Effects of estradiol and progesterone on the reproduction of the freshwater crayfish Cherax albidus

In this study we have investigated the role of 17β-estradiol and progesterone in the reproduction of the crayfish Cherax albidus by using vitellogenin (VTG) as a biomarker. Early-vitellogenic (EV), full-vitellogenic (FV) and non-vitellogenic (NV) females of Cherax albidus were treated with 17β-estradiol and/or progesterone for four weeks. Levels of VTG mRNA in the hepatopancreas were detected by RT-PCR. The PCR product was sequenced and showed 97% of homology with Cherax quadricarinatus VTG. 17β-estradiol was more effective than progesterone and 17β-estradiol plus progesterone in increasing vitellogenin transcript in the hepatopancreas of EV and FV females. On the contrary, progesterone was more effective than 17β-estradiol and 17β-estradiol plus progesterone in increasing the vitellogenin concentration in the hemolymph of EV and FV females. Hepatopancreas histology and fatty acid composition of females injected with hormones showed major modifications. No effects were registered in NV females. In conclusion, 17β-estradiol and progesterone influence VTG synthesis, although, based on our data, they act through different pathways and are not effective until the proper hormonal environment is established, as demonstrated by their inefficacy in NV females.