From an evolutionary perspective, the primary task of an organism is to pass along its genes to future generations. Such genetic transmission is usually assumed to be instinctive. However, a new study shows that species also learn to adapt to their surroundings in order to increase their “reproductive fitness”— the likelihood that they will successfully reproduce.
One form of learning that increases reproductive fitness is Pavlovian conditioning, the ability to associate a neutral stimulus with a stimulus of significance. The classic example comes from Ivan Pavlov and his dogs that eventually salivated at just the sound of a bell, because the bell had been preciously paired with a slab of meat. However, when it comes to reproduction, does learning contribute to more offspring?
Researchers from the University of Texas at Austin decided to test this in the laboratory. Nicolle Matthews and colleagues set out to examine whether learning can contribute to reproductive fitness in a particularly challenging situation — when two males compete to fertilize the egg of a single female.
Matthews hypothesized that if two males mate with the same female compete to fertilize her eggs, paternity will favor the male that received a signal or conditioned stimulus before the mating session.
Using quail, Matthews put the males into two chambers for thirty minutes; they repeated this for five days. One chamber was green and was located on the floor near a noisy room and the other chamber was white, had a tilted floor, and was located in an isolated room on a table. Whenever the quails were in one of the two chambers, they were allowed access to a female. Thus, the quail learned to anticipate a chance to copulate whenever they were placed in this chamber but not when they were in the other.
On the test day, each female was allowed to copulate with two males. One of the males was in the chamber where he expected to receive access to a female and the other male was in a chamber where he did not expect a female. Using genetic markers, the researchers then collected the eggs of the female quail and tested the paternity.
The results, which appear in the September issue of Psychological Science, a journal of the Association for Psychological Science, are clear: The males who were placed in the context that led them to anticipate access to a female just before copulation fertilized seventy-two percent of the eggs laid by the female quail. In other words, the quail who knew they were going to have the opportunity to mate produced more offspring. This is a significant finding because typically when two males mate in quick succession with the same female, no differences in paternity are found, which Matthews confirmed in a follow-up experiment.
The researchers point out that the conditioning most likely had an effect on the rate of sperm release without changing sperm quality or concentration. “Learning and individual experience can bias genetic transmission and the evolutionary changes that result from sexual competition,” write the authors.
Source: Association for Psychological Science
Related stories:
Female art students more sexually active than male science nerds: study
Female arts students at university are the most sexually active while male science students are the most likely to be virgins, Australian researchers said Thursday.
100-meter sprint world record could go as low as 9.48 seconds
2008 was a great summer for sports' fans. World records tumbled at the Beijing Olympics. Usain Bolt shattered both the 100m and 200m world records, knocking tenths of a second off each. People have been getting faster and faster over the last few decades, which made marathon runner Mark Denny, from Stanford University, wonder whether last century's massive increase in population could account for these dramatic improvements. He also wondered whether there are absolute limits on running speeds and, if so, how close are we to them?
Scientists discover a new way in which epigenetic information is inherited
Hereditary information flows from parents to offspring not just through DNA but also through the millions of proteins and other molecules that cling to it. These modifications of DNA, known as "epigenetic marks," act both as a switch and a dial – they can determine which genes should be turned on or off, and how much message an "on" gene should produce.
Sex between electric fish is a current affair
Sex among electric fish in the Congo River is a rather charged business, according a to new study reporting on an unusual experiment.
Adiponectin is a metabolic link between obesity and bone mineral density
Researchers at the University of Toronto, Faculty of Medicine, Toronto, Canada, have discovered that adiponectin, a protein secreted from adipocytes, is a metabolic link that can explain, in part, the known positive relationship between obesity and both bone mineral density and reduced susceptibility to fractures. This study appears in the December issue of
Experimental Biology and Medicine.
Two from one: new research maps out evolution of genders from hermaphroditic ancestors
Research from the University of Pittsburgh published in the Nov. 20 edition of
Heredity could finally provide evidence of the first stages of the evolution of separate sexes, a theory that holds that males and females developed from hermaphroditic ancestors. These early stages are not completely understood because the majority of animal species developed into the arguably less titillating separate-sex state too long ago for scientists to observe the transition.
Research sheds light on benefits of multiple mates
New research could explain why females of many species have multiple partners. Published on Friday 21 November 2008 in leading journal
Science, the study was carried out by a team from the Universities of Exeter (UK), Okayama (Japan) and Liverpool (UK).
Employees who are sexually harassed experience less job satisfaction and lower job performance
A new study in the journal Psychology of Women Quarterly examined the effects of workplace sexual harassment and found that employees who were harassed report lower levels of job satisfaction, organizational commitment, and job performance. Employees also experienced higher levels of psychological distress and physical problems than those who were not harassed.