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Vommaro ML, Giglio A. Cytotoxic and genotoxic effects of a pendimethalin-based herbicide in Apis mellifera. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 280:116565. [PMID: 38870738 DOI: 10.1016/j.ecoenv.2024.116565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2024] [Revised: 05/22/2024] [Accepted: 06/04/2024] [Indexed: 06/15/2024]
Abstract
Public concern about the effects of pesticides on non-target organisms has increased in the recent years. Nevertheless, there is a limited number of studies that address the actual toxic effects of herbicides on insects. This study investigated the side effects of herbicides on non-target organisms inhabiting agroecosystems and performing essential ecological and economic functions such as crop pollination. We analysed morphological alterations in the gut, Malpighian tubules and circulating haemocytes of Apis mellifera workers as markers of exposure effects. A commercial formulation of a pendimethalin-based herbicide (PND) was administered orally under laboratory conditions at a realistic concentration admitted in the field (330gL-1 of active ingredient., 4 L ha-1 for cereal and vegetable crops). The worker bees were exposed to a single application of PND for a period of one week, to simulate the exposure that can occur when foraging bees accidentally drink drops of contaminated water upon treatments. Histopathological analyses of the midgut, ileum and Malpighian tubules showed alterations over time (from 24 to 72 h after the beginning of exposure) such as loss of epithelial organisation, cellular vacuolisation and altered pyknotic nuclei as well as disruption of the peritrophic membrane over time. Semiquantitative analyses of the midgut showed a significant increase in the organ injury index 24 and 72 h after the initial exposure in PND-exposed bees compared to control bees. In addition, a change in positivity to Gram staining was observed in the midgut histological sections. A recovery of cytotoxic effects was observed one week after the initial exposure, which was favoured by the periodic renewal of the intestinal epithelium and the herbicide dissipation time. Cytochemical staining with Giemsa of haemocytes from PND-treated workers over 24 and 72 h showed significant nuclear alterations such as lobed or polymorphic nuclei and micronuclei compared to bees in the control group. These results show that the dose of PND used to protect crops from weeds can lead to significant cytotoxic and genotoxic effects in non-target organisms such as honey bees. In croplands, the sublethal effects on cell morphology can impair vital physiological processes such as nutrition, osmoregulation, and resistance to pathogens, contributing to the decline in biodiversity and abundance of species that play a prominent ecological role, such as pollinators.
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Affiliation(s)
- Maria Luigia Vommaro
- University of Calabria, Department of Biology, Ecology and Earth Science, Rende, Italy
| | - Anita Giglio
- University of Calabria, Department of Biology, Ecology and Earth Science, Rende, Italy.
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Oliveira MSD, Pereira GDS, Martinez LC, Reis AB, Resende MTCSD, Silva LLD, Zanuncio JC, Serrão JE. Effects of chronic oral exposure to insecticide teflubenzuron on the midgut of the honey bee Apis mellifera workers: histopathological insights into pesticide toxicity. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:44908-44919. [PMID: 38955973 DOI: 10.1007/s11356-024-34066-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Accepted: 06/18/2024] [Indexed: 07/04/2024]
Abstract
The honey bee Apis mellifera plays a significant role as a pollinator of native and cultivated plants, by increasing the productivity of several cultures, preserving the flora, and producing forest seeds. However, bee populations are declining worldwide, including A. mellifera, due to Colony Collapse Disorder, mainly resulting from the constant use of pesticides in the crops. Teflubenzuron is a physiological insecticide that belongs to the benzoylurea group, which inhibits chitin synthesis, the main component of the insect integument classified as safe for non-target insects, including bees. However, its effect on non-target organs of insects remains unknown. The midgut is the main organ of the digestive tract, which works in digestion and absorption and may be exposed to pesticides that contaminate food resources. The present work aimed to verify if the insecticide teflubenzuron is toxic and has histopathological effects on the midgut of A. mellifera adult workers. Workers exposed orally and chronically to the field-realistic concentration of teflubenzuron present 81.54% mortality. The epithelium of the midgut of these bees presents high vacuolization, spherocrystals, cell fragments released to the organ lumen, apocrine secretion, nuclear pyknosis, loss of cell-cell contact, and damage to regenerative cell nests and to the peritrophic matrix. These results indicate that the chitin synthesis-inhibiting insecticide teflubenzuron is toxic to A. mellifera after chronic oral exposure, at realistic field concentration, although it is classified as non-toxic to adult and non-target insects.
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Affiliation(s)
- Mateus Soares de Oliveira
- Departamento de Entomologia, Instituto de Biotecnologia Aplicada À Agropecuária, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil
| | - Giovanna Dos Santos Pereira
- Departamento de Biologia Geral, Instituto de Biotecnologia Aplicada À Agropecuária, Universidade Federal de Viçosa, Av. Peter Henry Rolfs S/N - Campus Universitário, Viçosa, Minas Gerais, 36570 000, Brazil
| | | | - Aline Beatriz Reis
- Departamento de Biologia Geral, Instituto de Biotecnologia Aplicada À Agropecuária, Universidade Federal de Viçosa, Av. Peter Henry Rolfs S/N - Campus Universitário, Viçosa, Minas Gerais, 36570 000, Brazil
| | - Matheus Tudor Cândido Santos de Resende
- Departamento de Biologia Geral, Instituto de Biotecnologia Aplicada À Agropecuária, Universidade Federal de Viçosa, Av. Peter Henry Rolfs S/N - Campus Universitário, Viçosa, Minas Gerais, 36570 000, Brazil
| | - Laryssa Lemos da Silva
- Departamento de Biologia Geral, Instituto de Biotecnologia Aplicada À Agropecuária, Universidade Federal de Viçosa, Av. Peter Henry Rolfs S/N - Campus Universitário, Viçosa, Minas Gerais, 36570 000, Brazil
| | - José Cola Zanuncio
- Departamento de Entomologia, Instituto de Biotecnologia Aplicada À Agropecuária, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil
| | - José Eduardo Serrão
- Departamento de Biologia Geral, Instituto de Biotecnologia Aplicada À Agropecuária, Universidade Federal de Viçosa, Av. Peter Henry Rolfs S/N - Campus Universitário, Viçosa, Minas Gerais, 36570 000, Brazil.
