HMS Researchers Study Blind, Sighted Cavefish To Explore Genetics of Social Behavior

Harvard Medical School researchers have identified genomic regions that contribute to schooling behavior in cavefish, offering new insight into the genetic foundations of the evolutionary pathway of a complex social behavior. This knowledge may ultimately impact scientists’ understanding of similar social behaviors in other species.

The experiment, directed by Johanna E. Kowalko, a graduate student in the Department of Genetics at HMS, sought to explain the evolution of complex social behaviors exhibited by Mexican Tetra, a fish that exists in both a sighted surface-dwelling form and a blind cave-dwelling form.

The latter form of the fish is distinct from the first in both its lack of its eyes and of schooling behavior. These characteristics, according to Tess A. Linden ’15, who co-authored the research, would seem to suggest that the cavefish lost schooling behavior due to the loss of eyesight.

But statistical analysis of various crossbred generations of the fish showed a correlation between schooling and two genomic regions, one linked to eyesight and one entirely independent of eyesight.

This finding suggests that a gene might lead to a change in social behavior without impacting sensory reception.

“It is possible that the organisms are receiving exactly the same sensory inputs, but some individuals choose to respond in one way while others respond in another,” Linden said. “This difference is determined at least in part by their genes.”

The study, already online, will be published in the October edition of “Current Biology” and will be paralleled by another article exploring genetic correlates to schooling behavior in a species of fish called the Benthic Stickleback.

Abigail Wark, a research fellow in genetics at HMS, noted that these are some of the first instances in which researchers have been able to identify genetic loci that are affiliated with behavioral evolution in vertebrates.

While the study illuminated the genetic basis of a social behavior in fish, identifying the genetic basis of social behavior in more complex organisms like humans is likely to take much longer.

Clifford Tabin, director of the HMS lab that hosted the research, cautioned that such a jump is nowhere in the near future. Interest in questions regarding human social behavior might lead researchers to attempt to identify the specific gene potentially impacting the motivation to school. But as Tabin jokes “people don’t school.”

“If there’s any link it’s a long term link,” Wark agreed.

The experiments, according to Wark and Tabin, are directed at answering the nature of species’ evolution.