Zoological investigations: nudibranchs

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Welcome, welcome, my literate learners, to the first contribution, which will be the first of many, to this series of articles designed to delve into the wild and expansive realm of the lesser-known and too often ignored members of kingdom Animalia. No longer will the un-cuddly animals be ignored, we will leave no stone unturned as I, your journalistic host, solemnly vow to thrill your synapses with news of the humble exploits and existences of many of the contributing members to life here on Earth.

Today, I would like to draw your attention to the creatures known as nudibranchs. Once grouped with the sea slugs, these amicable marine gastropod molluscs have recently been awarded the Linnaean distinction of their very own order, Nudibranchia.

The word “nudibranch” means naked gills, in reference to the fact that nearly all of the nudibranchs have unprotected, external gills. There are over 3,000 species of nudibranchs placed into two main groups: dorids and eolids.

Nudibranchs are hermaphrodites, meaning that individuals are neither male nor female. Two individuals engage in simultaneous, reciprocal reproduction where each fertilizes the other (take a moment to imagine that!). They vary from 0.79 to 24 inches in length, are carnivorous, and usually venomous.

The dorid type of nudibranchs feed mainly on poisonous sea sponges and can store the sponge’s toxins to use for their own self-defence. The eolids frequently possess cerata, thin, tubular extensions of the digestive gland that run along the dorsal surface of their body. Members of this group have no gills, relying on gas exchange across the surface of their cerata, which are highly folded in order to increase their surface area, allowing the certa to absorb more oxygen which help the eolids meet their respiratory needs. Eolids feed primarily on cnidarians such as jellyfish, anemones, and corals. Cnidarians possess defensive stinging cells, or nematocysts, that can inject extraordinarily painful poisons into all who stand in their way. Incredibly, eolid nudibranchs have the ability to digest the stinging cells of their victims whole, passing them intact through the digestive gland to the surface of the cerata, where they are incorporated for use in the nudibranch’s own defense. Nematocyst theft!

Other nudibranchs, while still carnivorous, have developed a symbiotic relationship with algae that live in the surface layers of their skin. The nudibranchs rely on the sugars produced by the algae to supplement their own dietary needs when food is scarce. Solar power!

One of the most exciting things about nudibranchs is their amazing, electric colouration and psychedelic patterning. Blazing blues, purples, reds, yellows, greens, whites and blacks. Spots, stripes, swirls and decorative projections make these animals look like something out of a science fiction novel. These crazy molluscs are truly something wonderful — so check them out!

Interested in seeing pictures? Type “nudibranchs” into google.com and take a look at these beautiful creatures.