SAFE HAVEN FOR A CLOWN

are one of the favourite subjects for the underwater photographer. These

little fish are beautifully coloured, reliably found at the same place

every day, and are not shy. In fact they are quite brave and often swim

towards any intruder in the hope of chasing him or her away. For the photographer

this can be something of a problem for it is often impossible to focus

as close as the clownfish comes to the camera.

Another name for these animals is anemone fish because they live in

close association with sea anemones, themselves quite aggressive invertebrates

that feed upon small fish, crabs and plankton. The food is caught by the

anemone’s tentacles which are themselves armed with powerful stinging cells

called nematocysts, and coated by a sticky mucus. Biologists were at first

confused about how the clownfish could swim unharmed among the stinging

tentacles of the anemone.

The

answer to this conundrum was solved a number of years ago when it was realised

that the clownfish have a clever means of immunising themselves against

the stinging anemones. Before adopting an anemone as a safe haven the clownfish

carefully rubs itself against the mucus clad tentacles, coating its own

body with the anemone’s mucus. It seems that the anemones do not then recognise

the fish as either potential food or potential enemies and the clownfish

are then free to swim among the tentacles unharmed.

A problem arises however with the offspring of clownfish; how to protect

them from the potentially lethal adopted guardian? The parent fish deposit

their eggs on rock surfaces underneath the anemone and they regularly tend

to them by blowing water across them, ensuring a regular supply of oxygen-rich

water and preventing fungal growth. In order to protect the actual eggs

from the stinging anemone’s tentacles the parent clownfish takes a mucus

coated tentacle in its own mouth and then rubs it gently over the developing

embryos within the attached egg masses prior to them emerging as vulnerable

fry. As soon as the baby fish do hatch they can avoid predators by hiding

among the protective tentacles of the anemone. There they can grow up in

safety until they move off to establish their own new home.