Chitala Ornata Research Articles

Modulation of gill surface area does not correlate with oxygen loss in Chitala ornata.

Air-breathing fish risk losing aerially sourced oxygen to ambient hypoxic water since oxygenated blood from the air-breathing organ returns through the heart to the branchial basket before distribution. This loss is thought to help drive the evolutionary reduction in gill size with the advent of air-breathing. In many teleost fish, gill size is known to be highly plastic by modulation of their anatomic diffusion factor (ADF) with inter-lamellar cell mass (ILCM). In the anoxia-tolerant crucian carp, ILCM recedes with hypoxia but regrows in anoxia. The air-breathing teleost Chitala ornata has been shown to increase gill ADF from normoxic to mildly hypoxic water by reducing ILCM. Here, we test the hypothesis that ADF is modulated to minimize oxygen loss in severe aquatic hypoxia by measuring ADF, gas-exchange, and by using computed tomography scans to reveal possible trans-branchial shunt vessels. Contrary to our hypothesis, ADF does not modulate to prevent oxygen loss and despite no evident trans-branchial shunting, C. ornata loses only 3% of its aerially sourced O2 while still excreting 79% of its CO2 production to the severely hypoxic water. We propose this is achieved by ventilatory control and by compensating the minor oxygen loss by extra aerial O2 uptake.

The Chromosome-Scale Genome of Chitala ornata Illuminates the Evolution of Early Teleosts.

Teleosts are the most prolific vertebrates, occupying the vast majority of aquatic environments, and their pectoral fins have undergone remarkable physiological transformations throughout their evolution. Studying early teleost fishes, such as those belonging to the Osteoglossiformes order, could offer crucial insights into the adaptive evolution of pectoral fins within this group. In this study, we have assembled a chromosomal-level genome for the Clown featherback (Chitala ornata), achieving the highest quality genome assembly for Osteoglossiformes to date, with a contig N50 of 32.78 Mb and a scaffold N50 of 40.73 Mb. By combining phylogenetic analysis, we determined that the Clown featherback diverged approximately 202 to 203 million years ago (Ma), aligning with continental separation events. Our analysis revealed the intriguing discovery that a unique deletion of regulatory elements is adjacent to the Gli3 gene, specifically in teleosts. This deletion might be tied to the specialized adaptation of their pectoral fins. Furthermore, our findings indicate that specific contractions and expansions of transposable elements (TEs) in teleosts, including the Clown featherback, could be connected to their adaptive evolution. In essence, this study not only provides a high-quality genomic resource for Osteoglossiformes but also sheds light on the evolutionary trajectory of early teleosts.

Integrative taxonomy of the featherback fish genus Chitala (Osteoglossomorpha: Notopteridae) in Peninsular Malaysia

AbstractThe taxonomy of the freshwater featherback fish genus Chitala (Osteoglossomorpha: Notopteridae) remains unsettled because delimiting and naming Chitala species based solely on morphology led to different hypotheses. In this study, we aim to determine the number and identity of Chitala species present in Peninsular Malaysia by employing an integrative taxonomic approach that combines morphology and two mitochondrial markers: the cytochrome c oxidase subunit I (COI) and cytochrome b genes. A total of 60 specimens of Chitala were collected throughout Peninsular Malaysia. Initially, all specimens were sorted into three distinct categories based on their body marking patterns. A molecular phylogenetic analysis revealed that each of these groups was monophyletic, and an automated species partition method further recognized them as distinct species. These results support the presence of three Chitala species in Peninsular Malaysia, even though a multivariate morphometric analysis failed to fully differentiate each of these three species. Comparison with original species descriptions and genetic data from an additional 70 Chitala specimens from neighbouring regions allowed us to name these species as Chitala lopis, Chitala borneensis, and Chitala ornata. We also showed the presence of two undescribed species in Indonesia.

