Fábio Camargo Abdalla

Autophagy and its physiological relevance in arthropods: Current knowledge and perspectives

Autophagic process is one of the best examples of a conserved mechanism of survival in eukaryotes. At the molecular level there are impressive similarities between unicellular and multicellular organisms, but there is increasing evidence that the same process may be used for different ends, i.e., survival or death, at least at cellular levels. Arthropods encompass a wide variety of invertebrates such as insects, crustaceans and spiders, and thus represent the taxon in which most of the investigations on autophagy in non-mammalian models are performed. The present review is focused on the genetic basis and the physiological meaning of the autophagic process on key models of arthropods. The involvement of autophagy in programmed cell death, especially during oogenesis and development, is also discussed.

CCD imaging of basal bioluminescence in larval fireflies: clues on the anatomic origin and evolution of bioluminescence.

The anatomic and biochemical origin of beetle bioluminescence is still poorly understood. Through CCD imaging we report that larvae and pupae of the Brazilian fireflies Aspisoma lineatum and Cratomorphus sp emit a continuous weak glow throughout the entire body during all stages. This luminescence is especially developed after feeding, ecdysis and in the pupal stage, gradually disappearing as the cuticle becomes sclerotized and the adult emerges. This weak glow arises from the fat body, which consists of small lobes spread all over the body cavity. According to their pigmentation, these lobes can be divided in whitish and pinkish, and display different luciferase isozymes. Morphological studies suggest that the jelly-like ventral lanterns in the 8th abdominal segment evolved from these white lobes, providing a rationale for the widespread location of lanterns in larvae of different bioluminescent beetles. The biological and biochemical function of this weak diffuse bioluminescence is discussed in the context of the larval life-history.

Bioluminescent Fat Body of Larval Aspisoma lineatum (Coleoptera: Lampyridae) Firefly: Ontogenic Precursor of Lantern's Photogenic Tissue

ABSTRACT Previously, we found that the fat body of Aspisoma lineatum Gyll (Coleoptera: Lampyridae) firefly larvae is weakly bioluminescent. This tissue is very different from that of other insect larvae. It is macroscopically distinguished by its color (pinkish and whitish), morphology, and the absence of oenocytes. It is composed of trophocytes that are arranged in groups of globular units covered by a layer of basal lamina. The cytochemistry indicated that the trophocytes have glycoproteins, which are produced by a well-developed rough endoplasm reticulum (RER). Expanded RER cisterns indicated intense protein synthesis by the trophocytes. Lipid droplets are also present in the trophocytes. Charge-coupled device imaging showed that the fat body produces a continuous bioluminescence whose intensity is 2–3 orders of magnitude lower than that of the lanterns, a result that is explained by the lower contents of luciferin and luciferase in the fat body compared with the lanterns. Expression of different luciferase isozymes in the fat body and lanterns is confirmed by bioluminescence spectral and kinetic analyses. Trophocytes were identified as the emitting cells, suggesting that the larval and adult lanterns photocytes may have evolved from fat body trophocytes.

Negative impact of a cadmium concentration considered environmentally safe in Brazil on the cardiac performance of bullfrog tadpoles

A drastic amphibian decline has been observed worldwide, which can be attributed (among other factors) to exposure to pollutants. Considering that cadmium corresponds to the most rapidly increasing trace metal in the environment, the aim of this work was to evaluate whether the exposure (2 and 16 days) of bullfrog tadpoles to this trace metal, at the concentration currently considered environmentally safe (at 1ppb) in class 1 and 2 waters by the Brazilian Environmental Council, can affect the cardiac performance of these animals. The acute exposure (2 days) of tadpoles to cadmium resulted in a marked bradycardic response, which was correlated with an incomplete cardiac relaxation, without any compensation by improved cardiac twitch force (Fc) or contraction velocity (TPT), nor even by cardiac hypertrophy. Indeed, after 16 days of exposure, the cardiac function of tadpoles became even more depressed due to a marked decrease in Fc, a prolongation of TPT, and also incomplete relaxation (i.e. increases in the ventricle resting tension), without changes in ventricle relative mass. Altogether, the cardiodepressive effects of cadmium (especially after more prolonged exposure periods) impose negative alterations on a tadpole׳s development and also impede adequate homeostatic adjustments to respond appropriately to the exposure to cadmium with increase in energetic demand to counteract the deleterious effects of the xenobiotic. These disturbances can impair tadpoles׳ growth, development and reproduction. It is a fact that allows us to strongly suggest that cadmium concentrations, which are currently considered environmentally safe in Brazil, should be revised.

