Siltation in Zoo Negara Lake

In a study of Zoo Negara Lake, it was found that the turbidity and total residues were higher in the lake than in the upstream station where there is no effect of soil erosion. The immediate results of massive flows of erosion silt were the change of water colour and reduction in the depth of the lake. Effects of siltation such as the reduction in light penetration and aquatic organisms are discussed

Protein identification of vitellogenin in river catfish (Hemibagrus nemurus)

Mass production of fish broodstock with high quality eggs requires the knowledge on the chemical composition and physiochemical properties of vitellogenin (Vtg) during ovulation. Vtg is an egg yolk precursor phospholipoglycoprotein, and has been analysed to evaluate the reproductive conditions and determine the spawning period in captive and wild fish. In this study, Vtg was induced in male H. nemurus through three intramuscular injections of 17- estradiol (E2). The Vtg was purified from the serum using gel filtration chromatography and thepurified protein was reduced via SDS-PAGE. One major polypeptide corresponding to 130 kDa was observed. Vtg identification was done using peptide mass fingerprint (PMF) from the trypsin digestion of male H. nemurus Vtg induced with E2. The sequence homology of H. nemurus AYLAGAAADVLEVGVR matched the Vtg of other fish species when analysedusing MALDI-TOF. Vtg was confirmed by MASCOT at 95% significant level. The potential protein that controls the reproductive process and oocyte development isolated from this study was discussed to understand the structure and function of Vtg

Intraspecific polymorphism in mystus nemurus (C&V) detected by RAPD-PCR fingerprinting

Yellow catfish, Mystus nemurus (C&V), is becoming one of the majorfreshwater species farmed l7y aquaculturists in Southeast Asia. It was of interest to examine levels of genetic sub-population differentiation among samples of this species obtained from parts of its range, as well as to compare the genetics of wild and hatchery-bred fish. The genetic aspects of variation in the fish, which were collected from eight wild populations throughout Thailand and a hatchery stock, were determined at molecular (DNA) level using the technique ofRAPD-PCRfingerprinting. Five arbitrary primers namely OPA-11, OPA-14, OPA-18, OPA-19 and OPA-20 were chosen to amplify products, which showed 28 polymorphic loci in 9 populations. The highest genetic distance (D) was found between Chainat and Suratthani populations with the value of 0.289, while the lowest was found in Songkhla population and hatchery stock with the value of 0.087. The dendrogram depicts the genetic relationship among populations of M. nemurus, which are grouped into four clusters according to their regional areas

The effects of dietary supplements of polyunsaturated fatty acid on pearl oyster, Pinctada margaritifera L., gonad composition and reproductive output

Black-lip pearl oyster, Pinctada margaritifera broodstock was collected from the wild. Egg production, hatching rate and larval development were compared between oysters induced to spawn within 2 days after collection in the wild (T1), oysters fed a pure microalgae diet during 24 days before spawning (T2) and oysters fed the same microalgal diet in which 10% of the algae were replaced with 2 μm polyunsaturated fatty acid (PUFA)-rich microspheres (T3). Administration of lipid microspheres resulted in larger sized eggs, a higher percentage of D-larvae and larger sized 48-h-old larvae (P0.05). The gonads of oysters fed supplementary PUFA contained more docosahexaenoic acid (DHA) and less monounsaturated fatty acids. Higher level of DHA in gonads of T3 was associated with oogenesis and embryogenesis success. The n-3/n-6 ratio in the neutral lipid fraction provides a good indication of the spawning condition and predicting egg size and hatching rate

Population Characterization of Planktonic Shrimp, Acetes japonicus (Decapoda: Sergestidae) using RAPD Technique

