Castro Diego A, Podolsky Robert D
College of Charleston, Department of Biology, Charleston, SC 29424, USA.
Biol Bull. 2012 Dec;223(3):300-11. doi: 10.1086/BBLv223n3p300.
Staying attached at a favorable site can be a major challenge for organisms in flow. Meeting this challenge depends on properties of the attachment structure and substrate, the nature of fluid flow, and the ability to adjust attachment force in response to hydrodynamic conditions. A broad taxonomic range of adult stages use adhesion or suction to attach to hard substrates in intertidal habitats, which experience flow from waves and tidal currents. We address the unique challenges of attachment to soft sediment in reproductive structures deposited on tidal flats. Egg masses of the opisthobranch mollusc Melanochlamys diomedea are anchored to the sediment by a buried tether composed of gel and sediment. In the field, populations differed in absolute tethering force and tethering force per unit size (= tenacity). Population differences in tenacity persisted for egg masses oviposited under common conditions in the laboratory. Adults exposed to greater flow produced tethers with greater tenacity but without an increase in tether size. Tethers tended to fail by slippage rather than breakage, indicating that tethering force depends more on frictional interaction with sediment than on strength of the tether axis. These results suggest that adults respond to variation in risks of embryo dislodgment by adjusting the tethering properties of egg masses, and that these adjustments involve more than simple changes in tether length or mass.
对于处于水流中的生物来说，附着在适宜的位置可能是一项重大挑战。应对这一挑战取决于附着结构和基质的特性、流体流动的性质以及根据流体动力学条件调整附着力的能力。在潮间带栖息地，许多成年阶段的生物会利用附着力或吸力附着在坚硬的基质上，这些地方会受到海浪和潮流的水流影响。我们研究了附着在潮滩上生殖结构中的软沉积物上所面临的独特挑战。后鳃亚纲软体动物黑壳海牛的卵块通过由凝胶和沉积物组成的埋藏系绳固定在沉积物中。在野外，不同种群的绝对系绳力和单位尺寸的系绳力（=韧性）存在差异。在实验室常见条件下产卵的卵块，其韧性的种群差异依然存在。暴露在更强水流中的成年个体产生的系绳具有更高的韧性，但系绳大小并未增加。系绳往往因滑动而非断裂而失效，这表明系绳力更多地取决于与沉积物的摩擦相互作用，而非系绳轴的强度。这些结果表明，成年个体会通过调整卵块的系绳特性来应对胚胎脱落风险的变化，而且这些调整不仅仅涉及系绳长度或质量的简单变化。
