Meeting Abstract
The distal part of the crocodilian phallus consists of a bulbous glans containing well-developed vascular tissues that can inflate prior to 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 changes shape 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). Using histochemical staining and polarized light microscopy, we visualized and defined collagen and elastin fiber densities and orientations in these tissues. Extracellular matrix architectures provide insights about phallic glans material properties and how they may affect tissue strength and flexibility during inflation and in response to copulatory forces. We also investigated the potential sources of fluids that induce inflation in alligator phalli. Combining serial sectioning, in-vivo CT scans and three-dimensional reconstruction, we identified a pair of paralymphatic bodies at the proximal end of the alligator phallus that extend distally adjacent to ventro-medial sulcus tissues. These structures are similar to those observed in ratite intromittent phalli that provide fluid for lymphatic erection, which suggests a shared homology for lymphatic erectile structures and a putative common role across archosaurian phalluses.
