Tuna
Fugu. Almost all of the fish is poisonous except for a small part, which is considered a delicacy.
Islet...it's a type of cell also.
The term small (er) part of the body is more often used.
lungs
its body
Scales on the fish body helps fish in some ways like:- Firstly it acts as a protective layer so that harmful objects, fungus, bacteria, and parasites cannot enter the fish body Secondly they are present in an overlapping pattern and only a small part of the scale is visible which makes the fish body smooth but itself the scales are hard.
Cartilage is the part of the skeleton that never stops growing.
front
scales
front
A fish breaths through it's gills.
each part is used to protect a fish from danger in its own specific way