Larvae Research Articles

Garden Snail Predatory Insects’ Modus Operandi Under Laboratory Conditions

Heliciculture farms are susceptible to significant biotic issues that can impact snail breeding, among them, the entomofauna predation of snails. Predatory insects can cause damage to snail shells during predation, and sometimes, the specific type of damage may be characteristic of certain insect families or species. Under laboratory conditions, we analysed the predatory activity of the species Silpha tristis Illiger, 1798 (Coleoptera: Silphidae), Ocypus olens (Müller, 1764) (Coleoptera: Staphylinidae), Carabus (Macrothorax) morbillosus constantinus Kraatz, 1899 (Coleoptera: Carabidae), and Lampyris sardiniae Geisthardt, 1987 (Coleoptera: Lampyridae) against the gastropod Cornu aspersum (Müller, 1774) reared on snail farms located in the Sardinian region. The adult and larval stages of each species were tested, except for L. sardiniae, as only the larval stage preys upon snails. This study showed that among all of the species considered, only two insects were able to damage the shell of C. aspersum: C. morbillosus constantinus and O.olens. This may prove valuable in C. aspersum breeding for the recognition of specific lesions, even in the absence of the predator.

Tolerance of free-living larval stage of a parasite from coastal mining areas in northern Humboldt Current to copper pollution at low and high temperatures.

Metal pollution is a worldwide problem and one of the greatest threats to ecosystem integrity due to its toxicity, persistence, and bioaccumulation in biological systems. Anthropogenic pollution impacts marine organisms and host-parasite dynamics, with the northern Chilean coast experiencing elevated copper levels in marine waters and sediments due to mining activities. In this study, we assessed the effects of exposure to copper concentrations at low and high-water temperatures on the survival and longevity of the marine parasite Himasthla sp. cercariae (Trematoda: Digenea) using the snail Echinolittorina peruviana as its first intermediate host. Snails were collected from intertidal rocky pools in northern Chile (23°S). To assess parasite survival and longevity, cercariae were collected from a pool of infected snails, and their mortality was recorded every 6 hours until all cercariae were dead. In a preliminary experiment conducted at 19°C, cercariae were exposed to different copper concentrations (0.2, 1.5, 3.0, and 6.0 mg/L) for 78 hours. Cercariae showed tolerance to copper. However, at the higher copper concentration (6 mg/L), survival was negatively impacted (50%) at 54 hours. In contrast, at the lower concentration (0.2 mg/L) and in the control group, cercariae sustained a 73-90% survival rate even after 54 hours. Based on these findings, we conducted subsequent experiments involving two copper treatments (0.2 and 3.0 mg/L) and two temperatures (14 and 22°C). Survival and longevity were significantly higher at lower temperature and copper concentration (14°C and 0.2 mg/L). Conversely, at higher temperature and copper concentration (22°C and 3 mg/L), survival and longevity decreased to only 66 hours. Our results show that Himasthla sp. cercariae tolerated most copper concentrations, with vulnerability observed primarily in high water temperatures, indicating an adverse effect on cercariae performance. This study contributes valuable insights into how parasites respond to environmental pollution, in marine ecosystems influenced by anthropogenic activities.

Night-time light-traps and push–pull integrated system enhanced the control of different life stages of fall armyworm, Spodoptera frugiperda, (Lepidoptera: Noctuidae)

