IPA: /ˌmɛzəˈnɛfɹəs/
KK: /mɛzəˈnɛfros/
The second of the three organs that help remove waste in the body of a developing vertebrate, which works as a kidney in fish and amphibians but is replaced by another organ in more advanced animals.
In fish and amphibians, the mesonephros serves as the main kidney during their development.
Mesonephros → It is formed from "meso-" (from Greek "mesos", meaning middle) and "nephros" (from Greek "nephros", meaning kidney). The term refers to the middle kidney, which is a stage in the development of the excretory system in vertebrates.
Think of 'middle' ('meso-') and 'kidney' ('nephros') to remember that 'mesonephros' refers to the middle kidney in the development of an organism.