University of California, Berkeley, Department of Integrative Biology, 3060 VLSB No. 3140, Berkeley, CA 94720, USA.
J Exp Biol. 2010 Dec 15;213(Pt 24):4272-7. doi: 10.1242/jeb.049320.
The polychaete Cirriformia moorei burrows in muddy sediments by fracture, using its hydrostatic skeleton to expand its anterior region and exert force against its burrow wall to extend a crack. Burrowing occurs in four phases: stretching forward into the burrow, extending the crack anteriorly, thickening the burrowing end to amplify stress at the tip of the crack, and bringing the rest of the body forward as a peristaltic wave travels posteriorly. Here, we show that C. moorei is also able to burrow with its posterior end using a similar mechanism of crack propagation and exhibiting the same four phases of burrowing. Worms burrowed backwards with similar speeds and stress intensity factors as forward burrowing, but were thinner and less blunt and did not slip as far away from the crack tip between cycles of burrowing. The anterior end is more muscular and rigid, and differences in body shapes are consistent with having reduce musculature to dilate the posterior segments while burrowing. Backward burrowing provides a unique opportunity to study the effects of morphology on burrowing mechanics within the same species under identical conditions.
多毛类环节动物 C. moorei 通过断裂在泥泞的沉积物中挖掘，利用其流体静力学骨骼来扩张其前部区域，并对其挖掘壁施加力，以扩展裂缝。挖掘过程分为四个阶段：向前伸展进入挖掘通道，向前延伸裂缝，加厚挖掘端以放大裂缝尖端的应力，以及随着体节后部的蠕动波向前移动，将身体的其余部分向前移动。在这里，我们表明 C. moorei 也能够使用类似的裂缝扩展机制和表现出相同的四个挖掘阶段来用后端挖掘。与向前挖掘相比，蠕虫向后挖掘的速度和应力强度因子相似，但更细、更钝，在挖掘周期之间不会从裂缝尖端滑出那么远。前端更具肌肉和刚性，身体形状的差异与在挖掘时减少肌肉以扩张后段有关。向后挖掘为在相同条件下研究同一物种中形态对挖掘力学的影响提供了一个独特的机会。
