Nudibranch addiction and interesting facts about sea slugs

Nudibranch mating Halgerda wasinensis

Interesting facts about sea slugs and nudibranchs

  1. Nudibranchs are hermaphrodites but they do have sexual reproduction. They have a sexual organ on the right side, so when they meet each other they stay in a 69 position and connect to each other by touching this organ and introducing their penis in each other; you can just see the organ and it looks like there are holding hands. It is quite cute.
  2. There is an article describing a predation between a nudibranch and an anemone, it is quite amazing as the anemone unattached itself from the substrate and started to move away. However as nudibranchs are fast slugs, it won the fight!
  3. Their penis desire attention! They have a very interesting and complex anatomy.  Sea hares for example have their penis on the head! Some nudis have hooks in their penis to help during fecundation. Recently it was discovered that a species of nudibranch (Goniobranchus reticulata) can cut offs its own penis after copulation!!! More amazing it will re-grow in max. 24hours and the nudibranch will be ready for more one! It seems to be related to sperm selection and mating competition.
  4. Some sea slugs can steal the chloroplasts from the algae that they feed on and incorporate them into their own cells to then make photosynthesis! Experiments show that if they feed for 2 weeks they can live about 3 years just making photosynthesis. In the tank if you put a light on, we can see them opening their parabolas to increase the superficial area and make more photosynthesis. There are current investigations that indicate that some species can incorporate part of the plant DNA to their own DNA and pass it over to future generations!
  5. Other nudibranchs feed on sponges and steal the spicules from their prey to use for they own defence. The pelagic nudibranch Glaucosfeeds on blue bottles and also steals their nematocysts to protect itself. They accumulate the nematocysts on the edge of the ceratas, so when a predator comes close they lose their ceratas to escape. Just like lizard lose their tails.
  6. Sea slugs lost their shell (or most of their shells) during evolution, it made them relatively fast slugs, however with soft bodies in the sea they needed to find ways to defend themselves. So some are perfectly camouflaged while others have vivid colours as a warning to how poisonous they are. It is believed that predators like fish learn that those colours are dangerous by trying. They bite on the slug and split out due the terrible taste and never eat it again!
  7. There are more bizarre things…some species as Tambja are cannibals so when individuals meet each other they have a hard decision to make: to reproduce or to eat? Well, if one is much bigger than another usually the big guy eats the small one. If they are more or less the same size they will fight and if they see that it will not going anywhere, they mate. But even after mating they might try to eat each other. Not an easy life!
  8. They are good indicators for climate change. Despite the group having a highly diverse habitat and feeding behaviours, as species they are usually quite specialized. Therefore changes in their habitat can quickly cause an effect on their community.

    Nudibranch Facts @ SeaLife Station
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