The ideal habitat for leaf-cutting ant queens to build their nests.

Queens of Atta sexdens Forel (Hymenoptera: Formicidae) face biotic and abiotic environmental factors in the environment while establishing their nests. Biotic factors such as predation, microbial pathogens, successful symbiotic fungus regurgitation, excavation effort and abiotic factors such as radiant sunlight, temperature, density, and soil moisture exert selection pressures on ant queens. Biotic factors such as temperature and solar irradiation affect the survival of the initial colony differently, in different environments in the field. Queens of the leaf-cutting ant A. sexdens, were installed in sunny and shaded conditions to test this hypothesis. Two hundred A. sexdens queens were collected and individualized in two experimental areas (sunny and shaded), each in an experimental area (25 m2) in the center of a square (50 × 50 cm). Temperature, irradiance, nest depth, rainfall and queen mortality were evaluated. Atta sexdens colony development was better in the shaded environment, and the depth and volume of the initial chamber, fungus garden biomass and number of eggs, larvae, pupae and workers were greater. The queen masses were similar in both environments but mortality was higher in the sunny environment. The worse parameter values for A. sexdens nests in the sunny environment are due to the greater solar irradiance, increasing the variation range of the internal temperature of the initial chamber of the nest. On the other hand, the more stable internal temperature of this chamber in the shaded environment, is due to the lower incidence of solar irradiance, which is also more advantageous for queen survival and the formation and development of A. sexdens colonies. Shaded environments are a better micro habitat for nesting A. sexdens than sunny ones.

Carbon dioxide levels in initial nests of the leaf-cutting ant Atta sexdens (Hymenoptera: Formicidae).

Claustral foundation of nests by Atta sexdens Forel (Hymenoptera: Formicidae) involves great effort by its queens, solely responsible for the cultivation of the fungus and care for her offspring at this stage. The minimum workers, after 4 months, open access to the external environment to foraging plants to cultivate the symbiotic fungus, which decomposes the plant fragments and produces gongilidea nodules as food for the individuals in the colony. Colony gas exchange and decomposition of organic matter in underground ant nests generate carbon dioxide (CO2) emitted into the atmosphere. We described the carbon dioxide concentration in colonies in the field. The objective was to evaluate the carbon dioxide concentration in initial A. sexdens colonies, in the field, and their development. The CO2 level was also measured in 4-month-old colonies in the field, using an open respirometric system fitted with an atmospheric air inlet. The CO2 level of the respirometric container was read by introducing a tube into the nest inlet hole and the air sucked by a peristaltic pump into the CO2 meter box. The CO2 concentration in the initial colony was also measured after 4 months of age, when the offspring production (number of eggs, larvae, pupae and adult workers) stabilized. Ten perforations (15 cm deep) was carried out in the adjacent soil, without a nest of ants nearby, to determine the concentration of CO2. The composition of the nests in the field was evaluated after excavating them using a gardening shovel and they were stored in 250 ml pots with 1 cm of moistened plaster at the bottom. The CO2 concentration was higher in field nest than in adjacent soil. The concentration of carbon dioxide in A. sexdens nests in the field is higher than in those in the soil, due to the production of CO2 by the fungus garden and colony.

Contamination routes and mortality of the leaf-cutting ant Atta sexdens (Hymenoptera: Formicidae) by the insecticides fipronil and sulfluramid through social interactions.

