Accessing the subterranean ant fauna (Hymenoptera: Formicidae) in native and modified subtropical landscapes in the Neotropics / Avaliação da mirmecofauna subterrânea (Hymenoptera: Formicidae) em paisagens nativas e modificadas na região subtropical do Neotrópico

Abstract: Several studies have characterized and delimited subterranean ant assemblages. Soil extraction, one of the methods employed to access this fauna, employs the removal of monoliths. One of the most widely used methods for the extraction of soil sampling is called TSBF (developed by the Tropical Soil Biology and Fertility Programme). This method provides relevant data about the species associated with the soil. In the present study we characterized assemblages of subterranean ants using the TSBF method in different subtropical areas of the Neotropics. We considered two sampling designs in different localities. The first design resulted in 315 TSBF samples obtained from layers at distinct depths. The second design resulted in 270 TSBF samples and 270 epigaeic pitfall trap samples. This material was used to delimit the species that occur exclusively in the subterranean stratum (TSBF) and that are not found on the soil surface. A total of 281 species were recorded. Of these, 57 can be considered subterranean, based on their occurrence in subterranean strata. We also verified that the highest occurrence of ants was in the first 10 cm of soil depth. Due to the importance of using methods that efficiently extract the subterranean ant fauna in studies, we suggest the TSBF method should be used to sample ants or to associate this method with epigaeic pitfall traps to delimit strictly subterranean assemblages in specific community stratification studies.

Resumo: Vários estudos têm caracterizado e delimitado assembleias de formigas subterrâneas. A extração de solo, um dos métodos utilizados para amostragem dessa fala, implica na remoção de monólitos. Um dos métodos mais utilizados na extração de monólitos é chamado TSBF (desenvolvido pelo Programa Tropical Soil Biology and Fertility). Esse método fornece dados extremamente relevantes sobre as espécies associadas ao solo. No presente estudo, nós caracterizamos as assembleias de formigas subterrâneas usando o método TSBF em diferentes áreas subtropicais do Neotrópico. Utilizamos dois delineamentos amostrais distintos. O primeiro delineamento resultou em 315 amostras de TSBF obtidas a partir da estratificação do solo. O segundo resultou em 270 amostras de TSBF mais 270 provenientes de armadilhas pitfall epigeicas. Esse material foi utilizado para delimitar espécies que ocorrem exclusivamente no estrato subterrâneo (TSBF) e não são encontradas na superfície do solo. Registramos um total de 281 espécies. Destas, 57 podem ser consideradas subterrâneas (baseado na ocorrência no respectivo estrato). Também verificamos que a maior ocorrência de formigas se deu nos primeiros 10 cm de profundidade. Devido à importância do uso de métodos que coletem eficientemente formigas subterrâneas, sugerimos o uso do método TSBF em estudos de estratificação de comunidades ou sua associação a armadilhas do tipo pitfall epigeica para delimitar assembleias estritamente subterrâneas.

Soil macrofauna associated with cover crops in an Oxisol from the southwest of Piauí state, Brazil / Macrofauna edáfica associada a plantas de cobertura em um Latossolo Amarelo do sudoeste do estado do Piauí, Brasil

The soil macrofauna is fundamental for the maintenance of soil quality. The aim of this study was to characterize the soil macrofauna under different species of cover crops, including monoculture or intercropping associated to two types of soil management in the southwest region of Piauí state. The study was carried out in an Oxisol (Latossolo Amarelo, according to Brazilian Soil Classification System) in the municipality of Bom Jesus, Piauí, distributed in 30 m2 plots. Testing and evaluation of the soil macrofauna were conducted in a 9 × 2 strip factorial design, with combinations between cover crops/consortia and soil management (with or without tillage), with four replications. Soil monoliths (0.25 × 0.25 m) were randomly sampled in each plot for macrofauna at 0‒0.1, 0.1‒0.2, and 0.2‒0.3 m depth, including surface litter. After identification and counting of soil organims, the relative density of each taxon in each depth was determined. The total abundance of soil macrofauna quantified under cover crops in the conventional and no-tillage system was 2,408 ind. m-2, distributed in 6 classes, 16 orders, and 31 families. The results of multivariate analysis show that grass species in sole cropping systems and no-tillage presents higher macrofauna density, in particular the taxonomic group Isoptera. No-tillage also provided higher richness of families, where Coleoptera adult were the second more abundant group in no-tillage and Hemiptera in conventional tillage.(AU)

