Histological analysis of spermatogenesis within non-mammalian vertebrates

摘要

Data on spermatogenesis in vertebrates is vast and within mammals information on the morphology, ontogeny, molecular biology, and physiological mechanisms of sperm development is accelerating at a continuous pace. There is no better example of the data being generated on spermatogenesis than this fine journal, which is dedicated just to that process. In contrast, non-mammalian vertebrates historically have not received the intense attention that their synapsid kin have. This lag in data generation isunfortunate, especially since these basal taxa are the most speciose and have the greatest diversity ofreproductive strategies within both sexes within the Verte-brata. For example, squamate reptiles currently number over 9,000 different species and within lizards and snakes only a handful of studies have been performed on the fine morphology of germ cells as they pass through the phase of spermatogenesis. Because of this lack of data, our understanding of the mechanisms of endocrine control, seasonality, germ cell output, evolutionary implications, and reproductive strategy influences on spermatogenesis are not well understood. Key features such as what controls refractory period, recrudescence, or continuous versus seasonal spermatogenesis is unknown. Basic data on the morphology of germ cell development and the ultrastructural features of spermatogonia, spermatocytes, and spermatids would allow one to make better inferences on the control and mechanisms involved in the physiological timing of spermatogenesis in these fantastic vertebrates.