Most brachyuran crabs use their pereiopods as walking legs, but there are also a number of species, in which the last (5^th) pair of pereiopods (P5) are specialized to permit a unique mode of swimming. One of these P5-swimming crabs is Liocarcinus depurator, commonly found on European shores. We present 3-dimensional μCT-based reconstructions of the axial skeletons and 5^th pereiopods (P5), including the intrinsic and extrinsic musculature of the P5, of L. depurator and of two other non-swimming brachyuran crabs, Cancer pagurus and Carcinus maenas. In Liocarcinus, we also present a reconstruction of the 4^th pereiopod (P4) together with its intrinsic musculature. We further use 3-dimensional prints of the reconstructed P5 coxa and basi-ischium of L. depurator as well as thoracal parts near the thoracal−coxal arthrodial cavity to build a model which can simulate the effects of muscular activity based on muscle insertions in our 3D reconstruction and under various simulated tensile vectors. This enables us to test muscular functions that had previously been speculated upon. Reconstructed morphological structures are compared to find differences that may explain why of the three species, only L. depurator is able to swim. Significant differences between Liocarcinus and the non-swimmers Cancer and Carcinus were found in the shape of the axial skeleton, external P5 morphology and the dimensions and origin sites of the extrinsic P5 musculature, but not in the intrinsic musculature of the P5. Inclination angle measurements of P1 thoracal−coxal articulation axes against P5 axes showed that in Cancer and Carcinus, angles in the longitudinal plane were smaller than in the lateral one, whereas in Liocarcinus, they were greater. Inclination angles in the longitudinal plane were also much greater in Liocarcinus than in Cancer and Carcinus. 3D print muscular activity simulation showed that muscles inserting at the basi-ischium, which are often referred to as “levator” or “depressor” muscles, may actually also function as promotors or remotors, depending on the tensile vector within which the muscle is acting.

大多数腕足蟹将它们的脚足类动物作为行走的腿，但也有许多种类，其中最后一对（^第5^个）脚足类动物（P5）专门用于允许独特的游泳方式。这些P5游动蟹之一是Liocarcinus净化器，通常在欧洲海岸发现。我们轴向骨架的本3维基于μCT-重建和5^个胸部附（P5），包括P5的内在和外在的肌肉组织，的L.净化器和另外两个非游泳短尾蟹，普通黄道蟹和普通滨蟹。在Liocarcinus，我们还提出了4的重建^第骨足（P4）及其固有的肌肉组织。我们进一步使用重建的P5 coxa和L. depurator的基础坐骨以及胸-髋关节腔附近的胸部分的三维打印来建立一个模型，该模型可以基于我们肌肉插入而模拟肌肉活动的影响在各种模拟拉伸向量下进行3D重建。这使我们能够测试以前推测的肌肉功能。比较重构的形态结构以发现差异，这可以解释为什么这三个物种中只有提普劳德氏菌能够游泳。Liocarcinus与非游泳者癌症和Carcinus之间的显着差异在轴向骨架的形状，外部P5形态以及外部P5肌肉组织的尺寸和起源位置中发现了P，但在P5的固有肌肉组织中没有发现。针对P5 P1 thoracal-臀部关节轴的倾斜角的测量轴表明，在癌症和滨蟹属，在纵向平面的角度比在横向一个较小的，而在Liocarcinus，他们更大。倾斜角在纵向平面是在也大得多Liocarcinus比在癌症和滨蟹属。3D打印的肌肉活动模拟显示，在基础坐骨上插入的肌肉（通常称为“提肌”或“压抑”肌肉）实际上也可以充当启动子或反运动，具体取决于肌肉所作用的拉伸矢量。