PCR products of 1.1 and 0.9 kb were generated using Cherax quadricarinatus genomic DNA in the first case, and hepatopancreas and ovary cDNAs in the second case. These PCR products were cloned and analyzed for nucleotide sequences. The 1.1 kb fragment was used as a probe for Northern hybridization, revealing a transcript of approximately 8 kb in both tissues. Results from both Northern blot and RT-PCR analyses showed that the mRNA enconding the 3' end of the vitellogenin cDNA was present simultaneously in both hepatopancreas and ovary tissues in secondary vitellogenic at first maturation females, but was not detected in male hepatopancreas. The deduced amino acid sequences of Vitellogenin (Vg) cDNAs from ovary and hepatopancreas confirmed the existence at least two different Vg genes, and two different sites of synthesis.

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The e¡ect of eight diets with di¡erent protein-to-energy ratios (P^E ratio 510, 11, 14, 16, 18, 20, 22, 24 mg kJ À 1 ) on reproduction of female redclaw cray-¢sh Cherax quadricarinatus was tested under laboratory conditions. After 75 days, there was a signi¢cant e¡ect of the P^E ratio on ¢nal weight, spawning females and the number of juveniles per female. Using the broken-line and quadratic equations, optimal values for the P^E ratio were: 16.0, 17.1 and 16.0 mg kJ À 1 . The P^E ratio signi¢cantly a¡ected protein and carbohydrate content and energy in the hepatopancreas. The broken-line model indicated that the respective recommended values of the P^E ratio for these parameters were: 21.8, 16.7 and 18.6 mg kJ À 1 . The concentration of carbohydrates and energy in muscle tended to signi¢cantly diminish as the P^E ratio increased. From broken-line regression analysis, the recommended P^E ratio was 16.6 and 20.2 mg kJ À 1 respectively. No signi¢cant di¡erences were found in survival, fecundity, vitellin content in eggs, protein and lipid content in muscle and lipids in the hepatopancreas. We concluded that, overall, a P^E ratio of 18 AE 2 mg kJ À 1 is optimal for reproductive activity of female redclaw cray¢sh.