BackgroundMaize, Zea mays L (Cyperales: Poaceae), is one of the major cereal crops grown in Ethiopia for its food and feed values. Recently, the fall armyworm (FAW) (Spodoptera frugiperda) has become a major challenge of maize production threatening smallholder farmers in the country. Developing effective and smallholder farmers-friendly integrated pest management for FAW is vital. Therefore, a study was conducted to evaluate the effect of night-time light-traps and push–pull integrated system on controlling different life stages (adult, larvae and eggs) of FAW.MethodsThe study was conducted in Northern Ethiopia included four treatments; maize monocrop, maize plots with night-time light-trap, a push–pull system, and night-time light-trap and push–pull integrated system. Each treatment was replicated five times. The study was carried out twice involving a rain feed (from July to October 2018) and irrigated (from April to June 2019) experiments.ResultsA significantly greater number of FAW moths were captured on traps placed outside maize field plots treated with light-trap and push–pull integrated system than traps placed outside the maize monocrop, light-trap alone and push–pull alone treated plots during the 2018 and 2019 experiment seasons. As a result, a significantly lower number of moths was found inside maize field plots treated with light-trap and push–pull integrated system than the other treatments. The levels of FAW eggs and larval infestation were significantly lower in maize plots treated with the light-trap and push–pull integrated system than the maize monocrops, push–pull alone, and light-trap alone treated plots. The proportion of plants damaged by FAW larvae was significantly lower in maize plots treated with the light-trap and push–pull integrated system relative to maize plots treated with the other treatments.ConclusionThis study proved that a system integrating night-time light-traps and push–pull results in better and more effective control of different stages of FAW than a push–pull system or night-time light-traps alone.

Azoxystrobin Exposure Impacts on Development Status and Physiological Responses of Worker Bees (Apis mellifera L.) from Larval to Pupal Stages

Honeybee larvae and pupae form the cornerstone of colony survival, development, and reproduction. Azoxystrobin is an effective strobilurin fungicide that is applied during the flowering stage for controlling plant pathogens. The contaminated nectar and pollen resulting from its application are collected by forager bees and impact the health of honeybee larvae and pupae. The current study evaluated the survival, development, and physiological effects of azoxystrobin exposure on the larvae and pupae of Apis mellifera worker bees. The field-recommended concentrations of azoxystrobin were found to suppress the survival indices and lifespan in the larval as well as pupal stages; moreover, the rates of the survival and pupation of larvae as well as the body weights of the pupae and newly-emerged adult bees were significantly reduced upon long-term exposure to azoxystrobin. In addition, azoxystrobin ingestion induced changes in the expression of genes critical for the development, immunity, and nutrient metabolism of larvae and pupae, although the expression profile of these genes differed between the larval and pupal stages. Results indicated the chronic toxicity of azoxystrobin on the growth and development of honeybee larvae and pupae, which would affect their sensitivity to pathogens and other external stresses during the development stage and the study will provide vital information regarding the pollination safety and rational use of pesticides.

Fitness Costs in Diamondback Moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) Resistant to Lufenuron, A Chitin-Synthesis Inhibitor Insecticide

The diamondback moth (DBM), Plutella xylostella, is the main pest of Brassicas crops worldwide, and its recorded resistance to 101 active ingredients indicates it is difficult to control. The purpose of this study was to investigate the hypothesis that P. xylostella has fitness costs associated with its resistance to lufenuron, a chitin-synthesis inhibitor insecticide. Thus, concentration–mortality bioassays were performed for susceptible (REC-S), resistant (BZR-R) populations, their progenies F1 and F1′, and one established population without selection pressure (BZR-Rns) after four generations. A fertility life table was used to assess the biological performance of the REC-S and BZR-R. BZR-Rns of P. xylostella. The larval stage, longevity, and survival differed between populations. The reproductive rate (R0) was significantly lower in the F1 (♀R × ♂S) (28.19) and F1′ (♀S × ♂R) (34.06) progenies compared with their parents, but not with the relaxed BZR-Rns (39.39). The mean generation time (T), intrinsic rate of population growth (rm), and doubling time (DT) differed between REC-S and progenies, with fitness of 0.52 and 0.64 for F1 and F1′, respectively. Overall, the results suggest that the resistance of P. xylostella to lufenuron is stable and that low fitness costs appear to be associated with resistance to lufenuron, although heterozygotes showed lower fitness than their parents. Strategies such as preserving refuge areas, rotation of modes of action, etc., are essential for resistance management and prolonging the efficacy of control agents; this highlights the importance of integrated insecticide resistance management.

