Lillie Margo A, Vogl A Wayne, Raverty Stephen, Haulena Martin, McLellan William A, Stenson Garry B, Shadwick Robert E
Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.
J Exp Biol. 2017 Oct 1;220(Pt 19):3464-3477. doi: 10.1242/jeb.162289.
Internal pressures change throughout a cetacean's body during swimming or diving, and uneven pressures between the thoracic and abdominal compartments can affect the cardiovascular system. Pressure differentials could arise from ventral compression on each fluke downstroke or by a faster equilibration of the abdominal compartment with changing ambient ocean pressures compared with the thoracic compartment. If significant pressure differentials do develop, we would expect the morphology of the diaphragm to adapt to its loading. Here, we tested the hypothesis that significant pressure differentials develop between the thoracic and abdominal cavities in diving cetaceans by examining diaphragms from several cetacean and pinniped species. We found that: (1) regions of cetacean diaphragms possess subserosal collagen fibres that would stabilize the diaphragm against craniocaudal stretch; (2) subserosal collagen covers 5-60% of the thoracic diaphragm surface, and area correlates strongly with published values for swimming speed of each cetacean species (<0.001); and (3) pinnipeds, which do not locomote by vertical fluking, do not possess this subserosal collagen. These results strongly suggest that this collagen is associated with loads experienced during a dive, and they support the hypothesis that diving cetaceans experience periods during which abdominal pressures significantly exceed thoracic pressures. Our results are consistent with the generation of pressure differentials by fluking and by different compartmental equilibration rates. Pressure differentials during diving would affect venous and arterial perfusion and alter transmural pressures in abdominal arteries.
在游泳或潜水过程中，鲸类动物体内的压力会发生变化，胸腔和腹腔之间的压力不均衡会影响心血管系统。压力差可能源于每次尾鳍向下划水时腹部受到的腹侧挤压，或者与胸腔相比，腹腔在环境海洋压力变化时更快达到平衡。如果确实出现显著的压力差，我们预计横膈膜的形态会适应其负荷。在这里，我们通过检查几种鲸类和鳍足类动物的横膈膜，测试了潜水鲸类动物胸腔和腹腔之间会出现显著压力差的假设。我们发现：（1）鲸类横膈膜区域拥有浆膜下胶原纤维，可稳定横膈膜以防头尾方向的拉伸；（2）浆膜下胶原覆盖了胸腔横膈膜表面的5%至60%，其面积与已公布的每种鲸类动物游泳速度值密切相关（<0.001）；（3）不通过垂直尾鳍摆动进行运动的鳍足类动物没有这种浆膜下胶原。这些结果有力地表明，这种胶原与潜水过程中承受的负荷有关，并且支持了潜水鲸类动物在某些时段腹腔压力显著超过胸腔压力的假设。我们的结果与尾鳍摆动以及不同腔室平衡速率产生的压力差一致。潜水过程中的压力差会影响静脉和动脉灌注，并改变腹主动脉的跨壁压力。
