SEASONAL FARMING OF THE BRINE SHRIMP ARTEMIA
FRANCISCANA IN ARTISANAL SALT PONDS IN VIETNAM: EFFECTS OF TEMPERATURE AND
SALINITY
PhD Thesis by Nguyen Van Hoa, Faculty of Agricultural
and Applied Biological Sciences, Ghent University, Belgium, 2002, 184 pp.
Summary:
Artemia from San Francisco Bay (SFB) was inoculated in
Vinh Chau salt fields (Viet Nam) to study its adaptation to a novel
environment. Response of SFB to Vinh Chau environment was mainly considered
as affected by two major abiotic parameters: salinity and temperature. The
adaptation of SFB to Vinh Chau was considered through successive
generations, denoted as Y1, Y2 and Y3, Y4, referring to the sequence in
offspring. Therefore, similar set-ups were performed for Y1, Y2 and Y3
directly in the field conditions.
Results were all compared to VC (SFB origin), which
was first inoculated in Vinh Chau in 1986, and assumed to be well adapted to
the local conditions. However, strain/generation differentiations were
mainly found in cyst production and rarely in survival, number of oviparous
females and brood sizes.
To verify these parameters, a series of laboratory
tests was set up with VC, SFB, Y1, Y2, Y3 and Y4, at two salinities (80 ppt
and 120 ppt) and three water temperatures (26°C, 30°C and 34°C).
Difference in survival between VC, SFB and its successive generations were
found, but no differences were found in growth. Studies on life
characteristics and life span were not completed at 34°C as the animals
died soon after the start of the experiment. Differences in life
characteristics were displayed as an effect of different temperatures, not
different salinities. At 30°C at both salinities SFB showed lower numbers
of broods, lower total number of offspring, and shorter life span compared
to VC and to its following generations. Response of SFB to the site (Vinh
Chau) may be influenced by more complex environmental conditions and not
only by salinity and temperature. However, SFB displayed a lower living
performance than its following generations and VC at temperatures over 30°C
(prevailing conditions in Vinh Chau), finally resulting in lower cyst
production in the field. Nevertheless, a successful transplantation of SFB
to the site is feasible, as later generations show better survival and
higher production, compared to the original inoculum. In fact, the
transplantation of SFB into Vinh Chau in 1986 was successful and
consequently, presently, after full establishment of the site they have been
given the annotation VC strain. Responses of SFB to a warmer climate in Vinh
Chau and the gradual establishment in the field through following
generations is certainly related to the capacity of the strain to protect
itself to heat exposure (i.e. thermotolerance related to the presence of
heat shock proteins) and to some extent it depends on genetic aspects (i.e.
allozyme and mitochondrial DNA), which need, however, further investigation
and reconfirmation.