High Larval Mortality Research Articles

Competition is the main factor, compared to non-lethal threat of predation, affecting life-history traits of Aedes aegypti (Diptera, Culicidae) mosquitoes.

Mosquito larvae coexist with different species of predators in small freshwater bodies. These environments can vary widely in terms of the amount of food and larval densities. Our objective was to understand the impacts of the non-lethal threat of predation, combined with competition effects on Aedes aegypti development and adult life cycle. We tested the effects of two types of non-lethal threat of predation, divided into nine combinations of larvae densities and resource availability on Ae. aegypti larvae. We measured their isolated and combined impacts on larval mortality rate, time to reach pupation, adult size, and lifespan. Real non-lethal threat of predation resulted in a higher larval mortality (71%), compromised the sizes of the individuals (-7%) and prolonged the lifespan (19%) compared to control. Simulated treatment, the anti-predation behaviors led to an increase in larval mortality (21%) compared to the control treatment. Accelerating the larva's development time (-14%) to escape from a dangerous environment severely compromised the size of the individuals (-23%) and increased adult life (10%). The scarcity of food resources, high levels of competition, and non-lethal threat of predation as well, are effective stressors for Ae. aegypti. We observed that resources (food and space) were more important than predation risk for the fitness of the survivors. However, these stressors, individually or combined, can result in high larvae mortality, altered larval development and pupation, affecting the emergence of the adults, with small sizes and altered lifespan, ultimately reducing the fitness of the individuals. © 2024 Society of Chemical Industry.

Toxicity of pesticide cocktails in amphibian larvae: understanding the impact of agricultural activity on aquatic ecosystems in the Salado River basin, Argentina

Aquatic communities are increasingly exposed to complex mixtures of contaminants, mainly pesticides due to the impact of agricultural activity. The aim of this study was to evaluate the toxicity of an eight-pesticide cocktail on larvae of the South American common toad, Rinella arenarum. The cocktail represents a realistic mixture of insecticides (cypermethrin, chlorpyrifos and lambda-cyhalothrin), herbicides (glyphosate, glufosinate ammonium, prometryn and metolachlor), and a fungicide (pyraclostrobin) previously found in aquatic organisms (Prochilodus lineatus) from the Salado River Basin, an area with strong agricultural pressure. Computational simulations through the Density Functional Tight-Binding method indicated a strong spontaneous trend toward the formation of the cocktail, suggesting that it may act as a novel xenobiotic entity in the environment. The cocktail effects were evaluated in early-developing and premetamorphic larvae, at feasible concentrations found in real scenarios. The mixture led to high mortality and teratogenicity in early-developing larvae. Premetamorphic larvae showed endocrine disruption, oxidative stress, and impairments in detoxification and hepatic functioning. Neurotoxicity, genotoxicity, cardiotoxicity and high mortality under stress conditions were also observed in exposed larvae. This novel evaluation highlights the ecotoxicological risk for aquatic organisms exposed to complex mixtures and underscores the need to consider cocktail effects in studies regarding ecosystems health.

Larvicidal activity, molecular docking, and molecular dynamics studies of 7-(trifluoromethyl)indolizine derivatives against Anopheles arabiensis.