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Reis AB, Oliveira MSD, Souza DDS, Gomes DS, Silva LLD, Martínez LC, Serrão JE. Exploring the effects of the acaricide cyflumetofen on the vital organs of the honey bee Apis mellifera (Hymenoptera: Apidae) workers. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 929:172640. [PMID: 38670351 DOI: 10.1016/j.scitotenv.2024.172640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 03/25/2024] [Accepted: 04/18/2024] [Indexed: 04/28/2024]
Abstract
Bees are important for maintaining ecosystems, pollinating crops and producing marketable products. In recent years, a decline in bee populations has been reported, with multifactorial causes, including the intensification of pesticide use in agriculture. Among pesticides, cyflumetofen is an insecticide and acaricide used in apple, coffee and citrus crops, whose main pollinator is the honey bee Apis mellifera. Therefore, this bee is a potential target of cyflumetofen during foraging. This study evaluated the histopathological and cytological damage in the midgut, hypopharyngeal glands and fat body of A. mellifera workers exposed to LC50 of cyflumetofen. The midgut epithelium of exposed bees presented cytoplasmic vacuolization, release of vesicles and cell fragments, which indicate autophagy, increased production of digestive enzymes and cell death, respectively. The cytological analysis of the midgut revealed the dilation of the basal labyrinth and the presence of spherocrystals in the digestive cells. The hypopharyngeal glands produced greater amounts of secretion in treated bees, whereas no changes were observed in the fat body. The results indicate that acute exposure to cyflumetofen negatively affect A. mellifera, causing damage to the midgut and changes in the hypopharyngeal glands, which may compromise the survival and foraging of this pollinator.
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Affiliation(s)
- Aline Beatriz Reis
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil
| | - Mateus Soares de Oliveira
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil.
| | - Diego Dos Santos Souza
- Departamento de Entomologia, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil.
| | - Davy Soares Gomes
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil.
| | - Laryssa Lemos da Silva
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil.
| | - Luis Carlos Martínez
- Facultad de Ciencias Agrícolas, Universidad de Nariño, 602-7244309 Pasto, Nariño, Colombia.
| | - José Eduardo Serrão
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil.
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Güney G, Cedden D, Hänniger S, Hegedus DD, Heckel DG, Toprak U. Peritrophins are involved in the defense against Bacillus thuringiensis and nucleopolyhedrovirus formulations in Spodoptera littoralis (Lepidoptera: Noctuidae). INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2024; 166:104073. [PMID: 38215915 DOI: 10.1016/j.ibmb.2024.104073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 01/07/2024] [Accepted: 01/08/2024] [Indexed: 01/14/2024]
Abstract
The peritrophic matrix (or peritrophic membrane, PM) is present in most insects where it acts as a barrier to mechanical insults and pathogens, as well as a facilitator of digestive processes. The PM is formed by the binding of structural PM proteins, referred to as peritrophins, to chitin fibrils and spans the entire midgut in lepidopterans. To investigate the role of peritrophins in a highly polyphagous lepidopteran pest, namely the cotton leafworm (Spodoptera littoralis), we generated Insect Intestinal Mucin (IIM-) and non-mucin Peritrophin (PER-) mutant strains via CRISPR/Cas9 mutagenesis. Both strains exhibited deformed PMs and retarded developmental rates. Bioassays conducted with Bacillus thuringiensis (Bt) and nucleopolyhedrovirus (SpliNPV) formulations showed that both the IIM- and PER- mutant larvae were more susceptible to these bioinsecticides compared to the wild-type (WT) larvae with intact PM. Interestingly, the provision of chitin-binding agent Calcofluor (CF) in the diet lowered the toxicity of Bt formulations in both WT and IIM- larvae and the protective effect of CF was significantly lower in PER- larvae. This suggested that the interaction of CF with PER is responsible for Bt resistance mediated by CF. In contrast, the provision of CF caused increased susceptibility to SpliNPV in both mutants and WT larvae. The study showed the importance of peritrophins in the defense against pathogens in S. littoralis and revealed novel insights into CF-mediated resistance to Cry toxin.
