Biochemical and biophysical aspects of the tolerance of anhydrobiotic crustacean embryos to very high temperatures

Mechanisms associated with cellular desiccation tolerance in the animal extremophile artemia

Using differential scanning calorimetry, we demonstrated the presence of biological glasses and measured the transition temperatures in dry encysted embryos (cysts) of the brine shrimp, Artemia franciscana. Cysts from the following three geographic locations were studied: San Francisco Bay (SFB); the Great Salt Lake, Utah (GSL); and the Mekong Delta, Vietnam (VN; these cysts were produced from previous sequential inoculations of SFB cysts into growth ponds). Values for the glass transition temperature, T(g), were highest in VN cysts. This study indicates that the composition and properties of these biological glasses can be altered by natural selection and thermal adaptation. To our knowledge, T(g) values for all three kinds of cysts were significantly higher than those for any other desiccation-tolerant animal system. To gain insight into the significance of T(g), we examined the thermal stability of these dry cysts at 80 °C. GSL cysts were the least tolerant, by far, with VN cysts being extremely tolerant and SFB cysts not far behind. Those results correlated with the thermal transition values. Also measured were alcohol-soluble carbohydrates, ~90% of which is the disaccharide trehalose, a known component of biological glasses. Amounts in the GSL cysts were significantly less than those in the other two kinds of cysts. Several stress proteins were measured in the three groups of cysts, with all of them being in lesser amounts in GSL cysts compared with the SFB and VN cysts. We interpret the data in terms of mechanisms involved with desiccation tolerance and thermal conditions at the sites of cyst collection.

Two highly diverged New World Artemia species, A. franciscana and A. persimilis, from contrasting hypersaline habitats express a conserved stress protein complement

The brine shrimp Artemia is a well known animal extremophile adapted to survive in very harsh hypersaline environments. We compared the small stress proteins artemin and p26, and the chaperone hsc70 in encysted embryos (cysts) of the New World species, A. franciscana and A. persimilis. Cysts of the former, from San Francisco Bay, USA (SFB), were used essentially as a reference for these proteins, while both species were from locations in Chile where they occur in habitats at latitudinal extremes, the Atacama desert and Patagonia. These two species are phylogenetically distant, A. persimilis being closer to the Old World species, whilst A. franciscana is considered younger and undergoing evolutionary expansion. Using western blotting we found all three stress proteins in cysts from these five populations in substantial although variable amounts. The protein profiles revealed by Coomassie staining after electrophoresis (SDS-PAGE) were similar qualitatively, in spite of marked differences in the habitats from which these populations originated, and the long time since they diverged. We interpret these findings as further evidence for the adaptive importance of these three conserved proteins in coping with the variable, but severe stresses these encysted embryos endure.

Efficiency of Artemia cysts removal as a model invasive spore using a continuous microwave system with heat recovery

A continuous microwave system to treat ballast water inoculated with Artemia salina cysts as a model invasive spore was tested for its efficacy in inactivating the cysts present. The system was tested at two different flow rates (1 and 2 L x min(-1)) and two different power levels (2.5 and 4.5 kW). Temperature profiles indicate that the system could deliver heating loads in excess of 100 degrees C in a uniform and near-instantaneous manner when using a heat recovery system. Except for a power and flow rate combination of 2.5 kW and 2 L x min(-1), complete inactivation of the cysts was observed at all combinations at holding times below 100 s. The microwave treatment was better or equal to the control treatment in inactivating the cysts. Use of heat exchangers increased the power conversion efficiency and the overall efficiency of the treatment system. Cost economics analysis indicates that in the present form of development microwave treatment costs are higher than the existing ballast water treatment methods. Overall, tests results indicated that microwave treatment of ballast water is a promising method that can be used in conjunction with other methods to form an efficient treatment system that can prevent introduction of potentially invasive spore forming species in non-native waters.