Natural Inducers of Larval Settlement and Metamorphosis Associated With Mangrove Leaves: Identity and The Role of Bacteria In Their Production.

海洋无脊椎动物物种通常有浮游幼虫的生命周期，这些幼虫必须在底栖生物基质上定居，然后才能蜕变成成体。这些物种包括可食用的贝类，如贻贝、牡蛎和鲍鱼，以及污染生物，如藤壶、水生动物和苔藓动物。沉降和变形的过程不是随机的。许多被调查物种的幼虫(如果不是大多数的话)会对与其成虫环境相关的特定化学物质做出反应。人们对这些“自然”线索知之甚少，只有几个被部分或完全识别出来。这项研究将集中于鉴定和记录自然化学线索的起源，这些化学线索是“倒置”仙后座水母的浮萍幼虫的定居和变态。初步证据表明，该物种的幼虫优先在老的、降解的红树树叶上定居。幼虫似乎对叶子释放的可溶性化学物质有反应，要么直接从叶子扩散，要么是分解过程中细菌作用的结果。细菌在产生幼虫定居的特定线索方面的作用将被确定。另一种遗传实体(例如细菌可以在生命周期中发挥不可或缺的作用)在自然界中比最初认为的更常见。与贝类等更为复杂的高等无脊椎动物相比，水母幼虫是相对简单的动物。因此，定居和变态的细胞、分子和生理机制可能更容易被阐明，并为其他无脊椎动物物种提供一个“模型”。

Marine invertebrate species often have life cycles involving planktonic larvae which must settle on benthic substrates before they metamorphose into the adult form. Such species include edible shellfish likde mussels, oysters and abalone, as well as fouling organisms such as barnacles, hydroids and bryazoans. The process of settlement and metamorphosis is not random. Larvae of many, if not most of the species investigated respond to specific chemicals associated with their adult environment. Relatively little is known about these "natural" cues, and only a few have been either partially or completely identified. This study will focus on identifying and documenting the origin of the natural chemical cues of settlemlent and metamorphosis of planulae larvae of the "upside down" jellyfish Cassiopea xamachana. Preliminary evidence shows that the larvae of this species settle preferentially on old, degrading mangrove leaves. Larvae appear to respond to soluble chemicals released from the leaf, either diffusing directly from the leaf or the result of bacterial action during decomposition. The role of bacteria in producing specific cues for the settlement of larvae will be determined. The fact that another genetic entity (e.g. bacteria can play an integral role in the life cycle a different species is more common in nature than originally thought. Larvae of jellyfish are relatively simple animals, compared with more complicated "higher" invertebrates such as shellfish. Therefore the cellular, molecular and physiological mechanisms in settlement and metamorphosis may be easier to elucidate and provide a "model" for other invertebrate species.//