Arrow crabs

[Michelle Crossley]

l have had my Arrow Crab a while now. Luckily everything seems to be accounted for(fingers tightly crossed).
I decided to sit and watch it for a while.
I saw this flap open underneath the crab and it either put something in it or took it out.
Amazing.
Does anyone know what it is and the purpose it serves please

 

[cristata.reef]

https://forums.saltwaterfish.com/index.php?threads/arrow-crab-flap-underneath.369376/ This might help

 

[Michelle Crossley]

Thank you.That was very helpful