MORPHOLOGICAL CHANGES IN DAPHNIA GALEATA INDUCED BY A CRUSTACEAN TERPENOID HORMONE AND ITS ANALOG

Terpenoid hormones in insects (i e juvenile hormones) have various effects on physiology morphology and behavior producing a wide range of phenotypic variation Recent studies have shown that sex determination in cladoceran crustaceans is under the strong control of a major terpenoid hormone of crustaceans methyl farnesoatote (MF) It can be easily conceived that MF is also a major determinant of other traits in cladocerans In the present study morphological changes known as antipredatory responses in a cladoceran Daphnia galeata in response to exposure to MF and a juvenile hormone mimicking pesticide fenoxycarb were investigated Morphological change was studied using neonates less than 24 h old exposed either to MF at the concentrations from 1 9 to 30 mu g/L or fenoxycarb at the concentrations from 13 to 200 ng/L for 6 d Animals developed a longer helmet at I 9 mu g/L of MF and 25 ng/L of fenoxycarb and showed a concentration dependent elongation However the tail spine was reduced in size in a concentration dependent manner Results of the present study not only give new insight into the mechanisms of inducible defenses in cladocerans but also provide invaluable information to understand ecological and evolutionary consequences of endocrine disruption through the shift in biological interaction between predator and prey Environ Toxicol Chem 2011 30 232-238 (C) 2010 SETAC