Comparative study on thermotolerance of Artemia resting eggs from Qinghai–Xizang Plateau, China

Abstract

Artemia resting eggs are well-known to be extremely tolerant to harsh conditions. However, eggs from some hypersaline waters in Qinghai–Xizang Plateau (Q-XP) have recently been reported to be very sensitive to high temperatures. Thus, the thermotolerant capacity of Artemia eggs from four hypersaline waters [(Gai Hai (GH), Aqqikkol Hu (AQK), Xizang (XZ), Jingyu Hu (JYH)] in Q-XP were studied by comparing their structure, biochemical composition and physiology. Thermotolerance was markedly different among eggs of the four sites. GH eggs were found to be more thermotolerant than AQK eggs. Both eggs were much more tolerant than those from JYH and XZ. Water content had significant effect on heat resistance of “dry” eggs. Rate of water loss of GH eggs was markedly slower than that of AQK eggs; the latter slower than XZ and JYH eggs. The water loss from inner embryo (and the first embryonic cuticle) appeared not to be related to the nature of the tertiary envelope. Volatile factor(s) releasing from (or/and entering into) the eggs might play crucial role on the viability of encysted embryos under thermal stress. The thermotolerant capacity of Artemia eggs is likely to be negatively related to the permeability of egg shell/underlying membranes. The hypoplastic outer cuticular membrane (OCM) found in some eggs from Q-XP might be responsible for their thermal sensitivity.