Effects of Malathion on Survival, Growth, Development, and Equilibrium Posture of Bullfrog Tadpoles (Rana Catesbeiana)

Abstract

Bullfrog (Rana catesbeiana) tadpoles were exposed to malathion in water in a 28-d static renewal test. The effects of malathion on survival, growth, development, and loss of equilibrium posture were determined. Survival was significantly decreased at malathion concentrations of 2,500 micrograms/L and higher. Development of tadpoles was delayed significantly by malathion exposure as indicated by a dose-related decrease in developmental stage over time. Development of tadpoles in the 1,000-microgram/L and higher treatment groups was significantly delayed from that observed in the control. The effects of malathion on developmental stage suggest that malathion may decrease thyroid function in tadpoles, as it does in other species. Maintenance of equilibrium posture following agitation of the test containers was significantly impaired in tadpoles in all the malathion treatment groups (500 to 3,000 micrograms/L) relative to the control. Maintenance of equilibrium posture was thus the most sensitive end point measured in this study. Loss of equilibrium posture could increase predation losses and decrease feeding in populations of bullfrog tadpoles in the field. However, concentrations of malathion that produced adverse effects in our study are higher than published, measured concentrations found in wetlands or streams.

Survival and development of bullfrog tadpoles in microcosms treated with abamectin

“…2). Despite that these conditions differed from a laboratory study by Fordham et al (2001), control 25 G bullfrog tadpoles in the latter study also reached stage 33 ± 0.7 within 22 and 28 days. These authors also noted a decrease in biomass in controls, which was also Open symbols represent treatments without tadpoles, whereas closed symbols represent treatments with tadpoles observed in the present study in control tadpoles that remained in lower Gosner stages (Fig.…”

“…A delay in development can have pronounced effects on tadpole fitness in the field, which include (i) increased predation at the vulnerable tadpole stage; (ii) decreased reproductive potential because frogs that metamorphose late have been shown to have a reduced chance of breeding the 1st year following metamorphosis; and (iii) delay in development from an aquatic to an air-breathing stage could decrease tadpole survival if ephemeral ponds dry up (as is often the case in Brazilian freshwaters where this species is encountered) and the larvae cannot migrate (Fordham et al 2001;Bulen and Distel 2011). In addition, it is conceivable that multiple stresses to amphibians likely to occur in realworld field conditions, such as habitat fragmentation, competition for food and ultraviolet radiation, could be potentiated by, or potentiate, chemical stresses (e.g.…”

Using sets of behavioral biomarkers to assess short-term effects of pesticide: a study case with endosulfan on frog tadpoles

“…The normal posture is with the dorsal side upward. Lack of correct equilibrium posture is considered to be a good biomarker of toxicity (Fordham et al 2001). …”

Organophosphates as Endocrine Disruptors

“…Malathion induced a significant delay in the growth of tadpoles in water containing a malathion concentration of 1 mg/L, suggesting a decrease in thyroid function (Fordham et al, 2001). Malathion also decreased serum T3 level in the freshwater catfish, Clarias batrachus, but accelerated T4 synthesis in the pharyngeal thyroid.…”

“…Chlorpyrfos and dimethoate decreased serum T4 levels in ewes treated with these chemicals (12.5 mg/kg and 0.2 mg/kg, respectively, 3 times a week, 43 days; Rawlings et al, 1998). Treatment of bullfrog tadpoles (Rana catesbeiana) with malathion significantly delayed developmental progression (Fordham et al, 2001).…”