Biological performance of Bollgard II® Bt-resistant vs susceptible population of pink bollworm, Pectinophora gossypiella (Saunders) on non-toxic diet

BackgroundThe pink bollworm, Pectinophora gossypiella (Saunders), is a devastating global pest of cotton that has caused substantial economic damage to Bt Bollgard-II® cotton plants in recent years due to the evolution of Bt resistance. The associated fitness cost is assumed to be one of the factors delaying the development of resistance against Bt transgenic crops. Hence, the present study was undertaken to assess the biological performance of pink bollworms by comparing the life history and demographic parameters of a resistant (Field-R) and susceptible (Lab-S) population.ResultsProlonged larval duration (23.40 days in Field-R vs 18.80 days in Lab-S population), total life cycle (male = 50.00 vs 42.80 days; female = 53.60 vs 46.20 days), reduced fecundity (100.60 vs 154.20 eggs/female) and fertility (88.00 vs 138.00 fertile eggs/female) was observed. The demographic parameters indicated a significant reduction in the net reproductive rate (184.27 vs 276.72), innate capacity for increase in number (0.11 vs 0.15), finite rate of increase in number (1.12 vs 1.16 female progenies produced/female/day), weekly multiplication rate (2.16 vs 2.86), potential fecundity (545.06 vs 634.11 eggs), number of hypothetical F2 females (33 955.65 vs 76 572.41), but longer mean length of generation (47.54 vs 37.74 days) and population doubling time (6.30 vs 4.62 days) in Field-R compared with Lab-S population. A stage-specific life table demonstrated the differences in survival rates between susceptible and resistant populations at various life stages, with the resistant population having higher generation mortality (0.22 vs 0.19).ConclusionsThe study confirms the involvement of fitness costs associated with Bt resistance in P. gossypiella. Despite reduced reproductive fitness, the resistant population tried prolonging the larval stage as a compensatory mechanism to repair the damaged host tissues due to Bt intoxication and for accumulation of enough nutrient reserves for normal pupation and adult emergence. Presence of a high proportion of double Bt-resistant larvae in the field coupled with continued noncompliance with refug planting certainly favours the flaring up of this monophagous pest despite the observed fitness costs. The resistance cannot be effectively reversed unless suitable alternative management strategies are deployed.

Modular shadowgraph imaging for zooplankton ecological studies in diverse field and mesocosm settings

AbstractVarious iterations of shadowgraph imaging have been used to quantify zooplankton in situ with high spatial resolution. Because these systems can image relatively large volumes of water, they are especially useful for resolving less common meso‐ or macrozooplankton taxa (< 50 ind. m−3), such as larval fishes and gelatinous animals. However, larger volume imagers are typically integrated with heavy towed vehicles and deployed from research vessels, which introduces high costs and limits sampling approaches. Here we demonstrate that versatile configurations of shadowgraph imaging, including modular benchtop, handheld, and towed, compact vehicle systems (along with customizable software), allow for tailoring sampling to a variety of marine and freshwater settings (including mesocosms). These systems encompass a suite of possible architectures, designed for adapting the imaging depth of field, acquisition rates, sensor configuration, and deployment method to fit a wide range of sampling protocols, with high vertical resolution (~ 5 cm) and adequate taxonomic capabilities for > 0.5 mm organisms. The benchtop system facilitates an interactive approach to observe and quantify zooplankton behaviors and optical properties. Video footage from the benchtop system generates thousands of regions of interest min−1 for target organisms with variable orientations and swimming postures. When used in conjunction with in situ imaging, the benchtop system can build large machine learning training libraries targeted toward rare or morphologically diverse zooplankton, which often includes the larval stages of economically valuable taxa. These modular hardware and software components increase affordability and versatility while broadening the scope of scientific questions addressed by plankton imaging systems.

