Abstract

…The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), endemic to the middle and lower reaches of the Yangtze River and the adjoining Poyang and Dongting lakes (Gao and Zhou 1993), is one of the smallest toothed cetacean species. Capture-release surveys for the health assessment of wild Yangtze finless porpoises provided a rare opportunity to perform ultrasound imaging of their mammary glands. This study was conducted to examine the morphology and development of mammary glands of Yangtze finless porpoises using this noninvasive technology. The specific objectives of this study were (1) to describe the ultrasonographic appearances and measurements of mammary glands at different reproductive stages and (2) to reveal the developmental pattern of mammary glands throughout the reproductive cycle.

The animals examined in this study included live-captured Yangtze finless porpoises and the fresh carcasses of East Asian finless porpoises (Neophocaena asiaeorientalis sunameri). Ultrasonographic examinations of mammary glands were performed using capture-released practices (Appendix S1) on 28 Yangtze finless porpoises (Table 1) at Tian-e-Zhou Oxbow in November 2015 and at Poyang Lake in March 2015 (Fig. 1). Because of the difficulty of obtaining fresh Yangtze finless porpoise carcasses, anatomical examinations were conducted on East Asian finless porpoise carcasses, a closely related subspecies (Jefferson and Wang 2011), to compare with the ultrasound imaging on the Yangtze finless porpoises…