Geographic Variation in Testicular Morphometrics, Androgen Receptor Expression and Anti-Müllerian Hormone Levels in the Intermediate Roundleaf Bats across Distinct Regions in Thailand

SIMPLE SUMMARY: The intermediate roundleaf bat, Hipposideros larvatus, plays an ecological role in controlling insect populations. Studying its reproductive patterns, specifically testicular morphology, is essential for its conservation, especially in areas where it is at risk. This study focused on examining the testes morphology and the expression of two proteins, AR and AMH, in male H. larvatus bats from various parts of Thailand and during different sampling periods. Results indicated seasonal breeding patterns with significant differences in testes morphometric data, AR and AMH expression depending on the location and sampling period. Notably, bats from Dong Phayayen and Chiang Dao showed higher testicular activity in June, as evidenced by greater AR protein expression. By contrast, decreased AR expression was associated with lower testicular morphometric data and increased AMH expression. This suggests that AR is linked to active testicular functions, while AMH indicates a less active or regressive phase in H. larvatus bat in Thailand. ABSTRACT: The hipposideros larvatus (intermediate roundleaf bat) is one of the insectivorous bats which has an agro-ecological role as a controller of the insect population. The reproductive patterns of H. larvatus are intricately linked to its ecological role and survival. An understanding of the testicular morphology can contribute to conservation for this species particularly in areas where its populations might be declining or under threat. However, these bats may also be associated with zoonotic diseases which can have significant public health implications. The aims of the study were to examine the morphological data as well as the expression of the androgen receptor (AR) and anti-Müllerian hormone (AMH) in the male reproductive organs of H. larvatus from different areas of Thailand and at different sampling periods. Their testes were processed for histological investigation and immunohistochemistry for AR and AMH. The results showed differences among the various sampling areas and different sampling periods, which suggested seasonal breeding characteristics. The higher testicular morphometric data were observed in H. larvatus from the Dong Phayayen (DY) and Chiang Dao (CD) areas during June, while the size of seminiferous tubules decreased thereafter. High AR immunostaining was noticed when the testicular morphometric data were higher in DY bats during June. On the other hand, low AR was observed in bats during August and September, which was concomitant with the decreases in seminiferous tubule size and germinal epithelial height. The results suggest a potential correlation between AR immunostaining and the active phase of testicular functions in H. larvatus during June which may imply the involvement of AR with the enhancement of testicular activity. Conversely, the low expression of AR may contribute to the upregulation of AMH in the testes and may indicate lower testicular activity in H. larvatus in Thailand.