Autochthonous parthenogentic Artemia populations have been reported from Indian hypersaline habitats since 1950s. Exotic Artemia franciscana was imported and introduced into India as live food for aquaculture since the early eighties. To assess the present status of the Artemia populations and the possibility of invasion by the introduced A. franciscana in Indian Salinas, an extensive study was conducted using conventional and molecular approaches. Morphological and biometric observations, crossbreeding experiments and molecular and phylogenetic analysis using Internally Transcribed Spacer-1 sequence revealed the extensive presence of alien, sexual A. franciscana populations in various hypersaline areas. Individual culture experiments and crossbreeding studies further confirmed the absence of autochthonous parthenogentic Artemia populations. Lack of regional endemism in populations of distant origins was evident, indicating that the invaded populations have naturalized and are in the process of evolution. This forms the first report of invasion by A. franciscana in hypersaline habitats of Indian subcontinent and further studies are required to assess the biological implications of this invasion.

Recurring mortalities in£icted by the cirolanid isopodCirolana £uviatilis in the juveniles of the Asian seabass, Lates calcarifer, stocked in a cage farm in the Cochin backwaters, from November 2006 to May 2007, were investigated. Hatchery-reared ¢ngerlings (size 8^12 cm) were cultured in £oating cages and mortalities were observed after a rearing period of 1 month. The ¢sh were found dead in the cages, with only the remnants of ¢sh skeleton and all the £esh eaten away. Investigations revealed a very high abundance of isopods, identi¢ed as C. £uviatilis (Crustacea, Malacostraca, Isopoda and Ciroloanidae). During the ¢rst 2 months of stocking, 35% of the ¢ngerlings died, and the cumulative mortality reached 45% in 6 months, considerably reducing the pro¢ts from the venture. Management measures for the control of the isopods are discussed. This is the ¢rst report on the isopod, C. £uviatilis, in£icting serious mortalities in a tropical cage-rearing system in the southwest coast of India.

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The present study analysed the effect of salinity stress on survival, biochemical constituents such as soluble protein, amino acid, trehalose and fatty acid, as well as real time expression of the Artemia heat-shock protein 22 (ArHsp 22) gene in Artemia franciscana. Results of the study revealed that Artemia can withstand sudden salinity increase up to 200 ppt without any mortality up to 6 h. Significantly higher mortality percentage was recorded at 24 h of incubation at 200 ppt. Short-term exposure to hypersaline conditions significantly reduced the protein content in Artemia while the protein biosynthesis enhanced after 24 h of incubation at 150 ppt salinity. Long term exposure to 200 ppt salinity did not show any further increase in amino acid content as observed at 100 and 150 ppt conditions, indicating reduced rate of amino acid metabolism and stress. Salt stress induced the synthesis of total polyunsaturated fatty acids (PUFA) in Artemia especially the 22:6n-3 and 20:5n-3 after 24 h of incubation at 150 ppt . Exposure to higher salinity induced trehalose production which indicated its vital role in combating salt stress in Artemia. The present study also indicated that short-term salt stress can significantly enhance the ArHsp22 gene expression in Artemia adults.