Ramming the parasites: Evaluation of quarantine procedures against Haemonchus contortus at sheep markets in Sweden

In Sweden, it is recommended to treat rams at sheep markets with ivermectin and then keep them in quarantine to minimise the risk of transmission of Haemonchus contortus between farms. The aim of this study was to evaluate the effectiveness of this practise. Accordingly the gastrointestinal parasite status of 50 rams purchased at two sheep markets in central Sweden in autumn 2019 was investigated using faecal samples collected on the day of sale (test 1), 12 ± 3 days after ivermectin injection (test 2, in quarantine) and a few months later before inclusion in the new flocks (test 3). We used both traditional diagnostic methods (i.e. identification of nematode eggs in faeces or larvae in cultures when H. contortus eggs could not be identified) and a molecular test based on the digital droplet PCR platform to further identify positive samples. In test 1, conducted in autumn, 40 % of rams were FEC-positive, but only 12 % (six rams) were infected with H. contortus according to conventional routine diagnostics. In test 2, 8 % (four rams) were FEC-positive, including one with 1050 eggs, 90 % of which were identified as H. contortus. This ram was therefore returned to the supplier. However, ivermectin was found to be effective when this animal and a group of lambs from the same farm were treated and tested again. Test 3 was performed on 44 of the same rams (in addition to the returned ram, two rams died in quarantine and the samples from three rams were never provided by the owners). The proportion of FEC-positive animals was 42 %, with an even higher proportion (27 %) of animals being H. contortus-positive than in test 1. The corresponding results for tests 1, 2 and 3 with the ddPCR assay were 18 %, 4 % and 76 %, respectively. This study demonstrates the superiority of DNA detection over microscopy, which is the mainstay in most diagnostic laboratories. Although the combined results confirm that H. contortus survived quarantine in two rams, in the other cases it is not clear whether the spring infection rates are due to re-emergence of persistent larvae from quarantine or reinfection on the new farm. These results suggest not only that we should recommend that sheep farmers use a more sensitive molecular test when purchasing and introducing new animals to their flock, but also that the reliability of injectable ivermectin as a quarantine treatment for removal of adult and larval stages needs further investigation.

Embryonic and Pre-Larval Developmental Patterns in Cryptocentroides arabicus (Teleostei, Gobiidae).

The Arabian goby, Cryptocentroides arabicus (Gobiidae: Gobiinae), is a significant species in marine and brackish water ecosystems. However, limited information is available about the reproductive biology and the early life history of this species. This study aimed to understand the embryonic and pre-larval development of C. arabicus under controlled laboratory conditions using light microscopy. Ten fish pairs were placed in five 70-L glass aquaria, and environmental parameters were carefully monitored. After 4 months, spawning began, with each event yielding between 700 and 1500 eggs, totaling 10 spawning events. The elliptical-shaped eggs, measuring 3.9 ± 0.1 mm in length and 1.6 mm in maximum width, hatched after 7 days and 4 h at a water temperature of 28°C. This process resulted in the identification of eight distinct larval developmental stages. Parental care by both the male and female was observed during the incubation period. Documenting the morphological changes during incubation contributes to a better understanding of the reproductive behaviour and early life history of C. arabicus. This is essential for the conservation management of marine and brackish water environments.

Selection, inheritance, life-history traits, and flight capacity of Grapholita molesta (Lepidoptera: Tortricidae) resistant to lambda-cyhalothrin.

Grapholita molesta (Busck) (Lepidoptera: Tortricidae) is a globally significant fruit pest traditionally managed using chemical insecticides such as lambda-cyhalothrin. However, repeated applications have led to the development of resistance in field populations. The mechanisms and fitness costs associated with lambda-cyhalothrin resistance in G. molesta remain poorly understood. In this study, we established a lambda-cyhalothrin-resistant strain (RS) of G. molesta through continuous selection with lambda-cyhalothrin in the laboratory for 21 generations, resulting in a 249.6-fold increase in resistance. Bioassay data from the F1 progeny (F1RS and F1SR) of reciprocal crosses between RS and susceptible strain (SS) showed similar degrees of dominance (0.40 for F1RS and 0.32 for F1SR). Significant differences between observed and expected mortalities of backcross individuals suggested that resistance to lambda-cyhalothrin is polygenic. Compared to the SS strain, the RS strain exhibited significantly prolonged periods of larval, prepupal, and pupal stages, as well as a significant decrease in larval weight. In addition, the RS strain showed significant reductions in fecundity, cumulative flight distance, maximum flight distance, cumulative flight time, maximum flight time, and average flight speed. These results suggest that resistance to lambda-cyhalothrin in G. molesta is autosomal, incompletely dominant, and polygenic. Life-history traits such as fecundity and flight capacity were significantly reduced in RS strains compared with the SS strain. These findings provide valuable insights for mitigating lambda-cyhalothrin resistance development and promoting sustainable control of G. molesta in the field.

