Zoological Studies

Vol. 55, 2016

(update: 2016.5.31)

Effect of Photoperiod Extension on the Testicular Sonographic Appearance and Sexual Behavior of Captive Yangtze Finless Porpoise (Neophocaena asiaeorientalis asiaeorientalis)

Xueying Yu1,2, Yujiang Hao1,*, Brian CW Kot3, and Ding Wang1

1The Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences, Institute of Hydrobiology of the Chinese Academy of Sciences, Wuhan, China.E-mail: wangd@ihb.ac.cn
2College of Ocean, Qinzhou university, Qinzhou, China. E-mail: junzhi45@163.com
3Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China. E-mail: briankot@polyu.edu.hk

(Received 11 February 2015; Accepted 4 March 2016)

Xueying Yu, Yujiang Hao, Brian CW Kot, and Ding Wang (2016) Photoperiod plays an important role in the seasonal regulation of reproduction in mammals. In the present study, we examined the effect of an extended photoperiod (light/dark: 14 h/10 h) during the usual sexually inactive phase (Jan-Mar) on testicular sonographic appearance and sexual behaviors of two captive Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis, YFP). During the extended photoperiod treatment, the parenchyma pixel intensity, cross-sectional area of testicular sonographic images, as well as the frequency of sexual behaviors of the two male porpoises increased significantly compared to the control treatment. Parenchyma pixel intensity, the cross-sectional area of testicular sonographic images and the frequency of sexual behaviors of the two captive males all increased in response to extended photoperiod. These results may suggest that photoperiod is a potent factor regulating the reproductive seasonality in YFPs.

Key words: Photoperiod, Seasonal reproduction, Testicular changes, Ultrasonography, Sexual behavior, Yangtze finless porpoise.

*Correspondence: Present address: Institute of Hydrobiology, Chinese Academy of Sciences, 7th South Donghu Road, Wuchang District, Wuhan 430072, P.R. China. E-mail: hao.yj@ihb.ac.cn