A novel series of 7-(trifluoromethyl)indolizine derivatives (4a-4n) was synthesized using a 1,3-Dipolar cycloaddition reaction. Structure elucidation of the synthesized compounds was done using various spectroscopic techniques. Compounds were assessed for their larvicidal activity against Anopheles arabiensis. Exposure of Anopheles arabiensis larvae to a series of 7-(trifluoromethyl)indolizine at 4µg/mL for 24 and 48h resulted in moderate to high larval mortality rates. Among them, compounds 4b, 4a, 4g, and 4m exhibited the most promising larvicidal activities, with mortality rates of 94.4%, 93.3%, 80.00%, and 85.6%, respectively, compared to controls, Acetone and Temephos. The structural activity relationship analysis of the evaluated compounds revealed that substitution with halogens or electron-withdrawing groups (CN, F, Cl, Br) at the para position of the benzoyl group is crucial for achieving promising larvicidal activity. Molecular docking studies were carried out involving six potential larvicidal target proteins to predict how the tested compounds might work. Compounds 4a and 4b showed strong binding to the Mosquito Juvenile Hormone-Binding Protein (5V13). Molecular dynamics (MD) simulations confirmed the stability of the protein-ligand complexes over the simulation period, reinforcing the reliability of the docking results. Compounds 4a and 4b also exhibited favourable ADMET profiles, showing high oral bioavailability, good permeability, moderate distribution, low plasma protein binding, sufficient metabolic stability, efficient renal clearance and low toxicity. Given the crucial role of Juvenile Hormone in regulating gene expression and developmental pathways through receptor interactions, compounds 4a and 4b show promise as inhibitors of this protein. Inhibiting this process could hinder larval growth and reproduction, presenting a promising approach for early-stage mosquito larvicidal activity. Therefore, compounds 4a and 4b represent lead candidates for further optimization and the development of new larvicidal agents.

Developmental ecology in embryos of an estuarine pupfish endemic of the Yucatan peninsula: Survival out of water, metabolic depression, and asynchronous hatching.

Theory predicts that drought-resistant embryos with extended incubations are evolutionarily favored in environments with high mortality of larvae but safe for eggs. Here, we experimentally test, under common garden conditions, the effect of three incubation temperatures and media on embryonic developmental length, extended incubation out of the water, survival, metabolic rate, and hatching dynamics in the estuarine pupfish Garmanella pulchra. We also described the morphological changes of embryonic cortical structures related to air exposure. We found that embryos incubated out of water in low and medium temperatures present an extended incubation period beyond their hatching capability with a deep metabolic depression. Also, these embryos exhibited a hatching asynchrony not related to water availability. Embryos incubated at high temperatures did not show extended incubation, with decreased probability of survival out of water. Our morphological observations of the embryonic cortical structures reveal that the perivitelline space and hair-like filaments buffer the deleterious drought effects. Our results reveal that G. pulchra possesses life-history traits typical of two separate phenomena: delay hatching and diapause; supporting a true continuum between them, rather than a dichotomy. The evolution of these traits may respond to aerial exposure during low tides in the estuaries of Yucatán they inhabit.

Zootechnical performance, feed efficiency and larval composition of Zophobas morio (Coleoptera: Tenebrionidae) fed with poultry litter-based diets

Abstract The yellow mealworm, super worm, and house cricket are among the most widely produced insects, with high feed conversion efficiency. However, their nutritional composition and development rate generally vary with environmental conditions. From an economic point of view, rearing conditions such as diet, temperature, and development time; insect performance such as mortality and nutritional value are the most important factors. In order to assess the development, growth, feed conversion efficiency, and chemical composition of Zophobas morio (Coleoptera: Tenebrionidae) larvae fed with diets containing poultry litter, an experiment was conducted. Five diets with varying levels of poultry litter inclusion (0, 25, 50, 75, and 100%) were used to replace the control diet (broiler feed), with five replicates containing 25 larvae per sample unit. Larval growth and development were assessed, and the chemical compositions of both the diet and Z. morio larvae were determined. Significant differences were observed among treatments for development time, survival rate, pupa weight, adult weight of Z. morio subjected to different poultry litter-based diets, as well as in the nutritional index bioassay. The longest development time and the highest larval mortality were observed in the 100% poultry litter-based diets. The highest percentage of crude protein in larval meal (%CP) was obtained with the addition of 25 and 50% poultry litter and was lowest with 100%. The incorporation of poultry litter into the diet of Z. morio has a multifaceted impact on growth and feed conversion efficiency. Elevated levels of poultry litter inclusion led to an extension in development time, yet food conversion efficiency attains optimization with an inclusion rate of up to 50%. Consequently, the decision regarding the proportion of poultry litter in the diet should be carefully weighed, taking into account breeding objectives, efficiency considerations, and cost factors. This ensures the attainment of an optimal balance between larval growth and nutritional efficiency.