Ultrastructure of the Intramandibular Gland of Workers and Queens of the Stingless Bee, Melipona quadrifasciata

Abstract The intramandibular glands of workers and queens of Melipona quadrifasciata Lepeletier (Hymenoptera: Apidae), at different ages and from different functional groups, were studied using light and transmission electron microscopy. The results demonstrated that these glands are composed of two types of secretory structures: 1.A hypertrophied epidermis on the dorsal side of the mandible that is an epithelial gland. 2. Free secretory cells filling the inner spaces of the appendices that constitute a unicellular gland. The epithelial gland is larger in the young (1-2-day-old workers), and the gland becomes involuted during the nurse worker stage. The unicellular glands of the workers posses some secretion during all of the studied phases, but secretory activity is more intensive in the foraging workers. Vesicles of secretion are absent in the unicellular glands of queens. These results demonstrate that these glands show functional adaptations in different castes corresponding to the functions of each caste.

Hepatic effects of the clomazone herbicide in both its free form and associated with chitosan-alginate nanoparticles in bullfrog tadpoles.

The use of agrochemicals in agriculture is intense and most of them could be carried out to aquatic environment. Nevertheless, there are only few studies that assess the effects of these xenobiotics on amphibians. Clomazone is an herbicide widely used in rice fields, where amphibian species live. Thus, those species may be threatened by non-target exposure. However, nanoparticles are being developed to be used as a carrier system for the agrochemicals. Such nanoparticles release the herbicide in a modified way, and are considered to be more efficient and less harmful to the environment. The aim of this study was to comparatively evaluate the effect of clomazone in its free form and associated with nanoparticles, in the liver of bullfrog tadpoles (Lithobates catesbeianus) when submitted to acute exposure for 96 h. According to semi-quantitative analysis, there was an increase in the frequency of melanomacrophage centres, in the accumulation of eosinophils and in lipidosis in the liver of experimental groups exposed to clomazone - in its free form and associated with nanoparticles - in comparison with the control group, and the nanotoxicity of chitosan-alginate nanoparticles. The increase of melanomacrophage centres in all exposed groups was significant (P < 0.0001) in comparison to control group. Therefore, the results of this research have shown that exposure to sublethal doses of the herbicide and nanoparticles triggered hepatic responses. Moreover, these results provided important data about the effect of the clomazone herbicide and organic nanoparticles, which act as carriers of agrochemicals, on the bullfrog tadpole liver.

Larval development of Physocephala (Diptera, Conopidae) in the bumble bee Bombus morio (Hymenoptera, Apidae)

Larval development of Physocephala (Diptera, Conopidae) in the bumble bee Bombus morio (Hymenoptera, Apidae). In the summer of 2012, a high incidence of conopid larvae was observed in a sample of female B. morio collected in remaining fragments of semidecidual forest and Cerrado, in the municipality of Sorocaba, state of Sao Paulo, Brazil. The larval development of conopid flies was studied, beginning at the larval instars (LO to L3) and PUP, until the emergence of the imago under laboratory conditions and inside the host. At the first instar, or LO, the microtype larvae measured less than 1 mm in length. During the transition from L1 to L3, the larvae grew in length. At L3, the larvae doubled their length (4 mm) and then started to develop both in length and width, reaching the PUP stage with 10 mm in length and 7 mm in width. The main characteristic that differentiates L3 from the early instars is the larger body size and the beginning of posterior spiracle development. The development from PUP to puparium took less than 24h. The bees died ten days after the fly oviposition, or just before full PUP development. The early development stages (egg-LO to L1) were critical for larva survival. The pupa was visible between the intersegmental sternites and, 32 days after pupation, a female imago of Physocephala sp. emerged from one bee. The puparium and the fly measured approximately 10 mm in length. In a single day of collection, up to 45% of the bumble bees collected were parasitized by conopid flies.

