Wednesday 1 June 2016

Bryozoa Nudibranch

Image: Donna Pomeroy
This has to be one of the more eye-bending examples of camouflage out there.

It might be difficult to believe when it's so lacy and frilly and, er, uncooperatively resting on a dark background upon which it sticks out like an ornately gloved thumb...

Image: cassidy
But it works a lot better on the right background. Which, in this case, is Bryozoa.

Bryozoans, also known as Moss Animals or Ectoprocts (good alien name there) are tiny, colonial animals that are not coral... they just share a few ideas. Bryozoan colonies can be shaped like little bushes or curly lettuce but their most common form is a simple encrusting layer on stone or seaweed. The colony looks like a tiny brick wall or cobblestone street, except each cobblestone is actually a hole with a monster inside it. You'd think someone would complain about roads like that. You know its bad when the potholes have become residential.

The monsters in question are teeny-tiny creatures who catch the tiniest crumbs of food from the water using their crown of tentacles. For the Bryozoa Nudibranch, this sounds delicious.

There are several species of Bryozoa Nudibranch, all occupying the genus Corambe and found crawling all over Bryozoans in warm places like the Caribbean and South Africa. They themselves are tiny at about 1 or 2 cm (0.4 to 0.8 in) long and, with a bit of transparency and a few hazily drawn white lines, they quickly melt away as they plough their way through their chosen meal.

It's sort of eerie to see them slide over the cobblestones like a piece of curved glass. It feels like they should disappear the moment I blink and look again. I guess that what makes it such great camouflage: you know you're onto a winner when it makes everyone around you question their sanity.


Lear's Fool said...

You can almost see the poor bryozoans going 'not this way... go the other way...please go the other way!'

I suppose those guys can't form those little bird-beak-trap defenses? Or is the nudi just too awesome to be hurt by them?

Joseph JG said...

I don't know about the bird beaks exactly but apparently they can grow little spikes which are reasonably effective. Unfortunately it also means they grow a lot more slowly. It's all about balancing the pros and cons, alas!

Unknown said...

I've often wondered where the name nudibranch came from. Was there some biologist who was a nudist sitting on a tree branch who suddenly said "I've got it!"?

Susan said...

Disappointingly it just means naked gills... (AFAIK)

Joseph JG said...

Hahah! That would be funny! Newton saw an apple fall, maybe some other scientist saw a naked guy fall out of tree when the branch he was on snapped.

But yeah, it means naked gills. Nudibranch gills are either a kind of tree near their tail or they just breath through the skin of a bunch of tentacle-like things on their back.

Other gastropods are a rather more protective of their gills and don't have them freely visible. Which kinda makes more sense to me!