Assessing the In Vitro Individual and Combined Effect of Arthrobotrys oligospora and A. musiformis (Orbiliales) Liquid Culture Filtrates against Infective Larvae of the Sheep Blood-Feeding Nematode Haemonchus contortus (Trichostrongylidae).

Arthrobotrys species are nematophagous fungi that secrete extracellular nematocidal products (ECP). The individual and combined effects of ECP from Arthrobotrys oligospora (Ao) and A. musiformis (Am) growth in liquid media against Haemonchus contortus L3 (HcL3) were assessed. The isolation, morphological (MI) and molecular identification (Mol-I), assessment of nematocidal activity (NA) of fungal liquid culture filtrates (LCF) in two liquid media alone and in combination and the myco-compound profile identification (MCP) were performed. The MI suggested that the fungi corresponded to the species Ao and Am. This result was confirmed by PCR analysis followed by sequencing, alignment and a phylogenetic analysis. Likewise, the highest Hc mortalities were 91.4% with individual LCF of Am and 86.2% with those of Ao at the highest concentration (100 mg/mL) in Czapek-Dox Broth. The combination of both LCF resulted in a similarly high larval mortality with no statistical differences in relation to individual activity (p > 0.05). The MCP showed the presence of alkaloids in both fungi. Coumarins, sterols and saponins were found only in Ao. Both fungi produced ECP with a high NA that could be identified and assessed in future studies as potential natural anthelmintic compounds.

Roles of a newly lethal cuticular structural protein, AaCPR100A, and its upstream interaction protein, G12-like, in Aedes aegypti

Mosquitoes form a vital group of vector insects, which can transmit various diseases and filarial worms. The cuticle is a critical structure that protects mosquitoes from adverse environmental conditions and penetration resistance. Thus, cuticle proteins can be used as potential targets for controlling the mosquito population. In the present study, we found that AaCPR100A is a structural protein in the soft cuticle, which has flexibility and elasticity allowing insects to move or fly freely, of Aedes aegypti. RNA interference (RNAi) of AaCPR100A caused high mortality in Aedes aegypti larvae and adults and significantly decreased the egg hatching rate. Transmission electron microscopy (TEM) analysis revealed that the larval microstructure had no recognizable endocuticle in AaCPR100A-deficient mosquitoes. A yeast two-hybrid assay was performed to screen proteins interacting with AaCPR100A. We verified that the G12-like protein had the strongest interaction with AaCPR100A using yeast two-hybrid and GST pull-down assays. Knockdown of G12-like transcription resulted in high mortality in Ae. aegypti larvae, but not in adults. Interestingly, RNAi of G12-like rescued the high mortality of adults caused by decreased AaCPR100A expression. Additionally, adults treated with G12-like dsRNA were found to be sensitive to low temperature, and their eggshell formation and hatching were decreased. Overall, our results demonstrated that G12-like may interacts with AaCPR100A, and both G12-like and AaCPR100A are involved in Ae. aegypti cuticle development and eggshell formation. AaCPR100A and G12-like can thus be considered newly potential targets for controlling the Ae. aegypti mosquito.