BACKGROUND: Leaf-cutting ants (LCAs) of the genera Atta and Acromyrmex (Hymenoptera: Formicidae) are important pests of forest plantations, agriculture and livestock. Toxic baits containing the active ingredients fipronil or sulfluramid are the main method used to control LCAs. Insecticide dispersion among members of an LCA colony during control with toxic bait is not well understood. The objective of the study was to determine whether self-grooming, allogrooming or touching behavior among Atta sexdens (Hymenoptera: Formicidae) workers disperses the insecticides fipronil and sulfluramid among members of the colony. The insecticides were topically applied on groups of A. sexdens workers and social interactions between ants with and without insecticide, and group mortality were evaluated. RESULTS: Behavioral analysis showed an increase in interaction among LCA workers as the numbers of individuals increased, with touches between workers being the most frequent behavior. The frequency of observed behaviors was higher in groups treated with sulfluramid compared with fipronil. The mortality of groups treated with fipronil was almost twice as high compared with ants treated with sulfluramid. The insecticides are probably dispersed by excessive touching among workers and subsequent self-grooming and allogrooming. CONCLUSION: These behaviors were responsible for the rapid dispersion of insecticides among members of the colony. Corroboration of the hypothesis that social interactions contaminate nestmates is a model for future studies on contamination of ant workers with active insecticide ingredients. © 2021 Society of Chemical Industry.

Oviposition, Life Cycle, and Longevity of the Leaf-Cutting Ant Acromyrmex rugosus rugosus.

Studies related to the demography of individual members from ant colonies have received little attention, although they are the basis to understanding the population dynamics of colonies. Thus, the objective of this work was to study the queen oviposition rate and the duration of the life cycle and longevity of Acromyrmex rugosus rugosus workers. To determine the oviposition rate, queens from three colonies were individually placed in plastic containers, and the eggs laid were quantified over a 96 h period. The development of the immature forms was observed every 24 h, with which the duration of each stage of development was determined. To verify the longevity of workers, the newly emerged adults were marked and daily observations were made. According to the results, there is variation in the development time of immature forms within the colony itself and between colonies. In addition, the number of eggs deposited was also inconstant in the three colonies, ranging from 5 to 119 eggs per day, while the longevity of workers varied from 3 to 7 months. Occasionally, it was found that the workers feed on the eggs produced by the queen; besides, there was a disappearance of larvae and pupae during the research, indicating a possibility of the practice of cannibalism in this species.

Spatio-Temporal Dynamics of Foraging Networks in the Grass-Cutting Ant Atta bisphaerica Forel, 1908 (Formicidae, Attini).

Foraging networks are a key element for ant colonies because they facilitate the flow of resources from the environment to the nest and they allow the sharing of information among individuals. Here we report the results of an 8-month survey, extending from November 2009 to June 2010, of the foraging networks of four mature colonies of Atta bisphaerica, a species of grass-cutting ant which is considered as a pest in Brazil. We found that the distribution of foraging effort was strongly influenced by the landscape features around the nests, in particular by the permanently wet parts of the pasture in which the nests were located. The foraging networks consisted of underground tunnels which opened on average at 21.5m from the nests and of above-ground physical trails that reached on average 4.70m in length. The use of the foraging networks was highly dynamic, with few sections of the networks used for long periods of time. Three different phases, which could be linked to the seasonal change in the local rainfall regime, could be identified in the construction and use of the foraging networks. The first phase corresponded to the beginning of the rainy season and was characterized by a low foraging activity, as well as a low excavation and physical trail construction effort. The second phase, which began in February and extended up to the end of the humid season at the end of March, was characterized by an intense excavation and trail construction effort, resulting in an expansion of the foraging networks. Finally, in the third phase, which corresponded to the beginning of the dry season, the excavation and trail construction effort leveled off or decreased while foraging activity kept increasing. Our hypothesis is that ants could benefit from the underground tunnels and physical trails built during the humid season to maintain their foraging activity at a high level.

