Neurobiologist Donald Edwards of Georgia State University and
his colleagues Shih- Rung Yeh and Russell Fricke provide the first direct
evidence that social dominate/subordinate behavior of crayfish causes changes
in the crayfish’s nervous systems. The implications go beyond crayfish.
The Edward’s group findings are “the first time that one has been able
to link a social phenomenon to a change in a particular identified synapse.”
Researchers have suspected this might occur in higher animals. The
research found that serotonin injections caused crayfish to assume the
aggressive posture characteristic of dominant animals. Serotonin
is the substance that other researchers had linked to aggressive behavior
in lobsters and crayfish 15 years ago. This finding caused several
labs to study serotonin’s effect on behaviors like the tail-flip reflex.
Russell Fricke, one of the researchers, found that when he injected serotonin
into young crayfish, it inhibited the tail-flip reflex in some, while enhancing
it in others. That suggested that social status might have influenced
the results. Yeh found that serotonin enhanced the excitability of
the giant neurons from dominant crayfish, while it suppressed activity
of the neuron from subordinate crayfish. This indicated a biological
change in the receptors through which serotonin effects. The researchers
study the specific pathways through which social position gets translated
into cellular and molecular changes in the neuron.
Barinaga, Marcia. “Social Status Sculpts Activity Of Crayfish Neurons.” Science. Vol. 271 January 19, 1996: 290-291.