Efficacy of entomopathogenic fungi for the management of Trogoderma granarium Everts on wheat grains

Four species of Trichoderma genius (T. harzianum, T. citrinoviride, T. viride and T. asperellum) and Metarhizium anisopliae were assessed for their effects on larval mortality and progeny production of Trogoderma granarium Everts (Coleoptera: Dermestidae). The fungal strains were tested at 2.0 × 106, 2.0 × 107, 2.0 × 108 and 2.0 × 109 spores/kg. The larval mortality of T. granarium was recorded after 7, 14 and 21 days of treatment. The emerged adults (F1) from treated larvae were counted after 30 days of treatment, while F2 and grain weight loss were examined after 80 days of treatment. In general, increasing of spore concentration of all fungal strains enhanced the larval mortality. After 21 of treatment, all fungal strains induced notable larval mortality particularly at the highest concentration (2.0 × 109 spores/kg) except T. viride (19.4%). The highest larval mortality was observed in treatments with M. anisopliae (82.1%) and T. citrinoviride (69.0%) at 2.0 × 109 spores/kg, respectively. Furthermore, all spore concentrations of tested fungi decreased the emerged adults (F1 and F2) with M. anisopliae, T. citrinoviride and T. harzianum being the most potent, particularly at 2.0 × 109 spores/kg. After 80 days, M. anisopliae and T. citrinoviride at 2.0 × 109 spores/kg induced the highest protection of wheat grains against larvae of T. granarium with weight loss of 0.7 and 1.3%, respectively. The outcomes of the present study indicate that the two fungi, M. anisopliae and T. citrinoviride are highly effective seed protectants against T. granarium and could be applied in the integrated pest management programs (IPM) of khapra beetle as effective biological control agents.

Struggling to survive: A comparison of Vanessa cardui larval survivorship on putative host plants

AbstractThe painted lady butterfly (Vanessa cardui) is a generalist herbivore with a global distribution. In North America, over 100 species have been identified as V. cardui larval host plants. This cosmopolitan species is commercially available in all life stages and can be reared on an artificial diet. As a result, V. cardui commonly serves as a model organism for education and outreach. However, gaps in our knowledge remain with regard to V. cardui ecology and larval host plant suitability for supporting complete development of larvae to reproductive adulthood. In a laboratory setting, we tested host plant suitability of five reported host plants commonly found in California sage scrub ecosystems by assessing survival of V. cardui caterpillars in its entirety. We also assessed how commercially sourced larvae survived on artificial diet: both raising the caterpillars exclusively on artificial diet as well as switching diets from artificial to thistle (a commonly reported host plant) and switching from thistle to artificial diet. We found that all commercially sourced caterpillars exhibited both high larval mortality and low pupation rates when reared on host plants, although larvae reared on Malacothamnus fasciculatus and Sphaeralcea ambigua survived longest. Moreover, M. fasciculatus and S. ambigua were the only host plants tested that supported successful pupation. This contrasted with 63% higher survival of wild‐collected larvae. Our findings suggest that commercially obtained V. cardui may struggle to utilize wild host plants and that future investigations into host plant suitability in wild populations are needed. Additionally, future research using commercial larvae should consider the implications for interpreting host plant suitability as larvae may exhibit adaptations to artificial diet or the loss of adaptation to consuming plant material.

Larvicidal Efficiency of Citrus maxima against Aedes aegypti and Aedes albopictus

Mosquitoes transmit serious human diseases, causing millions of deaths every year and developed resistance to chemical insecticides resulting in rebounding vectorial capacity. Plants are the alternative sources of mosquito control agents. In the present study, various concentrations of 10, 20, 30, 40, and 50 mg of Citrus maxima (Brunnich) Merr. were tested against the third instar larvae of Aedes aegypti (Linn) and Aedes albopictus (Skuse). The highest larval mortality was found in the extract of C. maxima against third-instar larvae with P value = 0.0287. This study concluded that the increase in concentration of C. maxima extract increased the mortality of Aedes aegypti and Aedes albopictus.

