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RESEARCH ARTICLE
Contents Vol 19(3)

Increases in apoptosis and declines in Bcl-XL protein characterise testicular regression in American crows (Corvus brachyrhynchos)

Luwanda K. Jenkins A C , Wallace L. Ross B and Kelly A. Young A D
+ Author Affiliations
- Author Affiliations

A Department of Biological Sciences, California State University, Long Beach, Long Beach, CA 90840, USA.

B Predator Management, California Department of Fish and Game, San Diego, CA 92123, USA.

C Present address: Mammary Biology and Tumorigenesis Laboratory, Center for Cancer Research, NCI Building 37 Room 1106, 37 Convent Drive, Bethesda, MD 20892, USA.

D Corresponding author. Email: kyoung4@csulb.edu

Reproduction, Fertility and Development 19(3) 461-469 https://doi.org/10.1071/RD06079
Submitted: 26 July 2006  Accepted: 21 January 2007   Published: 19 March 2007

Abstract

The present study investigated the cellular changes observed during testicular regression in American crows. Testes from adults caught during the early (March), progressing (April), peak (early May), transitional (late May), and post- (June) breeding season were examined. Apoptosis was assessed by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) and Bcl-XL protein immunolabelling. Testis mass increased two-fold from March to early May (P < 0.05), then declined 19-fold by June (P < 0.001) without corresponding changes in body mass (P > 0.05). Testicular activity, evaluated using a spermatogenic index, increased nearly two-fold from March to early May and declined nine-fold in June (P < 0.001). Seminiferous tubule diameter declined four-fold in June compared with earlier months (P < 0.001). In all testes, TUNEL-positive germ cells were detected at low levels, with the highest levels observed in late May (P < 0.001). In contrast, TUNEL-positive Sertoli cells were maintained at low levels in March–April and increased nine-fold in early May (P < 0.001). The Bcl-XL immunostaining was detected in Sertoli cells in March–early May; however, staining was most intense in March–April and substantially weaker by early May. These data suggest that the seasonal rise in testicular competence occurs slowly in American crows; however, testis function is terminated rapidly after the breeding season. Furthermore, it is likely that Sertoli cell apoptosis followed by massive germ cell loss is responsible for the rapid reduction in testis mass.

Additional keywords: avian, seasonal reproduction.


Acknowledgements

The authors thank Drs Mason Zhang, Dessie Underwood, Esteban Fernandez-Juricic and Tom Douglas for technical support. The authors are also grateful for the critical advice from Coventry Dougherty, Greer McMichael and Chantelle Moffatt-Blue and other members of the CSULB Reproductive Biology Laboratory. This research was supported, in part, by the Howard Hughes Medical Institute Grant number 52002663 (LKJ) and the Research Initiative For Scientific Enhancement Fellows (RISE) program Grant number 07298405 (LKJ).


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