** Shares of cryptocurrency- and blockchain-related companies down premarket, on weakness in bitcoin

** Bitcoin , the world's biggest cryptocurrency, is down ~2.1%, while ether down ~5.5%

** Crypto exchange Coinbase Global down ~0.6%, U.S.-listed shares of blockchain farm operator Bitfarms Ltd

down ~1%

** Crypto miners Riot Platforms Inc , Hut 8 Mining

and Marathon Digital down between ~1% and ~1.3%

(Reporting by Jaiveer Singh Shekhawat in Bengaluru)

((JaiveerSingh.Shekhawat@thomsonreuters.com;))