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The Dalila effect: C57BL6 mice barber whiskers by plucking
J R Sarna1, R H Dyck, I Q Whishaw
1Department of Psychology and Neuroscience, University of Lethbridge, and NeuroDetective Inc., Alta, Canada.
Abstract:
Group-housed laboratory mice are frequently found with their whiskers and facial hair removed. It has been proposed that dominant mice are responsible for barbering the hair of the recipient (the Dalila effect), and early studies suggest that the hair is removed by nibbling. In the present study, pairs of C57BL6 mice, composed of a barber and recipient, were separated to allow hair to regrow. The animals were then placed together in an observation box and their social behavior was videorecorded. The videorecording was subjected to frame-by-frame analysis. Barbering was found to occur during acts of mutual grooming. During grooming, one member of a mouse pair removed the vibrissae of the conspecific and did so by grasping individual whiskers with the incisors and plucking them out. Although plucking appeared 'painful', recipients were passive in accepting barbering, and even pursued conspecifics for further grooming. Other measures indicated that barbers were heavier than recipients and brain weights were not different. Although cortical barrel fields appeared normal to cytochrome oxidization and zinc staining, Golgi analysis of layer three, barrel-field basilar dendrites indicated changes in cell morphology. The results are discussed in relation to the hypothesis that barbering is an expression of social dominance, the origins of the barbering behavior, and the consequences of barbering on brain function.
Insights
Dominant mice pluck out whiskers and facial hair from subordinate mice during grooming, a behavior termed barbering. This social dominance behavior in mice may alter brain structure.
Area of Science:
- Ethology
- Neuroscience
- Animal Behavior
Background:
- Group-housed laboratory mice often exhibit barbering, characterized by whisker and facial hair removal.
- The Dalila effect, or barbering, is hypothesized to be initiated by dominant mice through nibbling recipient mice's hair.
Purpose of the Study:
- To investigate the mechanism and social context of barbering behavior in C57BL6 mice.
- To examine the relationship between barbering, social dominance, and potential alterations in brain morphology.
Main Methods:
- Pairs of C57BL6 mice (barber and recipient) were observed after hair regrowth periods.
- Social interactions were videorecorded and analyzed frame-by-frame to detail the barbering process.
- Brain tissue was analyzed using cytochrome oxidization, zinc staining, and Golgi analysis for morphological changes.
Main Results:
- Barbering occurred during mutual grooming, involving dominant mice plucking vibrissae with incisors.
- Recipients remained passive, and barbers were heavier than recipients.
- While cortical barrel fields appeared normal, Golgi analysis revealed altered basilar dendrite morphology in layer three.
Conclusions:
- Barbering is an active plucking behavior during grooming, linked to social dominance in mice.
- The behavior, despite appearing painful, is accepted by recipients, suggesting complex social dynamics.
- Barbering may induce changes in neuronal morphology within the mouse brain, warranting further investigation.