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

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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.//