Question

what are book lungs and book gills?

Answer 1

A book lung is a type of respiration organ used for atmospheric gas exchange that is found in many arachnids, such as scorpions and spiders

Book gills are found externally, while book lungs are found internally. Book gills are still found in horseshoe crabs, which have five pairs of them, the flap in front of them being the genital operculum which lacks gills.

Answer 2

Book lungs are a couple of respiratory organs formed of several subtle lamellae. They are located in the stomach and have holes on the bottom.

A book gill exposed in the horseshoe shellfishes which comprises of membranous gatherings organized like the petals of a book.

However both of them have similar book-like formation, book gills can be detected on the external part, while book lungs are located on the internal part of the body.