- Intersex individuals of the crayfish Cherax quadricarinatus are functional males that also possess arrested ovaries. To study the role of eyestalk vs. androgenic gland factors in regulating the functional balance between the different components of the intersex reproductive system, andrectomy and/or unilateral destalking were performed. Andrectomized intersex specimens had atrophied testes and sperm ducts and showed a reduction in the number of testicular spermatogenic lobules. Large oocytes developed in their ovarian lobes, and the Gonadosomatic Index reached 1.60 ± 0.36 compared with 0.21 ± 0.03 for the control. In the polypeptide profiles of the ovarian lobes from andrectomized individuals, the 177-, 150-, and 106-kDa polypeptides predominated, resembling the profile of the secondary vitellogenic ovary. The andrectomized individuals neither lost their male external characteristics, such as the red patch on the propodus, nor developed ovigerous setae on their male-like pleopods. Unilateral eyestalk ablation did not cause significant differences in the male or the female components of the reproductive system compared with the control group. The maturation of the permanently arrested ovary and the arrest of the testis in andrectomized intersex individuals illustrated the central role of the androgenic gland in maintaining the endocrine balance in intersex C. quadricarinatus. J. Exp. Zool. 283:286–294, 1999. © 1999 Wiley-Liss, Inc.