Trypaea australiensis, known as the (marine) yabby or ghost nipper in Australia, or as the one-arm bandit due to their occasional abnormally large arm, and as the Australian ghost shrimp elsewhere, is a common species of mud shrimp in south-eastern Australia, the only species in the genus Trypaea. T. australiensis is a popular bait used live or frozen by Australians targeting a range of species. It grows to a length of 6 centimetres (2.4 in) and lives in burrows in mudflats or sandbanks, especially in or near estuaries.