Functional morphology of arborescent animals: strength and design of cheilostome bryozoan skeletons
Functional morphology of arborescent animals: strength and design of cheilostome bryozoan skeletons
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树状动物的功能形态：唇口动物苔藓动物骨骼的强度和设计
DOI：
10.1017/s0094837300004668
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发表时间：
1981
期刊：
影响因子：
2.7
通讯作者：
E. Thomsen
中科院分区：
文献类型：
--
作者：
A. Cheetham;E. Thomsen
在具有刚性乔木生长习性的苔藓虫中，在流水或与移动物体碰撞所产生的力下，对断裂的抵抗力取决于支撑骨骼部分的强度和设计。为了研究现代和第三纪唇口动物的抗断裂能力，我们测量了新鲜、保存和化石材料的弯曲强度；测量实际和模型菌落的阻力；计算了集中和均匀荷载作用下菌落内应力和破碎值。在9个现代物种、5个渐新世物种和4个古新世物种中，推断出的活弯曲强度（24-85 MNm−2）和刚度（42-65 GNm−2）似乎具有物种特异性，与类似的软体动物矿物-有机复合骨骼重叠。与软体动物不同，骨口动物的骨骼在弯曲方面表现为各向同性，其强度与微观结构或成分没有明显的关系。弯曲强度和骨架材料的形态组合产生了广泛的抗断裂能力。在生长早期，几乎所有品种都表现出高度抗性；在较晚的试验中，有些在速度<0.2 m sec−1或集中载荷< 2g时断裂，而另一些在速度<0.2 m sec−1或集中载荷> 100g时保持不断裂。强度和阻力之间的负相关表明，设计是这些苔藓虫承受这类力的能力中更重要的因素。从古新世到现代物种，有一种明显的趋势，那就是趋向于更具抗性的设计，这主要与树枝向群落基部加粗的速度增加有关。随之而来的设计上的变化甚至可能使现代物种能够使用较弱的骨骼材料，同时增加它们的整体抵抗力。
In cheilostome bryozoans with rigidly arborescent growth habits, resistance to breakage under forces generated by flowing water or collision with moving objects depends on the strength and design of supporting skeletal parts. To investigate the abilities of modern and Tertiary cheilostomes to resist breakage, we measured bending strength in fresh, preserved, and fossil material; measured drag on actual and model colonies; and calculated stress within colonies and breaking values under concentrated and uniform loads. Among nine modern, five Oligocene, and four Paleocene species, inferred live bending strength (24–85 MNm−2) and stiffness (42–65 GNm−2) appear to be species-specific properties overlapping those of similar mineral-organic composite skeletons of Mollusca. Unlike those of Mollusca, cheilostome skeletons appear isotropic in bending, with strength not clearly related to microstructure or composition. Bending strength and morphologic disposition of skeletal material combine to produce a wide range of abilities to resist breaking. At early growth stages, almost all species appear highly resistant; at later ones, some break at velocities <0.2 m sec−1 or concentrated loads <2 g, whereas others remain unbroken at velocities >2 m sec−1 or concentrated loads >100 g. A negative correlation between strength and resistance indicates that design is the more important factor in the abilities of these bryozoans to withstand forces of these kinds. An apparent trend toward more resistant designs from Paleocene to modern species is related chiefly to increasing rates at which branches thicken toward the colony base. The consequent change in design may even have permitted modern species to use weaker skeletal material while increasing their overall resistance.