Variation in sexual behaviors in a group of captive male Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis): motivated by physiological changes?
Most male mammals in temperate regions demonstrate seasonal sexual behaviors that coincide with seasonal variations in gonadal activities and androgen hormones. The Yangtze finless porpoise is a temperate freshwater cetacean species and an obvious seasonal breeder. To investigate the relationship between sexual behavior and gonadal activity in this animal, testicular size (volume) and structure (ultrasonogram pixel intensity) of two adult male porpoises (AF, AB) and one sub-adult male (TT) were longitudinally monitored from November 2008 to November 2009. Serum testosterone concentration was also monitored during the same period. Variations in the frequency of sexual behavior in AF and AB had similar, but seasonal trends. Their testicular size and pixel intensity also varied seasonally. Testicular size increased in March, peaked from April through June, and decreased gradually from August through September, whereas testicular pixel intensity started to increase in early February. The frequency of sexual behavior was positively correlated with testicular volume and pixel intensity (P = 0.000018 and P = 0.00012, respectively) in AF. Serum testosterone concentrations also varied. The sub-adult male porpoise, TT, was undergoing puberty, as evidenced by its marked increase in testicular volume, testicular pixel intensity, and serum testosterone concentrations from the beginning of 2009. Interestingly, TT exhibited the highest frequency of sexual behavior, most of which was same-sex pairing. However, its oversexed behavior neither quantitatively correlated with its smaller testicular volume (P = 0.61) nor with its testicular pixel intensity (P = 0.69).
Wu
Hai-Ping
HP
Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
Hao
Yu-Jiang
YJ
Yu
Xue-Ying
XY
Xian
Yi-Jie
YJ
Zhao
Qing-Zhong
QZ
Chen
Dao-Quan
DQ
Kuang
Xin-An
XA
Kou
Zhang-Bin
ZB
Feng
Kang-Kang
KK
Gong
Wei-Ming
WM
Wang
Ding
D
D000367:Age Factors; D000818:Animals; D008137:Longitudinal Studies; D008297:Male; D019576:Porpoises / Q000378:metabolism / Q000502:physiology*; D012621:Seasons; D012726:Sexual Behavior, Animal; D013737:Testis / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D013739:Testosterone / Q000097:blood; D014463:Ultrasonography
D013739:Testosterone