Juvenile hormone downregulates vitellogenin production in Ectatomma tuberculatum (Hymenoptera: Formicidae) sterile workers

In the ant Ectatomma tuberculatum (Olivier 1792), workers have active ovaries and lay trophic eggs that are eaten by the queen and larvae. Vitellogenins are the main proteins found in the eggs of insects and are the source of nutrients for the embryo in the fertilized eggs and for adults in the trophic eggs. In social insects, vitellogenin titres vary between castes and affect reproductive social status, nursing, foraging, longevity, somatic maintenance, and immunity. In most insects, vitellogenin synthesis is mainly regulated by juvenile hormone. However, in non-reproductive worker ants, this relationship is poorly characterized. This study determined the effects of juvenile hormone on vitellogenin synthesis in non-reproductive E. tuberculatum workers. Juvenile hormone was topically applied onto workers, and the effect on vitellogenin synthesis in the fat body and vitellogenin titres in the haemolymph were analysed by ELISA and qPCR. Juvenile hormone downregulated protein synthesis and reduced vitellogenin titres in the haemolymph, suggesting that in workers of E. tuberculatum, juvenile hormone loses its gonadotrophic function

Desenvolvimento, reprodução e performance predatória do percevejo zoofitófago Podisus distinctus (Hemiptera: Pentatomidae) alimentado com larvas de Musca domestica (Diptera: Muscidae) imobilizadas ou soltas

Researches with predatory true bugs are crucial for biological control programs. Pairs of Podisus distinctus were fed with immobilized or free Musca domestica larvae, aiming to verify the influence of prey mobility on predatory capacity and biology of the predator, compared to the use of Tenebrio molitor pupae. Consumption of M. domestica larvae was also compared between adults of P. distinctus and Podisus nigrispinus. The number of larvae consumed and female reproductive parameters were similar between treatments. However, females fed with T. molitor laid more eggs and clutches per female, and showed shortest oviposition interval, confirming that M. domestica larvae may be not appropriate preys to rear P. distinctus, independently of their mobility. P. nigrispinus had higher predation on M. domestica larvae than P. distinctus, suggesting that the former species can properly use this alternative prey.Pesquisas com percevejos predadores são fundamentais para programas de controle de pragas. Casais de Podisus distinctus foram alimentados com larvas de Musca domestica imobilizadas ou soltas, para verificar a influência da mobilidade na predação e biologia desse predador e comparar o consumo dessas larvas entre P. distinctus e Podisus nigrispinus. O número de larvas consumidas e os parâmetros reprodutivos de fêmeas foram semelhantes entre tratamentos. Entretanto, fêmeas desse predador apresentaram maior número de ovos, de posturas e menor intervalo entre as posturas alimentadas com Tenebrio molitor, confirmando que M. domestica não é uma boa presa para a criação de P. distinctus. Podisus nigrispinus consumiu maior número de larvas de M. domestica que P. distinctus, o que pode estar relacionado ao melhor desenvolvimento desse predador a esse tipo de presa alternativa

Vitellogenins in workers of the ant Ectatomma tuberculatum (Formicidae: Ectatomminae): synthesis, functions and endocrine regulation

