Morphological and behavioral identification of the sensory structures mediating pheromone reception in the blue crab, Callinectes sapidus

Scanning electron microscopy was used to survey the aesthetasc tuft on the outer flagellum of the antennule (1st antenna) in order to identify sensilla potentially involved in pheromone detection by the male blue crab. These studies showed that the tuft of each antennule is divided into a mesial and lateral half by a region of cuticle from which no sensilla arise. Two setal types were revealed: the aesthetascs and previously undescribed sensilla which originate exclusively on the mesial side of the tuft and project to the lateral half between the rows of aesthetascs. Experiments were performed in which the mesial half, lateral half, or entire aesthetasc tuft was bilaterally ablated from the antennules of test males. As revealed by behavioral tests, pheromone responses in "mesial half" and "lateral half" ablation groups were reduced 22% and 21%, respectively, relative to control (P > 0.10); whereas a highly significant (P < 0.005) response decrement (80% relative to control) occurred in the "entire tuft" ablated group. The data suggest that pheromone reception in the male blue crab is effected via the aesthetascs. The relationship of these findings to those for other decapod crustaceans is discussed.