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Affiliation(s)
- Gözde Güney
- Agricultural Entomology, Department of Crop Sciences, University of Göttingen, Göttingen, Germany; Max Planck Institute for Chemical Ecology, Department of Entomology, Jena, Germany; Ankara University, Molecular Entomology Lab., Dept. of Plant Protection, Faculty of Agriculture, Ankara, Turkey
| | - Doga Cedden
- Department of Evolutionary Developmental Genetics, Johann-Friedrich-Blumenbach Institute, GZMB, University of Göttingen, Göttingen, Germany; Ankara University, Molecular Entomology Lab., Dept. of Plant Protection, Faculty of Agriculture, Ankara, Turkey
| | - Sabine Hänniger
- Max Planck Institute for Chemical Ecology, Department of Entomology, Jena, Germany
| | - Dwayne D Hegedus
- Agriculture and Agri-Food Canada, Saskatoon, SK, Canada; University of Saskatchewan, Department of Food and Bioproduct Sciences, College of Agriculture and Bioresources, Saskatoon, SK, Canada
| | - David G Heckel
- Max Planck Institute for Chemical Ecology, Department of Entomology, Jena, Germany.
| | - Umut Toprak
- Ankara University, Molecular Entomology Lab., Dept. of Plant Protection, Faculty of Agriculture, Ankara, Turkey.
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Carneiro LS, Santos CG, Resende MTCSD, Souza DLLD, Souza DDS, Souza AMDC, Motta JVDO, Nere PHA, Oliveira AHD, Serrão JE. Effects of the insecticide imidacloprid on the post-embryonic development of the honey bee Apis mellifera (Hymenoptera: Apidae). THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 905:167278. [PMID: 37741377 DOI: 10.1016/j.scitotenv.2023.167278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 09/15/2023] [Accepted: 09/20/2023] [Indexed: 09/25/2023]
Abstract
The widespread use of pesticides in agriculture has been linked to declines in bee populations worldwide. Imidacloprid is a widely used systemic insecticide that can be found in the pollen and nectar of plants and has the potential to negatively impact the development of bee larvae. We investigated the effects of oral exposure to a realistic field concentration (20.5 ng g-1) of imidacloprid on the midgut and fat body of Apis mellifera worker larvae. Our results showed that larvae exposed to imidacloprid exhibited changes in the midgut epithelium, including disorganization of the brush border, nuclear chromatin condensation, cytoplasm vacuolization, and release of cell fragments indication cell death. Additionally, histochemical analysis revealed that the midgut brush border glycocalyx was disorganized in exposed larvae. The fat body cells of imidacloprid-exposed larvae had a decrease in the size of lipid droplets from 50 to 8 μm and increase of 100 % of protein content, suggesting possible responses to the stress caused by the insecticide. However, the expression of de cdc20 gene, which plays a role in cell proliferation, was not affected in the midgut and fat body of treated larvae. These results suggest that imidacloprid negatively affects non-target organs during the larval development of A. mellifera potentially impacting this important pollinator species.
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Affiliation(s)
- Lenise Silva Carneiro
- Department of General Biology, Federal University of Viçosa, Viçosa, Minas Gerais 36570-900, Brazil
| | | | | | | | - Diego Dos Santos Souza
- Department of Entomology, Federal University of Viçosa, Viçosa, Minas Gerais 36570-900, Brazil
| | | | | | | | | | - José Eduardo Serrão
- Department of General Biology, Federal University of Viçosa, Viçosa, Minas Gerais 36570-900, Brazil.
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Domingues CEC, Inoue LVB, Gregorc A, Ansaloni LS, Malaspina O, Mathias da Silva EC. Ultrastructural Changes in the Midgut of Brazilian Native Stingless Bee Melipona scutellaris Exposed to Fungicide Pyraclostrobin. TOXICS 2023; 11:1028. [PMID: 38133429 PMCID: PMC10748086 DOI: 10.3390/toxics11121028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 12/11/2023] [Accepted: 12/14/2023] [Indexed: 12/23/2023]
Abstract
Melipona scutellaris is a Brazilian stingless bee that is important for pollinating wild flora and agriculture crops. Fungicides have been widely used in agriculture, and floral residues can affect forager bees. The goal of our study was to evaluate the effects of sublethal concentrations of pyraclostrobin on the midgut ultrastructure of M. scutellaris forager workers. The bees were collected from three non-parental colonies and kept under laboratory conditions. The bees were orally exposed continuously for five days to pyraclostrobin in syrup at concentrations of 0.125 ng a.i./µL (FG1) and 0.005 ng a.i./µL (FG2). The control bees (CTL) were fed a no-fungicide sucrose solution, and the acetone solvent control bees (CAC) received a sucrose solution containing acetone. At the end of the exposure, the midguts were sampled, fixed in Karnovsky solution, and routinely processed for transmission electron microscopy. Ultrastructural analysis demonstrated that both the fungicide concentrations altered the midgut, such as cytoplasmic vacuolization (more intense in FG1), the presence of an atypical nuclear morphology, and slightly dilated mitochondrial cristae in the bees from the FG1 and FG2 groups (both more intense in FG1). Additionally, there was an alteration in the ultrastructure of the spherocrystals (FG1), which could be the result of cellular metabolism impairment and the excretion of toxic metabolites in the digestive cells as a response to fungicide exposure. The results indicate that ingested pyraclostrobin induced cytotoxic effects in the midgut of native stingless bees. These cellular ultrastructural responses of the midgut are a prelude to a reduced survival rate, as observed in previous studies.
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Affiliation(s)
- Caio E. C. Domingues
- Faculty of Agriculture and Life Sciences, University of Maribor, Pivola 10, 2311 Hoče, Slovenia (L.S.A.)