As operárias da formiga Ectatomma tuberculatum (Ectatomminae) apresentam ovários desenvolvidos e produzem ovos que são utilizados na alimentação da cria e da rainha (ovos tróficos). As vitelogeninas são as principais proteínas encontradas nos ovos de insetos, sendo potencial fonte de nutrientes para o embrião e adultos. Em insetos sociais, os níveis de vitelogenina variam entre os indivíduos e influenciam a determinação das castas reprodutivas e operárias, atividades de cuidado com a cria e forrageio, longevidade, manutenção somática e imunidade. Em formigas que produzem ovos tróficos, a vitelogenina é uma das fontes de alimento para larvas e rainhas. Em geral, a síntese de vitelogenina é regulada em nível transcricional principalmente por hormônio juvenil (HJ), mas em operárias de formigas essa relação não está muito bem caracterizada. Os objetivos deste trabalho foram verificar o período de produção de vitelogenina em operárias de E. tuberculatum e o efeito do HJ na síntese dessa proteína. A vitelogenina foi identificada a partir de extratos de ovos de rainhas e operárias por SDS-PAGE. Anticorpos anti-vitelogenina foram obtidos e utilizados para detecção dessa proteína no corpo gorduroso e na hemolinfa de operárias de diferentes idades. Também foi observado o efeito da aplicação de HJ III na síntese de vitelogenina no corpo gorduroso e nos níveis de vitelogenina circulantes na hemolinfa de operárias, através de PCR quantitativo em tempo real e ELISA. As vitelogeninas de E. tuberculatum são constituídas por dois polipeptídios de 31 e 156 kDa. Nos ovos de rainhas, a vitelogenina de 156 kDa é clivada em duas subunidades de 36 e 123 kDa. As análises da hemolinfa de operárias mostraram que a secreção de vitelogenina varia de acordo com a idade, com picos de produção entre os 20 e 60 dias de idade e cessando por volta dos 100 dias. Essa variação mostra uma relação com as diferentes atividades exercidas pelas operárias na colônia, sugerindo que a vitelogenina pode ter uma importante função na manutenção do polietismo etário em E. tuberculatum. As análises também mostraram que aplicação de HJ III reduz a síntese de vitelogenina no corpo gorduroso, assim como reduz os níveis de vitelogenina circulante na hemolinfa. Esses dados mostram que o HJ regula a produção de vitelogenina em operárias, sugerindo que em operárias adultas de E. tuberculatum o hormônio juvenil não tem função de gonadotropina.Workers of the ant Ectatomma tuberculatum (Ectatomminae) have active ovaries and lay eggs that are eaten by the queen and larvae (trophic eggs). Vitellogenins are the main proteins found in the eggs of insects and are a source of nutrients to embryo and adults. In social insects, the vitellogenin levels vary between the castes and influences the reproductive social status, nursing and foraging activities, longevity, somatic maintenance and immunity. In most of the insects, the vitellogenin synthesis is regulated mainly by juvenile hormone. However, in non-reproductive worker ants this relationship is poorly characterized. The aims of this study were to characterize the period of vitellogenin secretion in workers of E. tuberculatum and to verify the effects of juvenile hormone application in vitellogenin synthesis. The vitellogenin was identified from queen and worker eggs by SDS-PAGE. Anti-vitellogenin antibodies were obtained and used to detect this protein in the fat body and haemolymph of workers at different ages. Also, juvenile hormone III was applied topically in workers and their effect on vitellogenin synthesis in the fat body and vitellogenin levels in the haemolymph were analyzed by quantitative real time PCR and ELISA. Vitellogenin from E. tuberculatum consists of two polypeptides of 31 and 156 kDa. In the eggs of queens, the 156 kDa polypeptide is cleaved into two subunits of 36 and 123 kDa. The analysis of the haemolymph of workers showed that the secretion of vitellogenin varies with age. The secretion is initiated around the fifth day after emergence, with peak production from days 20 to 60, and stops around day 100. The analyses also showed that juvenile hormone down regulates the vitellogenin mRNA expression and protein synthesis in the fat body, and reduces the vitellogenin levels in the haemolymph. Our data showed that vitellogenin may have an important role in maintaining age polyethism and its synthesis is down regulated by juvenile hormone in E. tuberculatum.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Midgut ultrastructure of the tropical bed-bug Cimex hemipterus Fabricius (Hemiptera: Cimicidae)

