(40) Morphology Changes in Alligator Phallic Glans via Artificial Inflation

The distal glans of the Alligator mississippiensis phallus is an inflatable structure that engorges with blood during copulation to form a cup-like shape, putatively to facilitate effective gamete transfer and increase... [ view full abstract ]

The distal glans of the Alligator mississippiensis phallus is an inflatable structure that engorges with blood during copulation to form a cup-like shape, putatively to facilitate effective gamete transfer and increase probability of fertilization. Previous research has demonstrated extensive spongiform vascular spaces in the glans tissues that engorge via increased blood flow through paired vessels running the length of the ventral phallus. We utilized an artificial inflation technique to quantitatively measure the shape change during this transition to the copulatory state. By inflating dissected phallic tissues with liquid petroleum jelly, we achieved inflation, allowed evaluation of expansion by linear caliper measurements, photogrammetry through by Autodesk, and ex vivo silicone casting. Through photogrammetry, the internal lumen was isolated, allowing for volumetric differences of only this structure to be measured and compared between its flaccid and inflated states. Similarly, we were able to quantify the dynamic volume of the glans tissue in its transition to a copulatory state. Together, these results provide a better understanding of how the alligator phallus achieves a copulatory state lays the foundation for later study of how this morphology interfaces with female cloacal tissues and facilities insemination.