Beautiful Nudibranchs
I recently spent a couple of weeks at Tjärnö Marine Biological Laboratory where I learned to recognise various groups of marine invertebrates. It was a lot of fun, especially since I have never actually looked closely at live corals or sponges before, such organisms being absent from the dead brackish waters of the Baltic outside Stockholm.
One group that definitely drew the eye were the nudibranchs or sea slugs. Sure, we don’t have the graceful swimming kite-like ones of warmer waters, but you don’t have to be large to display striking colour or form. I took some pictures:
Some nudibranchs feed on hydroids and, somehow, manage to prevent their cnidocytes (the cells containing the stinging nematocysts, used for predation or protection or both) from discharging and utilise them in their own defenses. If anyone knows how they do this, I would love to get an explanation, as the course assistants were unable to answer that question!
ETA: These beauties have now boarded Friday Ark #169.