Meeting Abstract
Collagen fiber architecture plays important roles in maintaining tissue structure and influencing tissue function. In many male copulatory structures, collagen bundles contribute to the production of rigidity that allows intromission. Picrosirius red staining of histological tissues sections causes collagen fibers to emit birefringent light when viewed under a circularly polarized light microscope. We employed this simple and sensitive method to identify the collagen fiber architectures in American alligator (Alligator mississippiensis histological tissue sections. Collagen bundle thickness and orientations differed with phallic region. The collagen-dense phallic shaft displayed a basket weave of dense collagen, putatively imparting tensile rigidity necessary for intromission. In contrast, the distal glans containing spongiform inflatable regions showed regions of thick, dense bundles surrounding thinner, sparser bundles in the regions that engorges with blood during inflation. These results add insight to an understanding of the biomechanical properties of the alligator phallus. We hope to use this technique to understand phallic variation among crocodylians, identifying both conserved morphologies across species and species-specific phallic novelties, and to develop functional hypotheses incorporating the gross spatial relationships of reproductive tissues and detailed extracellular matrix characteristics.
