- Concurrent morphological, anatomical and physiological changes took place during the first reproductive cycle in the Australian red-claw crayfish Cherax quadricarinatus, which prepared the female for spawning and holding of the newly deposited eggs. The endopod became longer and wider than the exopod and developed a mixture of plumose and long thin simple (ovigerous) setae. Small oocytes (0.24±0.05 mm) were present in the immature ovary. The growing ovary contained two distinct oocyte populations: one consisted of small (0.55±0.07 mm), barely growing oocytes, while the other consisted of large oocytes, which increased in size continuously (0.73 to 2.55 mm) until egg laying took place. A gradual change in the relative abundance of ovarian polypeptides occurred until the late vitellogenic stage (large oocytes < 1.8 mm). Three predominant female-specific, SDS-PAGE separated, polypeptides were observed (103, 78 and 73 kDa) that may represent vitellin subunits. The most abundant carotenoid in the ovary was astaxanthin, while β-carotene was present at a lower concentration. The strong correlation between the increasing diameter of the oocyte and the concentration of astaxanthin in the ovary and in the hemolymph suggested an association of astaxanthin with vitellin and vitellogenin.