This report documents an emerging trend of identification of Megalocytivirus-like inclusions in a range of ornamental fish species intercepted during quarantine detention at the Australian border. From September 2012 to February 2013, 5 species of fish that had suffered mortality levels in excess of 25% whilst in the post-entry quarantine and had Megalocytivirus-like inclusion bodies in histological sections were examined by PCR. The fish had been imported from Singapore, Malaysia and Sri Lanka. Ninety-seven of 111 individual fish from affected tanks of fish tested were positive for the presence of Megalocytivirus by PCR. Sequence analysis of representative PCR products revealed an identical sequence of 621 bp in all cases which was identical to a previously characterized Megalocytivirus (Sabah/RAA1/2012 strain BMGIV48). Phylogenetic analysis of available Megalocytivirus major capsid protein (MCP) sequences confirmed the existence of 3 major clades of Megalocytivirus. The virus detected in this study was identified as a member of Genotype II. The broad host range and pathogenicity of megalocytiviruses, coupled to the documented spread of ornamental fish into the environment, render this a significant and emerging biosecurity threat to Australia.
Nucleotide sequences of a partial cytochrome c oxidase subunit I gene were used to assess the manner in which historical processes and geomorphological effects may have influenced genetic structuring and phylogeographic patterns in Channa striata. Assaying was based on individuals from twelve populations in four river systems, which were separated into two regions, the eastern and western, of the biodiversely rich state of Perak in central Peninsular Malaysia. In 238 specimens, a total of 368-bp sequences with ten polymorphic sites and eleven unique haplotypes were detected. Data on all the twelve populations revealed incomplete divergence due to past historical coalescence and the short period of separation. Nevertheless, SAMOVA and F(ST) revealed geographical structuring existed to a certain extent in both regions. For the eastern region, the data also showed that the upstream populations were genetically significantly different compared to the mid- and downstream ones. It is inferred that physical barriers and historical processes played a dominant role in structuring the genetic dispersal of the species. A further inference is that the Grik, Tanjung Rambutan and Sungkai are potential candidates for conservation and aquaculture programmes since they contained most of the total diversity in this area.
Seven polymorphic microsatellite loci were isolated and characterized for the snakehead murrel, Channa striata (Channidae), a valuable tropical freshwater fish species. Among 25 specimens collected from Kedah state in Malaysia, the number of alleles per locus ranged from 2 to 7. Observed and expected heterozygosities ranged from 0.120 to 0.880 and 0.117 to 0.698, respectively. A single locus (CS1-C07) was significantly deviated from Hardy-Weinberg equilibrium after Bonferroni correction. These novel markers would be useful for population genetic studies of the C. striata.
The optimization of protein content in earthworm-based fish feed formulation was investigated in the study. Full factorial design (FFD) and central composite design (CCD) were used as a statistical tool to screen the range of the selected parameters and to optimize the process, respectively. Three components were combined in the fish feed formulation
namely earthworm powder, chicken guts and soybean waste as the protein source. The optimum nutritional values were obtained at 25%, 25% and 5.95% for earthworm powder, soybean waste and chicken guts, respectively, to give an optimum protein content of 35.97%. Formulation of fish feed from earthworm powder can be an alternative in aquaculture industry in the near future.
This paper reports the findings of the ongoing studies on cryopreservation of the snakehead, Channa striata embryos. The specific objective of this study was to collect data on the sensitivity of C. striata embryo hatching rate to low temperatures at two different developmental stages in the presence of four different cryoprotectants. Embryos at morula and heartbeat stages were selected and incubated in 1M dimethyl sulfoxide (Me2SO), 1M ethylene glycol (EG), 1M methanol (MeOH) and 0.1M sucrose solutions at different temperatures for a period of time. Embryos were kept at 24 °C (control), 15 °C, 4 °C and -2 °C for 5 min, 1h and 3h. Following these treatments, the embryos were then transferred into a 24 °C water bath until hatch to evaluate the hatching rate. The results showed that there was a significant decrease of hatching rate in both developmental stages following exposure to 4 °C and -2 °C at 1h and 3h exposure in each treatment. Heartbeat stage was more tolerant against chilling at -2 °C for 3h exposure in Me2SO followed by MeOH, sucrose and EG. Further studies will be conducted to find the best method to preserve embryos for long term storage.
