A 45-year-old man died on Sunday in West Bengal's Howrah district after his wife hit him on the head with a fish-knife and chopped off his genitals over a family fight, police said.
The incident happened in Malipukur in Jujarsaha village in Panchla police station area, they said.
Police said they have sent the body of Mohsin Mallik for post-mortem and arrested his wife Manira.
The fish-knife she used to kill him has also been recovered, they said.
It is suspected that a family fight led to the killing, an officer said, adding that Manira is mentally challenged.
The couple has two sons, he said.
One of them told the police that after they woke up in the morning, their mother asked them to go to her bedroom and see what she has done.
When they rushed to the bedroom they saw their father, wrapped in a blanket, lying on the floor in a pool of blood, police said.
The wife was on medication for some time and the couple used to fight often, the officer said.
Further investigation is underway, police said.