Dwarf Gourami Research Articles

Superhydrophobic silicone/graphene oxide-silver-titania nanocomposites as eco-friendly and durable maritime antifouling coatings

In this work, a novel ecofriendly series of polydimethylsiloxane-polymethylmethacrylate (PDMS-PMMA) blend filled with silver nanospheres and titanium dioxide nanorods grafted on the graphene oxide surface (Ag–TiO2@GO) were produced by the catalytic hydrosilation method as outstanding marine antifouling coatings. Innovative Ag–TiO2@GO hybrid nanofillers, that would release fouling and confer surface robustness, were developed by a single-phase procedure. Ag nanospheres with 20 nm mean diameter were prepared by a controlled solvothermal method, while anatase TiO2 nanorods with 10 nm average diameter were grown by a hydrothermal technique. The solution casting method was used to distribute various Ag–TiO2@GO filler percentages throughout the silicone matrix. Atomic force microscopy, surface free energy, and water contact angle (WCA) were employed to examine the superhydrophobicity and roughness of the coatings. The mechanical durability and antifouling characteristics of the PDMS-PMMA nanocomposites filled with Ag–TiO2@GO composites were also investigated. Several microorganisms were employed to examine the fouling resistance of the coated specimens for 30 days. Trichogaster lalius fish and the bivalve Brachidontes variabilis species were used to examine the nanocomposites’ toxicity. Well-dispersion of Ag–TiO2@GO nanofillers in the PDMS-PMMA resin until 2.5 wt% exhibited the highest WCA (160° ± 2°), the lowest surface free energy (22.9 mN/m), rough topology, and improved bulk mechanical properties. Furthermore, the well-dispersed PDMSPMMA/Ag–TiO2@GO (2.5 wt%) nanocomposite presented the lowest biodegradability percentages and optical density against various gram-positive and gram-negative bacterial strains. Furthermore, it displayed non-toxicity against the tested species of fish and bivalve. The developed non-toxic and non-stick nanocoating exhibited various merits, including superhydrophobicity, mechanical robustness, and fouling retardancy, for using as maritime ship hull coatings.

Status, distribution, and morphometric analysis of the genus Trichopodus in Sumatra, Indonesia

Trichopodus, the genus of dwarf gourami fish, is the oldest genus in the Osphronemidae family, with six valid species, three of which are found in Sumatra. In this study, the status, distribution, and morphometrics of Trichopodus leerii, T. pectoralis, and T. trichopterus from Sumatra were observed and analyzed. Although these species can be distinguished based on phenotypic characteristics, it is still possible to misidentify them in small or preserved samples. In this study, analyses were carried out on specimens in the collection of the Museum Zoologicum Bogoriense, combined with literature on the species status. The results showed that T. trichopterus and T. pectoralis were in the least concern category. T. trichopterus had the widest distribution, followed by T. pectoralis. T. leerii had the smallest distribution and is in a near-threatened conservation status. Further analysis revealed that 23 of the 25 measured morphological characteristics were informative, with the first three axes of a principal component analysis on morphometric data explaining 51.28% of the total variance in the sample. The three species were distinguished using a combination of pectoral fin length, eye diameter, pelvic fin length, and anterior snout width. Cluster analysis showed that there is consistency in the morphometrics of the species from various sample locations, where the same species are in the same clade. This research contributes to our understanding of the status and distribution of the species in genus Trichopodus and employs morphometric analysis to provide a practical key to classifying them in Sumatra.

A New Cell Line Derived from the Caudal Fin of the Dwarf Gourami (Trichogaster lalius) and Its Susceptibility to Fish Viruses.

