The pH value of the seawater is a very important factor
for the hatching of the Artemia eggs. Optimal pH range
is 8.0 ± 0.5. If necessary, the pH should be adjusted using
NaOH or Na2CO3, to avoid lethality of the Artemia larvae
caused by decrease of pH during incubation (Vanhaecke et
al., 1981; Parra et al., 2001).
Temperature variations affect the hatching process of
Artemia cysts. Warmer medium temperature enables faster
hatching of the cysts (Table 1).
It has been shown that 50% of the cysts hatch within
30 hours at 20 °C, while at 24 °C this percentage is already
obtained after 21 hours. With regard to the molting rate,
it appears that at 24 °C more than 60% of the larvae molt
into the II instar stage 16 hours after hatching, whereas at
20 °C it takes 35 hours to arrive at the same stage (Sorgeloos
et al., 1978).
The light stimulus influences the hatching of Artemia
cysts significantly. Sorgeloos explained how the embryological
development of hydrated embryos that are not stimulated
by light, can be delayed until the light trigger is applied.
Apparently, the cysts started hatching after being exposed
to light, which gave statistically significant differences
between the dark and the light series (Sorgeloos,
1973).
Additionally, Vanhaecke et al. (1981) indicated that
the most sensitive age for the majority of the tested compounds
were the 48 hour-old nauplii at the stage of instar
II-III