Epigenetics at work, sure, but …
Flexible gene expression may regulate social status in male fish
For a small African fish species, a colorful dominant male does better in life, winning access to food and females. New research by Stanford biologists suggests that this lucky outcome is regulated at a genetic level, by turning genes on and off.
Fernald studies Astatotilapia burtoni, one of the hundreds of cichlid fish species inhabiting Lake Tanganyika in eastern Africa, because of the unique ways they have evolved over time. For male A. burtoni, dominance is everything. They battle frequently for territory, with the victor winning access to the two most important resources — food and females.
Sporting bright rainbow-colored scales, high-ranking males aggressively defend their foraging grounds and lure females into their territory to dine on decaying matter on the lakebed. In contrast, the low-ranking males, which are dull grey in color, comprise 80 percent of the population but cannot reproduce and must swim with the females to get access to food.
But some social mobility is possible. Because the flashy dominant males are more vulnerable to predation, whenever a boss fish disappears, a major battle ensues as non-dominant males fight to take over the vacant territory. The winner then ascends to dominant status resulting in an astonishing series of physiological changes, including rewiring of parts of the brain as previously reported by Fernald’s group.
“We could see the behavioral change in a matter of minutes, as one animal began to dominate the other,” Fernald said. “Videos of these confrontations showed that the fish injected with the methylating agent were much more likely to be the winners, while those receiving the methylation suppressor typically lost the fight for dominance. More.
But while this is certainly a “dominance” struggle, is it correct to call it a struggle over “social status”? The concept of social status presupposes not only a society but a relationship to that society consciously recognized by most actors within it. It is not only the behaviour, but also the consciousness—evident in human affairs, as people strive for social status, even from something as apparently abstract as area codes and zip codes. Purely virtual territory.
Shortly, I (O’Leary for News) will be writing about animals’ sense of self—the “minimal self” as Vincent Torley puts it. Should be fun.
See also: Epigenetic change: Lamarck, wake up, you’re wanted in the conference room!
Furry, feathery, and finny animals speak their minds
Does intelligence depend on a specific type of brain
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Here’s the abstract: Social status hierarchies are ubiquitous in vertebrate social systems, including humans. It is well known that social rank can influence quality of life dramatically among members of social groups. For example, high-ranking individuals have greater access to resources, including food and mating prerogatives that, in turn, have a positive impact on their reproductive success and health. In contrast low ranking individuals typically have limited reproductive success and may experience lasting social and physiological costs. Ultimately, social rank and behavior are regulated by changes in gene expression. However, little is known about mechanisms that transduce social cues into transcriptional changes. Since social behavior is a dynamic process, we hypothesized that a molecular mechanism such as DNA methylation might play a role these changes. To test this hypothesis, we used an African cichlid fish, Astatotilapia burtoni, in which social rank dictates reproductive access. We show that manipulating global DNA methylation state strongly biases the outcomes of social encounters. Injecting DNA methylating and de-methylating agents in low status animals competing for status, we found that animals with chemically increased methylation states were statistically highly likely to ascend in rank. In contrast, those with inhibited methylation processes and thus lower methylation levels were statistically highly unlikely to ascend in rank. This suggests that among its many roles, DNA methylation may be linked to social status and more generally to social behavior. (paywall)
– Kapa Lenkov, Mi H. Lee, Olga D. Lenkov, Andrew Swafford, Russell D. Fernald. Epigenetic DNA Methylation Linked to Social Dominance. PLOS ONE, 2015; 10 (12): e0144750 DOI: 10.1371/journal.pone.0144750