Williamson J E, De Nys R, Kumar N, Carson D G, Steinberg P D
School of Biological Science, University of New South Wales, Sydney, Australia.
Biol Bull. 2000 Jun;198(3):332-45. doi: 10.2307/1542689.
Most benthic invertebrates have complex life cycles with planktonic larvae that return to the substratum to settle and metamorphose into a benthic stage. Although naturally produced chemical cues have long been thought to be important for the settlement or metamorphosis of invertebrate larvae, few ecologically relevant chemical cues have been clearly identified. The marine echinoid Holopneustes purpurascens has a complex life cycle, with a planktonic, nonfeeding dispersive larva that metamorphoses into a benthic stage that lives in the canopy of subtidal benthic algae such as the red alga Delisea pulchra and the kelp Ecklonia radiata. Recently recruited juveniles are found primarily on D. pulchra, and we hypothesized that this was in response to a chemical cue produced by this alga. Competent larvae metamorphosed in the presence of D. pulchra, or seawater surrounding this alga, but not in response to the presence of E. radiata or its extracts. A cue for metamorphosis was isolated and characterized from D. pulchra and found to be a water-soluble complex of the sugar floridoside and isethionic acid in a 1:1 molar ratio. The floridoside-isethionic acid complex also triggered settlement in H. purpurascens; however, this response was less specific than metamorphosis and was reversible. Larvae of H. purpurascens also metamorphosed in the presence of several other species of red, but not brown or green, algae from their habitat. Floridoside is found only in red algae, suggesting that the floridoside-isethionic acid complex may be acting as a cue for metamorphosis in other red algae as well as in D. pulchra.
大多数底栖无脊椎动物具有复杂的生命周期，其浮游幼虫会返回底层进行附着，并变态发育为底栖阶段。长期以来，人们一直认为天然产生的化学信号对于无脊椎动物幼虫的附着或变态很重要，但很少有与生态相关的化学信号被明确识别。海洋海胆紫球海胆（Holopneustes purpurascens）具有复杂的生命周期，其浮游、不摄食的扩散性幼虫会变态发育为底栖阶段，生活在潮下带底栖藻类的冠层中，如红藻美丽德氏藻（Delisea pulchra）和海带辐射艾氏藻（Ecklonia radiata）。新附着的幼体主要在美丽德氏藻上被发现，我们推测这是对该藻类产生的化学信号的反应。有能力的幼虫在美丽德氏藻或其周围海水存在的情况下会变态发育，但对辐射艾氏藻或其提取物的存在没有反应。从美丽德氏藻中分离并鉴定出一种变态信号，发现它是一种糖基甘油醛和羟乙磺酸以1:1摩尔比形成的水溶性复合物。糖基甘油醛 - 羟乙磺酸复合物也引发了紫球海胆的附着；然而，这种反应比变态发育的特异性低，并且是可逆的。紫球海胆的幼虫在其栖息地的其他几种红藻存在的情况下也会变态发育，但在褐藻或绿藻存在的情况下不会。糖基甘油醛仅在红藻中发现，这表明糖基甘油醛 - 羟乙磺酸复合物可能在其他红藻以及美丽德氏藻中作为变态信号起作用。