Early ontogeny of the African bony-tongue (Heterotis niloticus) and the effect of Artemia and rotifer live feeds on larval digestive enzyme activity and performance

High larval and fry mortality has been a major challenge to the commercial culture of the African bony-tongue (Heterotis niloticus). Research indicates inadequate feeding to be a possible cause of the high mortality rates of larvae/fry grown in captivity. An experiment was conducted to first describe the developmental stages of H. niloticus eggs and larvae until schooling, 6 days after hatching (DAH), at 26°C. The morphological development, survival, growth (weight gain and length), and swimming behavior of the larvae were monitored. A follow-up feeding trial was conducted with H. niloticus fry from 6 to 27 DAH involving four treatments: feeding with Artemia nauplii; a combined feed of 50% Artemia nauplii and 50% rotifers (w/w); feeding with rotifers; and no feeding. The activities of three digestive enzymes (trypsin, lipase, and amylase) were assessed in fry exposed to the live feed treatments. At hatching, the larvae had a large, vascularized yolk sac filled with yolk platelets, which occupied approximately one-third of the total body length of the abdominal cavity. Yolk platelet reabsorption started at 1 DAH and was complete at 6 DAH. Metamorphosis was completed at 6 DAH, and schooling behavior was observed. For the feeding trial, the fry that received Artemia nauplii underwent the fastest development until 27 DAH. Similarly, the survival rate was considerably higher in fry fed with Artemia nauplii than in those that received a combination of Artemia nauplii and rotifers or only rotifers. Overall, the survival rates for fry fed with Artemia nauplii and larvae co-fed were 72.7% ± 0.9% and 41.2% ± 3.3%, respectively. Fry did not survive until 27 DAH in the rotifer-fed and unfed treatment groups. Digestive enzyme activity differed significantly (p< 0.05) between treatments and sampling dates. All digestive enzymes were detectable at the onset of mouth opening (5 DAH) and fluctuated through the 7 and 9 DAH. Lower enzyme activity was observed when the fry were subjected to starvation or the rotifer treatment. Results indicate that Artemia nauplii is the best live feed organism for H. niloticus larviculture.

Bazı Uçucu Yağların Kimyasal Yapısı ve Laboratuvar Koşullarında Ceratitis capitata ‘nın (Wiedemann) (Diptera: Tephritidae) Larva Canlılığı Üzerindeki İnsekitisidal Etkisi

Aims:The Mediterranean fruit fly, medfly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is a serious pest of many fruits and vegetables. This study was conducted to determine antifeeding and insecticidal activities of some essential oils extracted from Pelargonium graveolens (Geraniaceae), geranium, Lavandula intermedia Mill. (Lamiaceae), lavender, Nigella sativa L. (Ranunculaceae) black cumin, and Laurus nobilis L. (Lauraceae), laurel, against second instars of the Medfly on artificial diet.
 Material and Methods:The essential oils were obtained by Clevenger-type water distillation and a laboratory reared medfly colony was used in the study. Each tested essential oils with 6 different doses were distributed over the artificial diet in a Petri dish having 20 larvae. All experiments were performed under laboratory conditions of 23±1°C, 50% RH and 16: 8 (L:D) photoperiods. Probit MsChart was used to estimate LC50 and LC90 values of the tested essential oils. GGE Biplot analyzes were created with the larval mortality based on the different essential oil doses.
 
 Results: As results, the highest larval mortality was determined with addition of laurel and black cumin oils into the diet. The highest mortality was detected in black cumin oil at the lowest concentrations. Based on GGE Biplot analyzes, the essential oil of black cumin has observable larvicidal properties. 
 Discussion: The results were provided fundemental information about insecticidal and antifeeding properties of the medfly in laboratory.
 Conclusions:Further studies needed to integrate sustainable management programmes with natural insecticides against the medfly larvae.

