Pereira R C, Vasconcelos M A
Departamento de Biologia Marinha, Instituto de Biologia, Universidade Federal Fluminense - UFF, Niterói, RJ, Brazil.
Braz J Biol. 2014 Aug;74(3):545-52. doi: 10.1590/bjb.2014.0080.
Species of Plocamium are known as prolific sources of halogenated secondary metabolites exhibiting few explored ecological roles. In this study the crude extracts from specimens of P. brasiliense collected in two distinct places, Enseada do Forno and Praia Rasa, Búzios, Estado do Rio de Janeiro, were evaluated as defense against the sea urchin Lytechinus variegatus and the crab Acanthonyx scutiformis. These specimens produce a similar amount of crude extract and also halogenated monoterpene compound-types, but individuals of P. brasiliense from Praia Rasa exhibit a major compound representing about 59% of the total chemicals. Natural concentrations of the crude extracts obtained from both specimens of P. brasiliense significantly inhibited the herbivory by the sea urchin L. variegatus, but had no significant effect on the feeding by A. scutiformis, a crab commonly associated to chemically defended host. Crude extract from P. brasiliense collected at Praia Rasa was more efficient as defense against L. variegatus than that crude extract from populations of this alga from Enseada do Forno, probably due to presence of a major secondary metabolite. These two studied population live under different environmental conditions, but they are only about 30 Km apart. However, it is impossible to affirm that environmental characteristics (abiotic or biotic) would be responsible for the difference of defensive potential found in the two populations of P. brasiliense studied here. Further genetic studies will be necessary to clarify this question and to explain why populations of a single species living in different but close locations can exhibit distinct chemicals.
团扇藻属的物种是卤代次生代谢产物的丰富来源，但其生态作用鲜为人知。在本研究中，对从里约热内卢州布齐奥斯的福尔诺湾和拉萨海滩这两个不同地点采集的巴西团扇藻标本的粗提物进行了评估，以检测其对海胆多色刺海胆和螃蟹盾形长指蟹的防御能力。这些标本产生的粗提物数量相似，卤代单萜化合物类型也相似，但来自拉萨海滩的巴西团扇藻个体有一种主要化合物，约占总化学物质的59%。从这两种巴西团扇藻标本中获得的粗提物的天然浓度显著抑制了多色刺海胆的食草行为，但对盾形长指蟹（一种通常与具有化学防御能力的宿主相关的螃蟹）的摄食没有显著影响。从拉萨海滩采集的巴西团扇藻的粗提物对多色刺海胆的防御效果比从福尔诺湾采集的该藻类种群的粗提物更有效，这可能是由于存在一种主要的次生代谢产物。这两个研究种群生活在不同的环境条件下，但它们相距仅约30公里。然而，无法确定环境特征（非生物或生物）是否是造成这里研究的两个巴西团扇藻种群防御潜力差异的原因。需要进一步的遗传学研究来澄清这个问题，并解释为什么生活在不同但相邻地点的单一物种的种群会表现出不同的化学物质。
