This study was designed to elucidate the effects of arsenic (As) on the morpho-behavior, growth development and molecular mechanisms of a commercially important fish, rohu carp, Labeo rohita, in Bangladesh. Fish fry with an average weight of 387.5 ± 169.25 mg and an average length of 3.35 ± 0.37 cm were collected from a local hatchery in Mymensingh, Bangladesh and acclimatized for a week in the Department of Fisheries, University of Dhaka before starting the exposure with arsenic. Fishes were exposed for a period of 14 days with three treatments of NaAsO₂, namely treatment 1(T1)—2.5 mg/L; treatment 2 (T2)—15 mg/L; and treatment 3 (T3)—30 mg/L, along with a control (C)—0.0 mg/L, with three replicates. These concentrations were determined based on the LC₅₀ value for 96 h measured for this experiment. This study revealed remarkable morphological abnormalities and deformities in arsenic-exposed rohu carp. In fish exposed to 30 mg/L, caudal fin erosion was a frequent deformity. There was no significant difference in RNA:DNA ratio among the treatments. The overall weight of fish was decreased as the concentration of arsenic was increased. The T3 fish had a statistically significant negative weight gain (−0.05 ± 0.07 g), but the other treatments (T1 and T2) and control fish had no significant weight gain. Different types of histopathological changes were observed in the gills and intestines of arsenic-treated fish. Necrosis and severe damages were found in the secondary lamellae of gills at the highest arsenic concentration (30 mg/L). Epithelial lifting, irregular shape and damages in the gill raker were also observed in the primary lamellae of the gills for the same treatment. In this study, the expression of heat shock protein (HSP 60) and metallothionein (MT) genes was assessed by qPCR, and these genes were upregulated in different treatments compared to controls. The findings of the present study suggest that arsenic pollution significantly changes the morphology, behavior, growth, development, histopathology and molecular mechanisms of this economically important fish, rohu carp, in Bangladesh.

An experiment was carried out to find the salinity tolerance capability and growth performance of Climbing Perch, Anabas testudineus (Bloch, 1795). Anabas testudineus commonly cultured fish in Bangladesh was reared in laboratory conditions at different salinities of 0, 3, 6, 9, 12, 15, 18 and 21‰ for 60 days. Hundred per cent survivals were detected at 0, 3, 6 and 9‰ salinity while 100% mortality was recorded at 18 and 21‰ salinity. Various responses to threat and feeding were observed among the fish in different treatments. Lowest feed conversion ratio was found in the control group while the highest was detected at 15‰ salinity. On the other hand, decreasing trend of specific growth and average growth rate were observed in A. testudineus fingerlings from 0 to 15‰ salinity. Significantly higher specific growth rate and average growth rate were detected in A. testudineus fingerlings reared at 0 - 6‰ salinity (p < 0.05). The present study suggests that Climbing Perch fingerlings can be reared at fresh water growth rates in coastal water with salinity up to 6‰.Dhaka Univ. J. Biol. Sci. 25(1): 65-73, 2016

The present study was carried out to investigate the bacterial flora of mud crab (Scylla olivacea) meat collected from the five markets of Dhaka city. Faecal Coliform, Salmonella sp. and Shigella sp., E. coil, and Vibrio spp. were detected in most of the samples except the frozen ones from Agora super shop. The samples from Basabo and Karwan bazar had higher bacterial load than the others. The highest TBC counts were observed in the samples from Karwan bazar (38.1 ± 1.20 x 10⁴cfu/g) and the lowest were from Agora super shop (4.48 ± 0.26 x10⁴cfu/g). The total Vibrio spp. counts were found only in two markets, i.e. from Farmgate and Basabo. The total E. coli counts ranged from 1.25 ± 0.02 x 10⁴cfu/g to 4.33 ± 0.56 x 10⁴cfu/g. The Salmonella and Shigella counts varied between3.95 ± 0.28 x 10⁴cfu/g for Karwan bazaar and 16.76 ± 1.26 x 10⁴cfu/g for Basabo. Total Staphylococcus spp. counts ranged between 14.4 ± 1.1 x 10⁴cfu/g and 20.01± 1.94 x 10⁴cfu/g for normal crab samples and 0.37 ± 0.025 x 10⁴cfu/g for frozen samples. The results of this study showed that the bacterial load was significantly higher in live crab than the frozen crab indicating that later are safe for human consumption. Bangladesh J. Zool. 43(1): 55-62, 2015