Impacto socioambiental de la pesquería del pulpo maya en San Francisco de Campeche

The Maya octopus’ fishery in the Gulf of Mexico faces significant challenges. Although efforts to implement sustainable practices, overexploitation has occasioned socio-environmental issues in the Yucatán Peninsula. The red octopus (Octopus maya) has a unique reproductive cycle, lacking a larval stage, where females die after caring for their eggs, increasing natural mortality and complicating fishery management. Although it is a vital and cherished resource in local cuisine, the state of the fishery threatens its existence. This research aims to understand the socio-environmental impact of the octopus’ fishery in Campeche, examining the characteristics of the fisheries, the fishers, their economy, and the involved organizations. The study highlights the importance of participation in fishery management and the development of strategies to reduce the economic vulnerability of fishers. The results underscore the need for sustainable practices and proper marine resource management. Keywords: Overfishing, octopus’ fishery, Campeche.

Successful management of Stegasta bosqueella (Lepidoptera Gelechiidae) in peanut with an attract-and-kill strategy.

Rednecked Peanutworm Stegasta bosqueella control is primarily achieved using broad spectrum insecticides targeting the larval stage. However, due to inconspicuous behavior and limited movement of the larvae within the peanut crop, foliar insecticides alone have been insufficient to reduce S. bosqueella populations. The poor effectiveness of chemical products, combined with the necessity of frequent fungicide applications, leads to an overuse of pesticides in peanuts. Given the challenges associated with targeting the larval stage, alternative strategies are needed to improve pest management. Our hypothesis was that by targeting the adult stage, the most mobile stage of the insect, we could decrease the levels of S. bosqueella damage in peanut crops while being less aggressive to the environment. Over 2 years, our study demonstrated that semiochemical-food-based attract and kill treatments significantly reduced the number of S. bosqueella adults captured per food-baited trap per week. This reduction was associated with fewer larvae and decreased plant damage compared to untreated control areas. To optimize this strategy, several key practices must be followed: (a) Prompt treatment application (chemical associated with attractant) should be applied upon detection of an increase in adult trap catches; (b) Timing applications to coincide with peak adult movement (6 pm to 9 pm); and (c) Applying treatments strategically on two peanut rows, 50 m apart, per hectare. The attract-and-kill method can effectively reduce S. bosqueella damage in peanut crops, and has the potential to target other moth species that act as peanut defoliators. © 2024 Society of Chemical Industry.

Effects of Overexpression of Specific Subunits SAYP, BAP170 of the Chromatin Remodeling Complex in Drosophila Melanogaster.

The phenotypic manifestations of increased expression of the Bap170 and e(y)3 (SAYP) genes in D. melanogaster were analyzed. Using the wing disc model, we show that moderate co-expression of Bap170 and e(y)3 genes in wing discs leads to abnormalities in wing veining. which was probably caused by suppression of EGFR/Ras/MAPK signaling pathways. Strong induction of co-expression of the above genes in wing discs leads to complete suppression of wing development in adults. Ubiquitous co-expression of Bap170 and e(y)3 is lethal at the 1st instar larval stage and leads to the formation of melanotic tumors. The above phenotypes are observed exclusively when Bap170 and e(y)3 are co-expressed. This evidence suggests a robust synergistic effect of the combined action of these genes, which is manifested in the hyperactivity of cell proliferation and differentiation.

Modeling the Bioenergetics and Life History Traits of Chironomus riparius–Consequences of Food Limitation

Chironomids have a number of characteristics that make them a useful group for investigating the impact of environmental and chemical stressors on their life cycle stages. It is crucial to first understand sensitivities to environmental factors and provide a basis for interpreting the results of toxicity tests. We focused on Chironomus riparius–one of the most studied species in aquatic toxicity tests—to understand the changes during the larval stage under conditions of food abundance and limitation. We developed a model based on Dynamic Energy Budget (DEB) theory, a framework to capture the entire life cycle of an individual under varying food and temperature conditions. Available information from this study and the literature pointed out that the first three larval instars are immature and the fourth larval instar is mature, during which the organism saves, in two phases, energy for essential processes occurring during the subsequent non-feeding stages. The model can successfully predict the observed prolonged fourth instar duration under food limitation, the times of life history events (e.g., pupation and emergence), and egg production. This model has the potential to be integrated with toxicokinetic–toxicodynamic models to study the effects of toxicants on a variety of biological traits.

