Elaborate secondary sexual displays are often overlooked because many species attract mates through sensory modalities imperceptible to humans, including ultraviolet light, ultrasound, electrical signals, or pheromones. Also, sexual coloration may only be expressed briefly during courtship (ephemeral courtship dichromatisms) to avoid attracting predators. Zebrafish (Danio rerio) are a widely studied model organism, though there have been few studies on their mating behaviour. Like many schooling fish, zebrafish do not appear sexually dichromatic to humans; there are no obvious differences in the colour of males and females. Previous studies suggest that colour and stripe patterns influence their social and reproductive behaviour, but surprisingly, body colouration has not been quantitatively studied before in this fish.
The researchers studied sexually mature wild-derived zebrafish and a domesticated strain to compare the sexes and the two populations both in the morning, when mating and spawning occur, and again later in the day, when the fish only shoal. To assess the colour properties the scientists used non-invasive techniques such as digital photography, computer software and human observations and they photographed the fish in the water, while interacting with each other. The photographs allowed them to analyse hue, saturation, and brightness and to obtain numerical estimates of three colour properties.
They found that both males and females changed their colour (dark and light stripes) only during spawning, and that some sex differences in stripes were larger or only became apparent during this time. They also observed that individual males that appeared more colourful and conspicuous to the human eye engaged in courtship more often than less conspicuous males. These observations support the hypothesis that body colouration plays a role in the courtship and mating behaviour of zebrafish.
Both wild-derived and the laboratory strain of zebrafish showed this ephemeral dichromatism, but there were differences in the colour properties of the two populations, and reduced individual variation in the laboratory strain.
Further studies are needed to determine the underlying mechanisms and signalling functions of fleeting different colour expressions in zebrafish. Genetic analyses could help explain individual variation in nuptial colouration and provide insights into the evolutionary functions of this sexual dichromatism.
The article "Ephemeral sexual dichromatism in zebrafish (Danio rerio)" by Sophie Hutter, Attila Hettiyey, Dustin Penn, and Sarah Zala is published in the current issue of the journal "Ethology" (Vol. 118 (2012): 1208). http://onlinelibrary.wiley.com/doi/10.1111/eth.12027/abstract
University of Veterinary Medicine -- Vienna: http://www.vetmeduni.ac.at
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
Algorithms developed by Google designed to encode thoughts, could lead to computers with ‘common sense’ within a decade, says leading AI scientist
New fossil evidence suggests dogs emerged as a separate species from wolves far earlier than scientists previously believed
Researchers discover the 425-million-year-old remains of a new species of parasite - still clamped to the host animal it invaded.
It should be raptor egg blue instead of robin egg blue. Some modern birds lay colourful eggs, but now we know it's a trick their dinosaur ancestors used too
WASHINGTON (Reuters) - Scientists on Thursday unveiled the most comprehensive analysis ever undertaken of the world's ocean plankton, the tiny organisms that serve as food for marine creatures such as the blue whale, but also provide half the oxygen we breathe.
Scientists on Thursday unveiled the most comprehensive analysis ever undertaken of the world's ocean plankton, the tiny organisms that serve as food for marine creatures such as the blue whale, but also provide half the oxygen we breathe.
Researchers say they're excited about a new brain implant that allowed a paralyzed patient to control a robotic arm with his mind. Erik Sorto is the first in the world to have this new neural prosthetic device. Elaine Quijano reports.
Genetically, at least, not that much has changed in the billion years since you two last shared a relative. Roughly half the 500 genes yeast need for life are interchangeable with the human versions.
What controls aging? Biochemist Cynthia Kenyon has found a genetic mutation that can more than double the lifespan of a tiny worm, which points to how we might one day significantly extend human life.
Java sparrows amp up their tunes with acoustic beak taps synchronized with chirps