The nervous and visual systems of onychophorans and tardigrades: learning about arthropod evolution from their closest relatives

@article{Martin2017TheNA,
  title={The nervous and visual systems of onychophorans and tardigrades: learning about arthropod evolution from their closest relatives},
  author={Christine Martin and Vladimir Gross and Lars Hering and B Tepper and Henry Jahn and Ivo Sena Oliveira and Paul A Stevenson and Georg Mayer},
  journal={Journal of Comparative Physiology A},
  year={2017},
  volume={203},
  pages={565-590}
}
Understanding the origin and evolution of arthropods requires examining their closest outgroups, the tardigrades (water bears) and onychophorans (velvet worms). Despite the rise of molecular techniques, the phylogenetic positions of tardigrades and onychophorans in the panarthropod tree (onychophorans + tardigrades + arthropods) remain unresolved. Hence, these methods alone are currently insufficient for clarifying the panarthropod topology. Therefore, the evolution of different morphological… Expand
Assessing segmental versus non-segmental features in the ventral nervous system of onychophorans (velvet worms)
TLDR
It is suggested that the segmental ganglia of arthropods evolved by a gradual condensation of subsets of neurons either in the arthropod or theArthropod-tardigrade lineage. Expand
Brain and eyes of Kerygmachela reveal protocerebral ancestry of the panarthropod head
TLDR
It is shown that Kerygmachela from Sirius Passet, North Greenland, a primitive stem-group euarthropod, exhibits a diminutive brain that innervates both the eyes and frontal appendages, and it is suggested that the complex compound eyes in arthropods evolved from simple ocelli, present in onychophorans and tardigrades, rather than through the incorporation of a set of modified limbs. Expand
Organization of the central nervous system and innervation of cephalic sensory structures in the water bear Echiniscus testudo (Tardigrada: Heterotardigrada) revisited
TLDR
The central nervous system of the heterotardigrade Echiniscus testudo is reinvestigated using anti‐synapsin and anti‐acetylated α‐tubulin immunohistochemistry in order to visualize the number and position of tracts, commissures, and neuropils, supporting the hypothesis that the dorsal brain is serially homologous with the ventral trunk ganglia. Expand
Functional morphology of a lobopod: case study of an onychophoran leg
TLDR
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 as muscles for stabilization and haemolymph control. Expand
Analyses of nervous system patterning genes in the tardigrade Hypsibius exemplaris illuminate the evolution of panarthropod brains
TLDR
The results buttress the conclusion of the previous study of Hox genes—that the brain of tardigrades is only homologous to the protocerebrum of euarthropods. Expand
Low-resolution vision in a velvet worm (Onychophora)
TLDR
The findings suggest that adult specimens of E. rowelli cannot spot or visually identify prey or conspecifics beyond a few centimetres from the eye, but the coarse spatial resolution that the animals exhibited in the authors' experiments is likely to be sufficient to find shelter and suitable microhabitats from further away. Expand
Evolutionary history of major chemosensory gene families across Panarthropoda.
TLDR
The results suggest that the NPC2 gene family was the only family encoding soluble proteins in the panarthropod ancestor and that onychophorans might have lost many arthropod-like chemoreceptors, including the highly conserved IR25a receptor of protostomes. Expand
Comparison of ventral organ development across Pycnogonida (Arthropoda, Chelicerata) provides evidence for a plesiomorphic mode of late neurogenesis in sea spiders and myriapods
TLDR
The findings illustrate the importance of dense sampling in old arthropod lineages – even if as gross-anatomically uniform as Pycnogonida – in order to reliably differentiate plesiomorphic from apomorphic neurodevelopmental characteristics prior to outgroup comparison. Expand
Miniaturization of tardigrades (water bears): Morphological and genomic perspectives.
TLDR
Morphological and genomic data are interpreted together as evidence of miniaturization in the tardigrade lineage, while cautioning that the effects ofminiaturization may manifest in different ways depending on the organ or organ system under examination. Expand
Analysis of Pigment-Dispersing Factor Neuropeptides and Their Receptor in a Velvet Worm
TLDR
The detection of the onychophoran PDF receptor in cells that additionally express the two PDF peptides suggests autoreception, whereas spatial separation of PDFR- and PDF-expressing cells supports hormonal release of PDF into the hemolymph, which suggests a dual role of PDF peptide—as hormones and as neurotransmitters/neuromodulators—in Onychophile. Expand
...
1
2
...