- Centro de Estudos de Insetos Sociais (CEIS), Departamento de Biologia Geral e Aplicada, Instituto de Biociências (IB), Universidade Estadual Paulista (UNESP)—“Júlio de Mesquita Filho”, Rio Claro 13506-900, SP, Brazil; (L.V.B.I.); (O.M.)
| | - Lais V. B. Inoue
- Centro de Estudos de Insetos Sociais (CEIS), Departamento de Biologia Geral e Aplicada, Instituto de Biociências (IB), Universidade Estadual Paulista (UNESP)—“Júlio de Mesquita Filho”, Rio Claro 13506-900, SP, Brazil; (L.V.B.I.); (O.M.)
| | - Aleš Gregorc
- Faculty of Agriculture and Life Sciences, University of Maribor, Pivola 10, 2311 Hoče, Slovenia (L.S.A.)
| | - Leticia S. Ansaloni
- Faculty of Agriculture and Life Sciences, University of Maribor, Pivola 10, 2311 Hoče, Slovenia (L.S.A.)
| | - Osmar Malaspina
- Centro de Estudos de Insetos Sociais (CEIS), Departamento de Biologia Geral e Aplicada, Instituto de Biociências (IB), Universidade Estadual Paulista (UNESP)—“Júlio de Mesquita Filho”, Rio Claro 13506-900, SP, Brazil; (L.V.B.I.); (O.M.)
| | - Elaine C. Mathias da Silva
- Laboratório de Ecotoxicologia e Análise de Integridade Ambiental (LEIA), Departamento de Biologia (DBio), Universidade Federal de São Carlos (UFSCar), Sorocaba 18052-780, SP, Brazil;
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Toni ASB, Fialho VS, Cossolin JFS, Serrão JE. Larval and adult digestive tract of the carrion beetle Oxelytrum discicolle (Brullé, 1840) (Coleoptera: Silphidae). ARTHROPOD STRUCTURE & DEVELOPMENT 2022; 71:101213. [PMID: 36208618 DOI: 10.1016/j.asd.2022.101213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 09/20/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
Oxelytrum discicolle is a necrophagous beetle occurring in Central and South America, with potential use in forensic entomology for investigations in the context of legal medicine. The present work aimed to describe the morphology of the digestive tract of larvae and adults and contributes to the knowledge about the digestion associated with necrophagy. In the three larval instars, the foregut is short and narrow, the midgut is a dilated tube, elongated with a smooth surface, and the hindgut is narrow and long, with small lateral projections and a dilated terminal region. The gut epithelium in the second and third instar larvae is vacuolated in the mid- and hindgut, with high production of apocrine secretions in the midgut lumen. In adults, the foregut is short, with small spines in the cuticular intima that covers the flattened epithelium. The midgut is dilated, with many short gastric caeca with regenerative cells in the blind portion, which differentiate in digestive columnar cells towards the midgut lumen. The hindgut is long and narrow, with an enlarged distal portion with folded epithelium lined by a thin cuticle. The histochemical tests reveal the absence of protein storage granules in the gut epithelium of larvae and adults. The gut characteristics of the carrion beetle O. discicolle are similar to those of other predatory and phytophagous Coleoptera, which may indicate that ancestry may influence the alimentary canal morphology more than the feeding habits.
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Miotelo L, Mendes Dos Reis AL, Rosa-Fontana A, Karina da Silva Pachú J, Malaquias JB, Malaspina O, Roat TC. A food-ingested sublethal concentration of thiamethoxam has harmful effects on the stingless bee Melipona scutellaris. CHEMOSPHERE 2022; 288:132461. [PMID: 34624342 DOI: 10.1016/j.chemosphere.2021.132461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/30/2021] [Accepted: 10/01/2021] [Indexed: 05/26/2023]
Abstract
In recent years, the importance of bee's biodiversity in the Neotropical region has been evidencing the relevance of including native bees in risk assessments. Therefore, the sublethal effects of the insecticide thiamethoxam on the survival and morphological parameters of the stingless bee Melipona scutellaris were investigated in the present study. Cells from both non-target organs (Malpighian tubules and midgut) and target organs (brain) were analyzed for morphological alterations using light microscopy and transmission electron microscopy. The findings showed that when M. scutellaris foragers were exposed to a sublethal concentration of thiamethoxam (LC50/100 = 0.000543 ng a. i./μL), longevity was not reduced but brain function was affected, even with the non-target organs attempting to detoxify. The cellular damage in all the organs was mostly reflected in irregular nuclei shape and condensed chromatin, indicating cell death. The most frequent impairments in the Malpighian tubules were loss of microvilli, disorganization of the basal labyrinth, and cytoplasmic loss. These characteristics are related to an attempt by the cells to increase the excretion process, probably because of the high number of toxic molecules that reach the Malpighian tubules and need to be secreted. In general, damages that compromise the absorption of nutrients, excretion, memory, and learning processes, which are essential for the survival of M. scutellaris, were found. The present results also fill in gaps on how these bees respond to thiamethoxam exposure and will be useful in future risk assessments for the conservation of bee biodiversity.
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Affiliation(s)
- Lucas Miotelo
- Department of General and Applied Biology, Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, SP, Brazil.
| | - Ana Luiza Mendes Dos Reis
- Department of General and Applied Biology, Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, SP, Brazil.
| | - Annelise Rosa-Fontana
- Department of General and Applied Biology, Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, SP, Brazil.
| | - Jéssica Karina da Silva Pachú
- Department of Entomology and Acarology, Luiz de Queiroz College of Agriculture (ESALQ), Piracicaba, SP, 13418-900, Brazil.
| | - José Bruno Malaquias
- Department of Biostatistics, Institute of Biosciences e IBB, São Paulo State University (UNESP), Botucatu, SP, 18618-693, Brazil.
| | - Osmar Malaspina
- Department of General and Applied Biology, Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, SP, Brazil.
| | - Thaisa Cristina Roat
- Department of General and Applied Biology, Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, SP, Brazil.
