02373nas a2200277 4500008004100000022001400041245007400055210006900129260001500198300001200213490000600225520157100231653001601802653001501818653001601833653003701849653001501886653001601901100002201917700002201939700001601961700001801977700002001995700001702015856006302032 2019 eng d a2054-570300aFunctional morphology of a lobopod: case study of an onychophoran leg0 aFunctional morphology of a lobopod case study of an onychophoran c16/10/2019 a191-2000 v63 a

Segmental, paired locomotory appendages are a characteristic feature of Panarthropoda—a diversified clade of moulting animals that includes onychophorans (velvet worms), tardigrades (water bears) and arthropods. While arthropods acquired a sclerotized exoskeleton and articulated limbs, onychophorans and tardigrades possess a soft body and unjointed limbs called lobopods, which they inherited from Cambrian lobopodians. To date, the origin and ancestral structure of the lobopods and their transformation into the jointed appendages are all poorly understood. We therefore combined high-resolution computed tomography with high-speed camera recordings to characterize the functional anatomy of a trunk lobopod from the onychophoran Euperipatoides rowelli. Three-dimensional reconstruction of the complete set of muscles and muscle fibres as well as non-muscular structures revealed the spatial relationship and relative volumes of the muscular, excretory, circulatory and nervous systems within the leg. Locomotory movements of individual lobopods of E. rowelli proved far more diverse than previously thought and might be governed by a complex interplay of 15 muscles, including one promotor, one remotor, one levator, one retractor, two depressors, two rotators, one flexor and two constrictors as well as muscles for stabilization and haemolymph control. We discuss the implications of our findings for understanding the evolution of locomotion in panarthropods.

 

10amusculature10amyoanatomy10aOnychophora10athree-dimensional reconstruction10atomography10avelvet worm1 aOliveira, Ivo, dS1 aKumerics, Andreas1 aJahn, Henry1 aMüller, Mark1 aPfeiffer, Franz1 aMayer, Georg uhttps://royalsocietypublishing.org/doi/10.1098/rsos.191200