The detection of megalocytiviruses, especially the infectious spleen and kidney necrosis virus (ISKNV), in ornamental fish has increased with the rapid growth of the ornamental fish industry. In this study, dwarf gourami fin (DGF) cells derived from the caudal fin of the dwarf gourami (Trichogaster lalius), which is highly susceptible to red sea bream iridovirus (RSIV) and ISKNV, were established and characterized. The DGF cells were grown at temperatures ranging from 25 °C to 30 °C in Leibovitz's L-15 medium supplemented with 15% fetal bovine serum and were subcultured for more than 100 passages, predominantly with epithelial-like cells. DGF cells had a diploid chromosome number of 2n = 44. Although the initial purpose of this study was to establish a cell line for the causative agents of red sea bream iridoviral disease (RSIV and ISKNV), DGF cells were also susceptible to rhabdoviruses (viral hemorrhagic septicemia virus, hirame rhabdovirus, and spring viraemia of carp virus), exhibiting a significant cytopathic effect characterized by cell rounding and lysis. Additionally, viral replication and virion morphology were confirmed using virus-specific conventional polymerase chain reaction and transmission electron microscopy. Furthermore, both RSIV and ISKNV were replicated at high concentrations in DGF cells compared to other cell lines. Notably, the DGF cells maintained a monolayer during ISKNV infection, indicating the possibility of persistent infection. Thus, DGF can be used for viral diagnosis and may play a critical role in advancing our understanding of ISKNV pathogenesis.

Effect of anastrozole on masculinization in ornamental fish, dwarf gourami, <em>Trichogaster lalius</em> (Hamilton, 1822)

In ornamental fishery, for commercialization and efficient propagation of fish species in demand, controlling their sex, male or female, plays an important role as it influences reproduction, growth and product quality. In one such common aquarium fish, dwarf gourami, Trichogaster lalius (Hamilton, 1822), males look more attractive and fetch better market price encouraging masculinization of this species. In the present study, we evaluated the effect of anastrozole on masculinization potential in T. lalius. The experiment consisted of two trials, in trial 1; anastrozole was incorporated into feed at 50, 100, 150 and 200 mg/kg and fed to first feeding fry for 50 days. In trial 2, immersion treatment of anastrozole was carried out at different doses of 250, 500, 750 and 1,000 μg/L for 3 h each on 3rd, 5th and 8th day of post-hatching. Oral administration of anastrozole resulted in 90.32% masculinization at 200 ppm and the immersion treatment of anastrozole produced 100% masculinization at 1000 μg/L. Histological sections indicated that the anastrozole treatments suppressed ovarian development, leading to the atretic oocytes. However, the testicular development was unaffected. Testosterone level increased whereas estradiol level decreased with increased dose of the chemical. Cortisol level also showed a significant increase in male with increased doses of anastrozole, indicating stress which in turn helped to synthesize the testosterone. The results show that the immersion treatment of anastrozole is more effective than oral administration in inducing masculinization in T. lalius.

MOLECULAR DETECTION OF MEGALOCYTIVIRUS GENOTYPE: INFECTIOUS SPLEEN AND KIDNEY NECROSIS VIRUS IN MALAYSIAN OVIPAROUS AQUARIUM FISH

The Malaysian ornamental fish industry’s recent production is recorded at RM350 million per annum. An Infectious Spleen and Kidney Necrosis Virus (ISKNV), one of the Megalocytivirus strains has been related to significant systemic infections that has ravaged ornamental fish stocks and had a severe financial impact on businesses in the sector. It is vital to identify Megalocytivirus host species among Malaysian oviparous ornamental fish as the virus can cripple the ornamental fish trade which is a major contributor to the country’s export trade. The purpose of this research is to determine the prevalence of Megalocytivirus, ISKNV strain in oviparous aquarium fish, Betta splendens, Danio rerio, Trichogaster lalius, Hyphessobrycon anisitsi and Puntigrus tetrazona in Malaysia. The DNA of the Megalocytivirus in the samples was detected using the nested polymerase chain reaction (PCR) method. Out of 239 samples collected in January 2019 and January 2020, six pooled samples (n=30) tested positive for ISKNV infections in D. rerio and T. lalius. Positive P. tetrazona samples in this study showed a distended abdomen as the only observable clinical sign whereas all other samples were asymptomatic. All the positive samples were similar to each other. In terms of the nucleotide identity of the ISKNV, which stood at between 98% and 100%. In conclusion, the positive samples can be categorised into Megalocytivirus genotype I.

