Temperature effects on lipid properties of microalgae Tetraselmis subcordiformis and Nannochloropsis oculata as biofuel resources

Microalgae Tetraselmis subcordiformis and Nannochloropsis oculata were cultured at 15,20,25,30,and 35℃ and their properties as potential biofuel resources were examined.The results indicate that T.subcordiformis and N.oculata grew best at 20℃ and 25℃ and yielded the highest total lipids at 20℃and 30℃,respectively.With increased temperature,neutral lipid and polyunsaturated fatty acids(FAs)decreased while saturated FAs increased,accompanied by increased monounsaturated FAs(MUFAs) in T.subcordiformis and decreased MUFAs in N.oculata;meanwhile,the predicted cetane number of FA methyl esters increased from 45.3 to 47.6 in T.subcordiformis and from 52.3 to 60.3 in N.oculata.Therefore,optimizing culture temperatures is important for improving microalgal biodiesel production.

Influence of salinity on the early development and biochemical dynamics of a marine fish, Inimicusjaponicus

Fertilised eggs of the devil stringer(I nimicus japonicus) were incubated at different salinity levels(21, 25, 29, 33, and 37), and then the hatching performances, morphological parameters, and biochemical composition(protein, lipid and carbohydrate) of the larvae were assayed to determine the influence of salinity on the early development of I. japonicus. The tested salinity levels did not af fect the times of hatching or mouth opening for yolk-sac larvae. However, the salinity significantly influenced the hatching and survival rates of open-mouthed larvae, as well as the morphology of yolk-sac larvae. The data indicated that 30.5 to 37.3 and 24.4 to 29.8 were suitable salinity ranges for the survival of embryos and larvae of I. japonicus, respectively. Larvae incubated at a salinity level of 29 had the greatest full lengths, and decreasing yolk volume was positively correlated with the environmental salinity. With increasing salinity, the individual dry weights of newly hatched larvae or open-mouthed larvae decreased significantly. Newly hatched larvae incubated at a salinity level of 29 had the greatest metabolic substrate contents and gross energy levels, while the openmouthed larvae's greatest values occurred at a salinity level of 25. Larvae incubated in the salinity range of 33 to 37 had the lowest nutritional reserves and energy values. Thus, the I. japonicus yolk-sac larvae acclimated more readily to the lower salinity level than the embryos, and higher salinity levels negatively influenced larval growth and development. In conclusion, the environmental salinity level should be maintained at 29–33 during embryogenesis and at 25–29 during early larval development for this species. Our results can be used to provide optimum aquaculture conditions for the early larval development of I. japonicus.

Genetic and morphological differences between yellowtail kingfish (Seriola lalandi) from the Bohai Sea, China and the Southern Ocean, Australia

The aquaculture of yellowtail kingfish(Seriola lalandi)has expanded around the globe,including China.Genetic resource of Chinese S.lalandi urgently needs to be assessed for improving production.Here,we collected wild S.lalandi samples from the Bohai Sea,China and evaluated its genetic diversity based on 17,690 nuclear loci.A population from the Southern Ocean,Australia was used for comparison.The analyses showed that the Chinese and Australian S.lalandi formed two completely distinct clusters and there was no genetic introgression from the Australian S.lalandi into the Chinese S.lalandi population.The genetic diversity is slightly lower,but comparable in Chinese versus Australian yellowtail kingfish(Chinese population,expected heterozygosity:0.19,observed heterozygosity:0.19,nucleotide diversity:0.19±0.09;Australian population,expected heterozygosity:0.23,observed heterozygosity:0.22,nucleotide diversity:0.22±0.11).Overall,our results indicated that Chinese S.lalandi could be a potential subject for genetic breeding programs.We also investigated morphological characters and developed molecular markers for population identification.Comparison of meristic characters between the Chinese population and the Australian population revealed that main shape difference were in the number of dorsal spines,dorsal fin rays and the number of upper gill rakers.Geometric morphology based on eight landmarks also revealed significant difference between the two populations including the distance between the tip of snout to origin of pelvic fin and the distance between the tip of snout to origin of pectoral fin.These morphological characters can be used for easy identification of the Chinese S.lalandi.