Remember that really gruesome scene from the most recent version of King Kong (starring Jack Black) that took place at the bottom of the slimy gorge where an unsuspecting crew member was attacked by giant worms with massive hooks around their mouths?
(I used to have a film clip of the worms here, but it was too much, so I deleted it.)
The creature creators this time may well have gotten their inspiration from a small worm that lives in the intestines of other animals, uses their hooks to hang onto the wall of the intestine, and absorbs food from the predigested food moving past it...it doesn't even have a mouth or a stomach.
This small parasite is called an Acanthacephalan, commonly known as a spiny-headed worm. Over 1000 different species have been identified. Most species I've seen are only about one centimeter (less than 1/2") long, but the biggest ones can actually be over 20" in length.
Here's what an spiny-headed worm looks like:
Note the many hooks on the structure protruding out the animal at the left side of the photo. It's just an organ used for attachment...not feeding. Here's a drawing showing a little more detail:
These images can be found at Wikipedia under the entry for "Acanthacephalan". If you take a close look you will see that these animals do not have a mouth or a gut. That's the beauty of living in a constant supply of predigested food. There's no need for THESE animals to attack and kill unsuspecting sailors!
Once again, we are probably not quite as clever as we think we are...even so, it was pretty scary.