They are both called karaja kaya. However, karaja kaya of a gandhabba is MUCH FINER. A normal human cannot see a gandhabba.
When a gandhabba enters a womb, it sheds the fine karaja kaya due to aroma absorption that grew while waiting for a womb. P.S. Of course, the material discarded is too fine to be noticed by anyone; finer than dust that we can see.
A new karaja kaya starts when the gandhabba merges with the zygote in the womb:
“Buddhist Explanations of Conception, Abortion, and Contraception“.
P.S.
Tobias asked: “But the aroma “inhaled” is utu, right? It comes from “external”.”
No. utu does not mean “external”. It means “due to change”. Utuja kaya arises due to the “transformation” of the cittaja kaya. It is really the energy in the cittas transformed to an “energy field”.
– It is also called the “aura body” or “aura field”.