Artificially induced metamorphosis acetone inAcris gryllus

Abstract

The causative agents (hormones) involved in amphibian metamorphosis as well as the involved specific endocrine organs have been well established for decades. Tri-iodothyronine and thyroxin, both secretions of the larval thyroid gland, are directly responsible for metamorphosis under physiological conditions. High amounts of the element iodine (approximately 300 times the amount found in equally effective levels of thyroxin) can also induce metamorphosis in amphibians. In a search for an appropriate emulsifier to be employed in studying the effects of hydrophobic polychlorinated biphenyls (PCBs) on metamorphosis, reagent-grade acetone (a commonly used carrier molecule for PCBs) was found to be a potent inducer of metamorphosis inAcris gryllus. The acetone was employed as a component of an artificial pond water (APW) medium. Other test conditions included exposure to thyroxin and dimethyl sulfoxide (DMSO) for comparison. Not only was metamorphosis enhanced in the acetone-treated animals, but the effect was concentration-dependent when acetone levels of 10 mg/L and 50 mg/L were employed. The 50 mg/L acetone-treated group showed precocious metamorphosis at a rate not significantly different from that produced by thyroxin. Dimethyl sulfoxide exposure produced no significant increase in metamorphic rate.