Experimental Infection of River Catfish Mystus Nemurus with Vibrio Parahaemolyticus and Molecular Characterization of the Isolates

Declining marine fish resources in Malaysia have led to the innovation of rearing indigenous freshwater river catfish Mystus nemurus, locally known as 'baung' in brackishwater. This however will inevitably expose the fish to the pathogen, Vibrio parahaemolyticus that is ubiquitous in brackishwater. The present research was undertaken to study the virulence and pathogenicity of clinical and environmental V. parahaemolyticus isolates in M. nemurus. Vibrio parahaemolyticus isolates from various sources and locations in Peninsular Malaysia were identified based on morphological, biochemical and physiological characteristics. Virulence studies revealed that clinical V. parahaemolyticus from clinical cases were more virulent (p< 0.05) to M nemurus as compared to environmental isolates. The virulence was categorized as virulent, moderately virulent, weakly virulent and avirulent. The most virulent isolate (Fl) was used to infect fish via intraperitoneal (IP), intramuscular (IM) and immersion routes. The LD50 results revealed that IP exposure was most pathogenic, following by IM and immersion exposures. Intraperitoneal exposure caused toxemia in fish while 1M exposure caused localized lesions at the injection sites, and immersion exposure caused only mild inflammatory responses on the gills and the scraped skin. Random amplification polymorphic DNA (RAPD) revealed DNA polymorphism in all isolates tested, indicative of high variability among the V parahaemolyticus isolates. Dendrogram revealed a distant genetic relationship between the virulent (Fl) and avirulent (W4) isolates. Antibiogram showed resistance to intennediate to erythromycin, and 90% of the isolates were intennediate to cephalosporins and cefotaxim. The absence of plasmids in all isolates indicated that antimicrobial resistance of the isolates were chromosomally mediated. Partial sequence analysis of the toxR and toxS genes of isolates Fl and W4 revealed a very high homology (97%). The genetic variations of toxR fragment resulted in 59 to 77% amino acid homology. This might have contributed to the different degrees of virulence of the isolates. The toxS fragment showed lOO% amino acid homology, indicating that this fragment was more conserved than toxR gene fragment. It appeared that not all V. parahaemolyticus isolates could induce infection in M nemurus. However, slight genetic variations in toxR gene fragment of V parahaemolyticus isolates could contribute to different degree of virulence. Mystus nemurus was least susceptible to the immersion challenge of a virulent V. parahaemolyticus isolate

THE EFFECT OF MARINE SPONGE Aaptos aaptos EXTRACT IN VIBRIOSIS TREATMENT OF BLACK TIGER SHRIMP Penaeus monodon LARVAE

Black tiger shrimp Penaeus monodon post larvae were challenged with Vibrio harveyi and butanol extract of selected marine sponge Aaptos aaptos to determine its antibacterial bioactive potential in vibriosis treatment. Based on the preliminary toxicity study, the A. aaptos butanol extract with concentrations of 31.25, 62.5, and 125 mg/L were selected in the study. Black tiger shrimp post larvae were challenged with V. harveyi at 107 cfu/mL and immersed A. aaptos butanol extract with the concentration of 125 mg/L showed significantly in (P&lt;0.05) decrease mortality of the post larvae treated. Besides at this concentration, V. harveyi population in the rearing water and the post larvae treated decreased compared to control (untreated post larvae). Histological observation indicated that there was no changing on hepatopancreas of the black tiger shrimp post larvae. Based on this result, it is suggested that the butanol extract of A. aaptos is a potential bioactive compounds source in the treatment of vibriosis which may replaced the current antibiotics application

Quantitative Comparisons of Erythrocyte Morphology in Healthy Freshwater Fish Species from Malaysia

Abstract: Erythrocyte morphology of four freshwater fish species namely tilapia Oreochromis niloticus, Pangasius sutchi, catfish Clarias sp. and river catfish Mystus nemurus were studied. Variations of erythrocyte and nucleus size were observed among the fish species studied. The largest size of erythrocyte was observed in tilapia O.reochromis niloticus (60.79±3.00 µm ) and the smallest size of erythrocyte was observed in catfish 2 Clarias sp., (53.24±2.57 µm ) while the largest size of nucleus was also observed in O.reochromis 2 niloticus (12.18±0.70 µm ) yet smallest in P, sutchi, (9.37±0.97µm) . 2

IN VITRO ANTAGONISTIC ACTIVITIES OF INDONESIAN MARINE SPONGE AAPTOS AAPTOS AND CALLYSPONGIA PSEUDORETICULATA EXTRACTS AND THEIR TOXICITY AGAINST Vibrio spp.

