Study of Cysts Biometry and Hatching Percentage of the Brine Shrimp Artemia salina (Linnaeus, 1758) from the Sebkha of Sidi El Hani (Tunisia) According to Successive Generations

Artemia salina cysts harvested from the Sebkha of Sidi El Hani were hatched and cultivated in the laboratory. The obtained nauplii were acclimated at 90 ppt and fed with Dunaliella salina microalgae until the adult stage called generation 1 (G1) was reached. Ten couples were isolated and acclimated in the same conditions. Observations of the offspring lasted for a maximum of 60 days. Cysts obtained from G1 were collected and counted. Cyst diameter, chorion thickness and hatching percentage were established. Nauplii obtained from G1 were labelled G2. The third (G3) and the fourth (G4) generations were studied similarly. A significant variation of untreated cyst diameter between G1 (234.7±14.1 µm) and the subsequent generations, notably G3 (210.9±14 µm) were registered. Decapsulated cyst diameter delayed significantly from 218.5±12.8 (G1) to 190.8±10.1 (G3). The chorion thickness ranged between 8.1 (G1) and 10.5 (G2). Therefore, an interesting boost of untreated cysts hatching percentage was observed from 69±2.3% (G1) to 76±3.7% (G4). These results highlighted the variability of cyst diameter across successive generations, even cultivated under laboratory scale. An improvement of hatching quality was detected when environmental conditions became favorable.