Physiological effects of methyl farnesoate and pyriproxyfen on wintering female crayfish Cherax quadricarinatus

Ž . Methyl farnesoate MF , the predominant juvenile hormone-like compound of crustaceans, was found in the hemolymph of female Cherax quadricarinatus crayfish. Administration of MF to C. quadricarinatus females during their winter reproductive arrest period had no effect on reproduction; however, it did have a tendency to accelerate molting. However, since MF caused increased Ž . mortality ;47% survival in the high MF treatment , we were not able to draw definitive conclusions regarding its physiological affect. In contrast, administration of pyriproxyfen, a Ž juvenile hormone analog, did not cause significant mortality 95% survival in the high pyriprox. yfen treatment , although it accumulated in high quantities in the hepatopancreas and, to a lesser extent, muscle tissue, ovaries and gills. The highest dose of pyriproxyfen used in this study, 20 mgrgram animal body weightrweek, caused a delay in spawning, which became statistically significant from the seventeenth week. This dose of pyriproxyfen caused a tendency of acceleration of molting without any effect on molt increment. The results of this study show that ) Corresponding author. Tel.: q972-8-646-1364; fax: q972-8-647-2890. Ž . E-mail address: [email protected] A. Sagi . 0044-8486r01r$ see front matter q 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S0044-8486 01 00596-8 ( ) U. Abdu et al.rAquaculture 202 2001 163–175 164 pyriproxyfen does not seem to be toxic to the crayfish, even in relatively high doses, and might affect the energetic balance between molt and reproduction. q 2001 Elsevier Science B.V. All rights reserved.