Tokyo stocks opened lower Thursday, as investors sold shares after earlier locking in dividend rights before the end of the current fiscal year. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average fell 316.55 points, or 0.78 percent, from Wednesday to 40,446.18. The broader Topix index was down 20.91 points, or 0.75 percent, at 2,778.37. On the top-tier Prime Market, decliners were led by pulp and paper, iron and steel, and farm and fishery shares. At 9 a.m., the U.S. dollar fetched 151.26-29 yen compared with 151.27-37 yen in New York and 151.70-72 yen in Tokyo at 5 p.m. We…