Worms & Snails that Live On/In Sea Cucumbers!

There's something about sea cucumbers which seems to make them attractive as hosts for various other animals.
Some sea cucumbers got clams that live in their throat...
The sea cucumber anal region seems to be popular as a place to live as crabs and of course, pearlfish find good homes there..

This week.. More animals that have made sea cucumbers hosts to their lives!!

Worms!
This scale worm above was identified as Gastrolepidia clavigera, living on its host sea cucumber (apparently Bohadschia graeffei). Image by Arne Kuilman.

This one by Theresa Legler, shows another polynoid worm, but it looks like a different genus/species...

Another similar looking polynoid. Image by Kevin Lee.

This one, by Ben Naden,  seems to be taking advantage of the rough skin texture...


Snails! Most of the snails shown here appear to be members of the Eulimidae, which are a diverse group of snails, which has apparently adapted a parasitic lifestyle. Many of them live on echinoderms. I review some of them here.  

Eulimids basically feed on their hosts. They have a proboscis which is inserted into the bodywall and used to suck out precious bodily fluids and other nutrients!

Here's a neat pic by Eunice Khoo showing several embedded in the epidermis.


A different kind of snail, Melanella sp. living on the sea cucumber Thelenota ananais.


Images below by "wj", what looks to be another set of eulimid snails, feeding on the sea cucumber Colochirus.



and let us not forget that eulimid snails (in this case-the genus Stilapex) ALSO inhabit deep-sea sea cucumbers... (from the sea pig post)

(from the New Zealand R/V Tangaroa weekly log, photo cred-Stefano Schiaparelli, NZ IPY-CAML) 

What makes Sea Cucumbers such desirable housing?  While there's no immediately clear data on the topic, it seems to be important that sea cucumbers are all composed of a soft, edible yet durable, tissue. So, maybe a good house that these protects and feeds?