Complex sentence: Females lay up to 20000 small eggswhich are deposited in gelatinous tubes containing tens of eggs which they attach to debris and other solid objects on sandy to muddy bottoms.
Split into simpler sentences: Females lay up to 20,000 small eggs, which are deposited in gelatinous tubes containing tens of eggs each. These tubes are attached to debris and other solid objects on sandy to muddy bottoms.