Saturday, June 19, 2010

The Burglar Alarm Hypothesis: The Role Of Bioluminescence
Anyone who has disturbed water at night, especially during a bloom, will have seen the intense bioluminescence produced (see picture above). But why this occurs has long been the subject of scientific query. Dinoflagellates are one planktonic group that bioluminesce, and this occurs due to deformation of their cell membrane caused by shear forces. This is often caused by intense water movement such as breaking waves or a predators swimming movements. One hypothesis is that this is a form of communication. This certainly seems to be the case when you consider that the light emitted by dinoflagellates has a maximum emission of around 475nm (blue-green), which produces light that is visible over long distances. 

The authors in this paper propose that bioluminescence from the dinoflagellates serves to attract predators to the grazer. This 'burglar alarm' hypothesis argues that dinoflagellates become less attractive to grazers by increasing the risk of predation for the grazer. In other words, if a planktivore eats these dinoflagellates they will shine big bright lights saying 'food here' for predators within the area. Thus, dinoflagellates would be expected to be eliminated from the grazers diet. 

Experiments to test this hypothesis were undertaken in glass jars containing dinoflagellates (those that bioluminesce, and those that don't), copepods (predators of dinoflagellates) and three-spined sticklebacks (predators of copepods). Thus, these experiments were able to directly test the predation rate on grazers, while feeding on dinoflagellates that either bioluminesce or don't. After 3.5 hrs both grazer and prey were removed from the jars, and the number of dinoflagellates remaining were counted. What they found was that the predation rate was almost doubled in the jars containing bioluminescent dinoflagellates. This shows that the mortality rates on copepods feeding on bioluminescent dinoflagellates increased, confirming the burglar alarm hypothesis. 

It is important to note that the sticklebacks used in these experiments were never exposed to the experimental conditions. Thus, the light emitted by the dinoflagellates is a cue used in nature. Using signals to attract predators is not unique to dinoflagellates. Fear screams produced by birds and mammals is thought to be used for the same purpose.

Abrahams, M., & Townsend, L. (1993). BIOLUMINESCENCE IN DINOFLAGELLATES: A TEST OF THE BURGLAR ALARM HYPOTHESIS Ecology, 74 (1), 258-260 : 10.2307/1939521


  1. Great photo that accompanies this post Daniel, did you take that?

  2. That's am elegant experiment and explanation!
    But could another aspect of the 'burglar alarm' be that other dinos are warned that a predator is near? This experimental setup doesn't address this possibility, I think.

  3. Lucas very good question. It has been hypothesised that sudden flashes of bright light startles the predator allowing the dino's to escape. Although this benefits the dino's it is hard to explain why copepods continue to respond to the flashing lights (ie they move towards the dark). Although this doesn't specifically answer your question I would also question why the dino's continue to flash once the prey has escaped. Also, freshwater copepods that don't encounter bioluminescent dino's also don't respond to the flashing lights and simply continue feeding. Thus, this response must be adaptive in some way to the copepod.

  4. I took that image :-) Would be great if you could credit the photographer!

    Here's the story behind the image:


  5. I also Want to take this pics its really great..

  6. The link to the paper doesn't work (maybe the target disappeared). I found a PDF at

  7. Great pic. I was amazed. So refreshing to the eyes.
    Sydney Aquarium

  8. Over the past six weeks or so, I have been researching bioluminescence for a school project and I came across this website. I thought you did a great job explaining about how dinoflagellates are used for the ‘burglar-alarm system.’ You may already know, but the same ‘burglar-alarm system’ is used by sea animals that can emit bioluminescence without consuming dinoflagellates. The emitting of light is caused by a chemical reaction which is then converted into light energy. This makes it possible to divert attention to an animal’s (who can creates light) predator, in effect causing another animal to hunt it leaving the original prey safe. In comparison, it has the same ending effects as when predators consume dinoflagellates but it repels predators in two different ways. But I do have a question; what happens to dinoflagellates after they are consumed by an animal, and that animal is consumed by a predator? Is it a chain reaction making each predator emit light leaving it vulnerable to another predator?
    I would also like to recommend a TED talk that a woman named Edith Widder gave. She shows evidence that she recorded on camera of the ‘burglar-alarm system’ in effect. Here's the link.

  9. There are many things should be taken into consideration, but you've made a good point here. Thanks a lot for this informative lens. I will follow your future blog soon.
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