A) They have six legs, not eight. Use almost any insect instead. Rockroach?
B) Reminds me of Rock Lobster. Peppy '80s hit does exactly jive with this tale.
Rocktopi is a great name. Don't see why it would need to be changed. it also follows with how most things actually come by a name anyway. It makes sense.
Sigler could do both remember the silver-bugs/ALLs. Linus could easly come up with a more scientific name as a way to seperate himself from the others and make himself look smarter.