A phylogeographic study of an economically important freshwater fish, the striped snakehead, Channa striata in Sundaland was carried out using data from mtDNA ND5 gene target to elucidate genetic patterning. Templates obtained from a total of 280 individuals representing 24 sampling sites revealed 27 putative haplotypes. Three distinct genetic lineages were apparent; 1)northwest Peninsular Malaysia, 2)southern Peninsular, east Peninsular, Sumatra and SW (western Sarawak) and 3) central west Peninsular and Malaysian Borneo (except SW). Genetic structuring between lineages showed a significant signature of natural geographical barriers that have been acting as effective dividers between these populations. However, genetic propinquity between the SW and southern Peninsular and east Peninsular Malaysia populations was taken as evidence of ancient river connectivity between these regions during the Pleistocene epoch. Alternatively, close genetic relationship between central west Peninsular Malaysia and Malaysian Borneo populations implied anthropogenic activities. Further, haplotype sharing between the east Peninsular Malaysia and Sumatra populations revealed extraordinary migration ability of C. striata (>500 km) through ancient connectivity. These results provide interesting insights into the historical and contemporary landscape arrangement in shaping genetic patterns of freshwater species in Sundaland.
Aquaculture is a growing industry with a great potential towards the contribution of the country’s total
fish requirement. Serious efforts have been done to develop and improve the production of fish by rearing high value fish in tanks or ponds. Under the Third National Agricultural Policy (1998-2010), the target is to annually produce 1.93 million tonnes of fish worth approximately RM8.3 billion by the year 2010. Consequently, the development of an automatic fish feeding machine can be very beneficial to the growth of the aquaculture industry. This device was developed to overcome labour problems in the industry and introduce a semi-automatic process in the aquaculture industry. It has the ability to dispense dried fish food in various forms such as pellets, sticks, tablets or granules into fish tanks or ponds in a controlled manner for a stipulated time. The automatic fish feeder is controlled by a digital timer and it is capable of feeding the fish in accordance with a pre-determined time schedule without the presence of an operator, and at a feeding rate of 250g/min. The feeder can be adjusted to the desired height and conveniently moved around to be positioned adjacent to the pond or tank. Meanwhile, its hopper can be covered and easily dissembled to change the size of the hopper to accommodate different capacities of feed. This automatic fish feeder can be implemented in aquaculture system to convenience to fish culturists.
The aims of this study were to investigate (1) platelet phospholipid (PL) polyunsaturated fatty acid (PUFA) composition in subjects who were the Melbourne Chinese migrants, compared with those who were the Melbourne Caucasians and (2) the relationship between platelet PL PUFA and intake of fish, meat and PUFA.
The combtooth blenny (Blenniidae) genus Omobranchus contains small, cryptobenthic fishes common to nearshore habitats throughout the Indo-West Pacific. Recent molecular systematic studies have resolved Omobranchus as monophyletic but little research has been done to resolve species-level relationships. Herein, phylogenetic analyses of one mitochondrial (CO1) and four nuclear (ENC1, myh6, sreb2, and tbr1) genes provide evidence for the monophyly of Omobranchus and support for the elongatus and banditus species group. Sampling of multiple individuals from widespread species (O. ferox, O. punctatus, and O. elongatus) suggested that the Thai-Malay Peninsula is a phylogeographic break that may be a historic barrier to gene flow. Additionally, common meristics and other morphological characters are used to describe an early life history stage of O. ferox and O. punctatus.
Fish are a major source of beneficial n-3 LC-PUFA in human diet, and there is considerable interest to elucidate the mechanism and regulatory aspects of LC-PUFA biosynthesis in farmed species. Long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis involves the activities of two groups of enzymes, the fatty acyl desaturase (Fads) and elongase of very long-chain fatty acid (Elovl). The promoters of elovl5 elongase, which catalyses the rate-limiting reaction of elongating polyunsaturated fatty acid (PUFA), have been previously described and characterized from several marine and diadromous teleost species. We report here the cloning and characterization of elovl5 promoter from two freshwater fish species, the carnivorous snakehead fish (Channa striata) and zebrafish. Results show the presence of sterol-responsive elements (SRE) in the core regulatory region of both promoters, suggesting the importance of sterol regulatory element-binding protein (Srebp) in the regulation of elovl5 for both species. Mutagenesis luciferase and electrophoretic mobility shift assays further validate the role of SRE for basal transcriptional activation. In addition, several Sp1-binding sites located in close proximity with SRE were present in the snakehead promoter, with one having a potential synergy with SRE in the regulation of elovl5 expression. The core zebrafish elovl5 promoter fragment also directed in vivo expression in the yolk syncytial layer of developing zebrafish embryos.
