José Eduardo Serrão

Cost and mitigation of insecticide resistance in the maize weevil, Sitophilus zeamais

Abstract.  A common assumption in models of insecticide resistance evolution is the association between resistance and fitness costs in the absence of insecticides. There is empirical evidence of such associations, but their physiological basis (and mitigation) is little investigated. Pyrethroid‐resistant populations of the maize weevil Sitophilus zeamais (Coleoptera: Curculionidae) offer this opportunity. Pyrethroid resistance in this species was initially observed in five Brazilian states by 1995, but the phenomenon apparently decreased and did not spread to other regions, probably due to the occurrence of a fitness disadvantage in resistant individuals in the absence of insecticides. The present investigation aims to verify whether differences in respiration rate and fat body morphology are related to differences in rate of development in Brazilian populations of S. zeamais resistant to insecticides, and thereby provide evidence for the existence (or not) of a physiological fitness cost acting against insecticide resistance in maize weevils. This may occur due to a possible energy trade‐off between insecticide resistance and other physiological processes associated with development and reproduction. To achieve this, studies of the rate of development, respiration and fat body cytomorphology are carried out in one insecticide‐susceptible (from Sete Lagoas) and two resistant populations (from Jacarezinho and Juiz de Fora) of S. zeamais. The resistant population from Jacarezinho shows that higher body mass is associated with higher energy reserves (larger trophocyte area) for development and reproduction, as well as for insecticide resistance. However, the resistant population from Juiz de Fora does not appear to have large enough energy allocation for insecticide‐resistance expression and development and/or reproductive performance, suggesting a trade‐off between resistance and other life history traits.

As espécies de ephemeroptera (insecta) registradas para o Brasil

(The species of mayflies (Ephemeroptera: Insecta) recorded from Brazil). A checklist of the Brazilian Ephemeroptera fauna with all species, genera and families recorded from the country, including the states for which every species is reported, and the pertinent reference is presented. Comments on the status of knowledge of the Brazilian mayfly fauna are also provided. Up to date, 10 families, 63 genera, and 166 species are recorded. Baetidae and Leptophlebiidae have more than 50% of all records, while the North and Southeastern regions are significantly better studied than the other areas of the country.

Interplay between insulin signaling, juvenile hormone, and vitellogenin regulates maternal effects on polyphenism in ants

Polyphenism is the phenomenon in which alternative phenotypes are produced by a single genotype in response to environmental cues. An extreme case is found in social insects, in which reproductive queens and sterile workers that greatly differ in morphology and behavior can arise from a single genotype. Experimental evidence for maternal effects on caste determination, the differential larval development toward the queen or worker caste, was recently documented in Pogonomyrmex seed harvester ants, in which only colonies with a hibernated queen produce new queens. However, the proximate mechanisms behind these intergenerational effects have remained elusive. We used a combination of artificial hibernation, hormonal treatments, gene expression analyses, hormone measurements, and vitellogenin quantification to investigate how the combined effect of environmental cues and hormonal signaling affects the process of caste determination in Pogonomyrmex rugosus. The results show that the interplay between insulin signaling, juvenile hormone, and vitellogenin regulates maternal effects on the production of alternative phenotypes and set vitellogenin as a likely key player in the intergenerational transmission of information. This study reveals how hibernation triggers the production of new queens in Pogonomyrmex ant colonies. More generally, it provides important information on maternal effects by showing how environmental cues experienced by one generation can translate into phenotypic variation in the next generation.

