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.

At present the most common and most devastating disease of shrimp is caused by the white spot syndrome virus (WSSV), which has spread throughout the world mainly by different species of crustaceans carrying the virus. After experimental injection of Penaeus monodon with a known copy number of WSSV in the abdominal muscle, the rate of viral progression in different tissues at 12, 24, 36 and 48 hpi (hours post infection) was assessed using quantitative real-time PCR. At 12 hpi the viral load was highest in haemocytes followed by pleopod, muscle and gills whereas at 48 hpi, the gills, the main target of WSSV, showed the highest viral load followed by pleopod, muscle and haemocytes. Viral copy number in the haemocytes was the lowest beyond 12 hpi indicating a remarkable reduction in the rate of viral replication in haemocytes compared with other tissues. The viral load in haemocytes, though increased again beyond 36 hpi, never surpassed the load in the other tissues. The real-time PCR assay with its high sensitivity and wide dynamic range make it ideal for detecting low-level WSSV infections that can occur in apparently healthy P. monodon.

a b s t r a c tBecause of its capacity to rapidly convert superoxide to hydrogen peroxide, superoxide dismutase (SOD) is crucial in both intracellular signalling and regulation of oxidative stress. In this paper we report the cloning of a Cu/Zn SOD (designated as pfSOD) from the pearl oyster (Pinctada fucata) using rapid amplification of cDNA ends (RACE) PCR. The full-length cDNA of this Cu/Zn SOD contains an open reading frame (ORF) of 471 bp coding for 156 amino acids. No signal peptide was identified at the N-terminal amino acid sequence of Cu/Zn SOD indicating that this pfSOD encodes a cytoplasmic Cu/Zn SOD. This is supported by the presence of conserved amino acids required for binding copper and zinc. Semi-quantitative analysis in adult tissues showed that the pfSOD mRNA was abundantly expressed in haemocytes and gill and scarcely expressed in other tissues tested. After challenge with lipopolysaccharide (LPS), expression of pfSOD mRNA in haemocytes was increased, reaching the highest level at 8 h, then dropping to basal levels at 36 h. These results suggest that Cu/Zn SOD might be used as a bioindicator of the aquatic environmental pollution and cellular stress in pearl oyster.

Artemia, in all stages of its life cycle, is suitable food for most diversi¢ed groups of aquatic animals. Although its size at di¡erent stages restricts its use as a food for some groups of ¢sh, this problem can be overcome using selective breeding techniques. The formulation of any selective breeding programme calls for a proper understanding of the genetic architecture of the economically important traits of the population under study. Thus, heritability for certain important life history and reproductive traits was estimated in Artemia franciscana from the Great Salt Lake, Utah. In the present study, the sexwise heritability values for growth and reproduction traits were estimated using parent^o¡spring regression. The phenotypic parameters for the same traits are also recorded. The naupliar length was 487.072.0 and 490.671.8 mm for males and females, respectively, whereas the heritability values for naupliar length were 0.585170.2153 and 0.376670.1899 respectively. The length at 3 and 6 days of age were 1.8770.03 and 4.1070.08 mm, respectively, for males whereas1.8770.03 and 4.3070.08 mm, respectively, for females. The heritability values for length at 3 and 6 days of age for males were 0.327270.3651 and 0.496570.2466, respectively, whereas the respective values for the females were 0.116770.3841 and 0.022270.2971. The estimates of length at ¢rst brood, pre-reproductive period and number of o¡-spring in ¢rst brood were 10.0970.23 mm, 16.007 0.23 days and 53.5771.37 days, respectively, whereas the heritability values for respective traits were 0.040370. 1078, 0.323470.2874 and 0.340470.2202.

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Bidirectional mass selection for naupliar length was practised in Artemia franciscana from Great Salt Lake, UT, USA, with the aim of developing two divergent lines, namely small naupliar size (SNS) and bigger naupliar size (BNS). A random-bred control line was also maintained to quantify the environmental e¡ects. The mean naupliar length in the base population was 486.9972.11 mm in males and 490.5871.82 mm in females. Six generations of selection for smaller naupliar size in the SNS line resulted in a phenotypic response of^45.32 mm and^37.52 mm decreases in naupliar size in males and females respectively. In the BNS line, responses (increase in size) from ¢ve generations of selection for bigger size were 8.59 mm and 35.80 mm respectively. The cumulative genetic gain in males and females of the SNS were^41.72 mm and^38.76 mm compared with 12.64 mm and 39.48 mm, respectively, in the BNS line.

The performance of I and II meiotic triploids and control oysters (Crassostrea madrasensis) reared at Tuticorin Bay was compared to determine if the improvements in the growth of edible oysters were additive to faster growth in triploids. After a grow-out period of 12 months, both mean whole weights and shell heights were in order I meiotic triploid4II meiotic triploid4control. Mean whole weights and shell height of di¡erent oyster lines were all signi¢cantly di¡erent (Po0.05). On an average, larger morphological traits indicated that growth improvements from triploids were additive, and throughout the study triploid oysters maintained faster growth rate than their diploid siblings. Condition index and adductor muscle diameter of both triploids were higher than those of control.

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