Improved methods for harvesting and counting synchronous populations of Artemia nauplii for use in developmental toxicology.

Artemia nauplii have, within recent years, gained popularity as a test organism for short-term toxicity testing. Because nauplii exhibit rapid development and growth within 48 hr after hatch, their potential as a model organism for teratology screening has been considered. To do this, synchronous populations of nauplii at different developmental intervals must be available. A dual-chamber hatching vessel which enables multiple harvesting of synchronous populations of nauplii from one sample of prepared cysts has been developed. An accumulation period of 2 hr defines the synchronous population and produces around 1000 nauplii among five hatching vessels. The body lengths of nauplii harvested 2 to 9 hr after the initial harvest were equivalent to and lower than that of animals incubated at the hatching temperature (31 +/- 1 degree C); e.g., the body length of freshly harvested nauplii at 9 hr was 473 +/- 6.2 micron (+/- SE) and for nauplii incubated for 8 to 10 hr, the body lengths were 643 +/- 10.7 and 702 +/- 10.9 micron, respectively. A counting method was developed that enabled precise counting up to 400 nauplii in suspension and distinguishing dead from live nauplii. Measurements of body length, body water volume, and whole animal DNA and protein of nauplii harvested sequentially from the same sample of prepared cysts indicated that in addition to temporal differences in hatching, the nauplii may differ both physically and chemically.