Practical 1 – Acute Toxicity Testing: 24-hour lethality test using Daphnia carinata Test Report
Tan, C.L
BIOL2162
25 August 2015
, Introduction
Acute toxicity testing is a small-scale experiment where a chosen test organism is exposed to a
toxicant to determine effectiveness of the test chemical or lethality of the organism. The standard
test species, Daphnia carinata was the chosen bioassay for this experiment as their high rates of
productivity allow easy culturing in a laboratory. The reproductive cycle of the D. carinata is
unique as females do not require males for reproduction. Males are only produced for genetic
diversity during adverse environmental conditions hence a large population of male specimens are
indicators of declined functioning and health of the animals. (Nugegoda 2015) D. carinata are filter
feeders and is therefore sensitive to a variety of chemicals. Using larger animals such as fish would
require months of testing. Due to the small size of daphnia, only a small volume of dilutions is
required for testing and hence cost effective.
Cadmium is a highly toxic naturally occurring heavy metal and is widely used for industrial
purposes. It is not methylated hence does not accumulate in the food chain as most organisms are
able to excrete it. (Nugegoda 2015) Problems arise when cadmium is accumulated in humans,
affecting vitamin D levels and calcium metabolism. Exposure to the toxicant can be through intake
by contaminated food, or polluted air. ‘Itai-itai’ is one notable disease first occurring in a mining
area in Toyoma prefecture, Japan, where calcium in bones are replaced with cadmium and calcium
uptake is interfered. The type of compound formed determines the toxicity as solubility differs.
(Staessen et. al 1999)
The aim of this test was to observe the mobility and lethality of D. carinata when exposed to a
toxicant under varying concentrations, at 24 hours and to determine the dose required to kill 50% of
the population (LC50). In the OECD guidelines EC50 was instead determined. (OECD 2004)
Tan, C.L
BIOL2162
25 August 2015
, Introduction
Acute toxicity testing is a small-scale experiment where a chosen test organism is exposed to a
toxicant to determine effectiveness of the test chemical or lethality of the organism. The standard
test species, Daphnia carinata was the chosen bioassay for this experiment as their high rates of
productivity allow easy culturing in a laboratory. The reproductive cycle of the D. carinata is
unique as females do not require males for reproduction. Males are only produced for genetic
diversity during adverse environmental conditions hence a large population of male specimens are
indicators of declined functioning and health of the animals. (Nugegoda 2015) D. carinata are filter
feeders and is therefore sensitive to a variety of chemicals. Using larger animals such as fish would
require months of testing. Due to the small size of daphnia, only a small volume of dilutions is
required for testing and hence cost effective.
Cadmium is a highly toxic naturally occurring heavy metal and is widely used for industrial
purposes. It is not methylated hence does not accumulate in the food chain as most organisms are
able to excrete it. (Nugegoda 2015) Problems arise when cadmium is accumulated in humans,
affecting vitamin D levels and calcium metabolism. Exposure to the toxicant can be through intake
by contaminated food, or polluted air. ‘Itai-itai’ is one notable disease first occurring in a mining
area in Toyoma prefecture, Japan, where calcium in bones are replaced with cadmium and calcium
uptake is interfered. The type of compound formed determines the toxicity as solubility differs.
(Staessen et. al 1999)
The aim of this test was to observe the mobility and lethality of D. carinata when exposed to a
toxicant under varying concentrations, at 24 hours and to determine the dose required to kill 50% of
the population (LC50). In the OECD guidelines EC50 was instead determined. (OECD 2004)
