Arquivo da tag: Zoologia

Wimps or warriors? Honey bee larvae absorb the social culture of the hive, study finds (Science Daily)

Date:
October 29, 2015
Source:
University of Illinois at Urbana-Champaign
Summary:
Even as larvae, honey bees are tuned in to the social culture of the hive, becoming more or less aggressive depending on who raises them, researchers report.

Even as larvae, honey bees are tuned in to the social culture of the hive, becoming more or less aggressive depending on who raises them. The researchers don’t yet know how the social information is being transmitted to the larvae. Credit: © gertrudda / Fotolia

Even as larvae, honey bees are tuned in to the social culture of the hive, becoming more or less aggressive depending on who raises them, researchers report in the journal Scientific Reports.

“We are interested in the general issue of how social information gets under the skin, and we decided to take a chance and ask about very young bees that are weeks away from adulthood,” said University of Illinois entomology professor and Carl R. Woese Institute for Genomic Biology director Gene Robinson, who led the research with postdoctoral researcher Clare Rittschof and Pennsylvania State University professor Christina Grozinger.

“In a previous study, we cross-fostered adult bees from gentle colonies into more aggressive colonies and vice versa, and then we measured their brain gene expression,” Robinson said. “We found that the bees had a complex pattern of gene expression, partly influenced by their own personal genetic identity and partly influenced by the environment of the colony they were living in. This led us to wonder when they become so sensitive to their social environment.”

In the new study, the researchers again cross-fostered bees, but this time as larvae in order to manipulate the bees’ early life experiences. The larvae were from a variety of queens, with sister larvae divided between high- and low-aggression colonies.

The larvae were removed from their foster hives and put into a neutral laboratory environment one day before they emerged as adults. The researchers tested their aggressiveness by exposing them to an intruder bee.

They were surprised to see that the bees retained the social information they had acquired as larvae. Those raised in aggressive colonies were 10 to 15 percent more aggressive than those raised in the gentler colonies.

“Even sisters born of the same queen but reared in different colonies differed in aggression, demonstrating the potency of this environmental effect,” Robinson said.

The finding was surprising in part because bee larvae undergo metamorphosis, which radically changes the structure of their bodies and brains.

“It’s hard to imagine what elements of the brain are influenced during the larval period that then survive the massive reorganization of the brain to bias behavior in this way,” Robinson said.

The aggressive honey bees also had more robust immune responses than their gentler counterparts, the team found.

“We challenged them with pesticides and found that the aggressive bees were more resistant to pesticide,” Grozinger said. “That’s surprising considering what we know from vertebrates, where stress in early life leads to a diminishment of resilience. With the bees, we saw an increase in resilience.”

This finding also suggests that the effects of the social environment on young bees could extend beyond brain function and behavior, Robinson said.

The researchers don’t yet know how the social information is being transmitted to the larvae. They tested whether the bees differed in size, which would suggest that they had been fed differently, but found no size differences between aggressive and gentle bees.

“Adult honey bees are well known for their sociality, their communication skills and their ability to adjust their behavior in response to the needs of the hive,” Rittschof said.

“In mammals, including humans, the effects of early life social interactions often persist throughout adulthood despite additional social experiences,” she said. “A similar pattern in honey bees has broad implications for our understanding of social behavior within the hive and in comparison with other species.”

Video: https://www.youtube.com/watch?v=4amHuHnk5XM


Journal Reference:

  1. Clare C. Rittschof, Chelsey B. Coombs, Maryann Frazier, Christina M. Grozinger, Gene E. Robinson. Early-life experience affects honey bee aggression and resilience to immune challengeScientific Reports, 2015; 5: 15572 DOI: 10.1038/srep15572

Alternate mechanism of species formation picks up support, thanks to a South American ant (University of Rochester )

21-Aug-2014

 

By Peter Iglinski

A queen ant of the host species Mycocepurus goeldii.

A newly-discovered species of ant supports a controversial theory of species formation. The ant, only found in a single patch of eucalyptus trees on the São Paulo State University campus in Brazil, branched off from its original species while living in the same colony, something thought rare in current models of evolutionary development.

“Most new species come about in geographic isolation,” said Christian Rabeling, assistant professor of biology at the University of Rochester. “We now have evidence that speciation can take place within a single colony.”

The findings by Rabeling and the research team were published today in the journal Current Biology.

In discovering the parasitic Mycocepurus castrator, Rabeling and his colleagues uncovered an example of a still-controversial theory known as sympatric speciation, which occurs when a new species develops while sharing the same geographic area with its parent species, yet reproducing on its own.“While sympatric speciation is more difficult to prove,” said Rabeling, “we believe we are in the process of actually documenting a particular kind of evolution-in-progress.”

New species are formed when its members are no longer able to reproduce with members of the parent species. The commonly-accepted mechanism is called allopatric speciation, in which geographic barriers—such as mountains—separate members of a group, causing them to evolve independently.

“Since Darwin’s Origin of Species, evolutionary biologists have long debated whether two species can evolve from a common ancestor without being geographically isolated from each other,” said Ted Schultz, curator of ants at the Smithsonian’s National Museum of Natural History and co-author of the study. “With this study, we offer a compelling case for sympatric evolution that will open new conversations in the debate about speciation in these ants, social insects and evolutionary biology more generally.”

A queen ant of the parasitic species Mycocepurus castrator.

M. castrator is not simply another ant in the colony; it’s a parasite that lives with—and off of—its host, Mycocepurus goeldii. The host is a fungus-growing ant that cultivates fungus for its nutritional value, both for itself and, indirectly, for its parasite, which does not participate in the work of growing the fungus garden. That led the researchers to study the genetic relationships of all fungus-growing ants in South America, including all five known and six newly discovered species of the genus Mycocepurus, to determine whether the parasite did evolve from its presumed host. They found that the parasitic ants were, indeed, genetically very close to M. goeldii, but not to the other ant species.

They also determined that the parasitic ants were no longer reproductively compatible with the host ants—making them a unique species—and had stopped reproducing with their host a mere 37,000 years ago—a very short period on the evolutionary scale.

A big clue for the research team was found by comparing the ants’ genes, both in the cell’s nucleus as well as in the mitochondria—the energy-producing structures in the cells. Genes are made of units called nucleotides, and Rabeling found that the sequencing of those nucleotides in the mitochondria is beginning to look different from what is found in the host ants, but that the genes in the nucleus still have traces of the relationship between host and parasite, leading him to conclude that M. castrator has begun to evolve away from its host.

Rabeling explained that just comparing some nuclear and mitochondrial genes may not be enough to demonstrate that the parasitic ants are a completely new species. “We are now sequencing the entire mitochondrial and nuclear genomes of these parasitic ants and their host in an effort to confirm speciation and the underlying genetic mechanism.”

The parasitic ants need to exercise discretion because taking advantage of the host species is considered taboo in ant society. Offending ants have been known to be killed by worker mobs. As a result, the parasitic queen of the new species has evolved into a smaller size, making them difficult to distinguish from a host worker.

Host queens and males reproduce in an aerial ceremony, in the wet tropics only during a particular season when it begins to rain. Rabeling found that the parasitic queens and males, needing to be more discreet about their reproductive activities, diverge from the host’s mating pattern. By needing to hide their parasitic identity, M. castrator males and females lost their special adaptations that allowed them to reproduce in flight, and mate inside the host nest, making it impossible for them to sexually interact with their host species.

The research team included Ted Schultz of the Smithsonian Institution’s National Museum of Natural History, Naomi Pierce of Harvard University, and Maurício Bacci, Jr of the Center for the Study of Social Insects (São State University, Rio Claro, Brazil).