Control of phytopathogen organisms using bioactive compounds contained in orange wax

AbstractOrange wax (OW) is a waxy waste generated in the essential oil purification process (winterization). It has no commercial value. It is discarded or burnt, polluting the environment. The present study demonstrates the possibility of applying it to control phytopathogens. The ethanol‐soluble bioactive compounds of OW were identified and quantified. The effect of orange wax extracts on the growth inhibition of phytopathogenic fungi (Fusarium oxysporum and Colletotrichum gloeosporioides) and Spodoptera frugiperda larvae was evaluated. High‐performance liquid chromatography–mass spectrometry (HPLC‐MS) and gas chromatography–mass spectrometry (GC–MS) quantified 22 bioactive compounds representing 23% (w/w) of OW. Terpineol, limonene, and eremophilene were the most abundant bioactive substances in this material. The distortion of the radial growth of the fungal hyphae was measured in a potato dextrose agar (PDA), and all tested concentrations (6.3, 12.5, 25, 50, and 100 mg/mL) inhibited the radial expansion of C. gloeosporioides. In contrast, only the OW extracts at 50 and 100 mg mL−1 inhibited F. oxysporum. Spray treatments were performed using a Potter spray tower on third‐instar Spodoptera frugiperda larvae. Spraying OW extract at 50 mg mL−1 for 10 s caused the highest larval mortality. However, third‐instar larvae were attracted to consume corn leaves moistened with extract at lower concentrations. Up to 93% of the first‐instar larvae died after eating corn leaves moistened with the extract at 50 mg mL−1. As far as the authors are aware, this is the first scientific report about the use of bioactive compounds of orange wax to control fungi. Spodoptera frugiperda could form the basis for the manufacture of new biopesticides.

The effects of temperature on pathogenicity of entomopathogenic fungi for controlling larval populations of the European grapevine moth (Lobesia botrana) (Lepidoptera: Tortricidae)

The European grapevine moth (Lobesia botrana) is currently the most damaging pest in many viticultural regions of South and Central Europe and is highly responsible for the development of secondary infections by Botrytis cinerea to both table and wine grapes. Entomopathogenic fungi (EPF) are considered as substantial biological control agents of insect pests. However, they are able to infect their hosts only under a narrow spectrum of environmental conditions. In this study, the effects of temperature on pathogenicity of EPF for the control of L. botrana are reported. Among a collection of 33 EPF isolates, six virulent isolates were selected for the experiments. The bioassays took place at controlled conditions, under the temperature regimes of 20, 22.5, 25, 27.5, 30, and 32.5 °C. A conidial concentration of 1 × 108 conidia/ml was prepared for each isolate, and fungi were applied by spraying them on third-instar larvae (L3) of L. botrana. Both factors, fungal isolate and temperature, significantly affected mortality of L. botrana. Most fungal isolates exhibited their highest larval mortality rates seven days post-treatment at the temperatures of 25 and 27.5 °C. Some isolates caused considerably high larval mortality that exceeded 90% under specific temperature conditions. Overall, EPF showed great potential as bio-control agents for controlling larval populations of L. botrana.

In-vitro Study to Determine the Dose of Beauveria bassiana for Management of Spodoptera frugiperda

Pest insects known as fall army worm (Spodoptera frugiperda) can feed on over 80 different types of crops. It has the potential to significantly reduce the yields of major cereal crops including oats (Avena sativa L.). The oat crop is one of the preferred hosts of this pest. This fodder crop is directly used as animal feed so, chemical control of pests is not preferable. One of the alternatives for the management of fall army worm on fodder oats is the use of microbials which have some advantages over the use of chemical insecticides, as they are highly host specific with low environmental contamination. Beauveria bassiana is a fungus and can be used to control this pest. So, the present study was undertaken to standardize the dose of Beauveria bassiana for management of fall army worm. The virulence test was conducted against third instar larvae of S. frugiperda. The larvae were treated with three doses of B. bassiana of 1×1012spore/ml concentration i.e.,1, 2, and 3ml/L, by dipping them for 30 seconds in 10 ml of suspension. In case of control, larvae were treated with distilled water containing a drop of Tween- 80 (0.02%). At 24 hours after treatment, the differences in the mean larval mortality among different doses of B. bassiana were non-significant. However, at 48 and 72 hours after treatment, the differences in the mean larval mortality among different doses of B. bassiana were significant. Highest larval mortality was recorded at 48 and 72 hours after treatment in 3 ml/L (29.39 and 86.67%, respectively).

