KIM, Tae Won*; KIM, Tae Geun; CHOE, Jae Chun; Seoul National University; Seoul National University; Seoul National University: The evolution of courtship structure building in fiddler crabs: Has it evolved for predation avoidance in both sexes?

In some species of fiddler crabs, pair formation is composed of male claw waving, female attraction to semidome-like structures (e.g. hoods, semidomes, pillars), and underground mating. The sensory trap hypothesis, corroborated by arena experiments, suggests that the structures are used for searching females to avoid predators. In Uca lactea, such orientations by females to semidomes in the non-courtship context occur only in mating periods. During non-mating periods when males did not court females, females had no orientation bias between holes with and without semidomes. In the courtship context, females preferred males courting with semidomes. Thus our findings suggest that courtship structures in U. lactea might have evolved by female choice based on aesthetic preference. Our experiments also showed that males used the courtship structures as a landmark for homing while courting females. Furthermore, males with semidomes courted more freely than ones without semidomes by increasing the deviation between direction to the burrows and the lateral axis of the body. Therefore, the courtship structures might have originally evolved through pressures from predator avoidance in males.