Gusto por la fruta: primer registro de Rekoa marius (Lucas, 1857) (Lepidoptera: Lycaenidae: Eumaeini) sobre Averrhoa carambola L. (Oxalidales: Oxalidaceae)

Information on the natural history of Rekoa marius (Lucas, 1857) is presented through the first record of the species on Averrhoa carambola L. The larvae of this lepidopteran were collected on A. carambola and reared under laboratory conditions. Eggs were found on the flower bud, inflorescence and peduncle near the flower. All larval stages feed on flower buds, while the last larval stage also feeds on green and ripe fruits. Pupae with egress holes of different diameters were found, probably of parasitoids. Since Oxalidaceae species are rich in oxalic acid, R. marius may be a potential model for future studies on the mechanisms involved in the response of this species to oxalic acid present in its host plant.

The oldest tadpole reveals evolutionary stability of the anuran life cycle.

Anurans are characterized by a biphasic life cycle, with an aquatic larval (tadpole) stage followed by an adult (frog) stage, both connected through the metamorphic period in which drastic morphological and physiological changes occur1. Extant tadpoles exhibit great morphological diversity and ecological relevance2, but their absence in the pre-Cretaceous fossil record (older than 145 million years) makes their origins and early evolution enigmatic. This contrasts with the postmetamorphic anuran fossil record that dates back to theEarly Jurassic and with closely related species in the Late Triassic (around 217-213 million years ago (Ma))3. Here we report a late-stage tadpole of the stem-anuran Notobatrachus degiustoi from the Middle Jurassic of Patagonia (around 168-161 Ma). This finding has dual importance because it represents the oldest-known tadpole and, to our knowledge, the first stem-anuran larva. Its exquisite preservation, including soft tissues, shows features associated with the filter-feeding mechanism characteristic of extant tadpoles4,5. Notably, both N. degiustoi tadpole and adult reached a large size, demonstrating that tadpole gigantism occurred among stem-anurans. This new discovery reveals that a biphasic life cycle, with filter-feeding tadpoles inhabiting aquatic ephemeral environments, was already present in the early evolutionary history of stem-anurans and has remained stable for at least 161 million years.

Organ Tropism of Angiostrongylus vasorum Larval Stages in Infected African Giant Snails (Lissachatina fulica)

Angiostrongylus vasorum is a metastrongyloid lungworm causing severe cardiovascular disease in domestic and wild animals. During its heteroxenous life cycle, A. vasorum requires obligate gastropod intermediate hosts. Little is known about A. vasorum larval organ tropism and development in gastropod intermediate hosts. Thus, the aim of this study was to analyze in vivo development of A. vasorum larval stages in experimentally infected African giant snails (Lissachatina fulica). Adult L. fulica (n = 26) were orally infected with A. vasorum-L1 and thereafter continuously euthanized. Gastropod organs were artificially digested and microscopically analyzed for the presence of A. vasorum larvae. Moreover, paraffin-fixed organs were investigated histologically for snail-borne innate immune response. In the current study, the success of L. fulica oral infection was demonstrated, thereby reaching infection rates of up to 49.7%. During snail infection, an organ tropism of A. vasorum larvae was detected for the lungs and the foot muscular tissue. Overall, A. vasorum-driven gastropod innate immune reactions against larvae varied greatly. In some specimens, larvae were found effectively ensnared by recruited hemocytes, resulting in granuloma formation, whilst in others, hemocyte-mediated reactions were barely observed. Nevertheless, these evidences demand more studies on hemocyte-derived effector mechanisms against A. vasorum.