Survival of Nematode Larvae after Treatment with Eugenol, Isoeugenol, Thymol, and Carvacrol.

Helminthiases inflict annual losses on the meat and dairy livestock industries. The commonest species of ruminant parasites are the nematodes: Strongyloides papillosus and Haemonchus contortus, which lay eggs in the intestine and enter the feces. There, the eggs develop into larvae, which when voided with the feces crawl onto plants. In our experiment, we evaluated the survivability of the noninvasive and invasive (L1-2 and L3, respectively) larvae of S. papillosus, H. contortus (L3), and Muellerius capillaris (L1) in vitro by subjecting each to natural compounds present in the essential oils of many plants. In the experiment, we used aqueous emulsions of eugenol, isoeugenol, thymol, and carvacrol. Administering 1% concentrations of those compounds killed 100% of the nematode larvae following 24 h of exposure. Thymol, eugenol, and isoeugenol at a concentration of 0.1% also caused high larvae mortality (over 96%). Continuous usage of synthetic anthelmintic drugs in veterinary medicine has led to the parasites developing resistance, thus, a search for novel nematicidal drugs is required. Eugenol, isoeugenol, thymol, and carvacrol are promising compounds against nematodes. However, additional research is required regarding peculiarities in their actions toward the bodies of mammals and parasitic nematodes.

Survival potential and assessment of deformities in embryo and larvae of Chinese carps (Hypophthalmichthys molitrix and Ctenopharyngodon idella) under acute exposure of cadmium and nickel

ABSTRACT The effects of cadmium (Cd) and nickel (Ni) toxicity on embryonic and larval development of Hypophthalmichthys molitrix and Ctenopharyngodon idella was determined. Different concentrations (0.1, 0.3, and 0.5 mg/l) of Cd and Ni were administered in separate trials to the fish after spawning to 168 h post-hatching (hph) period. Cd was more toxic to the embryos of both fish, as highest embryonic mortality (%) of H. molitrix and C. idella was observed. However, Ni was found to be more toxic to the larvae of H. molitrix and C. Idella with highest larval mortality at 168 hph. However, Ni was found to be more toxic to the larvae of H. molitrix and C. idella with highest larval mortality at 168 hph. The study found a significant effect of heavy metal and metal concentration for causing deformities in H. molitrix. However, in C. idella only the effect of metal concentration on fish deformities was significant. Furthermore, Ni was found to cause more deformities as compared to Cd in H. molitrix. While Cd was found to cause more deformities as compared to Ni in C. idella. In conclusion, the study suggests that Cd and Ni may cause serious deformities in fish.

Laboratory-adapted and wild-type black soldier flies express differential plasticity in bioconversion and nutrition when reared on urban food waste streams.

The black soldier fly (BSF) offers a potential solution to address shortages of feed and food sources; however, selecting effective rearing substrates remains a major hurdle in BSF farming. In an urban area like Singapore, current practice is based on rearing BSF on homogeneous waste streams (e.g., spent brewery grains or okara) because heterogeneous food wastes (e.g., mixed kitchen/canteen waste or surplus cooked food) present several operational challenges with respect to the standardization of development, nutritional content, and harvesting. In this study, we compared two genetic strains of BSF larvae (wild-type and laboratory-adapted line) in a bioconversion experiment with diverse types of food waste (homogeneous/heterogeneous; plant/meat) and we quantified the phenotypic plasticity. Our results demonstrate different plasticity in bioconversion performance, larval growth and larval nutrition between the two BSF lines. This difference may be attributed to the selective breeding the laboratory-adapted line has experienced. Notably, larval lipid content displayed little to no genetic variation for plasticity compared with larval protein and carbohydrate content. Despite variation in larval development, heterogeneous food wastes can produce better performance in bioconversion, larval growth, and larval nutrient content than homogeneous food waste. All-meat diets result in high larvae mortality but larval survival could be rescued by mixing meat with plant-based food wastes. Overall, we suggest using mixed meals for BSF larvae feeding. Targeted breeding may be a promising strategy for the BSF industry but it is important to consider the selection effects on plasticity in larval nutrition carefully. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Detection of Aeromonas salmonicida subsp. salmonicida infection in zebrafish by labelling bacteria with GFP and a fluorescent probe based on the siderophore amonabactin