Os organismos da macrofauna edáfica são fundamentais para a manutenção da qualidade do solo. O objetivo deste trabalho foi caracterizar a macrofauna edáfica sob diferentes espécies de plantas de cobertura, incluindo monocultura ou cultivo consorciado associados a dois tipos de manejo do solo no sudoeste do Piauí. O estudo foi realizado em Latossolo Amarelo (Sistema Brasileiro de Classificação de Solos) no município de Bom Jesus, Piauí, distribuídos em parcelas de 30 m2. O experimento e avaliação da macrofauna edáfica foram conduzidos em um ensaio fatorial em faixas 9 × 2, com combinações entre culturas /consórcios de cobertura e manejo do solo (com ou sem preparo), com quatro repetições. Os monólitos de solo (0,25 × 0,25 m) foram retirados aleatoriamente de cada parcela, para contagem da macrofauna, nas camadas de 0‒0,1, 0,1‒0,2, e 0,2-0,3 m de profundidade, inclusive liteira de superfície. Após a identificação e contagem dos organismos, foi determinada a densidade relativa de cada táxon em cada profundidade. A abundância total da macrofauna edáfica quantificada no experimento foi de 2.408 ind.m-2, distribuídos em 6 classes, 16 ordens e 31 famílias. Os resultados da análise multivariada revelaram que espécies de gramíneas em sistemas de cultivo solteiro e plantio direto favoreceram maior densidade da macrofauna, em especial do grupo taxonômico Isoptera. A ausência de preparo também proporcionou maior riqueza de famílias, destacando-se o grupo taxonômico Coleoptera adulto em plantio direto e Hemiptera em plantio convencional.(AU)

Mercury critical concentrations to Enchytraeus crypticus (Annelida: Oligochaeta) under normal and extreme conditions of moisture in tropical soils - Reproduction and survival.

Soil provides many ecosystem services that are essential to maintain its quality and healthy development of the flora, fauna and human well-being. Environmental mercury levels may harm the survival and diversity of the soil fauna. In this respect, efforts have been made to establish limit values of mercury (Hg) in soils to terrestrial fauna. Soil organisms such as earthworms and enchytraeids have intimate contact with trace metals in soil by their oral and dermal routes, reflecting the potentially adverse effects of this contaminant. The main goal of this study was to obtain Hg critical concentrations under normal and extreme conditions of moisture in tropical soils to Enchytraeus crypticus to order to assess if climate change may potentiate their acute and chronic toxicity effects. Tropical soils were sampled from of two Forest Conservation Units of the Rio de Janeiro State - Brazil, which has been contaminated by Hg atmospheric depositions. Worms were exposed to three moisture conditions, at 20%, 50% and 80% of water holding capacity, respectively, and in combination with different Hg (HgCl2) concentrations spiked in three types of tropical soil (two natural soils and one artificial soil). The tested concentrations ranged from 0 to 512mg Hg kg-1 dry weight. Results indicate that the Hg toxicity is higher under increased conditions of moisture, significantly affecting survival and reproduction rate.

Soil ecotoxicology in Brazil is taking its course.

Soil ecotoxicology has been motivated by the increasing global awareness on environmental issues. Northern Hemisphere has been the main driver of this science branch; however, the number and quality of contributions from the Southern Hemisphere are increasing quickly. In this case study, Brazil is taken as an example of how soil ecotoxicology has developed over the last 30 years. It starts with a brief historical overview depicting the main events on soil ecotoxicology in the country. Following, an overview on the Brazilian legislation related to soil ecotoxicology is given, covering regulations with prospective focus, mainly on the registration of pesticides. Regulations with retrospective focus in contaminated areas are also given. Then, an outline of the actors in soil ecotoxicology and examples of prospective ecotoxicological studies performed with soil organisms and plants are given by stressor groups: pesticides, pharmaceuticals, metals, and residues. Experiences from retrospective studies, mainly looking at the assessment of industrial sites, are also covered. Emphasis is given on methodological aspects, pointing to needed actions, mainly regarding the different biotic and abiotic conditions of a tropical country. Finally, the last session discusses how soil ecotoxicology could be improved in methodological adaptations as well as legal requirements.

Toxicity of AMPA to the earthworm Eisenia andrei Bouché, 1972 in tropical artificial soil.

Aminomethylphosphonic acid (AMPA) - one of glyphosate's main metabolites - has been classified as persistent in soils, raising concern regarding the widespread use of glyphosate in agriculture and forestry. Glyphosate may have negative or neutral effects on soil biota, but no information is available on the toxicity of AMPA to soil invertebrates. Therefore our aim was to study the effect of AMPA on mortality and reproduction of the earthworm species Eisenia andrei using standard soil ecotoxicological methods (ISO). Field-relevant concentrations of AMPA had no significant effects on mortality in acute or chronic assays. Except at the highest concentration tested, a significant biomass loss was observed compared to controls in the chronic assay. The number of juveniles and cocoons increased with higher concentrations of AMPA applied, but their mean weights decreased. This mass loss indicates higher sensitivity of juveniles than adults to AMPA. Our results suggest that earthworms coming from parents grown in contaminated soils may have reduced growth, limiting their beneficial roles in key soil ecosystem functions. Nevertheless, further research is needed to better understand the mechanisms underlying the sublethal effects observed here.

Glutamine synthetase gene expression during the regeneration of the annelid Enchytraeus japonensis.

