Ctenophore kairomones and modified aminosugar disaccharides alter the shadow response in a larval crab
Ctenophore kairomones and modified aminosugar disaccharides alter the shadow response in a larval crab
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DOI：
10.1093/plankt/25.2.203
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发表时间：
2003-02-01
影响因子：
2.1
通讯作者：
Forward, RB
中科院分区：
文献类型：
--
作者：
Cohen, JH;Forward, RB
河口蟹Rhithropanopeus harrisii（古尔德）的幼体下降在水柱突然减少的辐照度，这是作为一个阴影响应，以避免浮游动物的捕食者，如栉水母。本研究验证了以下假设：（i）来自栉水母拟记忆鱼（Mnemiopsis leidyi）或异基底鱼（Fundulus heteroclitus）的利它素通过减少引起阴影反应所需的最小辐照度降低来增加阴影反应敏感性（即阈值）;及（ii）阴影的类似增加─如在栉水母利它素中发生的反应敏感性也由栉水母的外部粘液和修饰的氨基糖二糖诱导酸性粘多糖的水解产物。光适应R. harrisii阶段I的蚤状幼体适应化学处理3小时，并在模拟水下角光分布的装置中测试它们的光响应。在干净的海水中，阴影响应由辐照度（阈值）减少50%引起。阈值下降到30%，在海水中与鱼类利它素和9%，在海水中与栉水母利它素。降低阴影反应阈值需要1.0 g湿重栉水母粘液l（-1）的最低浓度。硫酸软骨素A二糖在降低阈值方面具有类似于利它素和粘液的作用，在10（-6）μ M浓度下作用最大。用其他二糖进行的试验表明，只有含乙酰胺的氨基糖才有效。测试假设得到支持;捕食利它素，栉水母外部粘液，和纯化的氨基糖二糖具有乙酰胺功能降低了阈值降低所需的辐照度，以唤起蟹幼虫的阴影反应。
Zoea larvae of the estuarine crab Rhithropanopeus harrisii (Gould) descend in the water column upon sudden decreases in irradiance, which serves as a shadow response for the avoidance of zooplankton predators such as ctenophores. This study tested the hypotheses that (i) kairomones from either the ctenophore Mnemiopsis leidyi or the fish Fundulus heteroclitus increase the shadow-response sensitivity by reducing the minimum decrease in irradiance necessary to evoke the response (i.e. threshold); and (ii) a similar increase in shadow-response sensitivity as occurs with ctenophore kairomones is also induced by the external mucus of ctenophores and modified aminosugar disaccharide hydrolysis products of acidic mucopolysaccharides. Light-adapted R. harrisii Stage I zoea were conditioned to chemical treatments for 3 h, and their photoresponses were tested in an apparatus that mimicked the underwater angular light distribution. In clean sea water, the shadow response was induced by a 50% reduction in irradiance (threshold). The threshold decreased to 30% in sea water with fish kairomones and 9% in sea water with ctenophore kairomones. A minimum concentration of 1.0 g wet weight ctenophore mucus l(-1) was required to reduce the shadow-response threshold. Chondroitin sulfate A disaccharides had an effect similar to kairomones and mucus in reducing the threshold, with the greatest effect at a concentration of 10(-6) m. Tests with other disaccharides indicated that only acetylamine-containing aminosugars were effective. The test hypotheses were supported; predator kairomones, ctenophore external mucus, and purified aminosugar disaccharides having acetylamine functionality reduced the threshold decrease in irradiance needed to evoke shadow responses in crab larvae.