Este trabalho avaliou a ultra-estrutura das células do intestino médio de Cimex hemipterus Fabricius (Hemiptera: Cimicidae) em diferentes períodos após a alimentação. Insetos adultos foram alimentados com sangue de codorna (Coturnix coturnix) e mantidos em privação alimentar por um, três, cinco, sete, dez e 15 dias, períodos os quais tiveram o intestino médio dissecado e separado em porções anterior (IMA), média (IMM) e posterior (IMP). O material obtido foi processado para análisesem microscópio eletrônico de transmissão. O intestino médio de C. hemipterus é formado por um epitélio simples de células cúbicas a colunares e células regenerativas, apoiadas sobre uma lâmina basal circundada por fibras musculares. Em geral, as células principais das três regiões apresentaram ápice com microvilosidades e membranas perimicrovilares. O citoplasma apical concentra mitocôndrias, enquanto a porção mediana apresentou núcleo esférico com cromatina descondensada e nucléolo desenvolvido. A porção basal apresentou labirinto desenvolvido, associado a mitocôndrias. As células estão apoiadas numa membrana basal contínua, circundada por células musculares longitudinais e transversais. As células regenerativas apresentaram citoplasma elétron-denso, com mitocôndrias, retículo endoplasmático rugoso e núcleo esférico. No IMA, as células apresentaram muitos esferocristais, inclusões lipídicas, depósitos glicogênio e vacúolos eletron-lucentes, sugerindo que esta região é responsável pela absorção de água, regulação iônica, digestão e armazenamento de lipídios e carboidratos. As células principais do IMM apresentaram grânulos de secreção na porção apical, lisossomos e grande quantidade de retículo endoplasmático rugoso, sugerindo que esta região está envolvida na secreção de enzimas digestivas e digestão intracelular de proteínas do sangue. As células do IMP também apresentaram grânulos de secreção, lisossomos e muito retículo endoplasmático rugoso, além de esferocristais, indicando atividades de digestão de proteínas do sangue e absorção de íons e água. Células endócrinas foram encontradas no IMP. Grânulos elétron-densos, provavelmente envolvidos na desintoxicação de heme e ferro, foram observados no citoplasma das células principais nas três regiões do intestino médio. A similaridade estrutural do intestino médio de C. hemipterus com a de outros hemípteros hematófagos sugere que o seu hábito alimentar tem origem ancestral comum.This work investigated the ultrastructure of the midgut cells of Cimex hemipterus (Hemiptera: Cimicidae) at different times after blood meal. Adults of C. hemipterus were feed on quail s blood (Coturnix coturnix) and starved for one, three, five, seven, ten and fifteen days, when the insects had their midgut dissected and divided in anterior portion (AMG), median portion (MMG) and posterior portion (PMG). The obtained material was processed for analyses under transmission electron microscopy. The midgut of C. hemipterus has a single layer of columnar or cubic digestive cells and regenerative cells onto a basal lamina surrounded by muscle cells. The midgut digestive cells have microvilli and perimicrovillar membranes at the apical portion. The apical cytoplasm has mitochondria, while the median portion showed rounded nucleus with descondensed chromatin and a well developed nucleolus. The basal region of the cells has a developed basal labyrinth associated with mitochondria. The regenerative cells have electron-dense cytoplasm with mitochondria, rough endoplasmatic reticulum and a rounded nucleus. In the AMG the digestive cells have many spherocristals, lipid inclusions, glycogen deposits and electron-lucent vacuoli, suggesting that this midgut region play a role in water absorption, ion regulation, digestion and storage of lpids and sugars. The MMG cells have secretory granules in the apical cytoplasm, lysosomes and large amounts of rough endoplasmatic reticulum, suggesting that this midgut region was active in the blood digestion. The PMG cells also presented secretory granules, lysosomes, rough endoplasmatic reticulum and spherocristals, indicating blood digestion and ion and water absorption activities. Endocrine cells were found in the PMG. Electron-dense granules, pobably involved in heme and iron detoxification were observed in the three midgut regions. The structural similarity of the C. hemipterus midgut with that organ of other blood-feeding Hemiptera suggests that their alimentary habit had a common ancestral origin.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Temporal variation of vitellogenin synthesis in Ectatomma tuberculatum (Formicidae: Ectatomminae) workers

Workers of the ant species Ectatomma tuberculatum (Ectatomminae) have active ovaries and lay eggs that are eaten by the queen and larvae (trophic eggs). Vitellogenins are the main proteins found in the eggs of insects and are a source of nutrients. The aim of this study was to characterize the period of vitellogenin production in workers of E. tuberculatum. The vitellogenin was identified from queen and worker eggs by SDS-PAGE. Anti-vitellogenin antibodies were obtained and used to detect this protein in the fat body and haemolymph of workers at different ages. Vitellogenin from E. tuberculatum consists of two polypeptides of 31 and 156 kDa. In the eggs of queens, the 156 kDa polypeptide is cleaved into two subunits of 36 and 123 kDa. The analysis of the haemolymph of workers showed that the secretion of vitellogenin varies with age. The secretion is initiated around the fifth day after emergence, with peak production from days 20 to 60, and stops around day 100. The variation in production is related to the different activities performed by the workers within the colony, suggesting that vitellogenin may have an important role in maintaining age polyethism

