Histological Investigation of the Nile Crocodile (Crocodylus niloticus) Phallic Glans

Abstract

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Morphological changes associated with Nile crocodile (Crocodylus niloticus) phallic glans inflation

“…Adult crocodylian glans tissues receive blood for inflation from bilateral vascular conduits that run from vascular tissues adjacent to the proximal phallic crurae to distal inflatable spongiform tissues, most notably through paired blood conduits that flank the ventral sperm‐conducting sulcus spermaticus. This morphology has been described in alligators (Moore & Kelly, 2015; Moore et al, 2016), crocodiles (Moore, Groenewald, & Myburgh, 2020), and Tomistoma (Moore, Fitri, & Augustine, 2020), representing all three modern crocodylians lineages, and suggesting that the anatomical Bauplan related to inflation is ancestral to the group.…”

“…In total, 15 phalli were dissected and 7 of those glans were inflated, as detailed below. The associated gross anatomy and histological analyses have been presented previously (Moore, Groenewald, et al, 2020). We performed MRI analysis and subsequent 3D‐reconstructions of this study on four specimens (snout‐vent lengths 93–96 cm; age ~ 3.0 years).…”

“…When pressurized fluid is experimentally directed through these conduits via syringe, it expands the glans spongiform tissues (Moore, Groenewald, et al, 2020) into a species‐specific reproductive morphology. The general features of erect glans morphology in both alligators and crocodiles include a cup‐like shape with an expanded distally‐facing glans lumen, a prominent ridge dorsal to the ventrally‐placed sulcus spermaticus, and an extension of the sulcus groove beyond the termination of the glans body termed the glans tip (Fitri et al, 2018; Johnston et al, 2014).…”

“…Histological studies, American alligators (Moore et al, 2016), Nile crocodiles (Moore, Groenewald, et al, 2020), Tomistoma (Moore, Fitri, et al, 2020), and broad‐snouted caimans (Tavalieri et al, 2019) have shown that the boundaries of the inflatable spongiform cavities are reinforced by collagen and elastin fiber matrixes. However, a more descriptive, visual understanding of how the three‐dimensional external and internal glans anatomy changes with inflation is lacking.…”

“…Flaccid and inflated 3D‐glans models can be paired with corresponding histology to operate as a framework to investigate male–female reproductive function (Cunha & Baskin, 2018). We have previously presented a histological investigation comparing the flaccid and artificially inflated Nile crocodile ( Crocodylus niloticus ; Laurenti, 1768) glans (Moore, Groenewald, et al, 2020). Here, we use serial MR‐images of four of those phalli to digitally reconstruct 3D‐models of external and internal structures and compare flaccid and inflated glans morphology.…”