Selden Rebecca, Johnson Amy S, Ellers Olaf
Department of Biology, Bowdoin College, 6500 College Station, Brunswick, ME 04011 USA ; Ecology, Evolution, and Marine Biology, University of California-Santa Barbara, Santa Barbara, CA 93106 USA.
Department of Biology, Bowdoin College, 6500 College Station, Brunswick, ME 04011 USA.
Mar Biol. 2009;156(5):1057-1071. doi: 10.1007/s00227-009-1150-0. Epub 2009 Feb 21.
Indirect predator-induced effects on growth, morphology and reproduction have been extensively studied in marine invertebrates but usually without consideration of size-specific effects and not at all in post-metamorphic echinoids. Urchins are an unusually good system, in which, to study size effects because individuals of various ages within one species span four orders of magnitude in weight while retaining a nearly isometric morphology. We tracked growth of urchins, (0.013-161.385 g), in the presence or absence of waterborne cues from predatory Jonah crabs, We ran experiments at ambient temperatures, once for 4 weeks during summer and again, with a second set of urchins, for 22 weeks over winter. We used a scaled, cube-root transformation of weight for measuring size more precisely and for equalizing variance across sizes. Growth rate of the smallest urchins (summer: <17 mm diameter; winter: <7 mm diameter) decreased by 40-42% in response to crab cues. In contrast, growth rate of larger urchins was unaffected in the summer and increased in response to crab scent by 7% in the winter. At the end of the 22-week experiment, additional gonadal and skeletal variables were measured. Cue-exposed urchins developed heavier, thicker skeletons and smaller gonads, but no differences in spine length or jaw size. The differences depended on urchin size, suggesting that there are size-specific shifts in gonadal and somatic investment in urchins.
在海洋无脊椎动物中，间接的捕食者诱导效应（对生长、形态和繁殖方面）已得到广泛研究，但通常未考虑特定大小的效应，且在变态后的海胆中完全没有相关研究。海胆是一个非常适合研究大小效应的系统，因为同一物种内不同年龄的个体体重跨度达四个数量级，同时保持近乎等比例的形态。我们追踪了海胆（体重0.013 - 161.385克）在有或没有来自掠食性乔纳蟹的水体线索情况下的生长情况。我们在环境温度下进行实验，夏季进行一次为期4周的实验，然后用另一组海胆在冬季进行为期22周的实验。我们使用体重的立方根缩放变换来更精确地测量大小，并使不同大小间的方差均衡。最小的海胆（夏季：直径<17毫米；冬季：直径<7毫米）的生长率因蟹的线索而下降了40 - 42%。相比之下，较大海胆的生长率在夏季不受影响，而在冬季因蟹的气味而增长了7%。在为期22周的实验结束时，还测量了性腺和骨骼的其他变量。接触线索的海胆发育出更重、更厚的骨骼和更小的性腺，但在棘长度或颚大小方面没有差异。这些差异取决于海胆的大小，表明海胆在性腺和体细胞投资方面存在特定大小的变化。
