For zebrafish mates, reproductive success requires the right combination or personalities. Photo by Oregon State University/ Flickr

Sept. 21 (UPI) -- For zebrafish mates, the proper pairing of personalities is the best way to ensure reproductive success.

Scientists know both behaviors and appearance influence mate selection, but deciphering which factors are most important is difficult. To better understand the sexual selection process, scientists tested the reproductive success of fish paired by both personality and appearance.


"Our research explored both areas -- coloration patterns and personality traits -- to see if they were linked in some way and how they impacted the fitness of the species," Rey Planellas, a researcher at the University of Stirling, said in a news release.

To conduct their matchmaking experiments, scientists selected male and female zebrafish for four different combinations of personality and appearance. The groups included: bold fish with well-defined coloration; bold fish with undefined coloration; shy fish with clear coloration; and shy fish with unclear coloration.

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Scientists allowed the different groups to breed and measure the reproductive success of each combination of mates.

"For all of the parameters of fertility and fitness of the species, proactive animals were the best, regardless of their external coloration pattern," said doctoral student Reynaldo Vargas, now working at the University of Panama. "However, both parameters were additive meaning that proactive fish with defined coloration patterns always achieved the best scores."

Researchers observed females guarding their eggs were most aggressively defended by bold mates.

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Scientists descried the results of their breeding experiments this week in the journal PLOS One.

"Our research concluded that personality plays an important role that surpasses the effect of external appearance in the reproductive success ... and therefore, in the fitness of the species," Planellas said. "This is important in understanding the evolutive drivers for the ecology and conservation of fish, and for the industry to select specific phenotypes that will perform better. It may also inform how we select fish for aquaculture, and the potential impact upon conservation."

While being bold may boost reproductive success, the personality trait comes with risks. Previous studies suggest bold fish are more likely to put themselves in harm's way, while more reactive fish enjoy better survival rates.