Vibriosis is one of diseases which often results in mass mortality of Penaeus monodon larval rearing systems. It attacks shrimp of all stages in zoea, mysis and shrimp postlarva stage. This disease is caused by Vibrio spp, particularly Vibrio harveyi (a luminescent bacterium). Several kinds of antibiotics and chemical material have been used to overcome the disease but they have side effects to environment and human. The searching of bioactive compounds as an alternative treatment has been done for multi purposes. In this study diethyl eter, butanol and aqueous extract of Indonesian sponges Aaptos aaptos and Callyspongia pseudoreticulata were tested for in vitro activity against Vibrio spp. and Vibrio harveyi by using disc diffusion method. The result showed that all extracts of Aaptos aaptos gave a positive antibacterial activity towards those pathogenic bacteria. Meanwhile, only butanol extract of Callyspongia pseudoreticulata obtained to exhibit an antibacterial activity on those pathogenic bacteria. The strong anti-vibrio activity were shown by butanol and aqueous extract of Aaptos aaptos with the minimum inhibitory concentration (MIC) value of 0.313 and 0.625 mg/mL, respectively. Whilst, the butanol extract of Callyspongia pseudoreticulata indicated a low antibacterial activity with the MIC value of 10 mg/mL. Toxicity of those active extracts was evaluated by Brine Shrimp Lethality Test (BST). Interestingly, butanol and aqueous extracts of Aaptos aaptos did not show any toxic effect in Artemia salina larvae up to 8 x MIC (2.504 mg/mL and 5.000 mg/mL). It is the first report for the anti-vibr io activity of both Aaptos aaptos and Callyspongia pseudoreticulata. This results suggest that Aaptos aaptos has a potential to be used as a source of alternative compound to vibriosis prevention for mariculture

First detection of white spot syndrome virus (WSSV) in wild mud crab Scylla spp. (de Haan, 1883) from Setiu Wetlands, Malaysia

In this study, tissue samples from 90 wild mud crabs (Scylla spp. including S. olivacea, S. Tranquebarica, and S. paramamosain) were collected during pre-monsoon, monsoon, and post-monsoon in the Setiu Wetlands, Terengganu, Malaysia. The tissue samples were screened for the presence of white spot syndrome virus (WSSV) by PCR. This study was conducted to detect the presence or absence of WSSV in wild Scylla spp. from the Setiu Wetlands at different times of sampling. WSSV DNA was detected in 36% of the mud crabs. The DNA sequence of a 941 bp genome region amplified from a crab by PCR was identified to be most similar (99% nucleotide sequence, 98% amino acid sequence) to a WSSV strain detected in Mexico (KU216744.1) and Taiwan WSSV 419 strain (AY850066.1). The data indicated that mud crabs in the Setiu Wetlands might act as a WSSV reservoir of risk to shrimp aquaculture. Our findings are the first detection of WSSV from wild mud crabs, Scylla spp. in the Setiu Wetlands, Terengganu, Malaysia

Betanodavirus: dissection of the viral life cycle

Progressive research has been recently made in dissecting the molecular biology of Betanodavirus life cycle, the causative pathogen of viral encephalopathy and retinopathy in economic important marine fish species. Establishment of betanodavirus infectious clone allows the manipulation of virus genome for functional genomic study, which elucidates the biological event of the viral life cycle at molecular level. The betanodavirus strategizes its replication by expressing anti-apoptosis/antinecrotic proteins to maintain the cell viability during early infection. Subsequently utilizes and controls the biological machinery of the infected cells for viral genome replication. Towards the late phase of infection, mass production of capsid protein for virion assembly induces the activation of host apoptosis pathway. It eventually leads to the cell lysis and death, which the lysis of cell contributes to the accomplishment of viral shedding that completes a viral life cycle. The recent efforts to dissect the entire betanodavirus life cycle are currently reviewed

Risk factors associated with viral nervous necrosis in hybrid groupers in Malaysia and the high similarity of its causative agent nervous necrosis virus to reassortant red-spotted grouper nervous necrosis virus/striped jack nervous necrosis virus strains

