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Research article - Peer-reviewed, 2019

Age and seasonal variation in testis and baculum morphology in East Greenland polar bears (Ursus maritimus) in relation to high concentrations of persistent organic pollutants

Sporndly-Nees, Ellinor; Holm, Lena; van Beest, Floris M.; Fakhrzadeh, Azadeh; Ekstedt, Elisabeth; Letcher, Robert; Magnusson, Ulf; Desforges, Jean-Pierre; Dietz, Rune; Sonne, Christian


Persistent organic pollutants (POPs) are found in high concentrations in the Artic. Polar bears (Ursus maritimus) are one of the most exposed mammals in the Arctic and are thereby vulnerable to reproductive disruption. The aim of this study was to investigate male polar bear reproduction based on a detailed evaluation of testis histology and to assess possible effects of environmental chemicals on male polar bear reproduction. Reproductive groups that were identified based on histology were as follows: actively reproductive (REP), non-reproductive either with degenerated testes (DEG), undeveloped seminiferous tubules (UND), or morphology in-transition (INT). Categorization into these groups was supported by significant differences in testis and baculum measurements among REP, DEG, and UND, as well as differences in the area and diameter of seminiferous tubules among REP, DEG, and UND. These results show that it is possible to identify the reproductive stage in polar bears even if capture date and or age is lacking. Based on testis morphology we suggest that adult male polar bears from East Greenland have active spermatogenesis in February to June, and inactive degenerated testes in August to January. January to February was the main period of reproductive transition, characterised by a shift between inactive and active spermatogenesis. Baculum and testis size measurements decreased significantly with increasing concentrations of the chlordane metabolite oxychlordane, suggesting a potential impact on male reproductive success. Half of the investigated polar bears in REP group displayed signs of disorganization of the spermatogenesis which might be a sign of disrupted reproduction. However, no correlations with levels of the investigated POPs were detected. Reproductive organ measurements in polar bears differed significantly between REP and DEG groups, which cannot be explained by age, and therefore should be considered when investigating the effect of POPs on male reproduction.


Reproduction; Bioaccumulative toxicants; Top predators; Ecotoxicology; Spermatogenesis

Published in

Environmental Research
2019, volume: 173, pages: 246-254

Authors' information

Swedish University of Agricultural Sciences, Department of Anatomy, Physiology and Biochemistry (AFB)
van Beest, Floris M.
Aarhus University
Fakhrzadeh, Azadeh
Iranian Res Inst Informat Sci and Technol IranDoc T
Ekstedt, Elisabeth
Swedish University of Agricultural Sciences, Department of Anatomy, Physiology and Biochemistry (AFB)
Letcher, Robert
Carleton University
Swedish University of Agricultural Sciences, Department of Clinical Sciences
Desforges, Jean-Pierre
Aarhus University
Dietz, Rune
Aarhus University
Sonne, Christian
Aarhus University

UKÄ Subject classification

Medical Bioscience

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