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Abstract
Bumblebees (Bombus) are charismatic and important pollinators. They are one of the best studied insect groups, especially in terms of ecology, behavior, and social structure. As many species are declining, there is a clear need to understand more about them. Microbial symbionts, which can influence many dimensions of animal life, likely have an outsized role in bumblebee biology. Recent research has shown that a conserved set of beneficial gut bacterial symbionts is ubiquitous across bumblebees. These bacteria are related to gut symbionts of honeybees, but have not been studied as intensively. Here we synthesize studies of bumblebee gut microbiota, highlight major knowledge gaps, and suggest future directions. Several patterns emerge, such as symbiont-host specificity maintained by sociality, frequent symbiont loss from individual bees, symbiont-conferred protection from trypanosomatid parasites, and divergence between bumblebee and honeybee microbiota in several key traits. For many facets of bumblebee-microbe interactions, however, underlying mechanisms and ecological functions remain unclear. Such information is important if we are to understand how bumblebees shape, and are shaped by, their gut microbiota. Bumblebees may provide a useful system for microbiome scientists, providing insights into general principles of host-microbe interactions. We also note how microbiota could influence bumblebee traits and responses to stressors. Finally, we propose that tinkering with the microbiota could be one way to aid bumblebee resilience in the face of global change.
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Affiliation(s)
- Tobin J. Hammer
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78703
- Corresponding author:
| | - Eli Le
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78703
| | - Alexia N. Martin
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78703
| | - Nancy A. Moran
- Department of Integrative Biology, University of Texas at Austin, Austin, TX 78703
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Luz GFD, Santana WC, Santos CG, Medeiros Santana L, Serrão JE. Cuticle melanization and the expression of immune-related genes in the honeybee Apis mellifera (Hymenoptera: Apidae) adult workers. Comp Biochem Physiol B Biochem Mol Biol 2021; 257:110679. [PMID: 34673246 DOI: 10.1016/j.cbpb.2021.110679] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 10/07/2021] [Accepted: 10/12/2021] [Indexed: 10/20/2022]
Abstract
The global decline of bee populations has several factors, including pathogens, which need overcome the insect defenses such as the physical barriers, the body cuticle and peritrophic matrix (primary defenses), as well as the secondary defenses with antimicrobial peptides (AMPs) and the enzyme lysozyme. The regulation of immune defenses according to the infection risks raises questions about the immunity of social bees due to their exposition to different pathogens pressures during the adult lifespan and tasks performed. This study evaluated the primary (body cuticle melanization, peritrophic matrix and cpr14 expression) and secondary (AMPs and lysozyme expression) defenses of the honeybee Apis mellifera workers according to the age and tasks. The expression of malvolio was used to detect precocious forage tasks outside the colony. Forager workers have higher amount of cuticular melanization in the body cuticle than nurse, but not when the age effect is retired, indicating the gradual acquisition of this compound in the integument of adult bees. The relative value of chitin in the peritrophic matrix and cpr14 mRNA are similar in all bees evaluated, suggesting that these components of primary defenses do not change according to the task and age. Differential expression of genes for AMPs in workers performing different tasks, within the same age group, indicates that the behavior stimulates expression of genes related to secondary immune defense. The expression of malvolio gene, accelerating the change in workers behavior, and those related to immune defense suggest the investment in secondary defense mechanisms when the primary defense of the body cuticle is not yet completed.
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Affiliation(s)
- Geisyane Franco da Luz
- Departamento de Biologia Geral/BIOAGRO, Universidade Federal de Viçosa, 36570-000 Viçosa, Brazil
| | | | | | - Luanda Medeiros Santana
- Instituto de Ciências Biológicas e da Saúde, Universidade Federal de Viçosa, 38810-000 Rio Paranaíba, Brazil
| | - José Eduardo Serrão
- Departamento de Biologia Geral/BIOAGRO, Universidade Federal de Viçosa, 36570-000 Viçosa, Brazil.
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Characteristics of the Peritrophic Matrix of the Silkworm, Bombyx mori and Factors Influencing Its Formation. INSECTS 2021; 12:insects12060516. [PMID: 34199436 PMCID: PMC8227122 DOI: 10.3390/insects12060516] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/25/2021] [Accepted: 05/28/2021] [Indexed: 11/16/2022]
Abstract
Simple Summary The insect midgut is an important digestive organ with the peritrophic matrix (PM) being a semi-permeable membrane secreted by the midgut cells. The PM plays an important role in improving midgut digestion efficiency and protecting the midgut from food particles and exogenous pathogens. The silkworm, Bombyx mori, is an economically important insect. Understanding the structure of the PM is necessary for studying its function, but characteristics of PM in B. mori have been rarely reported. In this study, we conducted a comprehensive study on the PM structure of the PM in silkworms and found its thickness increased gradually during growth, but there was no difference in the thickness comparing the anterior, middle, and posterior regions. Permeability of the PM gradually decreased from the anterior to posterior regions. In addition, we found the formation of the PM was influenced by food ingestion and the gut microbiota. Abstract The peritrophic matrix (PM) secreted by the midgut cells of insects is formed by the binding of PM proteins to chitin fibrils. The PM envelops the food bolus, serving as a barrier between the content of the midgut lumen and its epithelium, and plays a protective role for epithelial cells against mechanical damage, pathogens, toxins, and other harmful substances. However, few studies have investigated the characteristics and synthesis factors of the PM in the silkworm, Bombyx mori. Here, we examined the characteristics of the PM in the silkworms. The PM thickness of the silkworms increased gradually during growth, while there was no significant difference in thickness along the entire PM region. Permeability of the PM decreased gradually from the anterior to posterior PM. We also found that PM synthesis was affected by food ingestion and the gut microbiota. Our results are beneficial for future studies regarding the function of the PM in silkworms.
