Looks aren’t everything. At least that’s the case with a certain species of South American fish, according to a study co-authored by Syracuse University scientist Jorge Luis Hurtado-Gonzales.

The species of fish, Poecilia parae, are the focus of the study published Dec. 23 in BMC Evolutionary Biology. The study is the third in a series investigating Poecilia parae that have helped show the relationship between male mating methods and how predatory behavior has helped protect the Poecilia parae’s unique color variation.

Poecilia parae sexually reproduce like guppies, and their young are born live. Males can be one of five hereditary colors — blue, yellow, red, parae, which is clear with a stripe-colored tail, and immaculata, which is a drab gray color similar to young females.

The latest study found that although females prefer to mate with the red and yellow males, they will mate with the winner of fin-to-fin combat in most cases. The parae males were the winners of male-to-male combat in a significant number of cases and changed females’ initial mating preferences, said Hurtado-Gonzales, a Ph.D. candidate in the department of biology, in an e-mail interview.

But it wasn’t the size of the parae that gave it victory over the other four variations of Poecilia parae, as body length was controlled in the study. The aggressiveness of the parae proved it was the most dominant male type, despite its unattractive coloration, Hurtado-Gonzales said.

‘In particular, this study combined with the previous ones suggests that all males have a different way to achieve mating success and, therefore, remain represented in the population over time,’ said Hurtado-Gonzales.

The immaculata, the smallest male and least preferred by females, does not rely on muscle to mate with females. It instead uses its sneakiness. The immaculata has a plain color that gives it camouflage, allowing it to secretly mate with females while the red males are busy trying to gain the females’ affection, Hurtado-Gonzales discovered in a 2009 study published in the journal Animal Behavior, the first study in the series on Poecilia parae.

But females will mate with several males, which starts a race to fertilize the female’s eggs among the males. The immaculatas have become a frequent winner in this race by developing larger testes that allow them to produce more sperm, giving them a post-mating advantage to fertilize the female’s eggs before their male competitors, Hurtado-Gonzales said.

Together with the parae, the immaculata males are the most abundant in the total Poecilia parae population, even though the females prefer to mate with the red and yellow males.

‘If one male is constantly losing their reproductive success to others, that type of male will likely disappear from the population while the most successful ones perpetuate their presence,’ he said.

To finalize the first stage of his studies on Poecilia parae, Hurtado-Gonzales will be putting out another study that aims to understand how the color patterns of males are perceived by females and predators in unpredictable natural backgrounds. The second stage of his research will try to unravel the role of post-mating sexual selection in determining the outcome of males and females in relation to mating success, he said.

Hurtado-Gonzales said his findings have significance in the area of genetic variation, as scientists are still trying to understand the patterns that originate and maintain genetic diversity.

‘Evolution is a dynamic process, and we hear of species going extinct and others arising,’ he said. ‘The significance of documenting genetic variation could well help to predict the responses that organisms may have under sudden events disrupting their natural cycles.’

jdharr04@syr.edu

Published on January 17, 2011 at 12:00 pm

Contact Jon: jdharr04@syr.edu