The Scientific World Journal

Research Article

Are Fish and Standardized FETAX Assays Protective Enough for Amphibians? A Case Study on Xenopus laevis Larvae Assay with Biologically Active Substances Present in Livestock Wastes

Table 2

Endpoints studied at each exposure time for ivermectin (IVE), zinc (Zn), copper (Cu), selenium (Se). Lethal and effect concentrations in the 50% of the cases (EC₅₀ and LC₅₀) were shown at 24, 48, 72 and 96 hours. At each exposure time, the EC₅₀ values were related to the corresponding sublethal effect. For the water-soluble forms of the metals: zinc sulphate (ZnSO₄ * 7 H₂O) and sodium selenite (NaSeO₃ * 5 H₂O) the 96 h LC₅₀ were reported, and for copper chloride (CuCl₂ * 2 H₂O) both 48 h and 96 h LC₅₀s were showed.


Substance	Exposure time (hours)	LC₅₀ (mg/L)	95% confidence intervals (mg/L)	EC₅₀ (mg/L)	95% confidence intervals (mg/L)	NOEC^a (mg/L)	Sublethal effect

IVE	24	6.4 * 10⁻³		>1.1 * 10⁻³ <2.1 * 10⁻³			hyperactivity
	48	5.6 * 10⁻³	4.7 * 10⁻³–6.6 * 10⁻³	>1.1 * 10⁻³ <2.1 * 10⁻³			hyperactivity
	72	5.5 * 10⁻³	4.6 * 10⁻³–6.6*10⁻³	>1.1 * 10⁻³ <2.1 * 10⁻³			hyperactivity
	96	5.5 * 10⁻³	4.6 * 10⁻³–6.6 * 10⁻³	>1.1 * 10⁻³ <2.1*10⁻³		1.1 * 10⁻³	hyperactivity

Zn	24	14.0	12.0–16.8	7.4	3.6–12.3		edema
	48	13.4	11.3–16.1	4.5	2.6–6.3		edema
	72	13.4	11.3–16.1	7.6	5.1–11.2		edema
	96	12.8	10.8–15.6	8.5	6.4–12.0	1.4	edema

ZnSO₄ * 7 H₂O	96	56.4	47.4–68.7

Cu	24	1.3	0.6–2.0	>3.6			developmental delay^b
	48	0.9	0.3–1.3	>3.6			developmental delay
	72	0.9	0.3–1.3	0.4	0.4-0.5		developmental delay
	96	0.9	0.3–1.3	0.4	0.4-0.5	<0.2	developmental delay

CuCl₂ * 2 H₂O	48	2.4	1–3.7
CuCl₂ * 2 H₂O	96	2.3	0.8–3.6

Se	24	4.1					no detectable effect
	48	4.1					no detectable effect
	72	2.2					no detectable effect
	96	1.9					no detectable effect

NaSeO₃ * 5 H₂O	96	6.2

^aBased on sublethal effects observed at 96 hours.
^bApart from developmental delay at 72 and 96 hours, copper provoked and abnormal pigmentation (whitish) in all tadpoles at all tested concentrations (EC₅₀ < 0.22 mg/L).