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Serra RS, Cossolin JFS, Resende MTCSD, Castro MAD, Oliveira AH, Martínez LC, Serrão JE. Spiromesifen induces histopathological and cytotoxic changes in the midgut of the honeybee Apis mellifera (Hymenoptera: Apidae). CHEMOSPHERE 2021; 270:129439. [PMID: 33395581 DOI: 10.1016/j.chemosphere.2020.129439] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 12/21/2020] [Accepted: 12/23/2020] [Indexed: 06/12/2023]
Abstract
The honeybee Apis mellifera is an important pollinator that, similarly to other bees, undergoes colony losses due to several problems, including the use of pesticides in the agriculture. In addition to direct mortality, pesticides cause side-effects in some non-target organs, such as the midgut, which is the main organ for digestion and absorption. Spiromesifen is a pesticide used to control mites and whiteflies, which can be ingested by bees feeding on contaminated floral resources. This study evaluated the histopathological and cytological effects of the ingestion of spiromesifen on the midgut of A. mellifera workers. The bees were exposed per os to the field recommended dose of spiromesifen, and the midgut was analyzed after 24h and 48h of exposure to the pesticide. The midgut has a single layer of digestive cells, with spherical nucleus, nests of regenerative cells and layers of peritrophic matrix in the lumen. Bees treated with spiromesifen presented histological and cytological changes in the midgut, including disorganization of the epithelial architecture, release of cell fragments to the lumen, accumulation of mitochondria in the apical cytoplasm, alteration of the basal labyrinth, changes in the rough endoplasmic reticulum and cell degeneration. The occurrence of damage in the digestive cells of the A. mellifera midgut indicates that spiromesifen does not cause mortality in honeybees, but its side-effects can damage the midgut, which may affect the longevity and behavior of this pollinator.
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Affiliation(s)
- Raissa Santana Serra
- Departamento de Entomologia, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil.
| | | | | | - Mayara Arthidoro de Castro
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-000, Viçosa, Minas Gerais, Brazil.
| | - André Henrique Oliveira
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-000, Viçosa, Minas Gerais, Brazil.
| | - Luis Carlos Martínez
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-000, Viçosa, Minas Gerais, Brazil.
| | - José Eduardo Serrão
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-000, Viçosa, Minas Gerais, Brazil.
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13
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Carneiro LS, Martínez LC, Gonçalves WG, Santana LM, Serrão JE. The fungicide iprodione affects midgut cells of non-target honey bee Apis mellifera workers. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 189:109991. [PMID: 31780208 DOI: 10.1016/j.ecoenv.2019.109991] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 11/07/2019] [Accepted: 11/20/2019] [Indexed: 06/10/2023]
Abstract
The honey bee Apis mellifera is an important pollinator of agricultural crops and natural forests. Honey bee populations have declined over the years, as a result of diseases, pesticides, and management problems. Fungicides are the main pesticides found in pollen grains, which are the major source of protein for bees. The objective of this study was to evaluate the cytotoxic effects of the fungicide iprodione on midgut cells of adult A. mellifera workers. Bees were fed on iprodione (LD50, determined by the manufacturer) for 12 or 24 h, and the midgut was examined using light and transmission electron microscopies. The expression level of the autophagy gene atg1 was assessed in midgut digestive cells. Cells of treated bees had signs of apoptosis: cytoplasmic vacuolization, apical cell protrusions, nuclear fragmentation, and chromatin condensation. Ultrastructural analysis revealed some cells undergoing autophagy and necrosis. Expression of atg1 was similar between treated and control bees, which can be explained by the facts that digestive cells had autolysosomes, whereas ATG-1 is found in the initial phases of autophagy. Iprodione acts by inhibiting the synthesis of glutathione, leading to the generation of reactive oxygen species, which in turn can induce different types of cell death. The results indicate that iprodione must be used with caution because it has side effects on non-target organisms, such as pollinator bees.
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Affiliation(s)
- Lenise Silva Carneiro
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil
| | - Luis Carlos Martínez
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil
| | - Wagner Gonzaga Gonçalves
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil
| | - Luanda Medeiros Santana
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil
| | - José Eduardo Serrão
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil.
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14
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Oliveira AH, Fernandes KM, Gonçalves WG, Zanuncio JC, Serrão JE. A peritrophin mediates the peritrophic matrix permeability in the workers of the bees Melipona quadrifasciata and Apis mellifera. ARTHROPOD STRUCTURE & DEVELOPMENT 2019; 53:100885. [PMID: 31614307 DOI: 10.1016/j.asd.2019.100885] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 09/19/2019] [Accepted: 09/20/2019] [Indexed: 06/10/2023]
Abstract
The permeability of the peritrophic matrix, essential for its function, depends on its chemical composition. The objective was to determine if the permeability of the peritrophic matrix varies along the midgut and in the presence of anti-peritrophin-55 antibody in Melipona quadrifasciata and Apis mellifera bees. The thickness of the peritrophic matrix in both species varies between the anterior and posterior midgut regions in workers. In A. mellifera dextran molecules with 40 kDa cross the peritrophic matrix, whereas those ≥70 kDa are retained in the endoperitrophic space. In M. quadrifasciata the peritrophic matrix permeability was for molecules <40 kDa. Bees fed on anti-peritrophin-55 antibody showed an increase in peritrophic matrix permeability, but survival was not affected. In the bees studied, the peritrophic matrices have morphological differences between midgut regions, but there is no difference in their permeability along the midgut, which is affected by peritrophin 55.
