Asia’s Bee Mites Alarmingly Resistant

AsianScientist       Asian Scientist Newsroom     March 7, 2017

A study of the Tropilaelaps mercedesae genome has revealed that conventional mite control strategies might not work.

The genome of the parasitic bee mite Tropilaelaps mercedesae suggests that existing methods to prevent bee colony collapse might be ineffective. These findings have been published in GigaScience.

Although there are many potential causes for the decline in honey bee colonies, pathogens and parasites of the honey bee, particularly mites, are considered major threats to honey bee health and honey bee colonies. The bee mite T. mercedesae is honey bee parasite prevalent in most Asian countries, and has a similar impact on bee colonies that the globally present bee mite Varroa destructor has. With the global trade of honey bees, T. mercedesae is likely become established world-wide.

To preempt the impact of T. mercedesae infestation, an international team of researchers from Jiaotong-Liverpool University sequenced its genome and compared it to the genome of free-living mites.

 

As opposed to the free-living mites, T. mercedesae has a very specialized life history and habitat that depends strictly on the honey bee inside a stable colony. The researchers found that the T. mercedesae genome has been shaped by interaction with the honey bee and colony environment.

Interestingly, the authors found that the mite does not rely on sensing stimulatory chemicals to affect their behavior. The researchers noted that this discovery meant that, “control methods targeted to gustatory, olfactory, and ionotropic receptors are not effective.” Instead, control measures will have to use other targets when trying to disrupt chemical communication.

“There will be a need to identify targets for biological control,” they added.

Furthermore, the researchers found that T. mercedesae is enriched with detoxifying enzymes and pumps for the toxic xenobiotics, which help them quickly acquire resistance to miticides.

However, the study also revealed a potential alternative to miticides. The researchers found that Rickettsiella grylli commonly infect T. mercedesae, suggesting that targeting these bacteria might be one way to control the mite population.

They also found that R. grylli was involved in horizontal gene transfer of Wolbachia genes into the mite genome. Wolbachia is a bacteria that commonly infects arthropods, but is not present in T. mercedesae.

Although up to a horizontal gene transfer has been detected in as many as a third of all sequenced arthropod genomes, this is the first example of horizontal gene transfer in mites and ticks, the authors noted. Since Wolbachia bacteria do not currently infecting the mites, these findings indicate that Wolbachia was once a symbiont for T. mercedesae or its ancestor but has been replaced with R. grylli-like bacteria during evolution, they added.

The extent of honey bee colony destruction remains a complex problem, but one that has an extensive impact crop productivity since honey bees are needed for pollination of a variety of plants. Indeed, in several places in China, farm workers have begun to carry out manual pollination to maintain high crop yield in orchards. Thus, research and resources to help combat this global threat are needed now. These genome, transcriptome, and proteome resources from the T. mercedesae study add another weapon in the fight to save bee colonies.

The article can be found at: Dong et al. (2016) Draft Genome of the Honey Bee Ectoparasitic Mite, Tropilaelaps Mercedesae, is Shaped by the Parasitic Life History.” ——— Source: GigaScience. Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Read more from Asian Scientist Magazine at: https://www.asianscientist.com/2017/03/in-the-lab/tropilaelaps-mercedesae-genome-bee-mite/

Honeybee Hive Collapse Mystery Rooted In Hive Size

Phys.Org     February 24, 2016

Honeybee. Credit: Adam SiegelUniversity of Idaho professor Brian Dennis is helping scientists understand a baffling but vitally important puzzle: What is causing the decline of honeybees? Working in collaboration with William Kemp, a U.S. Department of Agriculture scientist and UI alumnus, Dennis has built a mathematical model that lays the blame squarely on the bees themselves.

"The tightly organized social lives of honeybees, once such an amazing adaptation for success in the world, turns out to lack resilience against the numerous environmental degradations contributed by humans across the landscape," said Dennis, who has a joint appointment in the UI College of Science and College of Natural Resources.

Humans depend on honeybees for pollinating many crops, especially orchard crops and vegetables. In the U.S. alone, the economic value of honey bees' crop pollination services has been estimated as high as $15 billion a year. If honey bees continue to decrease, it would lead to disastrous upheavals in agriculture and the food on our tables. The decrease is already pushing many beekeepers to the edge of economic viability.