Identification and Antibiotic Resistance Edwardsiella tarda from Clown Knifefish (Chitala chitala) in the Mekong Delta, Vietnam

This investigation is intended to isolate, identify, and assess the pathogenicity of Edwardsiella tarda, which originated from diseased clown knifefish. A total of 43 isolates were obtained from infected fish samples in Hau Giang and Dong Thap provinces of the Mekong Delta, Vietnam. Two isolates of DT37 and HG41 were identified as E. tarda by morphological, biochemical, and 16S rRNA gene sequencing. Experimental challenge studies revealed that isolate DT37 leads to 83.33% at a 108 CFU/ml concentration after 60 hours. Meanwhile, in isolate HG41, mortality reached 100% within 48 hours post-injection at the highest concentration of 108 CFU/ml. The challenged clown knifefish exhibited gross signs of abnormal swimming, skin ulcerations, and petechial hemorrhages in the body. Internally, ascites with hemoperitoneum, light-colored nodules on the liver, hemorrhagic kidneys, and splenomegaly were also recorded. The LD50 of two isolates, DT37 and HG41, was 4.89 × 105 and 4.07 × 105 CFU/ml, respectively. The antibiogram result showed that most of the isolates were highly susceptible to ampicillin (65%), enrofloxacin (85%), florfenicol (100%), flumequine (90%), cefotaxime (80%), and trimethoprim and sulfamethoxazole (70%). However, the bacterial isolates were highly resistant to doxycycline (75%) and streptomycin (100%).

COI-high resolution melting analysis for discrimination of four fish species in the family Notopteridae in Thailand

Species identification is an essential and vital basis for biological research. Since several fish species have similar appearances and shapes at different developmental stages and researchers lack experience identifying these fish species, molecular techniques are needed. In Thailand, fish species of the family Notopteridae consist of two genera and four species, including Notopterus notopterus, Chitala ornata, Chitala blanci, and Chitala lopis. The combination of the cytochrome c oxidase I (COI) gene sequences with a nonsequencing approach, high-resolution melting (HRM), was developed to discriminate four target species in a rapid, reliable and cost-effective manner. One of three designed primer pair sets, Notop-HRMF1/Notop-HRMR1, was the most appropriate and provided four distinct melting curves. In addition, ten fish species of other families were used for the specificity test, and only the four target species of Notopteridae were specific for this primer pair set. The results of this study indicated that COI-HRM analysis is an efficient approach for identifying species of Notopteridae in Thailand. Applications of this technique may be used to investigate species of this family in processed fish products or larval fish species in several spawning grounds for sustainable fishery resource management.

Effects of dietary protein and lipid levels on growth, feed utilization and meat quality of clown knifefish (Chitala chitala)

Effects of dietary protein and lipid levels on growth, feed utilization and fillet quality of clown knifefish (Chitala chitala) were implemented to determine the protein and energy requirements of this species at 400 g stage. A 4 x 3 factorial design with four dietary protein levels (25%, 30%, 35% and 40%) and three dietary lipid levels (6, 9, and 12%) corresponded to 3 energies levels 18, 19 and 20 MJ/kg. Clown knifefish (407 ± 5.0 g) was stocked at a density of 10 fish/m2. The experiment was arranged in a completely randomized design in triplicate tanks for 8 weeks. There was a significant interaction effect (P<0.05) between protein and lipid levels on weight gain and specific growth rate with the fish growth being highest in the 35 CP-9% lipid treatment. The survival rate of fish was not affected (P>0.05) by dietary protein and lipid levels and ranged from 93.3 to 100%. The feed efficiency of fish was influenced by dietary protein or lipid content as well as the interaction between these two factors. Protein utilization efficiency increased as protein content increased, and diet contained t 35% protein and 9% lipid, enhanced chewiness and hardness of fish paste. These results showed that clown knifefish fed 32.8% dietary protein and 19 MJ energy with a P/E ratio of 18.6 had the optimal growth and the best quality of fish meat.

Value chain and competitiveness of OCOP standardized clown knife fish products in Hau Giang province

The study was conducted to analyze the competitiveness of OCOP standardized clown knife fish products in Hau Giang province. The data were collected from 73 observations involved in the clown knife fish value chain. The research results show that most farmers culture knife fish intensively and the feed cost shares the highest proportion of the total production cost. Processed products from knife fish are mainly boneless fish and fish balls. The OCOP knife fish value chain operated through four main distribution channels and included actors: fish farmers, traders, processors, and retailers. The farmers normally sell fresh knife fish to middleman, accounting for 80.15%. The processing factories create and share the highest proportion of added value. The distribution channel that farmers are linked directly with processors create higher added value than others. The study also analyzed the Porter’s five forces of the knife industry. The study found that there are many potential risks in the farming process, high competitive pressures from substitute products, and limited negotiation ability of both farmers and processors.

