Negative feedback signal in a superorganism

It has long been understood that worker honey bees, Apis mellifera, coordinate foraging for nectar using a system for dances. The best understood of these dances is the ‘waggle dance’. The waggle dance is preformed by a worker who has recently returned to the hive from a lucrative nectar source. The bee gives off an olfactory cue that tells her hive-mates to pay attention. The worker then begins to move in a rough figure-eight, vibrating her abdomen at high frequencies between the loops. The angle and duration of the vibration convey the direction and distance to a promising nectar source.

Check out this video about the waggle dance:

Honey bees also preform a tremble dance that lets workers know that a nectar-laden forager needs to be offloaded, and another dance, originally though of as a ‘begging dance’. This dance is preformed by workers that approach waggle dancers and either butt heads or climb on top of the waggler before delivering a brief 380 Hz abdominal vibration. It was originally thought that this dance was a way of begging for nectar from a laden dancer. However, research has shown that this dance does not precipitate nectar exchange.

New research has shown that the begging dance is in reality a ‘stop dance’, that tells a waggler to stop sending others to a perilous location. The research, published in Current Biology, showed that the stop dance is caused by predator and conspecific attacks on foragers. Workers returning from this dangerous location seek out waggle dancers that are sending others into danger. The stop dance decreases waggle dancing and recruitment to that location.

This stop dance is especially interesting when considered within the superorganism concept of eusocial insects. In this view, the entire colony functions as a single organism; with different colony classes acting as different cell types, and individuals analogous to single cellular units. Previously, only positive recruitment signals had been modeled at the superorganism level. Now, the stop dance adds the first example of a negative feedback signal in a superorganism. The collective interplay of waggle and stop dancing by many members of a hive therefore results in a self-organizing labor allocation system similar to those that exist at the cellular level.

References:

Nieh, J. (2010). A Negative Feedback Signal That Is Triggered by Peril Curbs Honey Bee Recruitment Current Biology, 20 (4), 310-315 DOI: 10.1016/j.cub.2009.12.060

Arthropod Roundup: Crabzilla, altruistic ants, and neuronal recordings from Drosophila in flight.

Quick notes about recent Arthropod news and research:

• The National Sealife Centre in Birmingham, England is hosting a special guest, on loan from Japan. Meet ‘Crabzilla’, a not-quite full grown Japanese spider crab, Macrocheira kaempferi. Crabzilla has an impressive leg-span of about 10 ft, but members of this species can reach over 13 ft. By length, they are the largest know arthropods on the planet. You can read more about Crabzilla’s visit to the UK at the Daily Mail.
• New research on the ant species, Temnothorax unifasciatus, found compelling evidence of altruistic behavior. Altruism is commonly observed in social insects, as single individuals often sacrifice their energies or lives for the good of the colonial super-organism. In the present study, the researchers showed that ants infected with a deadly and contagious fungus would often leave the colony and die in seclusion. This prevents transmission of the disease to other members of the closely interacting colony. Read more at the BBC.
• Finally, researchers have developed new techniques for recording electrical signals from fruit fly neurons while the animals are in tethered flight. Fruit flies, Drosophila melanogaster are the go-to arthropod model organisms, and a plethora of molecular and physiological tools are available for studying any aspect of their biology. This new neuronal recording technique was applied to look at the activity of visual pathways in the brain during flight. The researchers found that the stimulus response time of the Drosophila visual system nearly doubles when the animal is in flight. This allows the flies to change direction rapidly mid-flight in order to avoid obstacles. This work was published in Nature Neuroscience. Read more at Science Daily.

  A tethered fruit fly in flight with a pink electrode in its brain. Photo by Gaby Maimon and Michael Dickinson.

Arthropod news roundup

Here are a few recent arthropod related news items from around the web:

• Sean Carroll has a nice piece up at the New York Times where he talks about antifreeze adaptations in arthropods, including springtails. Frost protection is a powerful selective pressure and it has led to the independent evolution of a variety of strategies for surviving the cold.
• Science Daily has an article about the social insect superorganism concept. This postulates that large social insect colonies, such as bees, ants, and termites, behave similarly to a single organism made up of a multitude of highly specialized component organisms. They liken this to how most organisms are made up of a multitude of specialized cells. This article references a new paper where researchers have,
  

  …taken the same mathematical models that predict lifespan, growth and reproduction in individual organisms and used them to predict these features in whole colonies. By analyzing data from 168 different social insect species including ants, termites, bees and wasps, the authors found that the lifespan, growth rates and rates of reproduction of whole colonies when considered as superorganisms were nearly indistinguishable from individual organisms.

  Its an interesting idea, but I would like to see what these mathematical models actually entail. The paper isn’t up online yet, but I’ll take a look at it when it comes out.

• The BBC has a slideshow up of some “strange” marine life photographs. There is one of a hermit crab with a protective anemone on its back and some photos of mollusk hermaphrodite mating trains. Also, one barnacle photo has an amazing non sequitur of a caption:
  

  A report will be released today by the trusts outlining how they hope to return UK waters to a thriving marine environment within a generation. Barnacles have the longest penis in relation to body size of any animal: the organ is ten times its height.

  Logical segues? We don’t need no stinkin’ segues. Let’s talk about barnacle pricks!