Fig. 1. Changes in gastrolith size, ecdysteroids levels and development of setae during an endocrinologically induced molt cycle in an XO–SG-extirpated male C. quadricarinatus. (A) Digital X-ray imaging of gastrolith growth during a representative endocrinologically induced molt cycle of XO–SG-extirpated male. White arrows point to the gastroliths. Times of endocrine induction and ecdysis are shown by gray arrows. (B) Changes in gastrolith size (squares) determined by MMI (molt mineralization index: gastrolith width as detected by X-ray imaging/carapace length), and circulating ecdysteroids levels (pg µl^–1; circles). The x axis is normalized to days from ecdysis. (C) Diagram and light microscope sections of the maxillar exopodite during intermolt (stage C, broken square) and three stages of premolt (D₀, D₁ and D₂). Arrows indicate apolysis regions. Magnification x20.