Under the loop, Exploring the small

Today Mack, one of our regular divers came back and told me how he is getting more and more comfortable underwater due to frequent dives.  One thing he noticed that he was spotting more nudibranchs than ever before!  He used to just see the sharks and the rays, but never realized how many little creatures are hidden away here in the Pacific.  His last dive he saw 10 Octopi!  Now he started asking me all these questions about nudibranchs and eels ( these I will cover in a next blog).  He just left the shop after a great chit-chat and I thought more people might be interested in these amazing little guys.


A nudibranch  is a member of a group of soft bodied, marine mollusk which shed their shell after their larval stage They are noted for their often extraordinary colors and striking forms. There are more than 3,000 described species of nudibranchs

The word “nudibranchs” comes from the Latin word nudus, naked, and the Greek word brankhia, gills.

Nudibranchs are often casually called sea slugs, but many sea slugs belong to several different groups which are not closely related to nudibranchs. Nudibranchs are benthic animals, found crawling over the bottom substrate. They vary in adult size from 20 to 600 mm (0.79 to 24 in).

This group includes some of the most colorful creatures on earth. In the course of their evolution, nudibranchs have lost their shell while developing alternative defense mechanisms. Some species evolved an external anatomy with textures and colors that mimicked surrounding plants to avoid predators. Other nudibranchs , have an intensely bright and contrasting color pattern that makes them especially conspicuous in their surroundings. This is believed to warn potential predators that they are distasteful or poisonous. Another method of protection is the release of an acid from the skin. Once the specimen is physically irritated or touched by another creature, it will release the mucus automatically.

Nudibranchs have a set of reproductive organs for both sexes, but they cannot fertilize themselves. All known nudibranchs are Carnivores. some eat other sea slugs or their eggs or, on some occasions, they are cannibals, and prey on members of their own species. Mean little creatures eh?


Next time I will tell you a bit more about eel behavior.


One thought on “Under the loop, Exploring the small

  1. I love Nudi’s, we had some in our reef tank last year, they came in on some coral (trying to eat the polyps). Only ever seen 4 diving but beautiful all the same!

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