The study was conducted to know the diversity of coral associated fishes of the Saint Martin Island from December 2017 to April 2019. A total of 46 coral associated marine fish species were recorded, among them 12 species; sunajtuLiughcliug , Lutjanus russellii, Parupeneus indicus, Siganus sutor, Thalassoma lunare, Gazza achlamys, Pomadasys andamanensis, Pomadasys kaakan, Lethrinus crocineus, Argyrosomus regius, Istigobius ornatus and Cryptocentrus cyanotaenia under six family were newly recorded from this Island. We assume that there are more species to be explored and need proper management strategy for conservation of coral reef and its associated biodiversity.
Bangladesh J. Zool. 48(2): 253-262, 2020
This study represents the comprehensive molecular identification of freshwater fishes of Bangladesh based on a fragment of the cytochrome c oxidase subunit I (COI) gene in the mitochondrial genome. A total of 315 mitochondrial COI barcode sequences were obtained from 153 species,114 genera, 49 families and 16 orders of fishes. The mean length of the sequences was 652 base pairs. For all the samples, %G was significantly lower compared to the other nucleotides and %GC was lower compared to %AT (p-value ˂ 0.05). Also, a significantly lower %GC content was observed in second and third codon position compared to the first one in all the samples (1st>2nd>3rd, p-value˂ 0.05). The average K2P distances within species, genera, families and orders were 0.38%, 7.02%, 12.75% and 18.68%, respectively. The mean interspecific distance was 18-fold higher than the mean intraspecific distance. The K2P neighbor-joining (NJ) trees based on the sequences generally clustered species according to their taxonomic position. A total of 12 species were newly recorded in Bangladesh. High efficiency in species identification were demonstrated in the present study by DNA barcoding, and concluded that COI sequencing can be used as an authentic identification marker for freshwater fish species.
Bangladesh J. Zool. 48(1): 1-19, 2020
Abstract:The effects of toxic Microcystis aeruginosa on the liver of Nile tilapia, Oreochromis niloticus were investigated in the laboratory. Four treatments were setup into aquariums for 15 days to investigate the histopathological changes exposed to Microcystis aeruginosa bloom. Fishes of treatment A1 were treated as a control group and given artificial feed. In the three treatments (A2, A3 and A4), the M. aeruginosa cell concentration were 35 × 10 2 , 72 × 10 2 , 149 × 10 2 colony/ml, respectively. In the control group, no histopathological change was observed. In exposed fish, histopathological alterations were characterized by swollen and granular cytoplasm, vascular proliferation, bile stasis, fatty change and focal necrosis. Histopathological changes were observed within five days of exposure when fish exposed to moderate (72 × 10 2 colony/ml) to high (149 × 10 2 colony/ml) bloom concentration, whereas it took 15 days in lower concentration (35 × 10 2 colony/ml). Histopathological changes proved that intake of toxic M. aeruginosa bloom by aquatic animals, particularly Nile tilapia has significant effects on its internal organs that may cause of massive mortality. Accordingly, cyanotoxin accumulation in fish tissue my pose a risk to human health through the food chain.
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