North American scientists have been noting with alarm the increasing collapse of honeybee colonies, during the last decade. In a typical hive collapse, the bees in the hive fail to thrive and end up abandoning the hive or dying. Research studies have tried to pinpoint the cause of hive collapse, investigating such factors such as viruses, fungi, poor nutrition, parasites, pesticides and global warming.

Dennis and Kemp's model indicates that any or all of the suspected environmental factors, alone or in combination, could lead to hive collapse by destabilizing a hive's adult bee population.

Hive Size Matters

Adult worker bees cooperate to make the hive function almost as a single organism. The workers feed and tend to the egg-laying queen and eggs, larvae and pupae; regulate the temperature of the hive; fight enemies and predators; search for food and communicate its location; and gather food and transport it back to the hive.

Beekeepers know that a hive that has too few workers will tend not to thrive. Dennis and Kemp noted the reason for this: a queen can lay only so many eggs in a time interval, and too few adult workers cannot maintain all the functions of the hive at a quality level where new workers are produced faster than deaths of existing workers. Like a hotel with inadequate staff, the hive with too few bees fails to serve its residents.

If the number of adult bees drops below a threshold known as critical hive size, the bees decrease in number, leading to collapse. Normally, critical hive size does not pose a problem for bees. With favorable environmental conditions, the critical size for a beehive is quite small, in the neighborhood of 1,000 bees. Commercial bee packages for starting a hive contain well over 10,000 bees.

However, Dennis and Kemp's model found an unexpected surprise: Critical hive size turned out to be extraordinarily sensitive to any degrading of cooperative hive functions.

Dennis and Kemp built a mathematical model of the growth of adult worker numbers in a beehive. The presence of more adult workers reduced the deaths of adult workers. Likewise, having more adult workers improved "rearing effectiveness," or how well eggs, larvae and pupae are nurtured and raised to adulthood.

The critical hive size increases in response to any environmental factors that reduce rearing effectiveness or increase deaths of  in the hive. In the presence of such an environmental factor, a beehive could find itself below the new, larger critical hive size. Loss of viability and hive failure would result.

Dennis and Kemp point out that a beehive is a severe example of an "Allee effect," a concept in ecology named after animal ecologist Warder Allee. Working in the 1930s, Allee suggested that a critical population size might exist when organisms become rare—for example, when mates cannot find each other, or when groups of cooperatively hunting predators are too small for effective hunting.

Help for Honeybees

In light of this study, how can honeybees be helped? Dennis and Kemp conclude that much might be gained from coordinated regional management of pesticides for beekeepers and crop producers and from conservation programs that contribute to improving foraging resources for all pollinator species.

Dennis and Kemp further warn that evidence of Allee effects has been found in many other species, and the prospect that minimum critical population sizes exist argues for adopting more stringent precautionary principles in environmental management.

Explore further: Honeybees entomb to protect from pesticides

More information: How hives collapse: Allee effects, ecological resilience, and the honey bee, PLoS ONEdx.doi.org/10.1371/journal.pone.0150055 

http://phys.org/news/2016-02-honeybee-hive-collapse-mystery-rooted.html

New "Tobacco" Virus Linked to Bee Colony Collapse Disorder

Los Angeles Times   By Geoffrey Mohan  1/21/14

A rapidly mutating virus has leaped from plants to honeybees, where it is reproducing and contributing to the collapse of colonies vital to the multibillion-dollar agricultural industry, according to a new study.

Tobacco ringspot virus, a pollen-borne pathogen that causes blight in soy crops, was found during routine screening of commercial honeybees at a U.S. Department of Agriculture laboratory, where further study revealed the RNA virus was replicating inside its Apis mellifera hosts and spreading to mites that travel from bee to bee, according to the study published online Tuesday in the journal mBio.

The discovery is the first report of honeybees becoming infected by a pollen-born RNA virus that spread systematically through the bees and hives. Traces of the virus were...

Read more... http://www.latimes.com/science/sciencenow/la-sci-sn-virus-bee-colony-collapse-20140120,0,3775756.story#ixzz2r417z9HF