Monday, February 29, 2016

Distressed Damselfish



Blue Damselfish

We’ve all heard the term ‘damsel in distress’ when describing some poor, helpless person who is screaming in the grips of a villain and is in need of the help of a heroic stranger to save their life.  That role has been played out in Hollywood countless times.  But what if it this scenario actually happened?  As it turns out, Damselfish (appropriately named) seem to do this type of thing when they are caught by predators.  These coral reef dwelling fish send out a chemical signal when injured that actually increases their chance for survival.
 
Scientists have known that Damselfish release chemicals from their skin when they are injured which causes other nearby fish to flee, but they recently have found that these chemicals also attract more predators to the scene of the crime.  Attracting more predators doesn’t sound like a good strategy for the Damselfish at first (MORE predators, are they nuts?!) but having more predators around causes interference with the initial predation event, giving the Damselfish a greater chance for escape.  The other predators are likely to try to steal the Damselfish from the initial attacker.  The commotion of competition gives the prey a greater chance to wiggle free and escape with its life.  A study found that when there is another predator at the capture site, the prey is up to 40% more likely to escape.

This is the first evidence scientists have found of the chemical signals released by captured prey actually increasing the prey’s chances for survival instead of just the other fish’s chances for survival by causing them to run away from the area.  Scientists have known for a long time that many organisms send out alarm cues but they didn’t know what advantage it served the sender until recent experiments.  It is thought that alarm cue cells originally evolved to protect fish from bacterial infection when there was tissue damage and they later developed secondary predator attracting qualities to help them escape from attackers.  They also think that the secondary predators have evolved to become sensitive to the chemical distress signals so they can gather important information from them, helping them decide whether or not it is worth trying to steal the potential meal.

If you’re a fish, being a damsel in distress can have its advantages.  In the case of the Damselfish, it may even be lifesaving. 

References

3 comments:

  1. When setting up aquariums in your homes the stores say you should use a damsel fish as your starter fish in your tank. After reading this I don't think I would want to use them because of the chemicals they realize that could cause the other fish in the tank to die.

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  2. I believe that damsels are suggested since they are very hardy and most likely to survive until the biological filter system in the tank has matured by growing a strong population of bacteria. According to Krista's post, it sounds like these chemical attractants would only be released during a predation event, and they don't harm other fishes.

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  3. That's very interesting! Another interesting characteristic of damselfish I found in a paper published last year is that they can identify predation risk through their sense of smell while they are larvae. As we have discussed in class, organisms are at such great risk of predation while larvae that larvae biomass is not reflective of mature population biomass. With this in mind, the ability to sense predators early on through smell could greatly benefit larval survival rates and possibly affect their settlement location and behavior, as the paper mentions.

    Source:
    Animal Behaviour
    http://www.sciencedirect.com/science/article/pii/S0003347215000433

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