Basic visible octopuses body parts for octopuses we see in the aquarium trade:
Arms (8, no tentacles or legs)
suckers (varying numbers, in single or double rows, without hooks - hooks are for squids )
gills (2 sets, ctenidium in picture)
siphon (1, also referred to as a funnel and can be moved to any position along the mantle ventral opening)
head (1, the part from the beak to just behind the eyes)
mantle (1, the sack like part behind the eyes, this is the body, not the head)
beak (1, the only hard part on most octopuses and restricts where they can go, it is about the size of the eye)
eyes (2)
hearts (3, 2 brachial and 1 systemic - visible in some of the more transparent species)
Not the best image for my list and it shows more than what I wanted but ...
Now, help me with what you are calling nostrils . I don't keep many fish so I don't know what parts might obviously resemble fish anatomy to someone accustomed to making a comparison.
Arms (8, no tentacles or legs)
suckers (varying numbers, in single or double rows, without hooks - hooks are for squids )
gills (2 sets, ctenidium in picture)
siphon (1, also referred to as a funnel and can be moved to any position along the mantle ventral opening)
head (1, the part from the beak to just behind the eyes)
mantle (1, the sack like part behind the eyes, this is the body, not the head)
beak (1, the only hard part on most octopuses and restricts where they can go, it is about the size of the eye)
eyes (2)
hearts (3, 2 brachial and 1 systemic - visible in some of the more transparent species)
Not the best image for my list and it shows more than what I wanted but ...
Now, help me with what you are calling nostrils . I don't keep many fish so I don't know what parts might obviously resemble fish anatomy to someone accustomed to making a comparison.