The present study, aimed at observing the total concentration of mercury (Hg) in edible finfish species with an implication to human health risk, was carried out from the Setiu mangrove wetlands on the east coast of Peninsular Malaysia. Out of 20 species observed, the highest Hg concentrations were found among carnivores-fish/invertebrate-feeders, followed by omnivores and carnivores-invertebrate-feeders, while the lowest concentrations in herbivores. The Hg concentrations varied widely with fish species and body size, from 0.12 to 2.10 mg/kg dry weight. A positive relationship between body weight and Hg concentration was observed in particular for Toxotes jaculatrix and Tetraodon nigroviridis. Besides the permissible range of Hg concentration up to 0.3 mg/kg (cf. United States Environmental Protection Agency (USEPA)) in majority of species, the carnivore feeders such as Acanthopagrus pacificus, Gerres filamentosus, and Caranx ignobilis have shown excess amounts (> 0.40 mg/kg flesh weight) that raising concerns over the consumption by local people. However, the weekly intake of mercury-estimated through the fish consumption in all three trophic levels-suggests that the present Hg concentrations are still within the range of Provisional Tolerable Weekly Intake (PTWI) reported by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Perhaps, a multi-species design for Hg monitoring at Setiu wetlands would be able to provide further insights into the level of toxicity transfer among other aquatic organisms and thereby a strong health risk assessment for the local communities.
Myxosporeans are known from aquatic annelids but parasitism of platyhelminths by myxosporeans has not been widely reported. Hyperparasitism of gill monogeneans by Myxidium giardi has been reported from the European eel and Myxidium-like hyperparasites have also been observed during studies of gill monogeneans from Malaysia and Japan.The present study aimed to collect new hyperparasite material from Malaysia for morphological and molecular descriptions. In addition, PCR screening of host fish was undertaken to determine whether they are also hosts for the myxosporean.
Epidemiological studies have been conducted to determine the association between fish and disease. The fish were obtained from rivers, streams, ponds and lakes but few from aquaculture farms. While no defined studies have been carried out in Malaysia, baseline data show that fish obtained from aquaculture farms (mixed farming) contributed to cases of opisthorchiasis and clonorchiasis.
Channa striatus, a fresh water snakehead fish, is reported to enhance dermal wound healing. Biochemical components such as amino acids and fatty acids are important for the synthesis of collagen fibers during wound healing. Arachidonic acid, a precursor of prostaglandin plays a vital role in healing the wounds. Haruan (C. striatus) contains all the essential amino acids for wound healing particularly glycine as well as high contents of arachidonic acid and polyunsaturated fatty acids that can promote prostaglandin synthesis. In the present work we have studied the wound healing effect of C. striatus in Sprague-Dawley rats. Cream formulations having different haruan fish extract concentrations as the active ingredient were prepared and stabilized, and they were applied to the wounds. The healing of wounds was characterized by an increase in the tensile strength of the skin, determined on the 7th post-operative day in each case. Haruan treatment of wounds promotes remodeling of collagen, by the synthesis of inter- and intra-molecular protein crosslinking and thus produces a marked increase (P<0.05) in tensile strength as compared to the cetrimide treated group. On the basis of our experiment we conclude that C. striatus helps in wound healing as indicated by the increase in tensile strength. We hypothesise that this effect may be due to its high content of arachidonic acid, glycine and polyunsaturated fatty acids. The mechanism of wound healing will be investigated in future studies.