Energy substrate used by workers of leaf-cutting ants during nest excavation

Energy substrate used by workers of leaf-cutting ants during nest excavation. In this study we aimed to ascertain whether leaf-cutting ant workers lose body reserves (fat or sugars) as a function of nest excavation. For each treatment, we isolated 10 workers of Atta sexdens into two experimental groups, Control (C- without excavation) and Soil (S- with excavation), which were kept for different time intervals (0, 24, 48 or 72 hours), totaling 700 tested workers. We then determined the concentration of soluble carbohydrates and total lipid content in them. The total carbohydrates were determined colorimetrically, based on the reaction between carbohydrates and sulfuric acid-phenol. For determination of lipids, the insects were immersed in organic solvent until they reached a constant weight. Our results showed that carbohydrates are consumed during nest excavation activities. In the experimental groups S24, S48 and S72, there was an average reduction of 5.82 (20.42%), 14.31 (44.96%) and 13.27 (43.96%) µ.mg-1 in soluble sugar when compared with the experimental groups that did not excavate. Furthermore, the lipids were not used during this activity. With respect to dry mass of the workers, their values were C0 = 8%, C24 = 10.4%, C48 = 9.2%, C72 = 10%, S24 = 9.2%, S48 = 8.7% and S72 = 8.5%. Our results show experimentally that the source of energy for nest excavation is carbohydrates, whereas lipids are conserved for other activities.

Aloetismo em Acromyrmex subterraneus brunneus Forel (Hymenoptera, Formicidae), durante o forrageamento, cultivo do jardim de fungo e devolução dos materiais forrageados / Alloethism in Acromyrmex subterraneus brunneus Forel (Hymenoptera, Formicidae), during foraging, fungus-garden cultivation and devolution of foraged materials

As formigas cortadeiras apresentam uma sofisticada divisão de trabalho durante o forrageamento, cultivo do jardim de fungo e devolução dos materiais forrageados. Materiais com diferentes graus de hidratação e dureza (esponja floral, isopor, plástico e argila) foram oferecidos a duas colônias de laboratório de Acromyrmex subterraneus brunneus Forel, 1911. As diferentes categorias de tamanho de operárias foram observadas durante a execução de 14 subtarefas. Probabilidade relativa de desempenho e as curvas aloéticas foram usadas para verificar a flexibilidade comportamental e os padrões comportamentais estereotipados das operárias. Os padrões comportamentais possibilitaram estabelecer papeis dentro de prováveis subcastas.

Clinicopathologic evaluation of thyroid tumors through p53 protein accumulation and proliferative activity measured using Ki-67 and PCNA monoclonal antibodies

Thyroid neoplasms frequently present difficulties in the diagnostic and prognostic evaluation due to the poor relation between morphology and tumor behavior. It is particularly important to define parameters to evaluate the potential of aggressiveness of such neoplasias with ancillary techniques in order to improve the clinical management of the patients with thyroid tumors. The potential of three markers - p53, Ki-67 and PCNA - in adenocarcinomas of the thyroid was evaluated and the relation of these markers to the prognostic behavior of the tumors were analyzed in a retrospective study. Seventy-seven cases of patients with neoplasms of the thyroid, submitted to thyroid surgery by the same surgeon (RSC), belonging to the team, were studied. Histological sections of the samples were submitted to immunohistochemical reactions with anti-p53 (cione D07), anti-Ki-67 (clone MIB1) and anti-PCNA (clone PC 10) monoclonal antibodies. The positive demarcations were counted in 200 cells of selected areas. The results were correlated with clinical and histopathologic parameters, selected among the survival distributions for each category of a same variable, through the Cox-Mantel test. There were 14 p53 positive cases, 17 Ki-67 positive and ali cases were PCNA positive. Although Ki-67 is theoretically present in ali the phases of cell division, it was not possible to identify it in ali cases; PCNA, was shown as an identification marker with expressive sensitivity. The immunohistochemical study showed ali follicular adenocarcinomas with PCNA positive immunoreaction, 11 (36,6 percent) Ki-67 positive and 8 (26,6 percent) p53 positive; 30 papillary tumors were PCNA positive, 5 (16,6 percent) Ki-67 positive, and 6 (20 percent) p53 positive. Medullary and Hürthle cell adenocarcinomas showed only PCNA positive immunoreaction, 3 and 2 cases respectively. Regarding the undifferentiated adenocarcinomas, 5 specimens presented PCNA positive immunoreaction, 1 was Ki-67 positive, 3 were p53 positive. PCNA monoclonal antibody showed a positive correlation with patient age and histologic type (p=0.005 and p= 0.032 respectively).

