About Austruca perplexa (H.Milne Edwards, 1852)
Austruca perplexa is a species of fiddler crab. Its range extends from the Ryukyu Islands, Japan to India, covers the entire Malay Archipelago, follows eastern Australian coasts from Queensland to New South Wales, and includes various Pacific islands such as Fiji, Tonga and Vanuatu. This species was formerly classified under the genus Uca. In 2016, it was moved to the genus Austruca, which was previously a subgenus of Uca. Like other fiddler crabs, male Austruca perplexa have a greatly enlarged claw that they use for signalling. Males that wave their claw higher have a greater chance of attracting a female, so claw size is subject to sexual selection. Larger male Austruca perplexa also wave their claws at a faster rate than smaller males, in order to attract larger females. Larger females are preferred because they produce more eggs than smaller females. Austruca perplexa typically inhabits sandy substrates near river mouths, or sheltered beaches in the mid-intertidal zone, most often near mangroves.
