The relationship of pores and mammillae on the inner surface of the eggshell of the alligator (Alligator mississippiensis).

The morphology of the eggshell of the alligator, Alligator mississippiensis, is similar to that of birds. In many avian species there is a positive linear correlation between the numbers of pores and mammillae on the inner surfaces of eggshells, indicating that the distribution and density of mammillae may determine the porosity of the shell. It is not known, however, if a relationship exists between pores and mammillae on the shell of the alligator. Using a scanning electron microscope, we counted pores and mammillae on the inner surfaces of pieces of shell from the middle of fertile and infertile eggs from wild and captive, pen-reared alligators. Data were analyzed by ANOVA, Duncan's multiple range tests and linear regression equations. Results demonstrate a positive linear correlation between the numbers of pores and mammillae on the shells of unincubated fertile and infertile eggs from wild and captive alligators; however, there is no correlation between pores and mammillae on shells of eggs that were incubated for 55 days. It is suggested that initially the porosity of the eggshell of the alligator is related to the density of mammillae on the inner surface of the shell and that erosion of the shell during incubation destroys the original relationship between pores and mammillae.