Chemical Mediation of Shell-related Behaviors in Hermit Crabs

小布鲁克斯9412679 寄居蟹拥有一个柔软的，盘绕的腹部，允许空出来的蜗牛壳占据。由于螃蟹的生长和壳被污损生物降解，寻找新的、更大的壳是这些甲壳类动物自然史的一个关键组成部分。寄居蟹可以通过不同的方式获得新的壳。一种机制涉及寄居蟹之间的种内和种间壳交换，这可能会导致一个更好的壳适合一个或两个参与者。另一种机制涉及受伤同种的位置。具体来说，几种螃蟹对它们各自同种的血液或血淋巴中的因子作出反应。血淋巴从同类和其他寄居蟹或brachyurans未能引起强烈的吸引反应。寄居蟹血淋巴中的引诱剂分子仅在一个物种中进行了研究，Clibanarius vittatus;它们的大小小于1000 D，可能是肽。 否则，很少有人知道的特定化学性质的血淋巴引诱剂或这种反应的普遍性在寄居蟹物种。寄居蟹获得新壳的第三种机制是通过定位被捕食者吃掉的蜗牛。由蜗牛的捕食者产生的蛋白水解酶触发从肉中释放信号肽。 寄居蟹对这些肽的反应是向源头移动，等待捕食者从壳上取下肉（或直接取出捕食者留下的剩余肉）。目前还不清楚这些引诱剂分子是否与螃蟹对血淋巴的反应相似。 先前的研究也表明，一些寄居蟹物种对某些蜗牛气味有优先反应。螃蟹如何区分这些肽信号是未知的。在所有三种获取贝壳的机制中，螃蟹当前贝壳的大小和适合程度会影响它的行为和反应。 也许其他变量，如共生体的存在也会影响寄居蟹的反应。在这个提议中，以下主题将被调查：（1）特异性反应的寄居蟹血淋巴;（2）鉴别化学信号的寄居蟹;（3）是否蜗牛线索和血淋巴从螃蟹的化学相似的分子;和（4）壳适合，性别和存在的共生体介导的作用壳可用性线索的反应。这项研究的结果将是显着的，因为肽介导的反应，涉及周围受体是罕见的。对这一新系统的研究将为化学生态学家以及行为和进化生物学家提供重要的知识。 ***

9412679 Brooks Hermit crabs possess a soft, coiled abdomen which allows the occupancy of vacated snail shells. Because of crab growth and shell degradation by fouling organisms, locating new, larger shells is a critical component in the natural history of these crustaceans. Hermit crabs can procure new shells in different ways. One mechanisms involves intra- and inter-specific shell exchanges between hermit crabs, which can result in a better shell fit for one or both participants. Another mechanism involves location of injured conspecifics. Specifically, several species of crab respond to factors in the blood or hemolymph of their respective conspecifics. Hemolymph from congeneric and other hermit crabs or brachyurans fails to elicit strong attraction responses. The attractant molecules in hermit crab hemolymph have only been investigated in one species, Clibanarius vittatus; they are less than 1000 D in size and likely peptides. Otherwise, very little is known about the specific chemical nature of the hemolymph attractant or the ubiquity of this response i hermit crab species. A third mechanism for hermit crabs obtaining new shells is by locating snails that are being consumed by predators. Proteolytic enzymes produced by predators of snails trigger the release of signal peptides from the flesh. Hermit crabs respond to these peptides by moving towards the source and waiting for the predator to remove the flesh from the shell ( or directly remove remaining flesh left behind by the predator). It is unclear whether these attractant molecules are similar to those involved in crab responses to hemolymph. Previous studies have also shown that some hermit crab species respond preferentially to certain snail odors. How crabs discriminate between these peptide signals is unknown. In all three mechanisms of shell procurement, the size and fit of the crab's present shell can influence its behavior and response. Perhaps other variables such as presence of symbionts als o influence hermit crab responses. In this proposal, the following topics will be investigated: (1) specificity of responses by hermit crabs to hemoplymph; (2) discrimination of chemical signals by hermit crabs; (3) whether snail cues and hemolymph from crabs are chemically similar molecules; and (4) the role of shell fit, sex, and presence of symbionts in mediating responses to shell availability cues. The results of this study will be significant because peptide-mediated responses involving perireceptors are uncommon. Investigation of this novel system will provide important knowledge to chemical ecologists, as well as behavioral and evolutionary biologists. ***