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Affiliation(s)
- André Henrique Oliveira
- Department of General Biology, Universidade Federal de Viçosa, 36570-000, Viçosa, MG, Brazil.
| | - Kenner Morais Fernandes
- Department of General Biology, Universidade Federal de Viçosa, 36570-000, Viçosa, MG, Brazil.
| | | | - José Cola Zanuncio
- Department of Entomology, Universidade Federal de Viçosa, 36570-000, Viçosa, MG, Brazil.
| | - José Eduardo Serrão
- Department of General Biology, Universidade Federal de Viçosa, 36570-000, Viçosa, MG, Brazil.
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15
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Oliveira AH, Gonçalves WG, Fernandes KM, Barcellos MS, Sampaio WMS, Lopes MP, Martins GF, Serrão JE. Morphology and Morphometry of the Midgut in the Stingless Bee Friesella schrottkyi (Hymenoptera: Apidae). INSECTS 2019; 10:insects10030073. [PMID: 30875839 PMCID: PMC6468588 DOI: 10.3390/insects10030073] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 03/08/2019] [Accepted: 03/10/2019] [Indexed: 12/23/2022]
Abstract
Friesella schrottkyi is a small stingless bee (3-mm long) important for agricultural and native forest pollination. This study describes the morphology and morphometry of the midgut in F. schrottkyi forager workers. The F. schrottkyi midgut presents a single-layered epithelium with digestive, regenerative and endocrine cells. The digestive cells are similar along the entire midgut length with a spherical nucleus, apex with long striated border, cytoplasmic granules in the apical region and well-developed basal labyrinth associated with mitochondria, suggesting they are multifunctional, synthesizing digestive enzymes and peritrophic matrix compounds and absorbing nutrients. Regenerative cells are located around the basal region organized in nests with some cells with a spherical nucleus. Phe-Met-Arg-Phe-NH2-amide (FMRFamide) positive endocrine cells are restricted to the posterior midgut region, suggesting a paracrine function in the midgut. This is the first morphological description of the F. schrottkyi midgut contributing to the comprehension of the digestive process of this bee.
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Affiliation(s)
- André H Oliveira
- Department of General Biology, Universidade Federal de Viçosa, 36570-000 Viçosa, MG, Brazil.
| | - Wagner G Gonçalves
- Department of General Biology, Universidade Federal de Viçosa, 36570-000 Viçosa, MG, Brazil.
| | - Kenner M Fernandes
- Department of General Biology, Universidade Federal de Viçosa, 36570-000 Viçosa, MG, Brazil.
| | - Marcelo S Barcellos
- Instituto Federal de Mato Grosso-IFMT. Campus avançado Diamantino, 78400-970 Diamantino, MT, Brazil.
| | - Wagner M S Sampaio
- Department of General Biology, Universidade Federal de Viçosa, 36570-000 Viçosa, MG, Brazil.
| | - Marcos P Lopes
- Department of General Biology, Universidade Federal de Viçosa, 36570-000 Viçosa, MG, Brazil.
| | - Gustavo F Martins
- Department of General Biology, Universidade Federal de Viçosa, 36570-000 Viçosa, MG, Brazil.
| | - José E Serrão
- Department of General Biology, Universidade Federal de Viçosa, 36570-000 Viçosa, MG, Brazil.
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16
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Carneiro LS, Teixeira SAMV, Gonçalves WG, Fernandes KM, Zanuncio JC, Serrão JE. Histochemistry, immunohistochemistry and cytochemistry of the anterior midgut region of the stingless bee Melipona quadrifasciata and honey bee Apis mellifera (Hymenoptera: Apidae). Micron 2018; 113:41-47. [PMID: 30007857 DOI: 10.1016/j.micron.2018.06.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 06/11/2018] [Accepted: 06/26/2018] [Indexed: 11/29/2022]
Abstract
The anterior midgut region of stingless bees is anatomically differentiated with tall and narrow cells, whereas in other social and solitary bees this anatomical gut region is lacking. The objective of the present study was to describe the histochemistry, immunohistochemistry and cytochemistry of the anterior midgut region of the stingless bee Melipona quadrifasciata in comparison with the honey bee Apis mellifera. The anterior midgut region of both species was evaluated for identification of the enzymes β- galactosidase, glucose-6-phosphatase, acid phosphatase, and alkaline phosphatase, the membrane transporter aquaporin, the hormone FMRF-amide, and lysosomes. Histology of the anterior midgut region showed that this region in M. quadrifasciata workers did not present external folds of the wall, whereas the following midgut wall presented many. In A. mellifera, folds in the midgut wall occur starting from the fore- midgut transition region. Despite these morphological differences, the tests evaluated were similar in both species. β-galactosidase was not found in the anterior midgut cells. Glucose-6-phosphatase and acid phosphatase occurred in the apical region of the gut epithelium. Alkaline phosphatase occurred in vesicles in apical cytoplasm and in the basal plasma membrane infoldings of the epithelial cells. Aquaporin was found in the basal region of the midgut epithelium and in the associated visceral muscles. FMRF-amide was found only in nerve endings in the anterior midgut region. All cells in the anterior midgut region were rich in lysosomes. These results suggest that in both bee species, although they have anatomically different anterior midgut regions, these regions present high metabolic activity and function in cellular homeostasis, lipid absorption and are under neurohormone control.
