Kümmerlen Katja, Blatt Johanna, Hoffmann Lena, Harzsch Steffen
Department of Cytology and Evolutionary Biology, Zoological Institute and Museum, University of Greifswald, Soldmannstrasse 23, D.-17489, Greifswald, Germany.
Cell Tissue Res. 2025 May 14. doi: 10.1007/s00441-025-03978-y.
Our current understanding of brain organization in malacostracan crustaceans is strongly biased towards representatives of the Decapoda ("ten legged" crustaceans) such as crayfish, crabs, clawed lobsters and spiny lobsters. However, to understand aspects of brain evolution in crustaceans, a broader taxonomic sampling is essential. The peracarid crustaceans are a species-rich group that embraces representatives of, e.g. the Isopoda, Amphipoda and Mysida ("opossum shrimps"), taxa whose neuroanatomy has not been carefully examined. The current study sets out to analyze brain morphology of the mysid Neomysis integer (Leach, 1814; Peracarida, Mysida) using immunohistochemistry against the presynaptic protein synapsin and the neuropeptides RFamide, SIFamide and allatostatin combined with three-dimensional reconstruction of elements of the central olfactory pathway. Furthermore, we studied the inventory of sensilla on the first pair of antennae using cuticular autofluorescence. Anterograde filling with neuronal tracers allowed visualisation the central projections of the sensilla on the first pair of antennae. This species is known to display a sexual dimorphism in both the peripheral and central olfactory pathway. We focussed our analysis on this aspect because in contrast to Hexapoda, reports on a sexual dimorphism of the olfactory system are extremely rare in malacostracan crustaceans. We provide a detailed description of the sensilla associated with a male-specific structure on the pair of first antenna the "lobus masculinus". Furthermore, we analyzed the projection patterns of theses sensilla into the "male-specific neuropil" in the deutocerebrum and critically discuss our results in comparison to examples of sexual dimorphism in the chemosensory pathways in other malacostracan crustaceans and hexapods.
我们目前对软甲亚纲甲壳动物大脑结构的理解，严重偏向十足目（“十只脚”的甲壳动物）的代表物种，如小龙虾、螃蟹、螯龙虾和多刺龙虾。然而，为了理解甲壳动物大脑进化的各个方面，更广泛的分类学抽样至关重要。囊虾总目甲壳动物是一个物种丰富的类群，包括等足目、端足目和糠虾目（“负鼠虾”）的代表物种，这些类群的神经解剖学尚未得到仔细研究。本研究旨在利用针对突触前蛋白突触素以及神经肽RFamide、SIFamide和抑咽侧体素的免疫组织化学方法，结合中央嗅觉通路元件的三维重建，分析糠虾Neomysis integer（利奇，1814年；囊虾总目，糠虾目）的大脑形态。此外，我们利用表皮自发荧光研究了第一对触角上的感觉器清单。用神经元示踪剂进行顺行填充，使我们能够观察到第一对触角上感觉器的中央投射。已知该物种在周围和中央嗅觉通路上都表现出两性异形。我们将分析重点放在这一方面，因为与六足动物相比，关于软甲亚纲甲壳动物嗅觉系统两性异形的报道极为罕见。我们详细描述了与第一对触角上一个雄性特异性结构“雄性叶”相关的感觉器。此外，我们分析了这些感觉器在中脑前部向“雄性特异性神经纤维网”的投射模式，并与其他软甲亚纲甲壳动物和六足动物化学感受通路中的两性异形实例进行比较，对我们的结果进行了批判性讨论。
