You are what you eat: resourceful slugs

Black-margined glossodoris nudibranch feeds on sponges, making it toxic.

Giving new meaning to the old adage "What doesn't kill you only makes you stronger" -- which I never believed until now, really -- this recent article by Sean B Carroll asks, and answers, the very simple question: how come some poisonous animals aren't killed by their own poison?

The deadly neurotoxin in pufferfishes and other animals like the mosaic crab and egg crab is called Tetrodotoxin. Just a mere 2 mg is enough to kill a human being. These animals evolved a resistance to the toxin, and thus can withstand high doses of it. The cool part is that the animals don't actually make the toxin themselves -- it is acquired from the environment by the ingestion of Tetrodotoxin-producing bacteria. Cool.

Posted on Wildsingapore a few days ago, the article caught my eye. For the bad pun on the old saying, and also because it gives a great explanation for the questions: "this one can eat or not?" and "but why like that?!". Also, it made me think of what other animals we can find on our shores that also acquire poisons from their environment.

Cuthona nudibranch feeds on stinging hydroids

Probably one of the most striking animals that also sequester poisons from the things they eat is the nudibranch, or sea slug. Some eat deadly stinging things like hydroids -- stinging cells called nematocysts pass through their digestive systems undigested, undamaged, and are stored on their bodies in cerata (the tentacle-like bits) as protection from predators. Examples of such nudibranchs are the Cuthona nudibranch and the striking Blue Dragon nudibranch. Similarly, nudibranchs like the Cerberilla nudibranch do this by eating sea anemones and corals.

Other poisonous sea slugs such as the Black-margined nudibranch and the Lined chromodoris nudibranch eat toxic sponges which make them dangerous to eat. Nature is certainly resourceful!

You can find sea slugs on our very own Singapore shores. A careful walk on the shores at low tide in places such as Labrador, Sentosa and our Southern Islands will not disappoint if it is slugs you are after. These colourful little animals are easy to spot and for some, are favourite photography subjects. Find out more about our sea slugs here.