Miotomia transversal como recurso auxiliar nas anastomoses esofagicas: estudo experimental em caes / Transverse miotomy as an auxiliary procedure in the esophageral anastomosis: an experimental study in dogs

Os autores operaram 24 caes de ambos os sexos, submetendo-os a esofagectomia cervical parcial com anastomose primaria em plano unico e miotomias transversais totais a montante e a jusante da anastomose. Os animais foram divididos em dois grupos: I e II. Os animais do grupo I foram observados por um periodo medio de 63 dias. Os sobreviventes foram submetidos ao estudo da circulaçao pelo metodo da fluoresceina, e em cinco animais de cada grupo, apos o sacrificio, procedeu-se o estudo da circulaçao esofagica pelo metodo da diafanizaçao de Spalteholtz. Observou-se ainda que a circulaçao fazia-se pela rede vascular submucosa e por vasos neoformados originarios do ramo esofagico das arterias tireoidianas cranial e caudal, e de outras estruturas anatomicas vizinhas. Concluiram que as miotomias justanastomoticas nao interferem com a circulaçao adjacente

Avaliaçäo do DNA pela citofotometria nos tumores papiliferos da tireoide / DNA evaluation by cytophotometry in papillary thyroid tumour

A avaliacao quantitativa do DNA tem sido realizada em varios tumores malignos, inclusive da tireoide. Tem sido encontrado aumento da percentagem de aneuploidia em tumores de mau prognostico, enquanto que os carcinomas com distribuicao do DNA euploide seguem um curso benigno. Neste trabalho estudamos o teor do DNA nuclear de vinte casos de carcinomas papiliferos propriamente dito e dezenove de variantes papilifero. O metodo utilizado foi da citofotometria de lamina. Os histogramas foram classificados de acordo com Auer. A aneuploidia (tipo IV) esteve presente em 35,90% de todos os casos estudados.Entre os dois grupos de carcinoma papilifero nao foi observada diferenca significativa na distribuicao dos valores de DNA. Embora a literatura mostre que as variantes papiliferas tem um prognostico pior, nao pudemos comprovar analisando o conteudo de DNA nuclear. Concluimos que a citofotometria para avaliacao do DNA pode fornecer dados que permitem melhor estabelecer o prognostico de um determinado paciente, isoladamente

Funçäo tireoidian e produçäo de AMP cíclico em nódulos autônomos da tiróide / Thyroid function and cyclic AMP production in autonomous thyroid nodules

Foram estudadas cinco pacientes eutiroidianas portadores de nódulos autônomos à cintilografia tireiodiana, com diàmetro superio a 3cm e näo supressíveis pela administraçäo de T, (100µg/dia durante 10 dias). Quatro das pacientes apresentaram exames laboratoriais (T4 livre, T3 TSH basal e captaçäo de 131I em 24h) normais. Fatias de tecido tireoidiano adenomatoso e paranodular obtidas pela tiroidectomia foram incubadas com concentraçöes crescentes de TSH e na presença ou näo de iodeto de potássio (KI)ou triiodotironina (T3). O incremento da produçäo de AMP cíclico (cAMP) provocado pelo TSH no tecido adenomatoso foi igual ao encontrado do tecido adjacente paranodular. No tecido paranodular a adiçäo de T3 ou KI inibiu significativamente a produçäo de cAMP, enquanto que, no tecido adenomatoso, a açäo inibitória ocorreu apenas com KI. Estes resultados sugerem: 1) a inibiçäo da secreçäo pode ocorrer na presença de níveis hormonais tiroidianos circulantes normais; 2) nâo há evidência de sensibilidade aumentada ao TSH no tecido autônomo quando avaliada pela produçäo de cAMP; 3) a ausência inibitória do T, na resposta do TSH no tecido nodular sugere alteraçäo celular ao nível de outros reguladores da geraçäo de cAMP.