A multiyear comparison of the male reproductive biology of the brown treesnake (Boiga irregularis) from Guam and the native range
Robert D. Aldridge A C , Dustin S. Siegel A , Angelo P. Bufalino A , Samantha S. Wisniewski A B and Benjamin C. Jellen AA Department of Biology, Saint Louis University, 3507 Laclede Avenue, St Louis, MO 63103-2010, USA.
B Caesar Kleberg Wildlife Research Institute, Texas A&M University, Kingsville, TX 78363-8202, USA.
C Corresponding author. Email: aldridge@slu.edu
Australian Journal of Zoology 58(1) 24-32 https://doi.org/10.1071/ZO09068
Submitted: 13 June 2009 Accepted: 3 February 2010 Published: 7 April 2010
Abstract
Previous studies have suggested that reproduction in the brown treesnake (Boiga irregularis) is reduced on Guam because of elevated stress hormones caused by limited food availability. This study examined the reproductive anatomy of male brown treesnakes on Guam over a 15-year period (1985–99) to determine whether the size at maturity and development of the testis and sexual segment of the kidney varied between years and to compare these data to those for snakes collected from the native range. On Guam, the average snout–vent length and body mass of B. irregularis has decreased from its high in 1985 and remained stable from 1989 to 1999. The snout–vent length at maturity was similar between years. Mean diameters of the seminiferous tubule and the sexual segment of the kidney were not significantly different between years. However, the number of sexual segment tubules hypertrophied per snake varied greatly. Snakes from the native range matured at smaller snout–vent lengths and had significantly more hypertrophied sexual segment tubules per kidney than populations on Guam. These data suggest that elevated plasma levels of corticosterone, potentially due to an increase in male–male interactions as a result the explosive population growth experienced on Guam, may be negatively influencing male reproduction.
Additional keywords: spermatogenesis, sexual segment of the kidney.
Acknowledgements
This project was funded by the National Biological Service to RDA. Animal Care Protocol 744 was approved through the Saint Louis University Animal Care Committee. We thank Mark Doles, Stan Kot, Gordon Rodda, Thomas Sharp, and Gad Perry for field and laboratory assistance on Guam, and Jennifer Pawlik, Tim Schmalz and Anna Arackal for laboratory assistance at Saint Louis University. We also thank George R. Zug, National Museum of Natural History, Smithsonian Institution; Howard L. Snell, Museum of South-Western Biology, University of New Mexico; and Alan E. Leviton, California Academy of Science, for permission to examine museum specimens.
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Appendix 1
Snakes examined from: Museum of Southwestern Biology MSB# 44012, 44025, 44027, 44031, 44035, 44040, 44042, 44047, 44054, 44094, 44097, 44098, 44099, 44134, 44227, 44237, 44241 (Guam); Smithsonian Institution USNM# 120067, 120068, 120070, 120236 (Cape Torokina, Bougainville Island); 195594 (Boroko, Papua New Guinea), 215939 (Indonesia); 506837, 506848, 506859, 506863, 506873, 506888, 506889, 506892, 506893, 507670, 507675, 507717 (Guam); California Academy of Sciences CAS# 114104 (Wahgi-Chimbu Junction, New Guinea), 121223 (Lake Murray, Maka, New Guinea), 133801 (Karemgok, New Guinea), 135568 (Daru Island, New Guinea), 135570 (Maka, Lake Murray, New Guinea).