Asian arowana, Scleropages formosus is a highly valued aquarium fish in the world, particularly in Asian countries, and has been listed as one of the most highly endangered species. This is a freshwater, carnivorous, fairly large mouth breeding fish belonging to the family Osteoglossidae. Arowana can be found in different colour varieties such as green, red, silver and golden. Among these varieties, Malaysian golden is the most valuable fish and is endemic to the Krian riverine system, Malaysia. However, overexploitation, habitat change and pollution have caused a serious decline of this arowana variety. Recently, arowana aquaculture industry is expanding rapidly in Southeast Asian countries. However, difficulties in an accurate differentiation of sex and strains, causing imbalanced stocking ratios for optimum spawning, remain major obstacles in maximizing arowana production. In addition, problems in sustainable water sources of suitable quality and prevention of diseases need to be addressed. Recirculating aquaculture system (RAS) and bioremediation are two possible technologies that could be used to minimize pollution and ensure adequate high-quality water for arowana culture. In addition, the application of appropriate molecular markers for sex and strain identification is also an important strategy required for the improvement of captive breeding. This review discusses several issues such as the importance of arowana as an aquarium fish, its market demand, current problems in the arowana aquaculture industry and the possible technologies to enhance reproductive capacity and increase culture production. ?
Epizootic ulcerative syndrome (EUS) causes by aquatic oomycete fungus, Aphanomyces invadans is a dangerous fish disease of a wide range of fresh and brackish water, wild and farmed fish throughout the world. The objective of the present study was to determine the susceptibility of a number of tropical fish species to the EUS and compare the severity of infection between experimental groups.
The caligid parasite Caligus coryphaenae has been reported in several marine fishes from Japan. In this study, a total of 223 wild yellowtail (Seriola quinqueradiata) were collected from Kagoshima fish market, separated into three groups according to total length (TL 70 cm), and examined for C. coryphaenae infection. A total of 518 specimens of C. coryphaenae were isolated giving an overall prevalence of infection and mean intensity of 24.2% and 4.7 ± 3.5, respectively. Body surface, fins and operculum of hosts TL > 50 cm were recorded as preferred sites for the attachment of C. coryphaenae. Of female specimens, 56.7% bore egg strings with various egg string lengths (7.1 ± 1.2 mm), carrying from 98 to 140 eggs (0.06 ± 0.005 mm in length) per each string. To our knowledge, this is the first report of C. coryphaenae infection from wild yellowtail in Japanese waters and globally. This parasite has not been reported in yellowtail culture to date, but the finding on wild specimens of yellowtail means that it poses a risk to their culture.
Adult Carukia barnesi medusae feed predominantly on larval fish; however, their mode of prey capture seems more complex than previously described. Our findings revealed that during light conditions, this species extends its tentacles and 'twitches' them frequently. This highlights the lure-like nematocyst clusters in the water column, which actively attract larval fish that are consequently stung and consumed. This fishing behavior was not observed during dark conditions, presumably to reduce energy expenditure when they are not luring visually oriented prey. We found that larger medusae have longer tentacles; however, the spacing between the nematocyst clusters is not dependent on size, suggesting that the spacing of the nematocyst clusters is important for prey capture. Additionally, larger specimens twitch their tentacles more frequently than small specimens, which correlate with their recent ontogenetic prey shift from plankton to larval fish. These results indicate that adult medusae of C. barnesi are not opportunistically grazing in the water column, but instead utilize sophisticated prey capture techniques to specifically target larval fish.
Mariculture in Southeast Asia began in the 1970s and expanded rapidly during the 1980s, with the commercial hatchery production of the seabass Lates calcarifer. Other important cultured species were Epinephelus coioides, Epinephelus malabaricus, Lutjanus johni, and Lutjanus argentimaculatus. Intensification in the polyculture of these species and the large-scale international movement of fingerlings or juveniles, as well as the rapid expansion and concentration of fish farms, have caused severe problems resulting from parasitic infections. Infections in maricultured fish are predominantly caused by monoxenous parasites, in particular the capsalid and diplectanid monogeneans. Heteroxenous blood parasites also successfully maintained transmission in the culture system despite their requirement for an intermediate host. Prophylactic chemical treatments helped to reduce parasitic infection but did not eliminate them and once introduced into the floating netcage culture system, these parasites managed to maintain their transmission successfully. Despite the current lack of information regarding the biology of many parasites affecting cultured marine fishes, it nevertheless is possible to develop methodologies to produce an integrated health management system specifically designed to the needs of the mariculture practiced in the Southeast Asian region. This system is important and should include a sequence of prophylaxes, adequate nutrition, sanitation, immunization and an effective system of marketing for farmed fishes.