Crustaceans provide a fascinating opportunity for studying adaptations to a terrestrial lifestyle because within this group, the conquest of land has occurred at least ten times convergently. The evolutionary transition from water to land demands various morphological and physiological adaptations of tissues and organs including the sensory and nervous system. In this review, we aim to compare the brain architecture between selected terrestrial and closely related marine representatives of the crustacean taxa Amphipoda, Isopoda, Brachyura, and Anomala with an emphasis on the elements of the olfactory pathway including receptor molecules. Our comparison of neuroanatomical structures between terrestrial members and their close aquatic relatives suggests that during the convergent evolution of terrestrial life-styles, the elements of the olfactory pathway were subject to different morphological transformations. In terrestrial anomalans (Coenobitidae), the elements of the primary olfactory pathway (antennules and olfactory lobes) are in general considerably enlarged whereas they are smaller in terrestrial brachyurans compared to their aquatic relatives. Studies on the repertoire of receptor molecules in Coenobitidae do not point to specific terrestrial adaptations but suggest that perireceptor events – processes in the receptor environment before the stimuli bind – may play an important role for aerial olfaction in this group. In terrestrial members of amphipods (Amphipoda: Talitridae) as well as of isopods (Isopoda: Oniscidea), however, the antennules and olfactory sensilla (aesthetascs) are largely reduced and miniaturized. Consequently, their primary olfactory processing centers are suggested to have been lost during the evolution of a life on land. Nevertheless, in terrestrial Peracarida, the (second) antennae as well as their associated tritocerebral processing structures are presumed to compensate for this loss or rather considerable reduction of the (deutocerebral) primary olfactory pathway. We conclude that after the evolutionary transition from water to land, it is not trivial for arthropods to establish aerial olfaction. If we consider insects as an ingroup of Crustacea, then the Coenobitidae and Insecta may be seen as the most successful crustacean representatives in this respect.

甲壳类动物为研究对陆地生活方式的适应提供了一个迷人的机会，因为在这个群体中，对土地的征服至少集中发生了十次。从水到陆地的进化转变需要包括感觉和神经系统在内的组织和器官的各种形态和生理适应。在这篇综述中，我们的目标是比较选定的陆地和密切相关的海洋生物代表之间的大脑结构，这些代表甲壳类动物类群片足类、等足类、短尾类和异类，重点是嗅觉通路的元素，包括受体分子。我们对陆地成员与其近亲水生亲属之间神经解剖结构的比​​较表明，在陆地生活方式的趋同进化过程中，嗅觉通路的元素经历了不同的形态转变。在陆地异常动物（Coenobitidae）中，主要嗅觉通路（触角和嗅叶）的元素通常显着扩大，而与它们的水生亲属相比，陆地短尾动物的体积较小。对 Coenobitidae 受体分子库的研究并未指向特定的陆地适应性，但表明受体周围事件（刺激物结合之前受体环境中的过程）可能在该组的空中嗅觉中发挥重要作用。然而，在片足类（Amphipoda：Talitridae）以及等足类（Isopoda：Oniscidea）的陆生成员中，触角和嗅觉感受器（aesthetascs）大大减少和小型化。最后，他们的主要嗅觉处理中心被认为在陆地生命的进化过程中丢失了。然而，在陆地 Peracarida 中，（第二）触角及其相关的三头脑处理结构被认为可以补偿这种损失或相当大的减少（半脑）主要嗅觉通路。我们得出结论，在从水到陆的进化过渡之后，节肢动物建立空中嗅觉并非易事。如果我们将昆虫视为甲壳纲的一个内群，那么在这方面最成功的甲壳类代表可能是虫科和昆虫纲。（第二）触角及其相关的三头脑处理结构被认为是补偿这种损失或相当大的减少（deutocerebral）主要嗅觉通路。我们得出结论，在从水到陆的进化过渡之后，节肢动物建立空中嗅觉并非易事。如果我们将昆虫视为甲壳纲的一个内群，那么在这方面最成功的甲壳类代表可能是虫科和昆虫纲。（第二）触角及其相关的三头脑处理结构被认为可以补偿这种损失或相当大的减少（deutocerebral）主要嗅觉通路。我们得出结论，在从水到陆的进化过渡之后，节肢动物建立空中嗅觉并非易事。如果我们将昆虫视为甲壳纲的一个内群，那么在这方面最成功的甲壳类动物代表可能是蝾螈科和昆虫纲。