Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, 5006 Bergen, Norway.
Max Planck Institute for Developmental Biology, Spemannstraße 35, 72076 Tübingen, Germany.
Open Biol. 2017 Aug;7(8). doi: 10.1098/rsob.170136.
Animal behaviour often comprises spatially separated sub-reactions and even ciliated larvae are able to coordinate sub-reactions of complex behaviours (metamorphosis, feeding). How these sub-reactions are coordinated is currently not well understood. Neuropeptides are potential candidates for triggering larval behaviour. However, although their immunoreactivity has been widely analysed, their function in trochozoan larvae has only been studied for a few cases. Here, we investigate the role of neuropeptides in the defence behaviour of brachiopod larvae. When mechanically disturbed, the planktonic larvae of protrude their stiff chaetae and sink down slowly. We identified endogenous FLRFamide-type neuropeptides (AFLRFamide and DFLRFamide) in larvae and show that the protrusion of the chaetae as well as the sinking reaction can both be induced by each of these peptides. This also correlates with the presence of FLRFamidergic neurons in the apical lobe and adjacent to the trunk musculature. We deorphanized the AFLRFamide/DFLRFamide receptor and detected its expression in the same tissues. Furthermore, the ability of native and modified FLRFamide-type peptides to activate this receptor was found to correspond with their ability to trigger behavioural responses. Our results show how FLRFamide-type neuropeptides can induce two coherent sub-reactions in a larva with a simple nervous system.
动物行为通常由空间分离的亚反应组成，即使是纤毛幼虫也能够协调复杂行为（变态、进食）的亚反应。这些亚反应是如何协调的目前还不是很清楚。神经肽可能是触发幼虫行为的潜在候选物质。然而，尽管它们的免疫反应性已经得到了广泛的分析，但它们在环节动物幼虫中的功能仅在少数情况下得到了研究。在这里，我们研究了神经肽在腕足动物幼虫防御行为中的作用。当受到机械干扰时，浮游幼虫会伸出坚硬的刚毛并缓慢下沉。我们在 幼虫中鉴定出内源性 FLRFamide 型神经肽（AFLRFamide 和 DFLRFamide），并表明这些肽都可以诱导刚毛的伸出和下沉反应。这也与顶端叶和躯干肌肉附近存在 FLRFamidergic 神经元相关。我们对 AFLRFamide/DFLRFamide 受体进行了去孤儿化，并在相同的组织中检测到了它的表达。此外，发现天然和修饰的 FLRFamide 型肽激活该受体的能力与其触发行为反应的能力相对应。我们的研究结果表明，FLRFamide 型神经肽如何在具有简单神经系统的幼虫中诱导两个协调的亚反应。
