Bermuda-based reinsurers Validus Holdings Ltd and Ariel Reinsurance Co called off merger talks after the Japan disaster caused uncertainty in insurance markets, Bloomberg reported today.The news agency said its sources were three people with knowledge of the matter.Validus had been close to an almost $1 billion stock-and-cash deal for Ariel said the sources, who spoke on condition of anonymity because the talks are private.Potential losses stemming from Japan’s earthquake meant that reaching a deal would take more time and effort than previously anticipated, contributing to a breakdown in talks, the people said.