Help needed identifying sea creature

Brunitski · #1 by **Brunitski** » Jan 30, 2012 5:28 am

Hi all, I was down on Redhead beach (mid-north coast NSW) a couple of weeks ago and found a number of these tiny fellas washing up. The one pictured measures roughly a centimeter long and just a little less across the "wings".

Anyone seen these before?

Fenrir · #2 by **Fenrir** » Jan 30, 2012 7:24 am

A nudibranch, possibly Glaucus atlanticus or Glaucilla marginata

Fenrir · #3 by **Fenrir** » Jan 30, 2012 7:40 am

They eat bluebottles

Ironclad · #4 by **Ironclad** » Jan 30, 2012 8:10 am

Fenrir wrote:They eat bluebottles

These beautiful creatures absorb the blue bottle's stinger (into a cyst of sorts) and use it for their own defence. Incredible! Cheeky!

Calilasseia · #5 by **Calilasseia** » Jan 30, 2012 3:33 pm

Yep, it's a Glaucid nudibranch, and Glaucus atlanticus, despite its name, is actually distributed worldwide between latitudes 50°N and 50°S. It's recorded as being found frequently on the east coast of Australia.

Do NOT try to pick it up without adequate protection, however. This nudibranch is one of those numerous cnidarian-feeding species with a sequestration capability. It feeds upon the cnidoblasts of Physalia, the Portuguese Man'O'War, and passes them through its digestive tract undischarged, before deploying them within the feather-like cerata for its own defence. As a consequence, these nudibranchs pack a powerful punch - the stings from the sequestered cnidoblasts will really make you sit up and take notice!

Incidentally, the nudibranch's digestive system appears to select the most venomous cnidoblasts for sequestering and re-use in the organism's own defence, and immature or previously discharged cnidoblasts are digested. Because it also has the remarkable ability to concentrate the venom even more powerfully in the sequestered cnidoblasts than its original host, it can deliver a worse sting than the original cnidarian!

More on this fascinating nudibranch here.

Ihavenofingerprints · #6 by **Ihavenofingerprints** » Jan 30, 2012 3:45 pm

If they are so small how do they eat bluebottles? (most bluebottles i've seen are about 3-5cm long)

Ironclad · #7 by **Ironclad** » Jan 30, 2012 3:54 pm

I'd like to know how, whilst it is munching an 'arm', does it avoid the prey entangling it with other stingers and harpooning it to death?

Calilasseia · #8 by **Calilasseia** » Jan 30, 2012 3:59 pm

It has an immunity to the cnidoblasts. The cnidoblasts need to detect specific sets of chemical stimuli in order to determine that they are in contact with either prey organisms for the cnidarian, or threat organisms in need of repulsion. The nudibranch's outer mucosal coating suppresses the triggers, by ensuring that the chemical stimuli required for firing are never sensed by the cnidoblasts.

Ironclad · #9 by **Ironclad** » Jan 30, 2012 4:42 pm

Snot, powerful stuff.

HughMcB · **#10** by **HughMcB** » Jan 30, 2012 4:45 pm

Ihavenofingerprints wrote:If they are so small how do they eat bluebottles? (most bluebottles i've seen are about 3-5cm long)

WHAT?!

Paul G · **#11** by **Paul G** » Jan 30, 2012 4:47 pm

A bluebottle is around a cm!

OP: Beatuful and fascinating. I think so anyway

Brunitski · **#12** by **Brunitski** » Jan 31, 2012 3:16 am

Paul G wrote:A bluebottle is around a cm!

OP: Beatuful and fascinating. I think so anyway

How I love these intertubes - and how deeply I appreciate this forum! Thank you all, and thank you Cali for the warning; I must have sensed something (maybe the violent blue coloration?) because I did pick 2 or 3 but I made sure they were in a handful of sand. I shudder now to think that I only casually warned my 6 year old daughter away from them! What an awesome little creature. Take that Man 0 wars.... or should that be men o war?

Ihavenofingerprints · **#13** by **Ihavenofingerprints** » Jan 31, 2012 3:24 am

Maybe I just get confused as to where the bluebottle starts and ends. When I see them washed up on the shore you can see their tentacles and everything looks puffed up.