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Affiliation(s)
- Lenise Silva Carneiro
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil.
| | | | - Wagner Gonzaga Gonçalves
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil.
| | - Kenner Morais Fernandes
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil.
| | - José Cola Zanuncio
- Departamento de Entomologia/BIOGRO, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil.
| | - José Eduardo Serrão
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, Minas Gerais, Brazil.
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17
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Santos HP, Gutiérrez Y, Oliveira EE, Serrão JE. Sublethal dose of deltamethrin damage the midgut cells of the mayfly Callibaetis radiatus (Ephemeroptera: Baetidae). ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2018; 25:1418-1427. [PMID: 29090441 DOI: 10.1007/s11356-017-0569-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 10/24/2017] [Indexed: 06/07/2023]
Abstract
In insects, the midgut performs multiple physiologic functions (e.g., digestion and nutrients absorption) and serves as a physical/chemical barrier against pathogens and chemical stressors such as deltamethrin, a pyrethroid insecticide, commonly used in insect control that are agricultural pests and human disease vectors. Here, we described the midgut cell ultrastructure of Callibaetis radiatus nymphs, which are bioindicators of water quality and the ultrastructural alterations in midgut under sublethal exposure to deltamethrin at three different periods (1, 12, 24 h). The digestive cells of deltamethrin-unexposed nymphs had long microvilli, many mitochondria in the apical cytoplasm, a rough endoplasmic reticulum, a basal labyrinth with openings for hemocele, and the midgut peritrophic matrix which is classified as type I. Nymphs exposed to deltamethrin exhibited digestive cells rich in autophagic vacuoles, basal labyrinth loss, and microvilli disorganization since the first hour of contact with deltamethrin. However, these midgut tissues underwent to autophagic cellular recovery along the 24 h of exposure to deltamethrin. Thus, the sublethal exposure to deltamethrin is sufficient to disturb the ultrastructure of C. radiatus midgut, which might reduce the abilities of these insects to survive in aquatic environments contaminated by pyrethroids.
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Affiliation(s)
- Helen Pinto Santos
- Departamento de Biologia Geral, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil
- Instituto Federal de Minas Gerais, São João Evangelista, MG, 39705-000, Brazil
| | - Yeisson Gutiérrez
- Institute of Landscape Ecology, University of Münster, D48149, Münster, Germany
- Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil
| | | | - José Eduardo Serrão
- Departamento de Biologia Geral, Universidade Federal de Viçosa, Viçosa, MG, 36570-000, Brazil.
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18
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Gutiérrez-Cabrera AE, Córdoba-Aguilar A, Zenteno E, Lowenberger C, Espinoza B. Origin, evolution and function of the hemipteran perimicrovillar membrane with emphasis on Reduviidae that transmit Chagas disease. BULLETIN OF ENTOMOLOGICAL RESEARCH 2016; 106:279-291. [PMID: 26639621 DOI: 10.1017/s0007485315000929] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The peritrophic matrix is a chitin-protein structure that envelops the food bolus in the midgut of the majority of insects, but is absent in some groups which have, instead, an unusual extra-cellular lipoprotein membrane named the perimicrovillar membrane. The presence of the perimicrovillar membrane (PMM) allows these insects to exploit restricted ecological niches during all life stages. It is found only in some members of the superorder Paraneoptera and many of these species are of medical and economic importance. In this review we present an overview of the midgut and the digestive system of insects with an emphasis on the order Paraneoptera and differences found across phylogenetic groups. We discuss the importance of the PMM in Hemiptera and the apparent conservation of this structure among hemipteran groups, suggesting that the basic mechanism of PMM production is the same for different hemipteran species. We propose that the PMM is intimately involved in the interaction with parasites and as such should be a target for biological and chemical control of hemipteran insects of economic and medical importance.
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Affiliation(s)
- A E Gutiérrez-Cabrera
- Departamento de Inmunología,Instituto de Investigaciones Biomedicas,Universidad Nacional Autónoma de México,Apdo. 70228,Circuito Exterior,Ciudad Universitaria,04510,Coyoacán,Distrito Federal,México
| | - A Córdoba-Aguilar
- Departamento de Ecología Evolutiva,Instituto de Ecología,Universidad Nacional Autónoma de México,Apdo. P. 70-275,Circuito Exterior,Ciudad Universitaria,04510,Coyoacán,Distrito Federal,Mexico
| | - E Zenteno
- Departamento de Bioquímica,Facultad de Medicina,Universidad Nacional Autónoma de México,Ciudad Universitaria,04510 D.F.,Mexico
| | - C Lowenberger
- Department of Biological Sciences,Simon Fraser University,Burnaby, B.C., V5A 1S6,Canada
| | - B Espinoza
- Departamento de Inmunología,Instituto de Investigaciones Biomedicas,Universidad Nacional Autónoma de México,Apdo. 70228,Circuito Exterior,Ciudad Universitaria,04510,Coyoacán,Distrito Federal,México
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