Prokaryotic cells found in extreme, harsh environments often belong to the domain:

Answer: Achaea.

Archaea are prokaryotic cells found in extreme, harsh environment.

Explanation:

Archaea are single celled prokaryotic microorganisms that lack cell nuclei. Archaea are extremophiles that live in extreme high and harsh environments like hot springs and salt lakes. They reproduce asexually by binary fission, fragmentation and budding. They are salt tolerant that use sunlight as energy.