Zebrafish (Danio rerio) is an excellent model to study bacterial infections in fish and their treatment. We used zebrafish as a model of infection for Aeromonas salmonicida subsp. salmonicida (hereinafter A. salmonicida), the causative agent of fish furunculosis. The infection process of A. salmonicida was studied by immersion of zebrafish larvae in 2 different doses of the bacteria and the fish mortality was monitored for three days. The bacterium caused a high mortality (65 %) in zebrafish larvae only when they were exposed to a high bacterial concentration (107 bacterial cells/mL). To evaluate the use of fluorescence microscopy to follow A. salmonicida infection in vivo, two different fluorescent strains generated by labeling an A. salmonicida strain with either, the green fluorescent protein (GFP), or with a previously reported siderophore amonabactin-sulforhodamine B conjugate (AMB-SRB), were used. The distribution of both labeled bacterial strains in the larvae tissues was evaluated by conventional and confocal fluorescence microscopy. The fluorescent signal showed a greater intensity with the GFP-labeled bacteria, so it could be observed using conventional fluorescence microscopy. Since the AMB-SRB labeled bacteria showed a weaker signal, the larvae were imaged using a laser scanning confocal microscope after 48 h of exposure to the bacteria. Both fluorescent signals were mainly observed in the larvae digestive tract, suggesting that this is the main colonization route of zebrafish for waterborne A. salmonicida. This is the first report of the use of a siderophore-fluorophore conjugate to study a bacterial infection in fish. The use of a siderophore-fluorophore conjugate has the advantage that it is a specific marker and that does not require genetic manipulation of the bacteria.

Eco-friendly approaches of zinc oxide and silver nitrate nanoparticles along with plant extracts against Spodoptera litura (Fabricius) under laboratory conditions.

The tobacco cutworm (Spodoptera litura) is a widespread pest that inflicts severe damage on various crops, including cotton, tobacco, and vegetables, with a particular preference for solanaceous plants. Traditional control methods often rely heavily on synthetic insecticides, leading to adverse effects on the environment, human health, and the development of insecticide resistance. In light of these challenges, this study explores the potential of nanotechnology as an innovative and sustainable approach to combat this notorious pest. Bioassays were conducted using laboratory-reared 3rd instar S. litura larvae. Eight different plant extracts coated with zinc oxide and silver nitrate nanoparticles were tested, with concentrations in both distilled water and ethanol at 3, 5, and 7 ml. Data were collected at 24, 48, and 72-h intervals. The results revealed that the highest larval mortality, reaching 98%, was observed in the group treated with silver nitrate nanoparticles derived from Cymbopogon citratus. In comparison, the group treated with zinc oxide nanoparticles dissolved in ethanol exhibited a larval mortality rate of 90%. Ethanol is a polar solvent that is widely used in the synthesis of nanocomposites. It is capable of forming strong hydrogen bonds with oxygen atoms, making it a good dispersant for zinc oxide nanoparticles. Additionally, ethanol has a low boiling point and a non-toxic nature, which makes it a safe and effective option for the dispersion of nanoparticles. Notably, the study concluded that silver nanoparticles combined with ethanol exhibited prolonged and more potent toxic effects against S. litura when compared to zinc oxide nanoparticles. Overall, this research underscores the potential of nanotechnology as a valuable component of Integrated Pest Management (IPM) strategies. By integrating nanotechnology into pest management practices, we can promote sustainable and environmentally friendly approaches that benefit both farmers and the ecosystem.