January 2015

Canal Critter

This critter was found in a local canal just off Moreton Bay. There seems to be a few of them around lately. Are they invasive? Can you please identify what type of animal it is?

Answer

Japanese Hooded Nudibranch (Melibe japonica). Note the expanded oral hood. Images courtesy Jan PhilipsClosing the hood to “trap” small crustaceans. Images courtesy Jan PhilipsThis animal is a nudibranch (sea slug) which is a type of mollusc – the same large group of animals that includes snails, clams, oysters, squid and octopuses. Nudibranchs are in fact snails without shells. The nudibranch in your photographs is the Japanese Hooded Nudibranch (Melibe japonica). This species is quite large reaching at least 50cm in length (there are some reports of individuals up to 70cm long) and is an active swimmer.  Despite this, they only live about one year and die soon after breeding.

The species is carnivorous, trapping small crustaceans using its expanded oral hood and transferring them to the mouth for ingestion. The Japanese Hooded Nudibranch is sporadically common in Moreton Bay, and because of this, and their strange appearance, they are often wrongly reported as an invasive species. Sometimes a number of them turn up in quieter areas like canals, perhaps to feed on the crustaceans that live there or possibly to mate or lay eggs. You can also occasionally find them washed up on beaches after rough weather.

Visit this page for more information on the Japanese Hooded Nudibranch.

The Museum has recently released an app called “Coastal Life of South East Queensland” that contains information on 540 species of invertebrate animals and marine plants including the Japanese Hooded Nudibranch. If you enjoy exploring your local coastal area then visit this page for information on how to get this app for your device.

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