Sharpshooting dwarf gouramis target dinner with dribbly jets

The roll call of animals that use tools continues growing; from twig-wielding birds and primates to dolphins stirring up prey with sponges and even water-squirting fish. ‘To be considered a tool, an object: must not be part of the animal itself; must be an unattached or manipulable attached environmental object; and be manipulated to achieve some beneficial outcome’, says Nick Jones from the University of St Andrews, UK. Targeted jets of water fall easily within this definition. Of course, the pre-eminent jet sharpshooter is the archerfish, famed for its precision and 2 m spurts. But dwarf gouramis (Trichogaster lalius) are also capable of aiming a squirt, albeit on a more diminutive scale. ‘Their shots reach a limited height of 5 cm’, says Jones, yet no one really knew if these fish spit water to dislodge lunch, simply do it for the sheer pleasure, or whether females even have the ability. Jones teamed up with animal tool use expert Barbara Klump (Max Planck Institute of Animal Behavior, Germany), Teresa Abaurrea (University of Helsinki, Finland), and Sophie Harrower, Clare Marr, Louise Scott, Luke Rendell and Mike Webster from the University of St Andrews to check out the spitting prowess of dwarf gouramis. ‘Male dwarf gouramis build nests of bubbles that they make by sucking in air at the surface and then blowing bubbles coated with their saliva’, says Jones, who was curious to find out whether bubble blowing provides jet-squirting male dwarf gouramis with an advantage over the females. Jones, Marr and Harrower trained both sexes to target a black bead with a jet of water, in return for fish food pellet rewards, to test their sharpshooting abilities and recall that the gouramis were very cooperative. ‘The first week we got females in the lab, one started shooting on day two’, says Jones.So, it was quickly clear that the females were equally as enthusiastic as the males at taking pot-shots. ‘I easily won my bet with my supervisor [Mike Webster] that they would shoot as well as males’, chuckles Jones. In addition, when the team tested whether five untrained female gouramis could dislodge a fly or cricket wandering along a dowel located 2 cm above the water, most successfully aimed their sloppy jets, enthusiastically taking a shot by the time the third insect came into range. Some of the successful hunters even stopped for a nibble after bringing down their prey.Then, Scott tested the range of the gouramis’ jets, spending days training the fish to spit at a blob of plasticine at heights ranging from 1 to 5 cm above the water, rewarding the fish with a tasty bloodworm snack even when they didn't hit the target, to ensure that the fish always took a shot. And it turned out that the popular pet-trade animals had steely determination, doggedly squirting at the target up to 10 times before successfully landing a shot. However, the fish seemed to have a good sense of their own limitations, hesitating longer and taking fewer shots at plasticine blobs placed toward the upper end of their range (4 and 5 cm). The team also noticed that the fish that were quicker on the draw tended to down their prey more often and kept firing for longer until they successfully struck the target; they are definitely determined sharpshooters.So, dwarf gouramis can add their name to the list of water squirters capable of downing dinner with a ballistic jet, albeit a shorter dribblier imitation of the archerfish's high-precision fluid missiles.

Short-range hunters: exploring the function and constraints of water shooting in dwarf gouramis.

Ballistic predation is a rare foraging adaptation: in fishes, most attention has focused on a single genus, the archerfish, known to manipulate water to shoot down prey above the water surface. However, several gourami species also exhibit apparently similar 'shooting' behaviour, spitting water up to 5 cm above the surface. In a series of experiments, we explored the shooting behaviour and aspects of its significance as a foraging ability in the dwarf gourami (Trichogaster lalius). We investigated sex differences in shooting abilities to determine whether gourami shooting is related to the sex-specific bubble nest manufacture where males mix air and water at the surface to form bubbles. We found that, actually, both sexes were equally able to shoot and could learn to shoot a novel target. In a second experiment, we presented untrained gouramis with opportunities to shoot at live prey and found they successfully shot down both fruit flies and crickets. Finally, we explored the effect of target height on shooting performance to establish potential constraints of shooting as a foraging ability. The frequency of attempted shots and success of hitting targets decreased with height, whereas latency to shoot increased. We also observed that repeatable individual differences account for variation in these measures of shooting performance. Together, our results provide evidence that gourami shooting has a foraging function analogous to that of archerfish. Gourami shooting may serve as an example of convergent evolution and provide opportunities for comparative studies into the, as yet unexplored, ecology and evolution of shooting in fishes.

