This paper investigates the toxicity of cadmium (Cd) on young stages of the common Asian toad Duttaphrynus melanostictus (Schneider 1799). Signs of acute toxicity were evident in tadpoles repeatedly exposed to five concentrations ranging from 0.002 to 2 mg L(-1)of Cd which included environmentally relevant levels. Mortality at concentrations of 0.02 mg L(-1) and above was enhanced from 2 % at 0.02 mg L(-1) to 100 % at 1 mg L(-1), in a dose-dependent manner. Significant growth impairment was evident at 0.20 mg L(-1) with the larvae being markedly smaller. Delayed metamorphosis and retarded swimming were also observed. Therefore levels of Cd recorded in some freshwater bodies in Sri Lanka (e.g. 0.2 mg L(-1)) may be detrimental to the young stages of D. melanostictus.

This study investigates the effects of Cadmium (Cd) on fry of the Mozambique Tilapia Oreochromis mossambicus using standard toxicity tests. Fry were repeatedly exposed to five concentrations (0.002 -2.0 mgl-1) of Cd and survival, growth and swimming activity were monitored over 10 days. These trials revealed that all the tested concentrations significantly enhanced mortality of the fry with concentrations above 1.0 mgl-1 resulting in 100% mortality. Mortality was positively related to the exposure level indicating dose-dependency. The LC50 1-10days ranged from 0.02 to7.26 mgl-1. Fry exposed to Cd also exhibited an increase in swimming activity in comparison to those that were not exposed indicating abnormal behaviour. Nevertheless, there was no apparent growth retardation and gross morphological defects during the brief exposure period. These findings are significant because the lethal and sublethal effects in fry were also apparent at Cd concentrations of 0.001 -0.2 mgl-1, which are typically recorded in fresh waterbodies in Sri Lanka.

Arsenic (As) and Cadmium (Cd) are two of the heavy metals that gained public and national attention of the Sri Lankan community. Globally, As and Cd are reported as two of the most toxic heavy metals that cause physiological and biochemical alterations and mortality in exposed organisms. Cadmium levels in the range of 0.001 to 0.138 mg l -1 have been reported in both ground and surface water sources of Sri Lanka. Few studies in the country have documented levels of arsenic in natural water bodies. Furthermore, studies assessing the potential toxicity of these two metals to species that are of importance to Sri Lanka, are scarce. The aim of this preliminary study was to investigate the effects of environmentally relevant levels of As and Cd on the commercially exploited fresh water prawn Macrobrachium rosenbergii, using its post larvae, which are initially released into reservoirs in Sri Lanka. Post larvae were collected from a culture facility in Pambala, Chilaw and were maintained in glass beakers. They were acclimatized before use for 96 hr acute toxicity trials, where they were exposed to a series of concentrations of either As (from 0.001 to 0.08 mg l -1 ) and Cd (from 0.001 to 0.05 mg l -1 ). Constant experimental conditions were maintained in both the control and treatment, each conducted in triplicate.