An electric flash? 电光灯?

46. They're pygmy sea horses, the world's smallest, less than two centimeters high.
    豆丁海马--全世界最小的海马,身长不到两公分
47. They are males, settling a territorial dispute,
    这2只雄性豆丁海马正在为争夺领地
48. by head butting.
    相互撞头攻击
49. An electric flash?
    电光灯?
50. No, the display of a file clam.
    当然不是,这是火蛤蜊在表演
51. Perhaps this extraordinary pulsation of the clam's fleshy mantle
    蛤的肉质外壳的这种非常特别的规律性闪电
52. is a warning to frighten away nibbling fish,
    是在警告咬它的小鱼?

来自《行星地球 第一季 第九集 Planet Earth S01E09 海洋》第 49 行