Fig. 1.

Mating-independent spicule protraction displayed by a sy557 mutant male. A depicts a diagram of the sex muscles that are associated with the spicules (right lateral view of the male tail). The drawing was adapted from Sulston et al. (1980). The spicule is shown in black. The dorsal and ventral protractor and retractor muscles, represented as striated cells, are attached to the body wall and the base of the spicule. The anal depressor muscle is attached to the body wall and contacts the dorsal protractor. B–D depict individual frames taken from a video recording of a <24 hr virginsy557 adult male. The arrow points to his copulatory spicules (lateral view). In B, thearrow points to copulatory spicules that are inside his tail. In C, the arrow points to the copulatory spicule as it starts to protrude from the tail. InD, the spicule is protracted completely. In all panels his anterior is to the left, and his dorsal side is to the top. Scale bar, 20 μm.