Nymphal Development and Reproduction of Podisus nigrispinus (Heteroptera: Pentatomidae) Fed With Combinations of Tenebrio molitor (Coleoptera: Tenebrionidae) Pupae and Musca domestica (Diptera: Muscidae) Larvae

The development and reproduction of Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) fed on Tenebrio molitor L. (Coleoptera: Tenebrionidae) and Musca domestica L. (Diptera: Muscidae) were studied in four treatments. P. nigrispinus was permitted to feed on: (1) T. molitor pupae (T 1 ); (2) Musca domestica larvae (T 2 ); (3) both prey supplied simultaneously (T 3 ); (4) both prey supplied on alternate days (T 4 ). Duration of the nymphal period of P. nigrispinus was similar in all diets studied with nymphal viability of approximately 75%. Heavier females were obtained in T 1 and T 4 , but no correlation between this factor and the reproductive rate of the predator was found. Therefore, the use of body weight as a parameter to evaluate rearing quality should be approached with caution. However, females of this predator showed higher egg and nymph production when they received both prey. For this reason P. nigrispinus should be reared with T. molitor and M. domestica simultaneously or on alternate days.

Baetidae (Ephemeroptera) na região sudeste do Brasil: novos registros e chave para os gêneros no estágio ninfal

Com o intuito de complementar e integrar o conhecimento relativo a fauna de Baetidae do sudeste brasileiro, treze especies e nove generos dessa familia sao registrados. Dos vinte generos da familia relatados para o Brasil, apenas cinco nao foram encontrados na Regiao Sudeste. Uma lista com todas as especies registradas, incluindo sua distribuicao e referencias bibliograficas pertinentes, e apresentada. Uma chave ilustrada e proposta para a identificacao dos generos no estagio ninfal registrados ate o momento para a regiao.

Ultrastructure of the Digestive Cells in the Midgut of the Predator Brontocoris tabidus (Heteroptera: Pentatomidae) after Different Feeding Periods on Prey and Plants

ABSTRACT Brontocoris tabidus (Signoret) (Heteroptera: Pentatomidae) is an obligate zoophytophagous predator because its population can be maintained in the laboratory when fed on both prey and plants. We evaluated ultrastructural changes in the midgut digestive cells of adult B. tabidus, subjected to different treatments (starvation or feeding on plant material and prey) for different periods. Their midguts were dissected, divided into anterior, medium and posterior sections, processed, and analyzed with light and transmission electron microscopy. The anterior region of the midgut of B. tabidus, starved or fed on eucalyptus leaves, contained no glycogen. B. tabidus fed on plant material showed multivesicular bodies in this region, and spherocrystals after 6 h of feeding on prey. The microvilli of the medium midgut were longer than those of the anterior and posterior midgut. The posterior midgut differed from the other two regions by an abundance of mitochondria, rough endoplasmatic reticulum and double membrane vesicles in the apical region, 6 h after feeding. The ultrastructural features of the digestive cells in the anterior, medium and posterior regions of the midgut suggest that they play a role in digestive enzyme synthesis, ion and nutrient absorption, and storage and excretion of substances.

Effect of temperature on life table parameters of Podisus nigrispinus (Het., Pentatomidae) fed with Alabama argillacea (Lep., Noctuidae) larvae

Abstract: The influence of temperature on life table parameters of Podisus nigrispinus (Dallas) (Het., Pentatomidae) fed with Alabama argillacea (Hübner) (Lep., Noctuidae) larvae was studied. This predator was kept at constant temperatures of 20, 23, 25, 28, 30 and 33±0.2°C, at relative humidity of 60±10% and photoperiod of L : D 14 : 10. Gross (GRR) and net (R0) reproductive rates of P. nigrispinus ranged from 1.6 to 366.6 and from 0.02 to 189.5 females/female at temperatures of 33 and 28°C, respectively; generation time (T ) ranged from 33.3 (33°C) to 85.5 (20°C) days; doubling time (D) from 0.82 (33°C) to 17.8 (20°C) days; intrinsic rate of increase (rm) from −0.13 (33°C) to 0.12 (28°C) per day; and the finite rate of increase (λ) from 0.88 (33°C) to 1.12 (28°C) females/female added to the population per day. The ideal age to release P. nigrispinus should be when this predator presents higher reproductive values (VRx); that is, its adults are about 7 days old, independent of prevailing temperature. Population growth of P. nigrispinus was affected by temperature with maximum numerical response between 28 and 30°C. The negative population growth shown at 33°C may not occur in natural conditions due to milder microclimate in the cotton agroecosystem and due to oscillations of temperature in the course of the day.