A molecular survey based on eDNA to assess the presence of a clown featherback (Chitala ornata) in a confined environment.

BackgroundThe importance of the inland fisheries sector in food security as a provider of much-needed protein and income supplier has been highlighted. This is especially the case in poor rural communities in developing countries. Inland capture fisheries in Thailand are in place nationwide in rivers, lakes, swamps and reservoirs. The clown featherback (Chitala ornata) is popularly consumed and is an economically important fish in Thailand which is often used in food products such as fish balls and fish cakes. Along with other fish species, the clown featherback is one of fish of inland fisheries at Phayao Lake. Recent fish surveys from 2016-2018 at Phayao Lake using netting and electrofishing found that the number of clown featherback have been reducing since 2016 and could not be detected at all by 2018. This is despite the fact that there are still reports of their presence in the lake from locals.MethodsWe developed an eDNA-based method for detection of the clown featherback in Phayao Lake as an alternative tool. Water samples were collected in three different sampling months (February, June and September) at six sites located in the lake. Species-specific primers and the probe were designed to amplify a 183 bp fragment of the cytB region of the clown featherback.ResultseDNA of the clown featherback can be detected in all different sampling months and sites. Concentration of the clown featherback found in Prayao Lake showed no difference over sampling month but between collecting sites. This proves that eDNA based survey is a sensitive and useful tool for monitoring and surveying the clown featherback at any time of the year.

Trophic status and diversity of fish species in selected tributaries of Bentota River

Present study was carried out to investigate the, abundance and trophic status of fishes inhabiting tributaries of the Bentota River. Fish were sampled using gill nets, seine nets, cast nets and some were also collected from fishermen’s catches harvested at the tributaries of the Benthota River in Katapola, Ganegoda, Avitthawa, Yagirala and Galatara. To investigate the trophic status, stomach contents were analyzed and quantified using the Point method based on the percentage of bio volume per food category. Ten species of fish were recorded from all five sites, including two endemic species, Clarias brachysoma, Channa orientalis and one invasive alien fish Chitala ornata. Some indigenous species such as Puntius vittatus (n=400), Rasbora daniconius (n=134), Puntius dorsalis (n = 42) and Trichogaster pectoralis (n=71) were also caught in reasonable number. Parts of fish (scales, fins and flesh), mollusks, adult insects, insects larvae, macrophytes and digested/detritus matters were identified as main food categories in the stomach. Based on the gut content analysis, three feeding guilds i.e. piscivorous, herbivorous and zooplanktivorous, were identified. High diet overlap values were recorded in species pairs belonged to the same feeding guild i.e. Chitala.ornata- Channa orientalis while low diet overlap values were recorded in species belonged to different feeding guilds. Remains of fins of Channa orientalis, and Rasbora daniconius and some invertebrates observed in stomach contents of C. ornata, indicated its negative impacts on biodiversity in study sites. Therefore urgent attention should be paid to population control of C.ornata and to prevent its further invasion into new habitats.

Comparison of acid-soluble collagen characteristic from three important freshwater fish skins in Mekong Delta Region, Vietnam.

The utilization of three important freshwater fish skins including tra catfish (Pangasianodon hypophthalmus), clown knifefish (Chitala ornata), and tilapia (Oreochromis niloticus) in Mekong Delta Region, Vietnam for acid-soluble collagen (ASC) extraction was investigated. From the SDS-PAGE profile, ASCs can be identified as type I collagen (consisting of two different α- chains and β component in protein pattern).The solubility among individual collagens was highest at pH 1-2, depending on fish species. FTIR spectra showed a close relationship between the lowest wavelength number in amide I and amide III regions and the stabilization of the triple-helical structure in ASC from clown knifefish. ASC from clown knifefish skin had highest ASC yield and contained highest amino acid content as well as the highest denaturation temperature (33.09°C) in comparison with ASCs from tra catfish and tilapia skin. PRACTICAL APPLICATIONS: Acid-soluble collagen (ASC) from three important fish skins in the Mekong Delta Region, Vietnam was characterized. ASC from clown knifefish skin showed the highest of extraction yield and denaturation temperature. The thermal stability of ASC from clown knifefish skin not only related to the content of imino acid but is also had the correlation with the transition of α-helix in amide I and III.

