” The question that we addressed in this research study is whether the resemblances we see in between sea slugs and more complex creatures evolved individually or whether those with segmented body parts and appendages may have acquired their underlying neural circuitry from a soft-bodied bilateral common ancestor,” he said.
To respond to that question, Gillette and his associates, former graduate trainees Colin Lee and Jeffrey Brown, videotaped sea slug motions and combined that information with taped responses to the stimulation of nerves and specific neurons in the sea slug brain.
From left, Ph.D. trainee Colin Lee, integrative and molecular physiology professor Rhanor Gillette and their colleagues found parallels in between the neural circuitry that guides locomotion in sea slugs and in more complex animals like mammals. Credit: Fred Zwicky
” The predatory sea slug we studied, Pleurobranchea californica, uses cilia on its foot to crawl, paddling through secreted mucous,” Gillette stated. “For a postural turn toward or away from a stimulus, it just reduces one side of its body and gets away from other predators with a frantic, rocking swim– all driven by the A-cluster.”
Previous studies from Gillettes laboratory showed that Pleurobranchaea participates in cost-benefit computations each time it experiences another animal in the wild. If it is extremely hungry, the neurons that manage its attack and feeding habits are at an increased state of arousal and it will go after almost anything that smells like food. Under other situations, it will not do anything or perhaps actively avoid the stimulus.
” This is an excellent concept if it does not require the food and can avoid other cannibalistic Pleurobranchaea brought in by it,” Gillete said. “All these habits include how the A-cluster collaborates with action choices.”
In mammals, a special hindbrain module called the reticular system equates particular instructions for action options from greater brain regions for posture and mobility, Gillette said. This region then sends the motor commands down to the spine for final transmission to the muscles.
” In specific, the reticular system depends on crucial serotonin-producing nerve cells to manage body language in posture and mobility,” he stated. “In the brand-new research study, we find that similar serotonin-producing neurons in the A-cluster of sea slugs are driving habits like escape, avoidance, and pursuit.
” In their relative simplicity, the sea slugs resemble in lots of methods the anticipated simpler forefather of todays complicated animals,” Gillette stated. “All the significant circuit modules of action choice, equating that choice into motor commands, and motor pattern-generation discovered in the nerve systems of complicated animals are likewise identifiable in the easier soft-bodied sea slugs.”
The research study uses the first proof that the circuits driving locomotion in animals with complicated bodies and behaviors “have close functional examples in the simpler gastropod mollusks and might share a common inheritance,” Gillette stated.
Referral: “Coordination of Locomotion by Serotonergic Neurons in the Predatory Gastropod Pleurobranchaea california” by Colin A. Lee, Jeffrey W. Brown and Rhanor Gillette, 24 April 2023, Journal of Neuroscience.DOI: 10.1523/ JNEUROSCI.1386-22.2023.
The research study was moneyed by the Office of Naval Research.
The sea slug, Pleurobranchea californica. Credit: Fred Zwicky
Prior to the advent of animals with segmented bodies, jointed skeletons, and appendages, the seas were dominated by soft-bodied invertebrates such as sea slugs. A recent study has found resemblances between the brain structure responsible for the movement of sea slugs and that of more advanced creatures with segmented bodies, jointed skeletons, and appendages.
According to the study which was published in the Journal of Neuroscience, the findings recommend that instead of developing a completely separate set of neural circuits to control the motion of segmented body parts, pests, shellfishes, and even vertebrates like mammals adapted a network of neurons, a module, that guided locomotion and posture in much simpler organisms.
” Sea slugs may still have that module, a small network of nerve cells called the A-cluster, with 23 nerve cells identified so far,” said University of Illinois Urbana-Champaign molecular and integrative physiology teacher Rhanor Gillette, who led the new research study.
