987

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

Donald E. Norris, Jr.

Advisor Department

Biological Sciences

Abstract

Infective larvae of Ancylostoma braziliense were tested for kinetic and orientational responses to gravity, light, and to a variety of compounds. Six hours following the introduction of larvae to the mid-point along a vertical gauze column, larvae were found at, above, and below the point of introduction. When retested in an identical manner, separate populations of larvae that had been recovered at, below, or above the point of introduction each showed patterns of distribution that were similar to that found in the original test. Results suggest that larvae were negatively geotaxic. Larva immersed in water within a capillary tube was exposed to a series of increasing and decreasing temperatures. Activity increased with increasing temperature to a maximum at 30 to 40 C. At comparable temperatures, activity was higher during the increasing temperature phase than during the decreasing temperature phase. In most cases, the larva stopped moving during the decreasing temperature phase at a temperature that was higher than that at which it began to move. The distribution of larvae in a horizontal column of moist gauze or of a slurry of calcium carbonate was determined 3 hours following the introduction of larvae at the mid-point along the column. Compared to the percentage of larvae that dispersed to either end of the column in the absence of a gradient, significantly more larvae accumulated at the heated end of a thermal gradient. Moreover, the degree of dispersion from the point of inoculation did not differ significantly at constant temperatures of 25, 30, 35, 40, 45, and 50 C. Results suggest that orientation to a heat source was a taxic, rather than a kinetic response. Larvae added onto the center of a 14 cm agar plate were exposed to a directional light source. The high percentages of larvae that remained at or near the point of inoculation 3 to 6 hours later suggest that a phototaxic sensitivity was either very weak, or absent. A variety of compounds were allowed to diffuse on agar plate. A high percentage of larvae accumulated at sources of rat or mouse plasma, rat plasma diffusate, concentrated rat plasma dialysate, and a variety of salts. (Abstract shortened with permission of author.)