Acute and Subchronic Toxicity of Arsenite and Zinc to Tadpoles of Rhinella arenarum Both Alone and in Combination

Abstract

The current study evaluated acute and subchronic toxicity of arsenite (As(3+)) and zinc (Zn(2+)) to stage 25 tadpoles of Rhinella arenarum in both single and joint laboratory exposures. LC50 values obtained for As(3+) were elevated and remained within the range of 46 to 50 mg/L of As(3+) between 4 and 17 d of exposure. Growth of tadpoles was completely inhibited with 30 mg/L of As(3+), demonstrating the presence of ecologically relevant sublethal effects at concentrations lower than those resulting in lethality. With respect to Zn(2+), a 96-h LC50 value of 2.49 mg/L was calculated in soft water. Contrary to results obtained for As(3+), LC50 values of Zn(2+) gradually decreased with increasing exposure duration, from 2.49 mg/L at 96 h to 1.30 mg/L after 21 d. In joint exposures to both metals, the type of interaction observed between As(3+) and Zn(2+) was concentration dependent. Lethal effects of As(3+) were mitigated, unaffected, or potentiated by 0.01, 0.1, and 1-2 mg/L of Zn(2+), respectively. However, although 0.01 mg/L of Zn(2+) significantly reduced lethality of As(3+)-exposed tadpoles, the same concentration of Zn(2+) did not help to reverse the stunt growth of these animals. Further studies need to examine which are the lowest concentrations As(3+) required to reduce growth and whether Zn(2+) serves to antagonize growth effects in this range of concentrations.

Acute toxicity of arsenic and oxidative stress responses in the embryonic development of the common South American toad Rhinella arenarum

“…Similar results were reported for R. arenarum tadpoles exposed to sodium arsenite from the complete operculum stage on (after the embryonic phase is concluded), where LC50 values varied between 46 mg/L and 57 mg/L As, and 4 d to 17 d of exposure were evaluated [15]. Noticeably, LC50 remained the same from the heartbeat stage to the complete operculum stage, averaging 24.3 mg/L As.…”

“…The LC50 could not be determined in embryos exposed to As from heartbeat stage, because the mortality values registered were below 50%, even when exposed to the highest concentration tested (50 mg/L As). Similar results were reported for R. arenarum tadpoles exposed to sodium arsenite from the complete operculum stage on (after the embryonic phase is concluded), where LC50 values varied between 46 mg/L and 57 mg/L As, and 4 d to 17 d of exposure were evaluated [15]. Other aquatic organisms exposed to sodium arsenite show LC50 values in the order of milligrams per liter As: the 96-h LC50 of sodium arsenite for juvenile rainbow trout (Oncorhynchus [27] were ordered to calculate the percentile distribution, and a probit regression was applied using the corresponding log-transformed concentration data.…”

“…It has been shown that R. arenarum has sensitivity toward diverse contaminants similar to other anurans [12][13][14]. Nevertheless, the study of As toxicity is particularly limited in amphibians [15]. Arsenic ecotoxicity in amphibians has been a matter of controversy, because they appear to be able to develop and survive in highly contaminated water, in spite of the fact that inorganic As has long been considered toxic to frogs [10].…”

“…Arsenic ecotoxicity in amphibians has been a matter of controversy, because they appear to be able to develop and survive in highly contaminated water, in spite of the fact that inorganic As has long been considered toxic to frogs [10]. Nevertheless, the study of As toxicity is particularly limited in amphibians [15]. Considering these facts, our aim in the present study was to assess the acute toxicity of As in water during the embryonic development of R. arenarum and to determine the biochemical responses elicited by the exposure to sublethal and lethal As concentrations.…”

Developmental toxicity of treated municipal wastewater effluent on Bombina orientalis (Amphibia: Anura) embryos

“…Similarly, a high concentration of N increased malformations in tadpoles, including swollen sac-like bodies, and in narrow-eyed frog (Nyctibatrachus major), cricket frog (Fejervarya limnocharis), green frogs (Rana clamitans), and bullfrogs (R. catesbeiana) [40][41][42]. Pollutants at low concentrations have mixed and additive toxic effects on the development of amphibian embryos [43][44][45][46][47]. Though heavy metals were not detected in TWE and TWE-mixed water samples in July, an increase in malformation of tadpoles suggests that unidentified pollutants at trace levels may increase the teratogenic activity of TWE in a mixed and additive manner.…”