Sexual dimorphism of invasive knifefish (Chitala ornata) in Laguna de bay, Philippines

Chitala ornata (J.E. Gray) (Osteoglossiformes: Notopteridae) has since established abundant and nuisance populations in Laguna de Bay. A fundamental prerequisite for the development of management strategies for invasive species like C. ornata is a full understanding of its life history characteristics including sexual dimorphism. In the present study, we examined the sexual dimorphism of C. ornata. Sexes of C. ornata can be distinguished through the examination of its genital papilla wherein females show distinct morphological adaptions for effective oviposition on a spawning substrate. Comparison of means and multivariate analysis of several morphometric characters showed that sexual size dimorphism in C. ornata is female-biased which is mainly attributed to the disparity of resource expenditure between sexes for reproduction and size-dependent advantages of females in the production of more progenies with better chances of survival.

Effects of nitrite at different temperatures on physiological parameters and growth in clown knifefish (Chitala ornata, Gray 1831)

The clown knifefish (Chitala ornata) is a facultative air breather that is cultured in freshwater farms in Mekong Delta, Vietnam. We report the effects of different temperatures (27 °C, 30 °C, and 33 °C) and nitrite exposure (1 mM) at these temperatures on haemoglobin derivatives, plasma ions, and acid-base status over 14 days. We also tested the effects of nitrite exposure at different temperatures on growth over 90 days of culture. An increase in temperature alone did not affect Na+, Cl−, HCO3−, and osmolality concentrations, whereas K+ was temporarily increased. Acid-base status was significantly affected by an increased partial pressure of carbon dioxide in the blood (PCO2) and reduction of extracellular pH (pHe) during elevated temperatures. Plasma nitrite levels and methaemoglobin (metHb) percentage reached the highest values at 33 °C compared to those at 27 °C and 30 °C with nitrite exposure after 3 days, but they decreased significantly at experimental termination by the detoxification process converting nitrite to nitrate. Plasma NO3− and the sum of [NO2−] and [NO3−] continuously increased during nitrite exposure at all three temperatures, reaching the highest values at 33 °C. Weight gain and survival rate increased at elevated temperatures with the highest value at 33 °C (29 g and 85%, respectively), while feed conversion ratio (FCR) values were unchanged at all temperatures. In contrast, elevated temperature caused a significant lowering of survival rate in nitrite exposure, but weight gain was highest with nitrite exposure at 30 °C and 33 °C.

Effects of temperature on acid-base regulation, gill ventilation and air breathing in the clown knifefish, Chitala ornata.

Chitala ornata is a facultative air-breathing fish, which at low temperatures shows an arterial PCO2 (PaCO2 ) level only slightly elevated above that of water breathers. By holding fish with in-dwelling catheters at temperatures from 25 to 36°C and measuring blood gasses, we show that this animal follows the ubiquitous poikilotherm pattern of reducing arterial pH with increasing temperature. Surprisingly, the temperature increase caused an elevation of PaCO2 from 5 to 12 mmHg while the plasma bicarbonate concentration remained constant at around 8 mmol l-1 The temperature increase also gave rise to a larger fractional increase in air breathing than in gill ventilation frequency. These findings suggest that air breathing, and hence the partitioning of gas exchange, is to some extent regulated by acid-base status in air-breathing fish and that these bimodal breathers will be increasingly likely to adopt respiratory pH control as temperature rises, providing an interesting avenue for future research.

Fish composition in Dong Nai biosphere reserve in Vietnam

Dong Nai biosphere reserve (DNBR) is well known for its high level of biodiversity and of global meaningful ecosystem. The fauna includes 84 species of mammals belonging to 28 families, 10 orders; 407 bird species; 141 reptile and amphibian species; 175 fish species; 2,017 insect species. The fish fauna of DNBR maintains many rare and endangered fish species recorded in the Vietnam red book and international union for conservation of nature red list (IUCN's red list) such as Scleropages formosus and many other rare fish species, such as Morulius chrysophekadion, Chitala ornata, Probarbus jullieni, Cyclocheilichthys enoplos… This study was aimed to identify fish composition distributed in DNBR. After the sampling period (01/2019 to 08/2019), a total of 114 fish species belonging to 11 orders and 28 families were recorded in DNBR. There were 09 species of fish on the list of rare and endangered fish species of Ministry of Agriculture and Rural Development of Vietnam, 3 species (Chitala ornata, Cosmochilus harmandi and Hemibagus filamentus) on the Vietnam red list book; 01 species (Ompok bimaculatus) on the IUCN's red list, 11 exotic species, 78 commercial species and 13 species having potential as aquarium fish. In addition, the study also found the first presence of a species of phallostethid, Phenacostethus smithi in DNBR

