Toxicity of arsenic (As3+), aluminum (Al3+), chromium(Cr6+) and nickel (Ni2+) to the embryos and juveniles of the freshwater snail, radix quadrasi von Moellendorf 1898

Date

2011

Degree

Bachelor of Science in Biology

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Emmanuel Ryan C. de Chavez

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Abstract

Heavy metals are one of the major toxicants affecting different freshwater organisms including snails. To examine this problem, the effects of arsenic (As3+), aluminum (Al3+), chromium (Cr6+) and nickel (Ni2+) on the trochophore larvae (2-day old embryos) and juveniles (4-day old upon hatching) of the freshwater pulmonate, Radix quadrasi, were determined. For the acute toxicity of individual metals, a total of 100 egg masses and 1000 juvenile snails were subjected to static renewal test (range finding and definitive) for 96h. Mortality data was processed for the calculation of median lethal concentration (LC50-96h) using probit analysis. To determine the toxic effect of metal combinations, a total of 30 egg masses and 300 juveniles were subjected to Warren’s test based on the LC50-96h. Sublethal toxicity test based on adjusted LC10-96h concentrations was conducted among embryos for 14 days. Based on the LC50-96h, the toxicity trend for embryos was Cr6+ (0.0263 mg/L) > As3+(1.0147 mg/L) > Ni2+ (1.5877 mg/L) > Al3+(1.8787 mg/L) while for juveniles the trend was As3+(0.0603 mg/L) > Al3+(0.1247 mg/L) > Cr6+ (0.1357 mg/L) > Ni2+ (7.8290 mg/L). Among embryos, joint toxicity test revealed additive interaction between Cr6++Al3+, Ni2++Al3+ and As3++Al3+ while antagonism between Cr6++Ni2+, Cr6++As3+ and As3++Ni2+. For juveniles, all heavy metal combinations were additive. Sublethal toxicity test showed growth retardation as the most common abnormality among embryos exposed to As3+, Al3+ and Ni2+, followed by edema and thinning of the shell. The hatchability and incubation period were also significantly decreased and prolonged in all treatment groups compared to the control. These observations showed toxicity and sensitivity variations between the two life stages. The present study demonstrated R. quadrasi (embryos and juveniles) as a potential bioindicator for heavy metals particularly for As3+, Al3+, Ni2+ and Cr6+

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Document Type

Thesis

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