692 GLASSMAN AND BENNETT 



Coulson and Hernandez (1964) were among the first to study 

 extensively the biochemistry of the alligator. They reported normal 

 chemical values and hemoglobin and hematocrit levels for uninfected 

 animals living at ambient temperatures. Colbert, Cowles, and Bogart 

 (1946) defined the alligator's preferred (32 to 35° C) and lethal (38 

 to 39° C) temperatures and the precision with which they can 

 regulate body temperature. Immunologic and hematomorphologic 

 data were not reported in either study. Heat energy budgets for 

 alligators were established by Spotila, Soule, and Gates (1972). 



Despite all these studies, however, little quantitative information 

 is available for the alligator on a variety of physiological parameters, 

 in particular the host defense mechanisms, the morphology of 

 peripheral blood (Reese, 1917), and the effects of thermal stress on 

 these responses. The purpose of our study was: (1) to examine the 

 effects of temperature alteration on the alligator's capacity to 

 respond to an infection of the bacteria Aeromonas hydrophila; (2) to 

 determine the route of infection to which the animal was most 

 susceptible at different temperatures; and (3) to devise methods for 

 quantifying the extent of infection and the capacity of recovery in 

 the alligator under a variety of thermal conditions. 



MATERIALS AND METHODS 



Phase 1 of the study was designed to generate information 

 regarding possible natural routes of infection and to follow the 

 development and progression of experimental infections. Alligators 

 were exposed to graded doses of A. hydrophila (1 x 10^ to 5 x 10^ 

 Aeromonas per milliliter of tank water). Control animals were 

 maintained in a separate tank where levels were from 10 to 25 

 organisms/ml tank water, and others were exposed by injection of A. 

 hydrophila intravenously, intramuscularly, or intraperitoneally. Con- 

 trol animals were given appropriate injections of buffer. 



In phase 2 we studied the susceptibility of alligators to A. 

 hydrophila as a function of varying levels of thermal stress. Water 

 temperatures of 20, 25, 30, and 35°C were used, and varying 

 Aeromonas doses (1 x 10-^ to 5 x lO^nil) were given at the 

 different temperatures. Hematologic data were collected before 

 exposure to Aeromonas and after infection. The effect of tempera- 

 ture on base-line and host-defense effectiveness was appraised. 



Aeromonas hydrophila in amounts from 1 x 10^ to 5 x 10^ 

 organisms/g body weight were pipetted down the animals' gullets in 

 phase 3 of the experiment. Controls were given buffer in an identical 

 manner. 



