Structure of the Spicules and Caudal Sensory Equipment in the Male of Aphelenchoides Blastophthorus (Nematoda: Tylenchida, Aphelenchina)

The spicules of Aphelenchoides blastophthorus are thorn-shaped, with a large dorsal and a smaller ventral limb, and a flattened base embedded in the tail tissues. When retracted, the spicule tips are not exposed through the cloacal opening as they are in some other genera. The large spicular nerve runs along the dorsal limb. Within the nerve a single dendritic process is differentiated and this passes to the outer edge of the dorsal limb, running just beneath the surface towards the tip, where there is a single pore. The spicules do not form an enclosed tube; the ventral limbs abut but the dorsal limbs gape open when extended. Two innervated cuticular processes from the wall of the cloacal sac are exposed when the spicule tips are protruded. These are probably mechanoreceptors. Three pairs of caudal papillae, in adanal, mid-tail and terminal positions, are probably chemosensory as the sensilla open to the exterior through a pore. The relationship between the morphology of spicules and accessory sensory structures and mating behaviour is discussed.