Could someone please clarify to me the meanings of "the gills" in following sentences from Nabokov's Lolita:
Thank you so much!She and the dog saw me off. I was surprised (this a rhetorical figure, I was not) that the sight of the old car in which she had ridden as a child and a nymphet, left her so very indifferent. All she remarked was it was getting sort of purplish about the gills. I said it was hers, I could go by bus. She said don’t be silly, they would fly to Jupiter and buy a car there. I said I would buy this one from her for five hundred dollars.