Summary: A study examining Cambrian fossils demonstrated that the ancient ecdysozoan probably had a one dorsal nerve cord, challenging previously held theories about how these structures evolved. Supporting the single-cord hypothesis, fossilized images of first Scalidophora varieties reveal similarities to contemporary priapulid brain cords.
This finding suggests that paired brain strings in arthropods, kinorhynchs, and loriciferans evolved freely, linked to brain classification and action difficulty. Experts believe that these adjustments made movement more effective during the Precambrian-Cambrian move.
Major Information
- Ancestral Design: Fossil evidence supports the existence of a second lateral nerve cord in first ecdysozoans.
- Independent Evolution: Combined muscle cords in arthropods, kinorhynchs, and loriciferans good evolved individually, reflecting convergent development.
- Efficient Linkage: In divided species, segmentation and improved locomotion are related to the evolution of combined nerve cords.
Origin: Queen Mary University of London
An international team of scientists has uncovered a fascinating part of the biological issue: how the lateral brain rope, a key component of the central nervous system, evolved in ecdysozoan species, a group that includes bugs, nematodes, and priapulid worms.
Their results, published in , Science Advances, provide useful insights into the roots of these constructions in the basic Mesozoic period.  ,
The research team, comprising Dr Deng Wang ( Northwest University ), Dr Jean Vannier ( Université de Lyon ), Dr Chema Martin-Durán ( Queen Mary University of London ), and Dr María Herranz ( Rey Juan Carlos University ), analysed exceptionally well-preserved fossils from key Cambrian deposits.
These remains include members of the early-evolving Scalidophora, a group of Ecdysozoa, offering a unique view into the nervous system architecture of ancient species.  ,
Ecdysozoans include arthropods ( such as insects and crabs ), nematodes ( roundworms ), and smaller groups like kinorhynchs ( “mud dragons” ) and priapulids ( “penis worms” ). Scientists have long been fascinated by their central nervous devices, which include the mind and the dorsal brain cord, in order to understand how these two groups evolved over time.  ,
For instance, priapulids have one ventral nerve cord, whereas loriciferans and kinorhynchs have paired nerve cords, and kinorhynchs also develop paired ganglia. Did the ancestor of the ecdysozoan have a single or paired ventral nerve cord?
Furthermore, while loriciferans and kinorhynchs share a similar nervous system design with arthropods, they are phylogenetically distant. Are these similarities the result of convergent evolution, or do they represent a shared evolutionary origin?  ,
Scalidophorans, which include priapulids, loriciferans, and kinorhynchs, first appeared in the early Cambrian. They are a significant lineage for studying the ventral nerve cord’s evolution in ecdysozoans.
By studying fossils from the Fortunian Kuanchuanpu Formation ( e. g., Eopriapulites and Eokinorhynchus ), the Chengjiang Biota ( e. g., Xiaoheiqingella and Mafangscolex ), and the Wuliuan Ottoia prolifica, the researchers identified elongate structures running along the ventral side of these ancient organisms.  ,
According to Dr. Deng Wang and Dr. Jean Vannier,” These structures closely resemble the ventral nerve cords seen in modern priapulids.”
Their analysis reveals that these fossils retain single ventral nerve cord impressions, which may provide insight into scalidophorans ‘ likely ancestral history.  ,
The single ventral nerve cord is the ancestral condition of scalidophorans, according to phylogenetic analysis. Moreover, the evolutionary grouping of nematoids and panarthropods ( a clade that includes arthropods, tardigrades, and onychophorans ) suggests their common ancestor also likely had a single nerve cord.  ,
According to Dr. Chema Martin-Durán,” we think that the ancestor of all ecdysozoans had a single ventral nerve cord.”
” The paired nerve cords observed in arthropods, loriciferans, and kinorhynchs likely evolved independently, representing derived traits” . ,
The study also highlights a connection between the evolution of paired ventral nerve cords, ganglia, and body segmentation. Loriciferans, kinorhynchs, and panarthropods exhibit varying degrees of body segmentation, suggesting that these structural changes may have co-evolved with nervous system modifications.  ,
Dr María Herranz noted,” The emergence of paired nerve cords likely facilitated greater coordination of movement, particularly in segmented animals. During the Precambrian-Cambrian transition, changes in the nervous and muscular systems were likely tied to the development of appendages, enabling more complex locomotion” . ,
This groundbreaking finding advances our understanding of ecdysozoan evolution and raises important issues regarding the role of the fossil record in early animal development.
The study provides a more in-depth understanding of how the various ecdysozoan lineages arose and evolved in response to their surroundings by fusing the nervous system structures with wider evolutionary trends.  ,
About this news release about research in evolutionary neuroscience
Author: Lucia Graves
Source: Queen Mary University of London
Contact: Lucia Graves – Queen Mary University of London
Image: The image is credited to Neuroscience News
Original Research: Closed access.
Deng Wang and colleagues ‘” Preservation and early evolution of the scalidophoran ventral nerve cord” Science Advances
Abstract
Preservation and early evolution of the scalidophoran ventral nerve cord
Diverse levels of neural organization, which reflect a complex evolutionary history, define the ecdysozoan worms ( Nematoida + Scalidophora ). Through the extraordinary preservation of extinct individuals, the fossil record offers a unique opportunity to reconstruct the nervous system’s early character evolution. Their nervous system, which can be seen in early and mid-Cambrian fossils, is what we’re looking at.
We demonstrate that some of the group’s oldest known members were either preserved in carbonaceous compression ( early and mid-Cambrian Burgess-type preservation ) or were phosphatized in three dimensions ( e .g., basal Cambrian Kuanchuanpu Formation, ca. An unpaired ventral nerve (VNC ) that ran along the trunk in an odd manner, as in contemporary priapulids and nematodes, existed for 535 million years.
These fossil records were incorporated into a phylogenetic analysis that suggested that ancestral scalidophorans had an unpaired VNC, and that paired nervous systems might have evolved independently in Kinorhyncha and Loricifera, as well as in panarthropods, in part due to their association with the development of paired appendages and bilaterally coordinated motricity.
