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A common modular design of nervous systems originating in soft-bodied invertebrates

Summary

Scientists have discovered that simple sea slugs have nervous systems organized in much the same way as human brains, with similar modules for making decisions and controlling movement. Even though sea slugs lack bones, brains, and complex bodies compared to humans, their basic neural architecture mirrors ours, suggesting that this organizational plan evolved long ago in simple ancestral organisms. This finding helps us understand how complex brains evolved and reveals that nature has reused the same fundamental neural designs across hundreds of millions of years of evolution.

Background

Nervous systems across vertebrates and invertebrates show common organizational principles for processing sensory information and making cost-benefit decisions. The evolution of complex nervous systems may have originated from simple ancestral soft-bodied organisms before the development of segmentation and jointed skeletons.

Objective

To demonstrate that soft-bodied invertebrates like the sea slug Pleurobranchaea californica possess a modular nervous system organization similar to vertebrates, suggesting a common ancestral neural blueprint. The study compares neuronal circuits mediating decision-making, action selection, and motor control between gastropods and vertebrates.

Results

The study identified striking functional analogies between Pleurobranchaea and vertebrates: the feeding network combines hypothalamic and basal ganglia functions; the A-cluster parallels the reticular formation for posture and locomotion control; the C-cluster resembles ascending serotonergic raphe nuclei; and the peripheral subepithelial network may represent a precursor to vertebrate pallial derivatives.

Conclusion

Soft-bodied invertebrates demonstrate a modular nervous system organization fundamentally similar to vertebrates but simpler in detail. This supports the hypothesis that the general neural blueprint for decision-making and motor control originated in ancestral soft-bodied bilaterians before the evolution of segmentation and complex body forms.
  • Published in:Frontiers in Physiology,
  • Study Type:Review,
  • Source: PMID: 37854468
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