Morphological characteristics regulating phallic glans engorgement in the American alligator.

The distal part of the crocodilian phallus consists of a bulbous glans containing well-developed vascular tissues that can inflate before or during sexual activity, enlarging and elaborating the glans into a complex, though still functionally undefined, copulatory structure. An enlarged glans putatively interacts with the female cloaca and may change the shape of her reproductive tract to facilitate insemination and increase the probability of fertilization. Here, we investigated the cellular-level properties of the glans and other inflatable phallic tissues associated with the sperm-conducting sulcus spermaticus in the American alligator (Alligator mississippiensis).