Morphological, chemical and developmental aspects of the Dufour gland in some eusocial bees (Hymenoptera, Apidae): a review

Morphological, chemical and developmental aspects of the Dufour gland in some eusocial bees (Hymenoptera, Apidae): a review. The present revision focused on the more recent data about the Dufour gland in some eusocial bees, taking in account general aspects of its morphology, secretion chemical nature, bio-synthetic pathway and development. Many functions have been attributed to this gland in eusocial bees, but none are convincing. With the new data about this gland, not only the secretion chemical pathway of the Dufour gland may be reasonable understood, as its function in some eusocial bees, especially Apis mellifera Linne, 1758, which has been extensively studied in the last years.

Ultrastructural studies of the mandibular gland of Melipona quadrifasciata Lepeletier, 1836 (Apidae, Meliponini): a comparison between workers and queens

Summary The mandibular glands of workers and queens of Melipona quadrifasciata Lepeletier 1836 were studied in different functional states under transmission electron and light microscopy. In both castes, the glands consisted of a cluster of class III secretory cells and a small, thin-walled reservoir. The glands of queens were smaller than those of workers. The gland of workers were more developed in nurses, in which they consisted of secretory cells rich in smooth endoplasmic reticulum and lipid-like secretion. Among workers, the stored secretion seemed to be used only by foragers. In queens, the gland is more active in virgin than in physogastric queens, being the secretion likely composed mostly of proteins. Our results suggest that the secretion is mainly useful for foragers and virgin queens. Secretion appears to play a role in pheromone activity.

Efeito do cádmio no fígado de girinos de rã-touro

O cadmio esta presente em todos os ambientes impactados pela acao antropica e age de forma negativa sobre sistemas biologicos. Devido as suas propriedades toxicantes, o cadmio e um dos varios elementos que contribuem para o declinio de populacoes de anfi-bios. Portanto, a acao do cadmio (Cd) durante o desenvolvimento pre-metamorfico em anfibios, figados de girinos de ra-touro, Litho-bates catesbeianus, foi analisada atraves de microscopia de luz. Os girinos foram expostos a 1µg Cd L-1, durante quatro e 16 dias, a partir do estagio 25 de Gosner. Para as analises histoquimicas fo-ram utilizadas as tecnicas PAS, Azul de Bromofenol e Azul da Prus-sia. A morfometria foi realizada pela contagem relativa da quantida-de de celulas melanomacrofagicas. Os resultados mostraram au-mento significativo das celulas melanomacrofagicas no grupo ex-posto a quatro dias, porem nao aos 16 dias. A tecnica de Azul da Prussia demonstrou intensa atividade de captacao de ferro pelas celulas melanomacrofagicas dos individuos do grupo exposto du-rante quatro dias. Com relacao aos hepatocitos, a tecnica de PAS-Azul de Bromofenol indicou diminuicao de glicoconjugados neutros e proteinas totais nos grupos expostos apos quatro e 16 dias. O Cd impactou de forma mais drastica os girinos apos quatro dias de exposicao, indicando a rapida resposta adaptativa destes animais aos efeitos nocivos do metal-traco. Conclui-se que o cadmio afeta o figado dos girinos em estagios iniciais do desenvolvimento, mesmo a concentracoes permitidas pelo CONAMA para corpos d’agua das classes I, II e IV.