Ventilatory responses of the clown knifefish, Chitala ornata, to arterial hypercapnia remain after gill denervation.

The aim of this study was to corroborate the presence of CO2/H+-sensitive arterial chemoreceptors involved in producing air-breathing responses to aquatic hypercarbia in the facultative air-breathing clown knifefish (Chitala ornata) and to explore their possible location. Progressively increasing levels of CO2 mixed with air were injected into the air-breathing organ (ABO) of one group of intact fish to elevate internal PCO2 and decrease blood pH. Another group of fish in which the gills were totally denervated was exposed to aquatic hypercarbia (pH ~ 6) or arterial hypercapnia in aquatic normocarbia (by injection of acetazolamide to increase arterial PCO2 and decrease blood pH). Air-breathing frequency, gill ventilation frequency, heart rate and arterial PCO2 and pH were recorded during all treatments. The CO2 injections into the ABO induced progressive increases in air-breathing frequency, but did not alter gill ventilation or heart rate. Exposure to both hypercarbia and acetazolamide post-denervation of the gills also produced significant air-breathing responses, but no changes in gill ventilation. While all treatments produced increases in arterial PCO2 and decreases in blood pH, the modest changes in arterial PCO2/pH in the acetazolamide treatment produced the greatest increases in air-breathing frequency. These results strengthen the evidence that internal CO2/H+ sensing is involved in the stimulation of air breathing in clown knifefish and suggest that it involves extra-branchial chemoreceptors possibly situated either centrally or in the air-breathing organ.

Effect of water pH and calcium on ion balance in five fish species of the Mekong Delta

Acidic freshwater habitats disrupt ion-homeostasis in fishes, yet the often acidic waters of the Mekong host the second highest diversity of freshwater fish in the world. To investigate how five Mekong fish species tolerate water acidity, we measured: time to loss of equilibrium (LOE) at sustained (4 days) low pH (3.5) and net ion flux in acute low pH (3.5 and 3) in Chitala ornata, Pangasianodon hypophthalmus, Osphronemus goramy, Trichogaster pectoralis, and Monopterus albus. Our sustained low pH exposures revealed that C. ornata was least tolerant, P. hypophthalmus and M. albus were moderately tolerant, and O. goramy and T. pectoralis were highly tolerant to low pH. In general, net ion loss in acute low pH exposures was greatest in species with the shortest time to LOE in the sustained low pH exposure. We also explored how low water [Ca2+] (relative to current Mekong levels) affected ion flux at low water pH in the least tolerant C. ornata and highly tolerant T. pectoralis. In C. ornata, low water Ca2+ (56 ± 1 μmol L−1) increased net ion loss relative to high Ca2+ (342 ± 3 μmol L−1) water while no effect was observed in T. pectoralis. Finally, we find that T. pectoralis is among the most acid-tolerant fish species examined to date.

Autolysis of Clown Featherback (Chitala ornata) Muscle

Autolysis of Clown Featherback (Chitala ornata) Muscle

Ventilatory responses of the clown knifefish, Chitala ornata, to hypercarbia and hypercapnia.

