Juvenile hormones in development of ixodoid ticks: a short review of current controversial situation in tick endocrinology

Abstract

The problem of juvenile hormones (JHs) in ixodoid ticks is quite controversial and disputable due to contradictions in data on effects of JHs, juvenoids and their antagonists in these chelicerate arthropods. It remains unsolved until now even after recent studies by R. M. Roe`s group (USA), whose conclusion that JHs are absent in ticks and do not control their metamorphosis and reproduction (Roe et al. 1999b, 2001; Neese et al. 2000), was supported by some insect physiologists (Gilbert et al. 2000; Wilson 2004). However my investigations on limb regeneration in ticks have demonstrated specific morphogenetic effects of JH-agonists and antagonists upon sensillar sets in Haller s organ regenerates (Belozerov 1999a, 2001 a,b,c, 2003 a,b, 2004). They provided evidence of similarity between ticks (as chelicerate arthropods) and insects (as mandibulate arthropods) in regard to JHs and their function as status quo factors in the control of developmental processes. This is confirmed also by the retinoic acid (RA) juvenilizing effects known in insects (Nemec et al. 1993), and discovered recently in ixodid ticks (Belozerov 2003a, 2004a). Action of RA in morphogenetic processes in ticks is revealed also by its specific teratogenic effect through axial duplication of some compartments in Haller s organ regenerates. The study of Haller s organ regeneration in ticks provides positive perspectives for investigations in tick endocrinology and developmental biology, particularly in bioassaying of compounds with JH-activity for chelicerate arthropods.