Background and aim: Viral nervous necrosis (VNN) is a serious disease of several marine fish species. VNN causes 100% mortality in the larval stages, while lower losses have been reported in juvenile and adult fish. This study aimed to detect the occurrence of VNN while identifying its associated risk factors and the genotypes of its causative agent in a hybrid grouper hatchery in Malaysia. Materials and methods: A batch of newly hatched hybrid grouper fry (Epinephelus fuscoguttatus × Epinephelus lanceolatus) were followed from the larval stage to market size. Samples of the hybrid groupers, water, live feed, and artificial fish pellets were collected periodically from day 0 to 180 in the hybrid grouper hatchery. Reverse transcription-polymerase chain reaction (RT-PCR) and nested PCR amplifications were carried out on VNN-related sequences. The phylogenetic tree including the sampled causative agent of VNN was inferred from the coat protein genes from all known Betanodavirus species using Molecular Evolutionary Genetics Analysis (MEGA). Pearson's correlation coefficient values were calculated to determine the strength of the correlation between the presence of VNN in hybrid grouper samples and its associated risk factors. Results: A total of 113 out of 146 pooled and individual samples, including hybrid grouper, water, and artificial fish pellet samples, demonstrated positive results in tests for the presence of VNN-associated viruses. The clinical signs of infection observed in the samples included darkened skin, deformation of the backbone, abdominal distension, skin lesions, and fin erosion. VNN was present throughout the life stages of the hybrid groupers, with the first detection occurring at day 10. VNN-associated risk factors included water temperature, dissolved oxygen content, salinity, ammonia level, fish size (adults more at risk than younger stages), and life stage (age). Detection of VNN-associated viruses in water samples demonstrated evidence of horizontal transmission of the disease. All the nucleotide sequences found in this study had high nucleotide identities of 88% to 100% to each other, striped jack nervous necrosis virus (SJNNV), and the reassortant strain red-spotted grouper NNV/SJNNV (RGNNV/SJNNV) isolate 430.2004 (GenBank accession number JN189932.1) (n=26). The phylogenetic analysis showed that quasispecies was present in each VNN-causing virus-positive sample, which differed based on the type of sample and life stage. Conclusion: This study was the first to confirm the existence of a reassortant strain (RGNNV/SJNNV) in hybrid groupers from Malaysia and Southeast Asia. However, the association between the mode of transmission and the risk factors of this virus needs to be investigated further to understand the evolution and potential new host species of the reassortant strain

Exploring Postgraduate Students’ Perceptions of Negotiated Curriculum

AbstractThis study aimed to explore postgraduate students’ perceptions of negotiated curriculum. The statement of problem is whether rigid curriculum is still relevant to postgraduate students’ learning. As the postgraduates are adult learners, they are generally working, family, and have other commitments than typical undergraduate students. This in turn suggests for a negotiated curriculum. Boomer (1992:227) defines classrooms in which teachers invite and allow students to help construct the learning journey as “negotiating the curriculum”. Comparatively, “curriculum negotiation involves giving students a voice in the choice and development of learning opportunities: both the “what” and the “how” of curriculum” (Carr & Kemmis, 1986, p. 171). A total of 30 TESL postgraduate students in UiTM participated in this study. An adapted questionnaire was used to collect the relevant data. Findings revealed that the respondents were aware of the existence of negotiated curriculum. It was also discovered that the main factor for the implementation of negotiated curriculum was hectic schedules of the postgraduate students. The major implication of negotiated curriculum is that it helps postgraduate students in managing their time to study and gives positive effect towards their learning strategies. The findings from this study will benefit students and also instructors at the same time through the implementation of negotiated curriculum in the classroom

Cosmos caudatus as a dietary supplement for Bagrid Catfish, Mystus nemurus

The optimal level of Cosmos caudatus supplementation in fish formulation was conducted by using Mystus nemurus fingerlings in two initial sizes (3.05±0.39 g and 4.45±0.71 g). For Experiment 1, crude leaves incorporated were 0.00, 0.50, 1.50, and 2.00% with 60 days of feeding trial. For Experiment 2, the level of leave extract was 0.00, 0.01, 0.05, 0.10 and 0.20% with an experimental duration of 90 days. Both experiments showed significant differences (P<0.05) for growth performance and condition factor. The highest weight gain for Experiments 1 and 2 were 13.28±3.07 g and 18.51±4.21 g, respectively. There were no significant differences in the whole body content and survival rate for both experiments (P>0.05). The protein level was in the range of 15.70±0.79 to 16.74±1.90% (Experiment 1) and 14.96±1.90 to 15.67±0.55% (Experiment 2). The optimal level of crude leaves and extracts was considered at 0.50% and 0.05%, respectively, for M. nemurus fingerlings