Allen Jonathan D
Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Biol Bull. 2008 Feb;214(1):42-9. doi: 10.2307/25066658.
Predation on planktonic larval stages is frequently a major source of mortality for the offspring of benthic marine invertebrates. Mortality rate likely varies with larval size and developmental stage, but few experiments have measured how these factors affect predation rates. I used experimental reductions in egg size to test how variation in larval size affects the likelihood of predation during planktonic development. Blastomeres of the sand dollar Dendraster excentricus were separated at the two-cell stage to produce half-sized zygotes. Larvae resulting from this manipulation were tested for their susceptibility to predation relative to whole-sized siblings at four ages. Individuals from each size class were simultaneously presented as prey items to five predators (crab zoeae, crab megalopae, chaetognaths, solitary tunicates, and postlarval fish) in the laboratory. Four predators consumed significantly more half-sized larvae than whole-sized larvae, but one predator type (postlarval fish) consumed more whole-sized larvae. Predators that consumed more half-sized larvae also preferentially consumed younger larvae. In contrast, postlarval fish showed no significant prey preference based on larval age. These results suggest that assumptions of constant mortality rates during development should be modified to account for the effects of larval size and age.
对浮游幼虫阶段的捕食常常是底栖海洋无脊椎动物后代死亡的主要原因。死亡率可能随幼虫大小和发育阶段而变化，但很少有实验测量这些因素如何影响捕食率。我通过实验减小卵的大小，来测试幼虫大小的变化如何影响浮游发育期间被捕食的可能性。在双细胞阶段将紫海胆的卵裂球分离，以产生一半大小的受精卵。将这种操作产生的幼虫与全尺寸的同胞幼虫在四个年龄段进行捕食易感性测试。在实验室中，将每个大小类别的个体同时作为猎物呈现给五种捕食者（蟹幼体、蟹大眼幼体、毛颚动物、独居被囊动物和幼鱼）。四种捕食者捕食的一半大小幼虫比全尺寸幼虫多得多，但有一种捕食者类型（幼鱼）捕食的全尺寸幼虫更多。捕食更多一半大小幼虫的捕食者也优先捕食较年幼的幼虫。相比之下，幼鱼对不同年龄幼虫没有明显的猎物偏好。这些结果表明，关于发育期间死亡率恒定的假设应加以修正，以考虑幼虫大小和年龄的影响。
