Trunk rings VI-VIII of O. gracilis during developmental stadia III-VIII. All male specimens except for the one in A, whose sex is undetermined because of the lack of sexual dimorphism at the corresponding developmental stadium. Ventral views, SEM. (A) Stadium III. (B) Stadium IV. (C) Stadium V. (D) Stadium VI. (E) Stadium VII. (F) Stadium VIII. Asterisk, trunk ring VII; s, spiracles associated with the eighth pair of appendages; arrowheads, gonopod primordia at their first appearance; arrows, gonopods. Anterior to the left, scale bars 200 μm.