Iridovirus isolated from marine giant sea perch causes infection in freshwater ornamental fish

Ornamental fish are frequently infected with iridoviruses and their transport via international trade can easily cause the spread of the viral pathogens. An iridovirus was isolated from farmed giant sea perch (Lates calcarifer) and identified as a grouper iridovirus of Taiwan (TGIV) belonging to the genus Megalocytivirus. High mortality rate in dwarf gouramis was observed when the freshwater ornamental fish dwarf gouramis (Trichogaster lalius) was challenged with spleen tissue extracts of the TGIV-infected giant sea perch. Similar results were obtained when dwarf gouramis were challenged with grouper iridovirus (GIV) isolated from marine fish. The spleen tissue extracts of dwarf gouramis infected with TGIV and GIV were also used to challenge swordtails (Xiphophorus helleri; freshwater ornamental fish); both viruses resulted in high mortality rates in swordtails, indicating that iridovirus, a marine fish pathogen, could also infect freshwater ornamental fish, resulting in high mortality rates. Furthermore, when orange-spotted groupers (Epinephelus coioides) were experimentally challenged with the tissue extracts of TGIV- and GIV-infected dwarf gouramis, both viruses caused infection in orange-spotted groupers. In contrast with the results obtained in freshwater ornamental fish, the mortality rate of the GIV-infected orange-spotted groupers was higher (with earlier deaths) than that of their TGIV-infected counterparts. The iridovirus isolated from infected freshwater ornamental fish also resulted in high mortality rates in marine fish. Finally, the tissue extracts of the TGIV- and GIV-infected dwarf gouramis were used to infect healthy dwarf gouramis, and TGIV and GIV were subsequently detected in the spleen tissues of healthy dwarf gouramis. The results showed that TGIV was more lethal than GIV in dwarf gouramis. The expression of the viral major capsid protein could be detected. GIV and TGIV infections also resulted in pronounced vacuolation and necrosis of the spleen tissue. Transmission electron microscopy revealed the accumulation of nearly icosahedral viral particles in the spleen tissues of dwarf gouramis infected with TGIV and GIV. This study demonstrated that iridoviruses can survive and be infectious in both fresh and marine water habitats.

Small Scale Home Drying of Indigenous Fish Species in Urban High-Rises at Dhaka Metro

Drying is one of the common and ancient methods of fish preservation and is generally done in a wide range of open space. This study attempt to evaluate fish drying method at high-rise urban households with three small indigenous fishes namely Mola (Amblypharyngodon mola), Chapila (Gudusia chapra) and Lal Khailsha (Trichogaster lalius). Fishes were dried at high-rise indoor veranda and outdoor rooftop conditions. The dry weight of Mola, Chapila and Lal Khailsha fishes were 70%, 69.5% and 72% in indoor condition and 71.1%, 70.5% and 73% in outdoor condition. The differences of drying capacity between the indoor and outdoor dried fishes were none (p<0.05), thus, the both drying methods are feasible for the urban lifestyle. In dry state, the moisture level in Mola, Chapila and Lal Khailsha were 6.45%, 7.89% and 7.82% whereas, the protein level were 66.51%, 72.26% and 62.02% respectively. The ash value found in the respective fishes was 10.05%, 12.18% and 16.07% and the amount of total fat was 11.14%, 11.28% and 12.32% respectively. The protein and moisture values showed an inverse relationship between the indoor and outdoor condition. The preference analysis of dried fish was found to be highly (100%) accepted among the dry fish-eating consumers from Chittagong, Lakhimpur, Mymensingh, Rangpur, Bandarban, Pabna and Sylhet districts. On the contrary, in case of the consumers of Barisal and Chandpur districts, the level of acceptance was none (0%), whereas the consumers of Kushtia district have accepted the dry fish moderately (60%). Bangladesh J. Zool. 49(1): 117-124, 2021

Growth, Condition, Maturity and Mortality of the Dwarf Gourami, Trichogaster lalius (Hamilton, 1822) in a Wetland Ecosystem (Beel Dakatia), Southwestern Bangladesh

The dwarf gourami, Trichogaster lalius, is a low-cost freshwater edible fish for the people of South Asian countries containing a variety of essential nutrients. The first wide-ranging explanation on the population parameters specifically; length-frequency distribution (LFD), length-weight relationships (LWRs), length-length relationship (LLR), form factor (a3.0), condition factors (allometric, KA; Fulton’s, KF; relative, KR; relative weight, WR), size at first sexual maturity (Lm) and natural mortality (Mw) of T. lalius were estimated. 768 specimens were collected over one calendar year (March 2019 to February 2020) from a wetland ecosystem named Beel Dakatia, Khulna, southwestern Bangladesh through various traditional fishing gears. Lengths (in cm) and weight (in g) were assessed through a wooden fitted measuring scale and digital balance with accuracy 0.1 cm and 0.01g, respectively. In the current study, the total length ranged from 2.6-9.9 cm while the bodyweight ranged from 0.63-23.80 g for T. lalius. The TL size for classes of 7.00 to 7.99 and 8.00 to 8.99 cm indicated numerically prominent groups. Moreover, the calculated allometric coefficient (b) of LWRs represented a negative allometric growth pattern (b<3.00) for T. lalius in the Beel Dakatia. Noticeably, the a3.0 was 0.015 signifying that the fish is fusiform in shape. KF is the best-suited tool to assess the well-being of T. lalius among the four types of condition factors. According to Wilcoxson signed-rank test, the WR revealed significantly dissimilarities from 100 (P<0.0001), signifying the unbalanced territory for T. lalius. Moreover, the estimated Lm was 5.91 (~6.0) cm TL and Mw was 1.28 year-1 in the Beel Dakatia, southwestern Bangladesh. Finally, the knowledge about the biological aspects of T. lalius may be used for improved management tools in the future.

Sulcus and outline morphometrics of sagittal otolith variability in freshwater fragmented populations of dwarf gourami, Trichogaster lalia (Hamilton, 1822)

Studies on the anatomy of sulcus and outline morphometrics of the three population groups of Trichogaster lalia were carried out to examine the effects of anthropogenic stressors (dams and barrages) on the function-related morphological variability of the fish. Altogether 150 samples of the fish were procured from three geographically isolated rivers namely Ganga, Gomti and Yamuna. The features based on images and morphological indices of sulcus, otolith and body shape of the fish were analysed and compared using uni and multivariate statistical procedures. Rostrum, anti-rostrum and margins of sagittal otolith and cauda of sulcus predominantly varied among three population groups of the fish. Variations in geometric morphometrics of sulcus, otolith-outline, combination of both and body shape indicated the existence of three distinct groups of the fish where individuals of river Gomti and Ganga were found to be closer to each other compared to that of river Yamuna. Mantel test showed an overall good correlation between the morphometric data-sets based on otolith and body shape in delineating three groups of the fish. Understanding of the environmental factors influencing the variations in function-related morphology of the different groups of T. lalia is essential to identify the boundaries of the different groups of the fish and to implement the appropriate strategies for their conservation.

Effects of dietary cortisol administration on sex ratios in dwarf gouramis and rosy barbs

AbstractSexual differentiation in teleosts is based on diverse and complex combinations of genetic and environmental factors. Environmental conditions during early development can alter gonadal differentiation leading to sex reversal, where the individual's genotypic and phenotypic sexes are opposite. In many species, the mechanism of environmental sex reversal has been linked to the stress axis and fluctuations in cortisol. This mechanism could be utilized to manipulate sex ratios in ornamental aquaculture, where the males of sexually dichromic species are often more economically valuable due to their brighter coloration. Dietary cortisol administration was used as a proxy for environmental stress to evaluate the effects on gonadal differentiation in two ornamental species, rosy barb, Pethia conchonius and dwarf gourami, Trichogaster lalius. Three experiments were run with each species to assess the following: (a) postprandial cortisol levels following dietary administration, (b) the effect of dietary cortisol concentration on sex ratios, and (c) the effect of developmental timing of cortisol feed administration on sex ratios. Whole‐body cortisol enzyme‐linked immunosorbent assays confirmed that cortisol feed did cause increased cortisol levels. However, despite cortisol feed being administered during the putative gonadal differentiation period, no effect was observed in the final sex ratios for any of the treatments evaluated.

The effect of dietary 17α‐methyltestosterone administration on secondary sex coloration in adult female Rosy Barbs and Dwarf Gouramis

AbstractSexual phenotype is highly plastic in teleosts and controlled by a variety of species‐dependent factors. In aquaculture, hormone manipulations applied at different life stages are used to control sex ratios and exploit desirable traits such as ornate coloration in male ornamental species. This study investigated the effects of dietary 17α‐methyltestosterone (MT) administration on adult female Rosy Barbs Pethia conchonius and Dwarf Gourami Trichogaster lalius and Dwarf Gouramis. A panel of judges evaluated male secondary sex coloration weekly during and after prolonged MT feeding. Growth parameters, survival, and gonadosomatic index (GSI) were assessed at the end of the feeding regime. In both species, none of the MT diet concentrations affected survival, and all resulted in coloration changes, highlighting both the efficacy and safety of MT administration. In Dwarf Gouramis, MT diets caused pronounced color changes and reduced their GSIs at all dietary concentrations. In Rosy Barbs, MT diets induced the expression of male coloration but generally did not reach the color intensity of naturally occurring males and did not result in differences in GSIs. This study suggests that postdifferentiation androgenic treatment may be a viable option to induce secondary male sex coloration in ornamental species.

The effect of Spirulina on reproductive parameters, body composition, immune indices and digestive enzyme in dwarf gourami (Trichogaster lalius)

Rearing of ornamental fishes allocated high levels of annual income from the aquaculture industry. Spirulina is a blue-green algae, spiral shape with a diameter of 12 microns and rich source of protein, vitamins, amino acids and essential fatty acids, minerals and antioxidant pigments. Using different levels of spirulina was evaluated on immune indicators, digestive enzymes and reproductive parameters (fecundity and sexual maturation) of dwarf gourami. 145 dwarf gourami with an average weight of 3.6±0.23g were randomly distributed in twenty 12-liter aquarium. Four diets were prepared consisting of spirulina at levels of 3%, 7% and 10% substituted by fish meal and with a control diet. Parameters related to body biochemical, reproductive, digestive enzymes and immune index were measured. Increasing spirulina up to 7% enhance the ovarian weight (p<0.05). Hatching percentage and fecundity working has shown a significant increase with spirulina increased (p<0.05). Lipase, amylase and protease has significantly increased with increasing spirulina (p<0.05). Lysozyme and serum bactericidal have significantly increased with the increase of spirulina (p<0.05). Based on results 3% of spirulina due to improved reproductive factors and 10% to enhance immune indices and digestive enzymes in dwarf gourami considered as the best levels of substitution with fishmeal.

Effects of 17α‐methyltestosterone feeding and immersion on masculinization of rosy barbs Pethia conchonius and dwarf gouramis Trichogaster lalius

AbstractHormone treatments have commonly been used to skew sex ratios toward desired phenotypes. In sexually dichromic ornamental species, males are often more ornately colored and therefore more valuable. The synthetic androgen 17α‐methyltestosterone (MT) is one of the most common hormones used in this practice. The rosy barb, Pethia conchonius, and dwarf gourami, Trichogaster lalius, are two sexually dichromic species that would benefit from masculinization. The larvae of T. lalius and Pethia conchonius were exposed to MT over the first 30–60 days posthatch either through a series of 4‐hr immersions (0, 100, 200, 400, or 800 μg MT/L) or via top‐coated feed (0, 15, 30, 60, 120, 150, or 250 mg MT/kg feed). Survival was determined at the end of each treatment regime, and sex ratios were determined via gross dissections. In rosy barbs, none of the 30‐day treatments resulted in significant masculinization. MT feeding for 60 days resulted in more than 85% males in P. conchonius, but this was not significantly different from the control (70%). In T. lalius, paradoxical feminization was observed in immersion concentrations and 50 days of MT feed treatments.

Larval growth, survival, and partial budget analysis related to replacing Artemia in larval culture of six freshwater ornamental fishes

AbstractCultured freshwater ornamental fish are primarily fed Artemia at early life stages. Development of alternative feeding strategies could decrease the Artemia reliance of ornamental producers, reduce labor costs, and improve industry resilience by diversifying larval feeding options. In this study, Corydoras aeneus, Synodontis eupterus, Synodontis nigriventris, Epalzeorhynchos bicolor, Pterophyllum scalare, and Trichogaster lalius larvae were offered one of four diets at first feeding: newly hatched Artemia or one of three microparticulate diets (MDs). After 14 days of feeding, survival and standard length (SL) were evaluated, and partial budget analyses (PBA) were conducted to evaluate the economic feasibility of replacing Artemia with MDs. For all species except E. bicolor, at least one MD performed as well as or better than Artemia with regard to the parameters in question. E. bicolor exhibited reduced survival when fed MDs compared to Artemia, although SL did not vary significantly among treatments. PBAs indicated that replacing Artemia with MDs at first feeding resulted in an average net benefit of $0.043 ± 0.004 for all species except E. bicolor, which resulted in a net cost of $0.048. These results indicate that MDs represent a physiologically and economically feasible alternative to Artemia for larval culture of many freshwater ornamental fishes.

Evaluation of the effect of larval stocking density, salinity, and temperature on stress response and sex differentiation in the Dwarf Gourami and Rosy Barb

There is a variety of sexual determination and differentiation mechanisms among teleosts. The phenotypic physiology may be influenced by environmental stress during development as well as genetic factors. In these species, increased levels of the stress hormone cortisol during the undifferentiated labile period correlates with masculinization. In ornamental aquaculture, production of monosex male cohorts is desirable in several species, including the Rosy Barb Pethia conchonius and Dwarf Gourami Trichogaster lalius, which exhibit sexual dichromatism, where the males are more vibrantly colored and therefore more commercially valuable than female conspecifics. Internationally, the use of the synthetic androgen 17α-methyltestosterone (MT) to masculinize cohorts of ornamental fish is common. However, in the U.S., it is currently prohibited to use MT in ornamental aquaculture, putting domestic producers at an economic disadvantage. The current study explored the feasibility and efficacy of using environmental stressors during early larval rearing to influence sexual differentiation and skew populations toward a male phenotype.A suite of experiments were conducted during the first 30 days post hatch with both Rosy Barbs and Dwarf Gouramis. The aim of each experiment was to elevate endogenous cortisol levels in developing larvae using environmental stressors, thus potentially inducing masculinization. Stocking density, salinity, and temperature were manipulated to elicit a natural increase in circulating cortisol. Whole body cortisol levels, survival, growth, and sex ratios of fish in replicate tanks were determined for each experimental treatment. In both species, experimental treatments resulted in differences in growth, survival, and whole-body cortisol levels in specific experiments, but only one experiment resulted in modified sex ratios. The first potential evidence of temperature influence on sex determination was observed in Dwarf Gouramis with a significantly reduced proportion of males found after larval rearing in 30 °C conditions compared to 25 °C. These results provide novel insights into the larval stress physiology of these two species, but also suggest limited sexual plasticity perhaps due to a strong genetic sex determination system.

Experimental transmission of infectious spleen and kidney necrosis virus (ISKNV) from freshwater ornamental fish to silver sweep Scorpis lineolata, an Australian marine fish.

The Australian native marine fish species, silver sweep Scorpis lineolata, is susceptible to the megalocytivirus Infectious spleen and kidney necrosis virus (strain DGIV-10) obtained from a freshwater ornamental fish, dwarf gourami Trichogaster lalius. This was demonstrated by direct inoculation and through cohabitation. Transmission by cohabitation was also demonstrated from inoculated freshwater Murray cod Maccullochella peelii to euryhaline Australian bass Macquaria novemaculeata and to marine silver sweep. The virus was also transmitted from infected marine silver sweep to euryhaline Australian bass and then to freshwater Murray cod. This study is the first to demonstrate the virulence of a megalocytivirus derived from ornamental fish in an Australian marine species and the first to show a feasible pathway for the exchange of megalocytiviruses between freshwater and marine finfish hosts. These results demonstrate that megalocytiviruses from freshwater ornamental fish have the potential to spread to diverse aquatic environments.

EXPERIMENT ON ARTIFICIAL REPRODUCTION OF BROCCOLI (Trichogaster Lalius) WITH HCG AT DIFFERENT DOSAGES

The trail on artificial reproduction of dwarf gourami(Trichogaster lalius) with HCG at different dosages is to identify the maturation ability of Gophers (Trichogaster lalius) and compare the influence of HCG at different doses on the reproductive efficiency of dwarf gourami.The experiment consisted of 4 treatments (NT): 3000UI(NT1), 4000UI(NT2), 5000UI(NT3), 6000UI/kg(NT4) females. Each treatment was repeated 3 times. The results showed that during the conditioning process, environmental factors such as temperature and pH were in the appropriate range for the maturation process of broodstock. The highest maturation rate is 40% in females and 45.83% in males. The survival rate in the conditioning process was quite low at 88.33% in males and 66.67% in females, which however did not affect the results of the experiment. For stimulation to reproduction by HCG at different doses, the fertility rate fluctuates from 33.33% - 66.67% fertility ability ranges from 268.56 to 389.72 eggs / g female, fertilization rate 61.50%, and hatching rate 98.71%. The most appropriate dose of HCG for broccoli is 4000UI and the highest fertility of the four treatments is 389.72 eggs/g females.

A narrative review of the control of mosquitoes by Larvivorous fish in Iran and the world

Background and purpose: Mosquitoes are responsible for the transmission of many pathogens such as malaria, yellow fever, dengue fever, and so on. The control of mosquitoes using chemical insecticides is not always a sensible approach, so, alternative biological control methods, especially the use of larvivorous fishes, can play a significant role in controlling of mosquito larvae.&#x0D; Materials and Methods: In this narrative review study, papers and dissertations were collected without time and language limits from international electronic databases in Google Scholar, PubMed, ScienceDirect, Web of Science, Ovid, Medline and WHO site, and Iranian scientific databases including: Barakatkns, SID, Civilica, Magiran, and Medlib using appropriate keywords from 1937 to 2018. Finally, 55 sources were selected and criticized, interpreted, and analyzed.&#x0D; Results: In the study, some of larvivorous fishes including Aphanius dispar, Carassius auratus (goldfish), Gambusia affinis, and Poecilia reticulate (guppy) have been investigated as important predators of mosquito larvae. Among these fish, Gambusia, Aphanius dispar, Colisa Lalia, Danio rerio, Goldfish, Guppy and Oreochromis mossambica are present in different regions of Iran.&#x0D; Conclusion: Given the fact that malaria carriers are present in many regions of Iran and the climate of Iran is also potentially suitable for the transmission of malaria, it is recommended to use larvivorous fishes that are compatible with the environmental conditions of each area.