Daphnia are small, planktonic crustaceans, between 0.2 and 5 mm in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because of their saltatory swimming style (although fleas are insects and thus only very distantly related). They live in various aquatic environments ranging from acidic swamps to freshwater lakes, ponds, streams and rivers.

The lifespan of a Daphnia does not exceed one year and is largely temperature dependent. For example, individual organisms can live up to 108 days at 3°C while some organisms live for only 29 days at 28°C. A clear exception to this trend is during the winter time in which harsh conditions limit the population in which females have been recorded to live for over six months. These females generally grow at slower rate but in the end are larger than ones under normal conditions.

Sometimes Daphnia may be used in certain environments to test the effects of toxins on an ecosystem. This makes Daphnia an indicator species, particularly useful in that area because of its short lifespan and reproductive capabilities. Because they are nearly transparent, their internal organs are easy to study in live specimens (an example might be to study the effect of temperature on the heart rate of these ectothermic organisms). They are often fed to tadpoles or small species of amphibians such as the African Dwarf Frog, Hymenochirus biettgeri. Daphnia are also a popular live food in tropical and marine fish keeping.

Several water flea species are considered threatened. The following are listed as vulnerable by IUCN: Daphnia nivalis, Daphnia coronata, Daphnia occidentalis, and Daphnia jollyi. Some species are halophiles, and can be found in hypersaline lake environments.

Antifreeze contains a rather subtle taste and smell that can easily be diluted and masked when combined with a hot liquid or a sweet tasting liquid. This exhibited itself as a problem after several cases, including the Julia Lynn Turner and Stacey Castor murder trials, showed antifreeze as a highly dangerous murder tool. Symptoms of antifreeze poisoning include severe diarrhea and vomiting and usually farther into the intoxication, signs of delirium, paranoia and intense hallucinations manifest. Antifreeze poisoning can be identified from the growth of calcium oxalate crystals in the kidneys.

Ethylene glycol poisoning is caused by the ingestion of ethylene glycol. Ethylene glycol is most commonly found as the primary ingredient of automobile antifreeze and hydraulic brake fluids. It is a toxic, colorless, odorless, almost nonvolatile liquid with a sweet taste. Following ingestion the symptoms of poisoning follow a three step progression starting with intoxication and vomiting, before causing metabolic acidosis, cardiovascular dysfunction, and finally acute kidney failure. The major cause of toxicity is not the ethylene glycol itself but its metabolites. The major metabolites causing toxicity are glycolic acid and oxalic acid.

For more information:
Antifreeze
Ethylene Glycol Poisoning

Source: Wikipedia (All text is available under the terms of the Creative Commons Attribution-ShareAlike License)