Effects of diet on development of Podisus nigrispinus (Dallas) (Het., Pentatomidae), a predator of the cotton leafworm

Abstract:  The effects of diet on development of Podisus nigrispinus (Dallas) (Het., Pentatomidae) were studied at 25°C, relative humidity of 60 ± 10%, and photoperiod of 14 h light : 10 h dark. Development times of P. nigrispinus nymphs were similar when fed with third or fifth instar larvae of cotton leafworm (Alabama argillacea Hübner) (Lep., Noctuidae) or Tenebrio molitor L. (Col., Tenebrionidae). When fed with housefly larvae (Musca domestica L.) (Dipt., Muscidae) or artificial diet, the predator had a longer development time. Independent of diet, instar or sex, the females of P. nigrispinus showed a longer longevity than the males. The total survival of the nymphal stage, on the different diets, varied from 22.46 (fed with housefly) to 77.33% (fed with T. molitor larvae). P. nigrispinus males were heavier when fed with third or fifth instar cotton leafworm larvae than when fed with artificial diet. The weight of the females varied from 37.91 (with artificial diet) to 64.68 mg (with fifth instar cotton leafworm larvae). Independently of the diet, newly emerged females of P. nigrispinus were heavier than the males. Females of P. nigrispinus which were fed with fifth instar cotton leafworm larvae had heavier ovaries than those fed other diets.

Morphology of female reproductive tract of the predator Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) fed on different diets

Este estudo apresenta a morfologia do sistema reprodutor feminino de Podisus nigrispinus (Dallas) alimentado com larvas de Alabama argillacea (Hubner), Musca domestica L. e de Tenebrio molitor L. ou dieta artificial. As gonadas internas desse predador apresentaram coloracao amarelada e, independente da dieta, cada ovario apresentou sete ovariolos unidos pelos filamentos terminais em uma estrutura em forma de cacho. A analise histologica revelou que o ovario de P. nigrispinus e do tipo meroistico telotrofico com cada ovariolo dividido morfologicamente em filamento terminal, trofario (câmara nutridora), vitelario e pedicelo. A dieta recebida por esse predador alterou o desenvolvimento e a morfometria de seus ovarios. Femeas de P. nigrispinus alimentadas com larvas de terceiro ou quinto estadio de A. argillacea apresentaram ovarios desenvolvidos com grande numero de ovocitos em estagio avancado de desenvolvimento nos ovariolos. Femeas com dieta artificial apresentaram ovarios atrofiados e ovariolos, praticamente, sem ovocitos em seu interior enquanto aquelas alimentadas com larvas de T. molitor ou M. domestica tiveram ovarios em estagios intermediarios de desenvolvimento. O comprimento do ovariolo central foi maior em femeas alimentadas com larvas de quinto estadio de A. argillacea e menor naquelas com dieta artificial. Ovocitos em estagios mais avancados de desenvolvimento foram observados para femeas alimentadas com larvas de terceiro ou quinto estadios de A. argillacea, enquanto ovocitos atrofiados foram observados para aquelas com dieta artificial.

Biochemical and Morphological Aspects of Salivary Glands of the Predator Brontocoris tabidus (Heteroptera: Pentatomidae)

The aim of this work was to study the feeding habits of the predator Brontocoris tabidus (Heteroptera: Pentatomidae) analyzing the salivary gland complex (SGC). The SGC was dissected and subjected to histological analyses and biochemical assays. Results showed that a pair of bilobed principal salivary glands and one pair of tubular accessory salivary glands form the SGC and different parts of salivary gland synthesizes similar substances. Lipases, a-amylase and trypsin-like enzymes were detected at both lobes of the principal salivary gland. These data together with observations related to the predators diet suggested that it could be considered an obligate zoophytophagous.