The aim of the present study was to determine the roles of externally versus internally oriented CO2/H+-sensitive chemoreceptors in promoting cardiorespiratory responses to environmental hypercarbia in the facultative air-breathing fish, Chitala ornata (the clown knifefish). Fish were exposed to environmental acidosis (pH ~ 6.0) or hypercarbia (≈ 30torr PCO2) that produced changes in water pH equal to the pH levels of the acidotic water to distinguish the relative roles of CO2 versus H+. We also injected acetazolamide to elevate arterial levels of PCO2 and [H+] in fish in normocarbic water to distinguish between internal and external stimuli. We measured changes in gill ventilation frequency, air breathing frequency, heart rate and arterial blood pressure in response to each treatment as well as the changes produced in arterial PCO2 and pH. Exposure to normocarbic water of pH 6.0 for 1h did not produce significant changes in any measured variable. Exposure to hypercarbic water dramatically increased air breathing frequency, but had no effect on gill ventilation. Hypercarbia also produced a modest bradycardia and fall in arterial blood pressure. Injection of acetazolamide produced similar effects. Both hypercarbia and acetazolamide led to increases in arterial PCO2 and falls in arterial pH although the changes in arterial PCO2/pH were more modest following acetazolamide injection as were the increases in air breathing frequency. The acetazolamide results suggest that the stimulation of air breathing was due, at least in part, to stimulation of internally oriented CO2/H+ chemoreceptors monitoring blood gas changes.

The effects of elevated environmental CO2 on nitrite uptake in the air-breathing clown knifefish, Chitala ornata

Nitrite and carbon dioxide are common environmental contaminants in the intensive aquaculture ponds used to farm clown knifefish (Chitala ornata) in the Mekong delta, Vietnam. Here we tested the hypothesis that hypercapnia reduces nitrite uptake across the gills, because pH regulation will reduce chloride uptake and hence nitrite uptake as the two ions compete for the same transport route via the branchial HCO3−/Cl− exchanger. Fish fitted with arterial catheters were exposed to normocapnic/normoxic water (control), nitrite (1 mM), hypercapnia (21 mmHg CO2), or combined hypercapnia (acclimated hypercapnia) and nitrite for 96 h. Blood was sampled to measure acid-base status, haemoglobin derivatives and plasma ions. Plasma nitrite increased for 48 h, but levels stayed below the exposure concentration, and subsequently decreased as a result of nitrite detoxification to nitrate. The total uptake of nitrite (evaluated as [NO2−] + [NO3−]) was significantly decreased in hypercapnia, in accordance with the hypothesis. Methemoglobin and nitrosylhemoglobin levels were similarly lower during hypercapnic compared to normocapnic nitrite exposure. The respiratory acidosis induced by hypercapnia was half-compensated by bicarbonate accumulation in 96 h, which was mainly chloride-mediated (i.e. reduced Cl− influx via the branchial HCO3−/Cl− exchanger). Plasma osmolality and main ions (Na+, Cl−) were significantly decreased by hypercapnia and by nitrite exposure, consistent with inhibition of active transport. We conclude that hypercapnia induces a long-lasting, and mainly chloride-mediated acid-base regulation that reduces the uptake of nitrite across the gills.

Effects of nitrite exposure on haematological parameters and growth in clown knifefish (Chitala ornata, Gray 1831)

Physiological responses and growth of clown knifefish (Chitala ornata) (initial weight of 11-12 g) exposed to nitrite were investigated with three separate experiments. The first experiment was to determine the nitrite concentration causing 50% mortality in 96 hours (96-h LC50). The second experiment examined the effects of different nitrite concentrations on haematological parameters. The third experiment investigated into the effects of different nitrite concentrations on fish growth including 4 treatments such as control, 0.2 mM nitrite, 0.4 mM nitrite, and 4 mM nitrite for measuring growth parameters at days 0, 30, 60, and 90 days (sampling 30 fish/tank). The results showed that the clown knifefish had high nitrite tolerance with 96-h LC50 of 7.82 mM. There were significant increases in methaemoglobin and leukocytes while other haematological parameters decreased during nitrite exposures at the treatment of 4 mM nitrite. Particularly, methaemoglobin and the number of leukocytes increased from 0.4 to 29.5%, and from 39.89x103 to 72.33x103 cells/mm3, respectively. Differently, there were significant declines in the number of erythrocyte (3.19x106–2.33x106 cells/mm3), haemoglobin (10.47-7.04 mM), and haematocrit (38.07-26.5%) at the highest nitrite treatment. After 90 days, daily weight gain (0.25±0.02 g/day), specific growth rate (1.18±0.07 %/day), survival rate (59%) at the treatment of 4 mM nitrite were significantly lower than those of the control, but no significant difference was observed in such parameters between the control and the treatments of 0.2 or 0.4 mM nitrite.