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Vol. 54, 2015
Topographical distribution of blubber in finless porpoises (Neophocaena asiaeorientalis sunameri): a result from adapting to living in coastal waters
Xianyuan Zeng1,2, Junhua Ji1,2, Yujiang Hao1* and Ding Wang1*
1Institute of Hydrobiology, Chinese Academy of Sciences, 7 South Donghu Road, Wuchang District, Wuhan 430072, China
2University of Chinese Academy of Sciences, 19 Yuquan Road, Shijingshan District, Beijing 100049, China
Abstract
Background: Blubber
has many functions, among which energy storage, thermoregulation,
buoyancy, and hydrodynamic streamlining are the most frequently cited.
Within and between taxa, variations in its structure and distribution
likely reflect different adaptations of a species to its life history
requirements, environment, health, and function. Here, we use
ultrasound to describe the distribution of blubber in the finless
porpoise (Neophocaena asiaeorientalis sunameri) based on examinations of 34 fresh cadavers recovered as accidental fisheries bycatch.
Results: Measurements
of blubber depth determined by ultrasound positively correlated with
conventional measurements using a scalpel and calipers. Whereas
conventional surgical incision and visual examination revealed two
layers of blubber, ultrasound revealed up to three layers; thus,
ultrasound reveals additional structural detail in blubber while crude
necropsy techniques do not. Across life history categories, ultrasound
revealed the distribution of inner blubber to be topographically
consistent with that of full-depth blubber. Blubber in the dorsal
region was stratified into three layers and was significantly thicker
than that in the lateral and ventral regions, in which a middle layer
was normally absent.
Conclusions: Ultrasound
provides a fast, effective, and accurate means to determine blubber
thickness and structure, and thus, assessment of the health of fresh
finless porpoise carcasses. Blubber depth is determined largely by the
thickness of the inner and middle layers, wherein lipids are
concentrated. The thickening of blubber in the dorsal
thoracic-abdominal region suggests multiple roles of thermal
insulation, lipid storage, and, we speculate, to facilitate vertical
stability in the complex shallow and estuarine waters in which this
animal absent of a dorsal fin occurs.
Key words: Blubber distribution; Finless porpoise; Cetacean; Postmortem; Ultrasound imaging.
*Correspondence: E-mail: hao.yj@ihb.ac.cn; wangd@ihb.ac.cn
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