Circannual Testis Changes in Seasonally Breeding Mammals

Area of Science:

• Reproductive biology
• Mammalian physiology
• Endocrinology

Background:

• Seasonal breeding is common in non-equatorial zones, leading to seasonal testis regression.
• Testis regression involves germinative epithelium depletion, blood-testis barrier permeation, and reduced androgenic function.
• Mechanisms controlling seasonal testis regression are not fully understood, with apoptosis previously assumed as the primary cause of germ cell depletion.

Purpose of the Study:

• To investigate the mechanisms controlling seasonal testis regression in mammals.
• To explore alternative pathways for germ cell depletion during seasonal testis regression.
• To understand the plasticity of reproductive cycles in mammals, particularly in response to environmental changes.

Main Methods:

• Comparative analysis of reproductive cycles in different mammalian species.
• Histological examination of testicular tissue to assess germ cell status and Sertoli-germ cell adhesion.
• Investigation of molecular mechanisms, including gene and protein expression related to cell adhesion.

Main Results:

• Seasonal germ cell depletion can occur via desquamation of meiotic and post-meiotic germ cells, not solely through apoptosis.
• Alterations in Sertoli-germ cell adhesion molecule expression and distribution facilitate germ cell desquamation.
• Observed plasticity in reproductive cycle control mechanisms across different mammalian species, including the Iberian mole, large hairy armadillo, and greater white-toothed shrew.

Conclusions:

• Seasonal testis regression employs diverse mechanisms, including germ cell desquamation, challenging the universal role of apoptosis.
• The adaptability of mammalian reproductive strategies suggests potential resilience in the face of climate change.
• Further research into these mechanisms is crucial for understanding mammalian reproductive health and evolutionary adaptation.