What are cirri?

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Matt Clarke explains what cirri are and why some fish have evolved them.

Cirri are small tassel-like appendages that grow on the surface of some fish and invertebrates.

Each cirrus is a little fleshy flap of skin and typically forms part of the fish’s camouflage.

In some species, such as the Weedy seadragon, Phyllopteryx taeniolatus, the cirri can be very large, while in other species, such as Antennarius frogfishes, they can give the fish a bearded appearance.

The cirri of some species have been shown to be linked to feeding, and they are often found around the mouth area, but the reasons for their presence on other fishes, such as the Hairy puffer, Tetraodon baileyi, are not yet known. 

This item was first published in the September 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.