Aquaporins in the honeybee crop—a new function for an old organ

Nectar used by bees as a food source is collected and stored in the crop, where it is transported and converted into honey. The production of honey involves water uptake from nectar. However, the crop is a portion of the insect foregut that has been characterized solely as a food storage organ. Aquaporins are integral membrane proteins that function as specific canal for water transport and are abundant in tissues with high water permeability. In this study, we detected five predicted genes for aquaporins in the gut of the honeybee Apis mellifera. We evaluated the aquaporins’ localization in the crop by using an anti-aquaporin antibody produced against the peptide sequence from one of the expressed genes, which was detected in the crop epithelium, particularly in the apical portions of the cells. Furthermore, we also showed an increase in sugar concentration in a sucrose solution collected from the crop lumen a few minutes after feeding, indicating that water uptake occurs during storage of nectar in the crop, suggesting a previously unidentified function for the honeybee crop

Melipona quadrifasciata (Hymenoptera: Apidae) fat body persists through metamorphosis with a few apoptotic cells and an increased autophagy

Fat body, typically comprising trophocytes, provides energy during metamorphosis. The fat body can be renewed once the larval phase is complete or recycled and relocated to form the fat body of the adult insect. This study aims to identify the class of programmed cell death that occurs within the fat body cells during the metamorphosis of the stingless bee Melipona quadrifasciata. Using immunodetection techniques, the fat body of the post-defecating larvae and the white-, pink-, brown-, and black-eyed pupae were tested for cleaved caspase-3 and DNA integrity, followed by ultrastructural analysis and identification of autophagy using RT-PCR for the Atg1 gene. The fat body of M. quadrifasciata showed some apoptotic cells positive for cleaved caspase-3, although without DNA fragmentation. During development, the fat body cells revealed an increased number of mitochondria and free ribosomes, in addition to higher amounts of autophagy Atg1 mRNA, than that of the pupae. The fat body of M. quadrifasciata showed few cells which underwent apoptosis, but there was evidence of increased autophagy at the completion of the larval stage. All together, these data show that some fat body cells persist during metamorphosis in the stingless bee M. quadrifasciata

Post-embryonic development of the antennal sensilla in Melipona quadrifasciata anthidioides (Hymenoptera: Meliponini)

The sensilla are sensory organs formed by cuticular and cellular structures specialized in reception of chemical and physical stimuli from the environment and transmission to the insect's central nervous system. In function of the great concentration of sensilla, the antennae are the main organs for interaction between bees and with the environment. This work studied the presence of antennal sensilla in the different phases of pupal development of the stingless bee Melipona quadrifasciata anthidioides by means of scanning electron microscopy and light microscopy. The results showed that antennal sensilla begin their development in the transition of the prepupae to the white-eyed pupae and finish it in the pigmented-body pupae phase. The antennal sensilla were exposed to the environment in the black-eyed pupae when the old cuticle is completely digested, suggesting that only in the final pupal phases can these bees perceive the environmental stimuli

Desenvolvimento, reprodução e performance predatória do percevejo zoofitófago Podisus distinctus (Hemiptera: Pentatomidae) alimentado com larvas de Musca domestica (Diptera: Muscidae) imobilizadas ou soltas

Researches with predatory true bugs are crucial for biological control programs. Pairs of Podisus distinctus were fed with immobilized or free Musca domestica larvae, aiming to verify the influence of prey mobility on predatory capacity and biology of the predator, compared to the use of Tenebrio molitor pupae. Consumption of M. domestica larvae was also compared between adults of P. distinctus and Podisus nigrispinus. The number of larvae consumed and female reproductive parameters were similar between treatments. However, females fed with T. molitor laid more eggs and clutches per female, and showed shortest oviposition interval, confirming that M. domestica larvae may be not appropriate preys to rear P. distinctus, independently of their mobility. P. nigrispinus had higher predation on M. domestica larvae than P. distinctus, suggesting that the former species can properly use this alternative prey.Pesquisas com percevejos predadores são fundamentais para programas de controle de pragas. Casais de Podisus distinctus foram alimentados com larvas de Musca domestica imobilizadas ou soltas, para verificar a influência da mobilidade na predação e biologia desse predador e comparar o consumo dessas larvas entre P. distinctus e Podisus nigrispinus. O número de larvas consumidas e os parâmetros reprodutivos de fêmeas foram semelhantes entre tratamentos. Entretanto, fêmeas desse predador apresentaram maior número de ovos, de posturas e menor intervalo entre as posturas alimentadas com Tenebrio molitor, confirmando que M. domestica não é uma boa presa para a criação de P. distinctus. Podisus nigrispinus consumiu maior número de larvas de M. domestica que P. distinctus, o que pode estar relacionado ao melhor desenvolvimento desse predador a esse tipo de presa alternativa

