If asked to name their favorite sea creatures a group of people might add penguins, dolphins, or clownfish to the list. It is unfortunate that the nudibranch is so poorly known and under appreciated that it would not be called out as a favorite. The nudibranch, a squishy, bottom-dwelling sea slug, is a feisty creature with a variety of fascinating adaptations and defense mechanisms.
Sea Slugs Come in a Variety of Shapes and Colors
From stripes to polka-dots, from bright blue to pink, nudibranchs display a wide variety of colors and patterns. As PBS describes on its John-Michel Cousteau page “Nudibranchs – Splendid Sea Slugs” the bright coloration of the nudibranchs may be a warning to predators saying that they are poisonous. In other cases, the colors may provide camouflage as the sea slug blends in with the colorful corals around it.
Nudibranchs Eat Meat and Use the Sun
Nudibranchs are carnivorous animals eating sponges, barnacles, corals, and sometimes other sea slugs. However, some species of nudibranch have developed a way to harness the power of light by developing a symbiotic relationship with zooxanthellae, writes W.B Rudman of the Australian Museum in the Sea Slug Forum’s “Solar-Powered Sea Slugs”. Another type of sea slug, called a sacoglossan is able to save and use the chloroplasts found in its diet of algae.
Sea Slugs Obtain Deadly Stings From Their Diet
Sea slugs have developed an array of defense mechanisms to protect their soft fleshy bodies. For example they use stingers called nematocysts to keep away predators. However, nudibranchs are not born with these stingers. Rather, they eat creatures that do have stinging cells such as jellyfish. According to Ross Piper’s 2007 book Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals the nudibranch Glaucus atlanticus will eat the tentacles of a Portuguese man-of-war, but instead of digesting the nematocyst cells the nudibranch will move the stingers to its own skin and tentacles. The nudibranch is then primed to defend against its own predators.
The Importance of Nudibranch Slime
Similar to land snails, sea slugs leave a trail of slime behind them when traveling and this slime trail provides a great deal of information to other nudibranchs. According to James McClintock and Bill Baker in the book Marine Chemical Ecology an attacked sea slug can release chemicals into its slime trail to warn other slugs or follow a slime scent to find a mate.
Nudibranchs are Simultaneous Hermaphrodites
Many ocean fish are hermaphrodites and nudibranchs find it useful to be hermaphroditic as well. As a small critter in a big ocean it can be hard to find a mate, so sea slugs up their odds by having two genders. As the National Geographic points out in its ‘Nudibranch profile’, these sea slugs are simultaneous hermaphrodites. This means they have both male and female reproductive organs and can mate with any mature individual of the same species they happen to find.
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