Cratena peregrina

The tri-coloured Cratena peregrina

is commonly found in waters around the  Mediterranean Sea.  It favours a subtropical climate zone and clear, light filled areas. With its psychedelic colour the Cratena peregrina is quite easy to spot and are very photogenic. They are found in well sunlit areas attached to flora at a depth of 5m to 20m


The Cratena peregrina falls into the category Gastropod, and is often referred to as a nudibranch. It has an appetite for hydroids, usually hydroids that have already captured plankton. The Cratena peregrina ingests both the plankton and the hydroid polyp. This weird phenomena is put down to the Cratena nudibranchs appetite for plankton, something it cannot capture for itself. Ingesting hydroids that capture plankton, enables the Cratena nudibranch to gain access to plankton. Plankton form at least half of the nudibranchs diet. This rare feeding method, falls under the behavioural category of kleptoparasitism.


is a form of feeding behaviour, where one animal takes prey/food from another animal that has caught or collected the food.

In this case, the Cratena nudibranch ingests Hydroids that have consumed plankton, enabling it to get access to nutritional plankton. The Hydroid polyp is just a by-product that will be eaten as a means to an end.



Members of the category Nudibranch are simultaneous hermaphodrites. This means that all nudibranch act as males. During the mating period, both males shoot out their penis toward each other, hoping to induce its opponent in to acting as a female. The most dominant Cratena peregrina will penetrate the body wall and act as a male, the other one will take on the role as a female. Eggs are laid on a substratum, here they develop and hatch as planktonic, vestigial veliger larval stage and will go on to become grown adults. The life cycle continues once the adults are fully grown.

Photo taken by Janet Bulmer at Dive Smart Gozo

Dive Site: Comino on the P31