Saturday, August 22, 2009

Nature's Tale: You scratch my back, I scratch your back

102th Discovery Posting:

You would have probably heard of the saying, "You scratch my back, I scratch your back". This saying basically means: if you help me, I will help you; we work in a cooperative relationship, etc.

This kind of relationship exist not only in our context but also in the natural world.

Let's use one classic example from our seas to illustrate this: the relationship between the clownfishes and carpet anemones...

Yes, you might be surprise to know that one can find and see clownfishes in Singapore's waters.
Below is a series of photos taken @ Semakau during today's morning there for Project Semakau (

Clown or Anemone Fishes made famous by the Pixar movie, "Finding Nemo", is one of the few organisms/fishes which can live amongst anemones or to be more exact, the tentacles of sea anemones. This is pretty interesting considering the fact that other organisms/fishes would be stung and most probably killed by the sea anemones.
There are basically two theories to why the tentacles of the sea anemone would not sting the clown fish.

"One theory is that the fish smears mucus from the anemone all over itself thus preventing the sea anemone from stinging it. Another theory is that the mucus of the fish (All fishes are coverd in mucus) lacks substances that trigger a sea anemone to discharge its stingers."
Now let's dive deeper into the "you help me, I help you" or biologist use the term "mutualism" relationship between the two.

Information from: &

Experiments and observations suggest that clownfishes can help to defend their host anemone from specialized tentacle eating fishes like Butterfly fishes. The "anemones might directly ingest particles dropped by the fish or absorb their wastes, which could provide sources of regnerated nitrogen, sulfur, and phosphorous in addition to small prey and plankton they capture."

The host anemone in turn "help" the clown fish by:
1) providing an enemy free space for clown fishes from its predators.
2) acting as a nest site for an anemonefish: the anemonefish lay their eggs on the hard substrate beneath the oral disc of the anemone, where they are tended by the male fish.

A study on done on this very topic also concludes that the presences of clown fishes affects the anemone's growth, reproduction and survival. Here are some of the details (from
  • Anemones that harbored anemonefish grew nearly 3x faster than those that did not.
  • The average daily growth increment was similar for those anemones that hosted 1 or 2 adult anemonefish, and both these growth rates were significantly greater than for anemones that lacked fish.
  • Asexual reproduction was enhanced by the presence of anemonefish: anemones occupied by 2 fish underwent fission much more often (~2x expected rate) than those containing 1 (~expected rate) or 0 fish (~ ½ expected rate)
  • Anemones that harbored fish experienced a much lower-than-expected probability of dying than those lacking fish: of 14 deaths, 11 were anemones without fish, 2 were anemones with 1 fish, and just 1 was an anemone with 2 fish.
So these about concludes this posting. Thanks for reading. =D

For further reading:

No comments: