Effects of satiation on feeding and swimming behaviour of planktivores

Hunger affects the feeding and swimming behaviour in fish. After 36 h of food deprivation, the feeding and swimming behaviour of Pseudorasbora parva (Cyprinidae) was studied under different prey densities (0.5, 1, 2, 5, 10 and 25 of Daphnia pulex per liter). The initial feeding rates showed marked variations in relation to prey availability. Under high prey densities, the initial feeding rate of fish was higher and subsequently decreased faster, when compared to those feeding under low prey densities. At higher prey densities, two factors were involved: that of higher prey encounter rates and also the attainment of food satiation at a faster rate. Across all prey densities, the feeding rates of fish reached a plateau after satiation. The swimming speed of fish was found to be negatively related to the prey density and a significant change in swimming speed was noted as being directly related to the level of satiation. It was found that the increasing satiation level greatly influenced the handling time and reactive volume of predator, which finally caused reduced feeding rates.     

Development of paratransgenic Artemia as a platform for control of infectious diseases in shrimp mariculture

Aim: To study the accumulation and retention of recombinant proteins in Artemia gut for optimizing paratransgenic disease control in shrimp aquaculture. Methods and Results: Transgenic Escherichia coli expressing fluorescent marker proteins and the transgenic cyanobacterium Synechococcus bacillarus expressing a functional murine single chain antibody, DB3, were fed to Artemia franciscana. Stable expression and retention of several marker molecules (e.g. GFP, DS Red and DB3) up to 10 h after of feeding with E. coli were evident within the gut of Artemia. Engineered strains of S. bacillarus expressing DB3 accumulated within the gut of Artemia with detectable antibody activity for 8–10 h of feeding via ELISA, coincident with the time period of the highest density of transgenic S. bacillarus in the Artemia gut. Conclusions: Artemia fed transgenic bacteria or algae accumulated recombinant proteins for up to 10 h that retained biological activity. Co‐delivery of multiple recombinant proteins simultaneously in the gut of Artemia was also demonstrated. Significance and Impact of the Study: Expression of molecules that target infectious agents of mariculture in shrimp via commonly deployed feed organisms such as Artemia could potentially offer powerful new tools in the ongoing global effort to increase food supply.     

Hunger-induced foraging behavior of two cyprinid fish: Pseudorasbora parva and Rasbora daniconius

The feeding and swimming behaviors of Pseudorasbora parva and Rasbora daniconius (Cyprinidae) with two different prey types (Daphnia pulex and Artemia salina) at different densities (0.5, 1, 2, 5, 10, or 25 per l) were studied after 36 h of food deprivation. Full satiation was defined as the cumulative number of attacks performed until fish attain a constant attack rate which for P. parva was 425 and R. daniconius was 390 attacks. Initial feeding rates showed marked variation with prey availability. Feeding rates of fish in high prey concentrations were higher at the beginning of the experiment and decreased faster than in low prey densities. Decreases in the feeding rate at high prey densities were due to faster attainment of satiation. Feeding rates of fish across high prey densities reached a steady level after satiation. Swimming speeds of fish were inversely proportional to prey density. Moreover, the change in swimming speeds was directly related to the level of satiation. The ratios of the attack rate and the encounter rate against prey density of both fish reveal that the search for prey triggered swimming and thereby feeding during the transition from hungry to satiation. The findings of this study demonstrate that satiation plays an important role in fish foraging that should be considered a significant factor in foraging analysis.     

Neural and molecular dissection of a C. elegans sensory circuit that regulates fat and feeding

A major challenge in understanding energy balance is deciphering the neural and molecular circuits that govern behavioral, physiological, and metabolic responses of animals to fluctuating environmental conditions. The neurally expressed TGF-β ligand DAF-7 functions as a gauge of environmental conditions to modulate energy balance in C. elegans. We show that daf-7 signaling regulates fat metabolism and feeding behavior through a compact neural circuit that allows for integration of multiple inputs and the flexibility for differential regulation of outputs. In daf-7 mutants, perception of depleting food resources causes fat accumulation despite reduced feeding rate. This fat accumulation is mediated, in part, through neural metabotropic glutamate signaling and upregulation of peripheral endogenous biosynthetic pathways that direct energetic resources into fat reservoirs. Thus, neural perception of adverse environmental conditions can promote fat accumulation without a concomitant increase in feeding rate.     

A model for growth of Artemia franciscana cultures based on food ration-dependent gross growth efficiencies

Laboratory cultures of Artemia franciscana grown under batch regimes at constant temperatures (28 °C) and salinity (35 g l^–1), three initial food concentrations (0.1, 0.4 and 1 M cells ml^–1), various daily food rations (0.1–9M Dunaliella tertiolecta cells Artemia ^–1), and different population densities (1–16 ind ml^–1) were used to develop a model of population growth. Growth rates and gross growth efficiencies (K ₁) were largely independent of population densities and initial food concentrations but determined by age and daily amount of food ingested. While maximum growth rates were found with the highest rations, K _{1 max} peaked at rations of 0.5 million cells d^–1 and decreased at feeding levels above this. A contour plot showing the trend relating K ₁ to Artemia size and ingestion rate in combination and was used to model growth in analogous controlled feeding conditions. Computer simulations using this model paralleled published results of final 15-day average individual sizes of Artemia. Optimal results for near constant food utilization are predicted for high initial population densities (100 Artemia nauplii ml ^–1) and daily culls of enough animals to equilibrate food demand with food availability. This strategy could permit a range of Artemia sizes harvested, maximize final individual sizes and retain high total yields (> 1.2 kg dry wt 1^–1). Effects of different culture strategies are discussed.     

Solving post-prandial reduction in performance by adaptive regurgitation in a freshwater fish

Foraging animals must balance benefits of food acquisition with costs induced by a post-prandial reduction in performance. Eating to satiation can lead to a reduction in locomotor and escape performance, which increases risk should a threat subsequently arises, but limiting feeding behaviour may be maladaptive if food intake is unnecessarily reduced in the prediction of threats that do not arise. The efficacy of the trade-off between continued and interrupted feeding therefore relies on information about the future risk, which is imperfect. Here, we find that black carp (Mylopharyngodon piceus) can balance this trade-off using an a posteriori strategy; by eating to satiation but regurgitating already ingested food when a threat arises. While degrees of satiation (DS) equal to or greater than 60% reduce elements of escape performance (turning angle, angular velocity, distance moved, linear velocity), at 40% DS or lower, performance in these tasks approaches levels comparable to that at 0% satiation. After experiencing a chasing event, we find that fish are able to regurgitate already ingested food, thereby changing the amount of food in their gastrointestinal tract to consistent levels that maintain high escape performance. Remarkably, regurgitation results in degrees of satiation between 40 and 60% DS, regardless of whether they had previously fed to 40, 60 or 100% DS. Using this response, fish are able to maximize food intake, but regurgitate extra food to maintain escape performance when they encounter a threat. This novel strategy may be effective for continual grazers and species with imperfect information about the level of threat in their environment.     

Fatty acid composition of Turbatrix aceti and its use in feeding regimes of Coregonus maraena (Bloch, 1779): is it really a suitable alternative to Artemia nauplii?

By incorporating the free‐swimming nematode Turbatrix aceti into early feeding regimes of the European whitefish Coregonus maraena, the suitability of this nematode species was investigated as an alternative to Artemia nauplii. During a 14‐day feeding trial in a total of 25 aquaria each 1.7 L (each treatment n = 5, 255 larvae/tank) T. aceti was used either as the sole live food or in combination with Artemia nauplii or microdiet to determine the effect of T. aceti on growth performance and survival rate of C. maraena. By analysing the fatty acid composition of T. aceti prior to and after enrichment with INVE spresso^® it was investigated whether the amount of n3‐polyunsaturated fatty acids (n3‐PUFA) in T. aceti could be further enhanced. Supplementation of Artemia nauplii with T. aceti increased growth significantly within the first 5 days of rearing in comparison to the non‐supplemented food treatments (14.39 ± 0.15 mm compared to 13.44 ± 0.18 mm; mean ± SE). However, growth and survival of juvenile C. maraena on nematode‐supplemented Artemia nauplii did not differ significantly from non‐supplemented Artemia nauplii at the end of the 14‐day rearing period (15.22 ± 0.15 mm compared to 14.86 ± 0.24 mm). All feeding treatments containing Artemia nauplii showed significantly higher growth and lower mortality at the end of the experiment in comparison to diets containing only the microdiet or T. aceti or a combination thereof. The overall low performance of T. aceti alone can most likely be explained by an insufficient capacity of C. maraena to digest this nematode species efficiently. Enrichment with INVE spresso^® successfully increased the proportion of DHA in the T. aceti tissue. The results reveal that T. aceti cannot be considered a full alternative to Artemia nauplii, at least not in the rearing of C. maraena, but might be a useful vector of essential fatty acids within the early rearing period of this and potentially other fish species when provided as live food along with Artemia nauplii.     

Larval rearing of chub, Leuciscus cephalus (L.), using decapsulated Artemia as direct food

Little is known about the larviculture of the chub, Leuciscus cephalus (L.), an endangered cyprinid species endemic to European flowing waters. The use of decapsulated Artemia cysts as food for chub larviculture was investigated. After 3‐day feeding with the rotifer Brachionus calyciflorus, the larvae were fed on different diets: (i) dried decapsulated Artemia cysts, (ii) Artemia nauplii, (iii) rotifers for seven more days and then Daphnia collected from a pond, and (iv) an artificial diet. After a 24‐day rearing period, the highest survival rate was obtained with the larvae receiving decapsulated Artemia cysts. Feeding of the larvae with an artificial diet resulted in a significantly lower survival rate compared with the other groups. At the end of the experiment, the larvae fed on Artemia nauplii yielded a significantly higher mean length compared with the other groups. Feeding an artificial diet resulted in a significantly lower average weight and mean length gain compared with the other groups.     

Parametric analysis of gastric distension responses in the parabrachial nucleus

The parabrachial nucleus (PBN) is regarded as an important locus for the processing and integration of sensory inputs from oral, gastrointestinal, and postabsorptive receptor sites and is thus thought to play an important role in regulating food intake. Gastric distension is an important satiation cue; however, such responses have been qualitatively characterized only over a limited area of the PBN. To more fully characterize gastric distension responses throughout the PBN, the responses of single units to gastric distension were tested using computer-controlled balloon inflation (3-18 ml air) in pentobarbital sodium- and/or urethan-anesthetized male rats. Distension-responsive neurons were indeed distributed throughout the nucleus from rostral areas typically considered to be visceral to more caudal areas associated with gustatory function, providing further anatomical support for the hypothesis that the PBN integrates taste and visceral signals that control feeding. Most PBN neurons had thresholds of 6 ml or less, similar to vagal afferent fibers. However, in contrast to the periphery, there were both excitatory and inhibitory responses. Increases in volume were associated with two distinct effects. First, as volume increased, the response rate increased; second, the duration of the response increased. In fact, in a subset of cells, responses to gastric distension lasted well beyond the stimulation period, particularly at larger volumes. Prolonged gastric distension responses are not common in the periphery and may constitute a central mechanism that contributes to satiation processes.     

Filter feeding in the hermit crab

Summary The hermit crab, Pagurus bernhardus is able to remove both Artemia nauplii and unicellular algae from suspension. Crabs with wet weights of 1.1–9.2 g consumed all of the 300 Artemia nauplii contained in 200 ml of sea water within 1 h. Crabs weighing 0.7–1.1 g wet weight filtered suspended Dunaliella algae (8 m) from concentrations of 10–350 million cells per liter at a rate of 26% and 47% within 2 and 5 h, respectively. A similar result was obtained with an 11 g crab. During filter feeding activity a water current is generated by the flagella of the exopods of the second and third maxillipeds. Artemia nauplii are caught by grasping movements of the endopods of the third maxillipeds, whereas filtering of unicellular algae is probably achieved by the two maxillae. It is assumed that filter feeding activity depends on the same structures and behavior as in deposit feeding. P. bernhardus is one more example of a benthic marine animal which may use any food source which becomes available in the course of the seasons.     

The influence of feeding on the metabolic activity of Antarctic krill (Euphausia superba Dana)

Summary The influence of feeding on the metabolic activity of juvenile krill was assessed from 24h experiments in which krill were incubated with various concentrations of diatoms (Chaetoceros calcitrans, Phaeodactylum tricornutum, Thalassiosira eccentrica, Fragilariopsis vanheurkii), newly hatched Artemia nauplii and latex beads. Krill fed on the larger food more efficiently, with reluctant feeding on latex beads. Feeding of krill expressed as clearance rates was poorly correlated with their oxygen uptake rates. Instead, a positive correlation was found between the oxygen uptake rates and ingestion rate (except for latex beads). The result implies that the specific dynamic action is the major cause of the increased oxygen uptake of krill. Krill fed diatoms increased both ammonia and phosphate excretion with increasing ingestion rate, but only phosphate excretion was increased in parallel with ingestion rate for those fed Artemia nauplii. Assuming the daily ration of krill in the field is 5% of the body weight, and the major food source is phytoplankton, oxygen uptake, ammonia excretion and phosphate excretion rates of wild krill are estimated to be 1.6, 4.5 and 7.8, respectively, times the rates of non-feeding krill in 24h laboratory experiments. Krill offered various kinds of food showed different metabolic quotients (O/N, N/P and O/P ratios). While no functional relationship was seen between the metabolic quotient and the ingestion rate of krill fed Artemia nauplii, those fed Fragilariopsis showed a progressive decrease in O/N, N/P, and O/P ratios as their ingestion rates increased.     

Larval rearing of burbot (Lota lota L.) using Brachionus calyciflorus rotifer as starter food

Burbot Lota lota L. is one of the endangered freshwater fish species in western Europe for which the development of controlled larval rearing procedures could produce enough material for stock enhancement. The suitability of the freshwater rotifer Brachionus calyciflorus as a start food for larviculture of burbot was investigated. After yolk‐absorption, the larvae were stocked in 40‐L tanks under different feeding conditions: clear water rearing conditions with rotifers (Brachionus calyciflorus) for 10 days (R), green water conditions (Chlorella sp.) with rotifers offered for 10 days (MALR), green water conditions (Chlorella sp.) for 3 days followed by clear water in combination with rotifer feeding for 7 days (AL3R), and clear water conditions with Artemia nauplii offered for 10 days (Art). After the 10‐day feeding, all groups received Artemia nauplii up to 35 days post‐hatching. Larval survival was counted at day 10 and at the end of the 35‐day rearing experiment. At day 35, a significant survival difference was noted between the groups where rotifers were supplemented with algae vs only Artemia. At the end of the experiment, the highest survival rate (69.20%) was obtained with larvae receiving only algae in the first 3 days of feeding. Lowest survival rate (24.90%) was obtained with larvae receiving only Artemia for 35 days. This indicates that smaller prey are essential for burbot at first feeding. Larval length and wet weight were measured at the time of mouth opening, at days 7, 10, and 21, and at the end of the experiment (day 35). On day 35, mean length of the larvae varied significantly between the treatments. However, the final wet weight of the larvae did not vary significantly between the treatments.     

Feeding habits ofMysis relicta — an overview

Mysis relicta has been recognized as an important component of many limnetic food webs. The first approach to studying the feeding habits ofM. relicta was the analysis of stomach contents. Assumptions regarding stomach content analysis have been tested and seasonal feeding estimates ofM. relicta have been reported recently. Laboratory grazing and/or predation experiments have recently been completed usingM. relicta primarily from Lakes Michigan and Tahoe.Mysis relicta is concluded to be opportunistic, capable of utilizing a variety of food resources. It may play an important role in structuring limnetic food webs.     

A Very-Low-Calorie Conventional Japanese Diet: Its Implications for Prevention of Obesity

A very-low-calorie conventional Japanese diet of 370 kcal/day has been shown to be useful for weight reduction and its long-term maintenance. Sources of the diet were mainly from chicken fillet, egg white, fish white-meat, mushroom, seaweed and low-or non-calorie fiber-rich vegetable, and contained 4.4g fat, 38.1g protein, 45.2g carbohydrate and essential minerals and vitamins. However, metabolic and neural implications of a commercial very-low-calorie liquid formula diet have rarely been investigated from the view point of food intake and appetite regulation. Animal studies have demonstrated the rationale for efficacy of the very-low calorie conventional Japanese diet as follows: (1)Increased hypothalamic histamine suppressed food intake through H₁-receptors in the ventromedial hypothalamus (VMH) and paraventricular nucleus, the satiety centers. (2) Low energy intake enhanced satiety and decreased food intake through histaminergic activation of VMH neurons. (3) Mastication activated afferent signal transmission from proprioceptors in the oral cavity to the mesencephalic trigeminal nucleus(Me5). Histaminergic systems in the hypothalamus were activated by mastication and low energy supply, which was accompanied by satiation through the action of histamine in the VMH. Usefulness of the very-low-calorie conventional Japanese diet derives from utilization of conventional Japanese food stuffs as a fiber rich, low energy food source, and from enhancement of satiation by increased mastication required of the diet. The properties of the diet seemed to effect a closed positive feedback loop between histaminergic activation in hypothalamic satiety centers and behavioral changes to enhance satiation and cause feeding suppression.     

Growth response of African catfish,Clarias gariepinus (B.), larvae and fingerlings fed protease‐incorporated diets

African catfish, Clarias gariepinus (B.), is one of the promising freshwater fish species in African aquaculture but the expansion of its farming needs more production of its larvae. The use of live food organisms at first feeding for larvae is still obligatory. That increases the cost of larvae production. Hence, the incorporating of exogenous enzymes especially protease in artificial microdiets may provide affordable alternatives for enhancing the larvae performance. The present study was carried out to evaluate the growth and survival of larvae or fingerlings of African catfish fed artificial diets incorporated with different protease levels. Four artificial diets were formulated and enriched with protease enzyme at levels of 0.0, 750, 1,000, and 1,250 unit/kg diet; after that diets were made into crumbles (100–200 µm diameter). After absorption of the yolk sac, diets were offered to fish larvae (3.6 ± 0.2 mg) in triplicates as a starter feed up to apparent satiation every two hours for 30 days. In another treatment, fish larvae were fed on newly hatched Artemia nauplii (2,500 Artemia/L) as a starter food. In another experiment, African catfish fingerlings (10.1 ± 1.6 g) were fed on the same diets up to satiation twice a day for 2 months. It was noticed that the dietary protease improved larval growth and survival but not as Artemia nauplii did where fish larvae fed on Artemia nauplii showed highest growth and survival followed by those fed a diet enriched with 1,250 unit/kg diet of protease. The mortality of larvae fed protease‐enriched diets as well as the control diet was occurred mostly at the first week reaching its maximum at the third week. The poor growth was observed with fish larvae fed the control diet. Meanwhile, catfish fingerlings fed protease‐enriched diets showed higher growth over those fed the control diet. The larvae survival (11.0%–41.7%) was enhanced by increasing protease levels and it was lower than that of fingerlings (95.6%–100.0%). Furthermore, protein retention and digestibility were significantly improved with protease supplementation over the control diet especially at a level of 1,000 unit/kg diet. As compared with the previous studies, live food should be used in larvae rearing for the first week after that a starter diet enriched with protease at levels of 1,250 unit/kg diet should be used. In case of fish fingerlings, the dry diets should be enriched with 1,100 unit/kg diet to improve diet digestibility and subsequently enhance their growth.     

The adaptive value of gluttony: predators mediate the life history trade‐offs of satiation threshold

Animals vary greatly in their tendency to consume large meals. Yet, whether or how meal size influences fitness in wild populations is infrequently considered. Using a predator exclusion, mark–recapture experiment, we estimated selection on the amount of food accepted during an ad libitum feeding bout (hereafter termed ‘satiation threshold’) in the wolf spider Schizocosa ocreata. Individually marked, size‐matched females of known satiation threshold were assigned to predator exclusion and predator inclusion treatments and tracked for a 40‐day period. We also estimated the narrow‐sense heritability of satiation threshold using dam‐on‐female‐offspring regression. In the absence of predation, high satiation threshold was positively associated with larger and faster egg case production. However, these selective advantages were lost when predators were present. We estimated the heritability of satiation threshold to be 0.56. Taken together, our results suggest that satiation threshold can respond to selection and begets a life history trade‐off in this system: high satiation threshold individuals tend to produce larger egg cases but also suffer increased susceptibility to predation.     

Diatom–salinity relationships in wetlands: assessing the influence of salinity variability on the development of inference models

We determined in situ feeding rates of three co-occurring coastal mysid species using [methyl-³H]-thymidine-labelled algal detritus (Lessonia corrugata), NaH¹⁴CO₃-labelled phytoplankton (Isochrysis galbana) and zooplankton (Artemia sp. nauplii). All three species showed a wide and overlapping range of feeding rates on the three food types, suggesting they were broadly omnivorous. However, selectivity studies often showed a strong preference for animal prey. Although there was an overlap in the types of food the mysids ingested, some degree of feeding niche partitioning was demonstrated. Paramesopodopsis rufa tended to be more carnivorous, Tenagomysis tasmaniae fed least on zooplankton and phytoplankton, and largely on algal detritus, and Anisomysis mixta australis ingested few zooplankters, and moderate amounts of algal detritus and phytoplankton. Handling editor: P. Viaroli     

Rearing tench (Tinca tinca L.) larvae on live feed (Artemia) and on two transition schedules from live to dry diets

Two 60‐day experiments were carried out on tench (Tinca tinca L.) from day 5 post‐hatch. Density was 20 larvae L^?1 and temperature 24 ± 0.5°C. In experiment 1, Artemia nauplii were the sole food, testing nauplii amounts and feeding frequency. High survival rates (between 79.5% and 95.5%) were obtained. Growth was faster as nauplii amounts were greater; the highest growth rate (11.00), weight (265.5 mg) and Fulton’s coefficient (1.40) were obtained when fish were fed in excess once a day, without significant differences from the growth obtained by feeding in excess of eight times a day. In experiment 2, a dry diet for marine fish was tested as a replacement for Artemia nauplii, following two transition protocols, one faster than the other; high survival rates (between 77.7% and 87.1%) were again obtained. The slower transition allowed a growth rate of 10.14, length of 23.1 mm, weight of 158.3 mg and a Fulton’s coefficient of 1.28, without significant differences from the faster transition. At all stages, growth values were significantly higher from feeding nauplii in excess as the sole food, but the required nauplii quantity was six times higher than the amount supplied to the animals fed the dry diet.     

Comparison of some live organisms and artificial diet as feed for Asian catfish Clarias macrocephalus (Günther) larvae

Experiments were conducted to evaluate the efficacy of five live organisms (Artemia, Brachionus calyciflorus, Chironomus plumosus, Moina macrocopa and Tubifex sp.) and an artificial diet (40% protein) in the larval rearing of Asian catfish Clarias macrocephalus. The larvae were fed three times daily starting at the onset of exogenous feeding. Results showed that the catfish larvae utilized the live organisms more efficiently than the artificial diet. The Tubifex‐fed larvae consistently showed the highest growth rate. In trial 1, length increment (64.9 mm), weight gain (3192 mg) and specific growth rate (13.1%) after 8 weeks of feeding were significantly higher (P < 0.05) in catfish larvae given Tubifex than those in all other treatments. In trial 2, length increment after 4 weeks of feeding was highest in larvae fed Tubifex (22.9 mm) although it did not significantly differ from that of larvae given Moina (21.0 mm). However, weight gain of larvae fed Tubifex (253.0 mg) was significantly higher than that of larvae fed Moina (171.6 mg). The specific growth rate was highest for larvae fed Tubifex (15.0%) followed by larvae fed Artemia (14.5%), Moina (14.4%) and Chironomus (12.0%). Survival rates of the catfish larvae ranged from 9 to 39% after 8 weeks in trial 1 and from 26 to 83% after 4 weeks in trial 2. The present results suggest that Tubifex is an excellent food and a potential substitute for Artemia in the rearing of catfish larvae.     

Evaluation of the Impacts of Long-Term Enriched Artemia with Bacillus subtilis on Growth Performance,Reproduction, Intestinal Microflora,and Resistance to Aeromonas hydrophila of Ornamental Fish Poecilia latipinna

The present study investigated the effect of enriched Artemia with Bacillus subtilis on growth performance, reproductive factors, proximate composition, intestinal microflora, and resistance to Aeromonas hydrophila of ornamental fish, Poecilia latipinna. Using a completely randomized design, the experiment included three groups. The first group was fed with commercial food without any probiotic. The second group was fed with unenriched Artemia, and the last group consumed long-time enriched Artemia with Bacillus subtilis. The bacteria B. subtilis with a density of 1 × 10⁵ CFU mL⁻¹ was added daily to Artemia culture medium. The total microflora and Bacillus subtilis counts were significantly increased in enriched Artemia compared to the unenriched group (P < 0.05). In fish fed groups, growth factors did not show any significant difference (P > 0.05). The maximum relative fecundity (28.65 ± 2.52 egg number g⁻¹), fry production (62.93 ± 4.6 individual per female), and fry survival (70.97 ± 1.56%) obtained in the third group were found to be significantly more than those in the first and the second groups. Moreover, intestinal bacterial count for Bacillus revealed that the higher concentration of bacteria was significantly related to the third group (6.24 ± 0.11 log CFU g⁻¹) (P < 0.05). Maximum protein and fat contents were observed in fish fed with Bacillus-enriched Artemia; however, no significant difference was found between control and unenriched Artemia groups (P > 0.05). The highest amount of ash was observed in fish fed with commercial food without any probiotic (P < 0.05). At the end of the feeding period, each of the three groups along with positive group (oxytetracycline 100 mg kg⁻¹ of commercial food) was exposed to A. hydrophila (BCCM5/LMG3770) bacteria intraperitoneally. Based on the results, the lowest cumulative mortality was significantly found in group three (68.75 ± 3.6%) and positive group (62.5 ± 7.0%) compared to control and unenriched Artemia groups (P < 0.05). Hence, B. subtilis with a concentration of 1 × 10⁵ CFU mL⁻¹ during the period of Artemia culturing can improve the reproductive parameters, intestinal microflora, and resistance to pathogenic bacteria of Poecilia latipinna.