References

SHOWING 1-10 OF 271 REFERENCES
Selective neuronal staining in tardigrades and onychophorans provides insights into the evolution of segmental ganglia in panarthropods
TLDR
The organisation of the nervous system in three tardigrade species using antisera directed against tyrosinated and acetylated tubulin, the amine transmitter serotonin, and the invertebrate neuropeptides FMRFamide, allatostatin and perisulfakinin shows correspondences that support the homology of segmental ganglia in tardsigrades and arthropods. Expand
The origins of the arthropod nervous system: insights from the Onychophora.
TLDR
An evolutionary scenario is suggested, by which the arthropod nervous system evolved from a system of orthogonally crossing nerve tracts present in both a presumed protostome ancestor and many extant worm-like invertebrates, including the onychophorans. Expand
Structure and development of onychophoran eyes: what is the ancestral visual organ in arthropods?
  • G. Mayer
  • Biology, Medicine
  • Arthropod structure & development
  • 2006
TLDR
It is suggested that the last common ancestor of arthropods bore only one pair of ocellus-like visual organs that were modified in several arthropod lineages and is supported by recent paleontological data. Expand
Onychophoran cephalic nerves and their bearing on our understanding of head segmentation and stem-group evolution of Arthropoda.
TLDR
The model allows the onychophoran cephalic nervous system to be interpreted as a modified circumoral nerve ring, similar to that seen in the nematodes and other cycloneuralians, which is regarded as supporting the Ecdysozoa model of arthropod relationships. Expand
The Evolution of Arthropod Nervous Systems: Insights from Neural Development in the Onychophora and Myriapoda
TLDR
Current understanding of mechanisms for neurogenesis and the establishment of early axon pathways in the central nervous system (CNS) of Onychophora and Myriapoda are reviewed. Expand
A revision of brain composition in Onychophora (velvet worms) suggests that the tritocerebrum evolved in arthropods
TLDR
It is suggested that the last common ancestor of Onychophora and Arthropoda possessed a brain consisting of protocerebrum and deutocere brum whereas the tritocere Brum evolved in arthropods. Expand
Opsins in onychophora (velvet worms) suggest a single origin and subsequent diversification of visual pigments in arthropods.
TLDR
It is concluded that the diversification of visual pigments and color vision evolved in arthropods, along with the evolution of compound eyes-one of the most sophisticated visual systems known. Expand
The morphological and molecular processes of onychophoran brain development show unique features that are neither comparable to insects nor to chelicerates.
TLDR
It is shown that the development of the onychophoran brain is considerably different from arthropods, and the developmental processes that generate the brain have considerably diverged in onyChophorans and arthropod. Expand
Neuronal tracing of oral nerves in a velvet worm—Implications for the evolution of the ecdysozoan brain
TLDR
The overall innervation pattern of the oral lip papillae in E. rowelli is incompatible with the interpretation of the onychophoran brain as a modified circumoral ring, which shows a collar-shaped, circumoral organization in cycloneuralians but a ganglionic architecture in panarthropods. Expand
Assessing segmental versus non-segmental features in the ventral nervous system of onychophorans (velvet worms)
TLDR
It is suggested that the segmental ganglia of arthropods evolved by a gradual condensation of subsets of neurons either in the arthropod or theArthropod-tardigrade lineage. Expand
...
1
2
3
4
5
...