Revival of cryopreserved larvae from the important aquaculture species Pacific White Shrimp (Litopenaeus vannamei) using vitrification and ultra-rapid laser warming.

Cryopreservation of aquatic embryos or larvae is needed to help safeguard genetics from important wild and captive species, increase aquaculture output, and meet the global demand for protein. To this end, the development of a cryopreservation protocol for nauplius larvae of the commercially important aquaculture species Litopenaeus vannamei, or Pacific white shrimp, was pursued. Toxicity screening was performed using multiple cryoprotective agents (CPA), and a multi-constituent CPA cocktail was developed to achieve reliable vitrification of shrimp larvae encapsulated in 1.0-μL droplets containing gold nanoparticles. Vitrification and ultra-rapid laser warming were used to cryopreserve and revive nauplius-V stage larvae. Laser warming parameters were optimized to protect the pigmented eye spot from laser-induced ablation, and ice recrystallization inhibitors (IRIs) were tested to induce long-term survival. Approximately 54% of revived larvae resumed active swimming, but all failed to molt to the zoea-I stage of development or live beyond 15 hours post warming.

Cry1Ac toxin binding in the velvetbean caterpillar Anticarsia gemmatalis: study of midgut aminopeptidases N

The velvetbean caterpillar Anticarsia gemmatalis is one of the main soybean defoliators in Brazil. Currently, the main biopesticide used to control insect pests worldwide is the bacteria Bacillus thuringiensis (Bt), which produces entomopathogenic Crystal toxins (Cry) that act in the midgut of susceptible insects, leading them to death. The mode of action of Cry toxins in the midgut involves binding to specific receptors present on the brush border of epithelial cells such as aminopeptidase N (APN), alkaline phosphatase (ALP), cadherin, and others. Mutations in these receptors, among other factors, may be involved in the development of resistance; identification of functional Cry receptors in the midgut of A. gemmatalis is crucial to develop effective strategies to overcome this possible scenario. This study’s goal is to characterize APNs of A. gemmatalis and identify a receptor for Cry1Ac in the midgut. The interaction of Bt spores with the midgut epithelium was observed in situ by immunohistochemistry and total aminopeptidase activity was estimated in brush border membrane vesicle (BBMV) samples, presenting higher activity in challenged individuals than in control ones. Ten APN sequences were found in a A. gemmatalis’ transcriptome and subjected to different in silico analysis, such as phylogenetic tree, multiple sequence alignment and identification of signal peptide, activity domains and GPI-anchor signal. BBMV proteins from 5th instar larvae were submitted to a ligand blotting using activated Cry1Ac toxin and a commercial anti-Cry polyclonal antibody; corresponding bands of proteins that showed binding to Cry toxin were excised from the SDS-PAGE gel and subjected to mass spectrometry analysis, which resulted in the identification of seven of those APNs. Quantitative PCR was realized to compare expression levels between individuals subjected to sublethal infection with Bt spores and control ones, presenting up- and downregulations upon Bt infection. From these results, we can infer that aminopeptidases N in A. gemmatalis could be involved in the mode of action of Cry toxins in its larval stage.

Mathematical Model to Study the Effect of Refuge on Cannibalism in Atractosteus tropicus

Cannibalism is a behavior that different species of fish exhibit in the early stages of their life, and it has been widely reported. In Tabasco, Mexico, the ancestral species Atractosteus tropicus is farmed, which is a freshwater fish with a high nutritional and economic value. This species exhibits high cannibalistic behavior both in its larval and juvenile stages, which considerably decreases its production. Therefore, strategies have been developed to mitigate the effects of this behavior. One of them is the placement of shelters (rocks and artificial vegetation), which allow the vulnerable population to protect themselves from cannibals. The goal of this work is to study the effect of shelters on the cannibalistic behavior of the A. tropicus population through a mathematical model. The population is divided into two classes, the vulnerable population (prey) and the cannibal population (predator). Moreover, a system of ordinary differential equations is established, which is analyzed, and sufficient conditions for the coexistence of the two species are shown. Numerical simulations show coexistence by varying levels of refuge. The results obtained in this work can be applied to other populations that exhibit cannibalistic behavior.