Fig. 2 a–g in When dwarf males and hermaphrodites copulate: first record of mating behaviour in a dwarf male using the androdioecious barnacle Scalpellum scalpellum (Crustacea: Cirripedia: Thoracica)

Fig. 2 a–g Penis structure in dwarf males of Scalpellum scalpellum. A hermaphrodite photographed in vivo and carrying dwarf males in the receptacle area on either side of the brood chamber (mantle cavity). b One of the males in close up, revealing the tube-like penis still inside its body. c Another male with the penis already extended for mating; note the length of the penis relative to the small male body; another deeply buried male situated close by. d SEM of dwarf male with penis almost fully extended and showing the side branches. e Tip of the penis furnished with sensory setae; note the central opening. f SEM of dwarf males located symmetrically on either side of the brood chamber; one male with penis extended; note in both d and f how the males are located outside the brood chamber when the mantle valves are fully closed. g SEM of dwarf male fixed when the penis is extended into the brood chamber for mating; the cirri of the hermaphrodite hovering over the male