Morphology of the digestive tract of Cladomorphus phyllinus (Phasmatodea: Phasmidae)

The digestive tracts of insects may indicate life history and phylogenetic relationships among different species. Phasmatodea are chewing herbivores with an elongated body shape, which camouflages them on the vegetation on which they feed. This work evaluated the gut structure of the walking stick insect, Cladomorphus phyllinus (Gray 1835) (Phasmatoidea: Phasmidae), with light and scanning electron microscopy. The digestive tract of C. phillynus is an elongated tube with minimal external anatomical differences along its length. There is a short gastric caeca-like structure in the posterior midgut. The crop is an extensively folded storage organ and the proventriculus is covered by a thick cuticle with spine-like projections, which play a role in grinding food. The midgut has 2 anatomical regions probably involved in digestion and absorption of nutrients. The epithelial cells of the anterior midgut have bubbles of apocrine secretion, while the posterior midgut cells have a striated border. Gastric caecae-like projections are found in the posterior midgut. They are enlarged close to the midgut wall, and follow a thin and long filament, which is free in the body cavity. The epithelial cells lining the gastric caecae-like projections are cuboidal with well development striated borders, suggesting involvement in nutrient absorption. The hindgut is divided in an ileum and a rectum. The ileum epithelial cells are covered by cuticle and have cytological traits characteristic of electrolyte and water absorption. The rectum epithelial cells have no obvious absorptive features, but the rectal pads may be involved in water and electrolyte reabsorption. This work reinforces the concept that the anatomy of gut is related to the diet and body shape, and shows that the general pattern of compartmentalization of digestion in insects was maintained in Phasmatodea, but that it differs from other Orthopteroidea in some aspects.O trato digestivo dos insetos pode indicar a história de vida e as relações filogenéticas entre espécies diferentes. Phasmatodea são herbívoros mastigadores com corpo alongado que se camuflam na vegetação. Este trabalho avaliou a estrutura do intestino do bicho-pau Cladomorphus phyllinus através de microscopia de luz e microscopia eletrônica de varredura. O trato digestivo de C. phyllinus é um tubo alongado sem diferenças anatômicas ao longo de seu comprimento, exceto pela presença de uma estrutura semelhante ao ceco gástrico na região posterior do intestino médio. O papo é um órgão de armazenamento amplamente dobrado e o proventrículo é coberto por cutícula espessa com projeções na forma de espinhos. O intestino médio tem duas regiões anatômicas, e está provavelmente envolvido na digestão e absorção de nutrientes. As células epiteliais do intestino médio anterior apresentam bolhas de secreção apócrina na sua porção apical, ao passo que as células do intestino médio posterior possuem borda estriada no ápice. Estruturas semelhantes a cecos gástricos foram encontrados no intestino médio posterior, com células cúbicas que apresentam microvilosidades longas, provavelmente envolvidas na absorção de nutrientes. O intestino posterior é dividido em íleo e reto. As células do íleo são cobertas por cutícula e têm características de absorção de eletrólitos e água. As células epiteliais do reto não apresentam características de células absortivas, diferentemente das células das papilas retais, provavelmente envolvidas na reabsorção de água e eletrólitos. Este trabalho reforça que a anatomia do intestino está relacionada com a forma do corpo do inseto, e mostra que o padrão geral de compartimentalização da digestão nos insetos é mantido em Phasmatodea, mas com algumas diferenças em comparação com outros Orthopteroidea