Enchytraeus japonensis is a highly regenerative oligochaete annelid that can regenerate a complete individual from a small body fragment in 4-5 days. In our previous study, we performed complementary deoxyribonucleic acid subtraction cloning to isolate genes that are upregulated during E. japonensis regeneration and identified glutamine synthetase (gs) as one of the most abundantly expressed genes during this process. In the present study, we show that the full-length sequence of E. japonensis glutamine synthetase (EjGS), which is the first reported annelid glutamine synthetase, is highly similar to other known class II glutamine synthetases. EjGS shows a 61-71% overall amino acid sequence identity with its counterparts in various other animal species, including Drosophila and mouse. We performed detailed expression analysis by in situ hybridization and reveal that strong gs expression occurs in the blastemal regions of regenerating E. japonensis soon after amputation. gs expression was detectable at the cell layer covering the wound and was found to persist in the epidermal cells during the formation and elongation of the blastema. Furthermore, in the elongated blastema, gs expression was detectable also in the presumptive regions of the brain, ventral nerve cord, and stomodeum. In the fully formed intact head, gs expression was also evident in the prostomium, brain, the anterior end of the ventral nerve cord, the epithelium of buccal and pharyngeal cavities, the pharyngeal pad, and in the esophageal appendages. In intact E. japonensis tails, gs expression was found in the growth zone in actively growing worms but not in full-grown individuals. In the nonblastemal regions of regenerating fragments and in intact worms, gs expression was also detected in the nephridia, chloragocytes, gut epithelium, epidermis, spermatids, and oocytes. These results suggest that EjGS may play roles in regeneration, nerve function, cell proliferation, nitrogenous waste excretion, macromolecule synthesis, and gametogenesis.

Molecular approach to annelid regeneration: cDNA subtraction cloning reveals various novel genes that are upregulated during the large-scale regeneration of the oligochaete, Enchytraeus japonensis.

To identify genes specifically activated during annelid regeneration, suppression subtractive hybridization was performed with cDNAs from regenerating and intact Enchytraeus japonensis, a terrestrial oligochaete that can regenerate a complete organism from small body fragments within 4-5 days. Filter array screening subsequently revealed that about 38% of the forward-subtracted cDNA clones contained genes that were upregulated during regeneration. Two hundred seventy-nine of these clones were sequenced and found to contain 165 different sequences (79 known and 86 unknown). Nine clones were fully sequenced and four of these sequences were matched to known genes for glutamine synthetase, glucosidase 1, retinal protein 4, and phosphoribosylaminoimidazole carboxylase, respectively. The remaining five clones encoded an unknown open-reading frame. The expression levels of these genes were highest during blastema formation. Our present results, therefore, demonstrate the great potential of annelids as a new experimental subject for the exploration of unknown genes that play critical roles in animal regeneration.

Effects of photoperiod, temperature and melatonin on nymphal development, polyphenism and reproduction in Halyomorpha halys (Heteroptera: Pentatomidae).

Influences of photoperiod, temperature and melatonin were examined on development and color patterns of nymphs, and sternum color and reproductive fate of adults in Halyomorpha halys (brevis). Short-day accelerated nymphal development, whereas long-day accelerated reproductive maturation. The two types of photoperiodic responses at different stages may help maintain the univoltinism of this species in the field, assuring the right timing for diapause and reproduction. The pronotum of fifth instar nymphs reared under LD 11:13 shows a brown-marbled color pattern darker, with less creamy-yellowish speckles, than that of nymphs reared under LD 16:8. Short-day-reared fifth instar nymphs, which are destined to diapause in adults, had shorter white stripes on the pronotum, smaller body size, less frequent feeding and more lipid accumulation than the long-day-reared. The longer the exposure to LD 13:11 at 20 degrees C during the nymphal stage, the greater the expression of short-day associated characteristics observed in the fifth nymphal instar and adult stage. Melatonin orally administered (500 microg/ml) to insects under LD 16:8 produced slightly reduced body size, suppressed feeding, extended nymphal period and increased accumulation of lipid compared to the untreated bugs, but did not affect the incidence of diapause in females. In males, melatonin retarded gonadal development under LD16:8. These results may suggest a possible role of melatonin for the control of seasonal polyphenism and development.

Color changes in Halyomorpha brevis (Heteroptera: Pentatomidae) correlated with distribution of pteridines: regulation by environmental and physiological factors.

Halyomorpha brevis (Heteroptera: Pentatomidae) produces adults with different color patterns, most noticeable in the sternum. The color, ranging from ivory to red, depends on the extent of the accumulation of red pigment. The present work investigated the effects of photoperiod, temperature and aging on the pigmentation. The red pigment was identified as erythropterin by comparing the Rf with standard pteridines in paper chromatography in three solvent systems. Erythropterin was found in all organs, red or light red. Uric acid was detected prominently in ivory or light red sternum. A negative correlation was found between the extent of red pigmentation and that of uric acid content. The relative proportion of males and females with a red sternum progressively increased as they aged from day 0 to day 20 after adult emergence, particularly in males reared under a long day (non-diapausing). In males, an age-dependent decrease in red pigmentation was observed in the gastric ceca and tracheae. The sternum was lighter in short-day adults (diapausing) than that in non-diapausing adults at the same age, and the latter never achieved the intense red color. The possible functions of pteridines are discussed.