Do Crabs and Lobsters change shells or start like how mussels start? They are Crustations right?

Question

I remember something about crustations all start in water and its like the eggs and sperms just form together in the water and forms the animal when it clings on to something. Or was that mollusks? And also do crabs and lobsters change shells?

i actually wanted to know do crabs and lobsters start the same as what i described, sorry.

Answer 1

Crabs and Lobsters are Crustaceans but they are of the order Arthropoda, the same as Scorpions and Spiders.
All of the above shed the whole exoskeleton.
During the molting process, the creature is extremely vulnerable and hides out somewhere.
I have noted that Hermit Crabs sometimes eat their molt or leave it.
The creatures are vulnerable for about a week after the process occurs.
Sometimes because of are inactivity before the molt, people mistakenly think they are dead.

Answer 2

Depends on what you mean by "change" shells. Yes, crabs and lobsters are crustaceans. Only hermit crabs move from one shell to another, and those shells are not really their own. They are empty snail shells. Crabs and lobsters molt. The new shell (actually exoskeleton, not a true shell) forms under the old one. Then the old one peels off and is left behind. the new exoskeleton is rather soft at this time, and the animal usually hides for a few days or more until the new exoskeleton hardens.