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Asian red-tailed catfish (Hemibagrus wyckioides) were raised at five different stocking densities in cages (submerged and with a volume of 1 m 3 ) suspended in a fish pond from July to August 2012. H. wyckioides fries (mean weight 0.8 ± 0.1 g) were stocked at densities of 25, 50, 100, 200, and 400 fish/m 3 . At the end of 56 days, the mean fish weights among the stocking densities of 25 and 50 fish/m 3 were significantly lower than those of the 100, 200, and 400 fish/m 3 density. The specific growth rates and final mean weights amongst fish reared in higher stocking densities of 100, 200, and 200 fish/m 3 were higher than those of the low stocking densities of 25 and 50 fish/m 3 . Asian river catfish performed poorly at the lowest density. The results indicate an initial lower stocking threshold for Asian red-tailed catfish fries of above 100 fish/m 3 . The Asian red-tailed catfish fries reared in small cages placed in a pond reached the size 5-6.6 g within a 56-day nursing period.

The complete cDNA sequence of the Nile tilapia T-cell receptor (TCR) β chain was cloned using 5' RACE. The full-length, 1263-bp cDNA contained a 942-bp open reading frame (ORF) encoding a 314-amino-acid protein. Sequence analyses revealed that the Nile tilapia TCR β chain contains four conserved cysteine residues involved in the formation of disulphide bridges and a conserved amino acid motif believed to be important for assembly and signalling of the TCR αβ/CD3 complex, both of which are normally found in the TCR β chain of other vertebrates. As detected using semi-quantitative and quantitative RT-PCR, the highest expression level of TCR β was detected in the thymus. Interestingly, Streptococcus agalactiae significantly induced the up-regulation of the TCR β chain, and the strongest up-regulation was detected in the brain and peripheral blood leucocytes (PBLs). In in vitro experiments, concanavalin A and Aeromonas hydrophila were found to significantly increase the expression of the TCR β chain in PBLs after 48 h (P< 0.01) and 72 h (P < 0.05), respectively. Furthermore, real-time PCR analysis showed that intraperitoneal injection (IP) of 10(7) cfu mL(-1) of S. agalactiae could induce TCR β expression that was greater than the expression observed following administration of 10(9) cfu mL(-1). The presence of the TCR β chain in fish detected in this study suggests the presence of T-cell populations that have been found in higher vertebrates, which may play a crucial functional role in the response to fish pathogens.

Summary Karyological characteristics of the Barramundi, Lates calcarifer (Bloch 1790) from Andaman Sea, Thailand, were analyzed in the present study. Kidney cells of two male and two female fish were directly used in the mitotic chromosome preparation. The mitotic chromosome preparations were conducted directly from kidney cells. Chromosomes were stained by using conventional staining and Ag-NOR banding techniques. The results showed that the diploid chromosomes number of L. calcarifer was 2n=48 and the fundamental number (NF) were 54 in both sexes. The chromosome types comprise the 2 large metacentric, 2 large submetacentric, 2 large acrocentric, 24 large telocentric, and 18 medium telocentric chromosomes. No strange sized chromosomes related to sex were observed. The Ag-NOR banding technique indicated that the single pair of nucleolar organizer regions/NORs is located on the short arm telomeric region of large acrocentric chromosome pair 3. The karyotype formula could be deduced as:2n (

Summary Karyological analysis of the rice frog (Fejervarya limnocharis) from Northeast Thailand was conducted. Frog chromosome preparations were obtained by the squash technique from bone marrow and testis. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosome with Giemsa s solution. The results showed that the number of diploid chromosome is 2n = 26, while the fundamental number (NF) is 52 in both males and females. The types of autosome were 4 large metacentric, 6 large submetacentric, 8 small metacentric, 4 small submetacentric and 2 small acrocentric chromosomes. The present study also revealed that the sex chromosome system of F. limnocharis was XY, in which the X and Y were classified as small metacentric and small submetacentric chromosomes, respectively. Nucleolar organizer regions (NORs) are located at the secondary constriction of the short arm near the centromere in submetacentric chromosome pair 6. We found that during metaphase I the homologous chromosomes showed synapsis, which can be defined as the 13 ring bivalents and 13 haploid chromosomes at metaphase II as diploid species. The karyotype formula is as follows: 2n (26) = L 4 m +L 6 sm +S 8 m +S 4 sm +S a 2 +sex-chromosomes (XY)