laevis blastula the 96h LC50 value was 3.6mg/L [26]. Thus, the 96h LC50 of 56.44mg/L for ZnSO3, obtained in the present study, showed that X. laevis sensitivity was lower than one order of magnitude compared with FETAX and fish assays. nevertheless The ivermectin LC50 for X. laevis tadpoles was in the same range of fish and at least 100-fold less than are Daphnia. In fact, the 96h LC50 for ivermectin on rainbow trout is 3.3��g/L and the 48h LC50 value for D. magna is 25ng/L [27]. Due to ivermectin mechanism of action, Daphnia has been determined to be the most sensitive laboratory indicator organism [27]. Table 396h lethal concentration in the 50% of the cases (LC50, mg/L) for early-life-stage amphibians and fish exposed to copper (Cu), zinc (Zn), selenium (Se) and manganese (Mn). (Source: [18]).

The available data about acute effects in FETAX assay are generally more protective than the values found out in the current study for X. laevis 47 stage larvae, but previous data derived from fish assays could not be always enough protective. For example, X. laevis larvae exposed to NaSeO3 showed a higher sensitivity than rainbow trout [19] (Table 2). In addition, the presence of no-lethal effects caused by IVE, Zn, and Cu suggested that these substances have been able to cause an organism response. For example, larvae affected by Cu were underdeveloped and colourless, while IVE impaired their locomotion and orientation. Similar effects could be problematic in natural environments by increasing the susceptibility of larvae to predation, as reported by Yuan [28] for the whitish caused by triphenyltin exposure, or reducing foraging success resulting in decreased grown and development.

Changes in cognitive and psychomotor function, such as the hyperactivity induced by IVE, are commonly related to toxic neuropathy [29], while renal dysfunction, or more generally, an alter metabolism, could have caused the edema in the animals exposed to Zn (Figure 1). Based on the studies, FETAX assay appears to be useful in ecotoxicological hazard assessment, but fish assays might be not always protective enough for amphibian. Moreover, data from several studies indicate that late-stage amphibian larvae may be more sensitive to some chemical than traditional aquatic bioindicators [30], as occurred in the present study for metals, and for those species of amphibians that spend their entire life cycle in water (e.

g., Pipidae, Cryptobranchidae), larval exposure would be more accurate than FETAX assay [18]. It is necessary to highlight the need to study and prevent amphibian species. Brefeldin_A The presence of sublethal effects caused by different compounds should be investigated considering other endpoints that may affect several physiological mechanisms in a sublethal pattern, such as immunotoxicity, or a wider range of animal larvae stages.DisclosureThe authors do not have any financial relation with the commercial identities mentioned in the paper.