Genomic DNA of sergestid shrimp, Acetes japonicus was successfully extracted by using the Promega Wizard Genomic DNA Purification Kit. Population genetic characterization of A. japonicus along the western coast of Peninsular Malaysia (state of Perak, Malacca and Kedah) was examined using the Random Amplified Polymorphic DNA (RAPD) marker. Twenty oligonucleotides from operon A kit were used to screen the populations, of which 6 were able to be amplified (OPA03, OPA04, OPA07, OPA09, OPA10, OPA16). The percentages of polymorphic bands of the three populations investigated varied from 57.77 to 87.77%. Genetic distances between populations and cluster analysis from UPGMA grouped the populations into two major clusters. The Perak and Malacca populations were in one cluster, while the Kedah population was clustered by itself, indicating a different population. The genetic distance was highest as 0.0999 for the Kedah and the Malacca populations while lowest value was 0.0413 for the Perak and the Malacca populations, which probably have a closed ancestral relationship. The results of this study suggested that RAPD analysis, if carried out carefully and accurately would give a good indication of the separation between individuals of different populations and is suitable for identification of closely related genotypes

Association of annual hormonal profile with gonad maturity of mahseer (Tor tambroides) in captivity.

Annual gonad hormonal profile of wild, matured mahseer (29 males and 23 female) averaging in weight between 0.95 ± 0.26 and 1.19 ± 0.23 kg for males and females, respectively, were investigated from November 2007 to November 2008 using enzyme-linked immunosorbent assay (ELISA) technique. Blood was collected from caudal vein, monthly and plasma separation by centrifugation was done to measure reproductive hormones: 17β-estradiol (E2), testosterone (T), and 11-keto-testosterone (11KT). Gonads were sampled for histology processing to observe their maturity. Highest T level in females and males was recorded at 0.22 ± 0.016 and 0.88 ± 0.014 ng/ml, respectively. The 11KT showed several peaks and the highest value was noted at 0.7 ± 0.018 ng/ml in November 2008. The female E2 initially was at 1.48 ± 0.16 ng/ml and significantly increased (P < 0.05) to 1.53 ± 0.39 ng/ml in November 2008. Ovaries were laden with oocytes in several stages in all the samples while testes gonad showed a high level of spermatids throughout the year. Changes in plasma level of the gonadal hormones were correlated with the ovarian and testes maturities. In conclusion, the study suggests that mahseer can be categorized as asynchronized and multiple spawner. The information gathered is important for appropriate breeding and conservation programs of the Malaysian mahseer

Ovarian Development of a river catfish Hemibagrus nemurus (Valenciennes, 1840) in captivity.

Hemibagrus nemurus is a riverine catfish with high economic and nutritive values. Investigations on ovarian development of this fish were carried out to determine the mode of ovarian development and describe the oocyte developmental stages. Histological studies were done on ovaries using light microscopy and scanning electron microscopy. Fish were sampled monthly for a period of six months (August 2009 to January 2010). The mean oocyte diameter (OD) ranged from 871 ± 161.41 µm to 1,167 ± 26.77 µm and the highest OD was in November. Oocyte size-frequency distribution showed a polymodal distribution. The mean gonadosomatic index (GSI) ranged from 1.14 ± 0.87% to 7.06 ± 1.40% and highest GSI was in November. The ovaries exhibited three phases of oocyte growth, which were primary growth, secondary growth and maturation phases. Based on histological criteria, the oocyte developmental stages were divided into seven stages as chromatin nucleolar, early perinucleolar, late perinucleolar, cortical alveolar, vitellogenesis, mature oocyte and germinal vesicle migration stages. All the seven stages of oocyte development were observed in the ovaries. Oogonia were always present throughout the developmental stages. The ovaries had more than two stages of oocyte development. This is the first report on the mode of ovarian development of H. nemurus. These findings indicated that H. nemurus has asynchronous mode of ovarian development and is capable of spawning several times in a year under favourable conditions

Embryonic and larval development of river catfish Hemibagrus nemurus (Valenciennes, 1840).

The aim of this study was to characterize embryonic and larval developmental stages of the river catfish, Hemibagrus nemurus. Fertilized eggs were spherical, adhesive and demersal with a mean egg diameter of 1.5±0.3 mm. Seven embryonic periods were characterized for timing and features: zygote, cleavage, blastula, gastrula, segmentation, pharyngula and hatching. Mean hatch was 23±1 h post fertilization at 27°C. The newly hatched larvae measured 3.0±0.2 mm in total length. Morphogenesis was completed in a day. The yolk sac was completely absorbed in three days. H. nemurus has a short embryonic developmental period in comparison with other catfish species. The information obtained from this study will be useful for egg incubation and larval rearing during the culture of H. nemurus