Do Workers from Subspecies Acromyrmex subterraneus Prepare Leaves and Toxic Baits in Similar Ways for Their Fungus Garden?

Toxic baits are the most efficient method to control leaf-cutter ants in eucalyptus forests for paper and cellulose production. For the proper use of these baits, insecticide compounds must reach workers and contaminate them. Thus, understanding how these baits are processed inside the nests is vital for a successful control, especially when it comes to genus Acromyrmex. Lack of information on toxic baits and on contamination of Acromyrmex workers raises the question: do workers from subspecies Acromyrmex subterraneus (Forel) prepare leaves and toxic baits in similar ways for their fungus garden? To answer it, this study described and analyzed the behavioral repertoire executed by A. subterraneus workers during the preparation of leaf disks and baits and their incorporation into the fungus garden. Results show that the act of licking the substrate was the most frequently executed behavior, regardless of subspecies or size categories. Moreover, additional behaviors have been observed when workers processed the baits, such as licking and scraping their jaws on the surface of the bait pellet, as well as licking and biting fragments of bait pellets, moistening them. Thus, it is concluded that the preparation of baits is different from that of leaves; baits are more processed and can therefore contribute to contaminating workers via insecticides.

Fat-Soluble Substance Flow During Symbiotic Fungus Cultivation by Leaf-Cutter Ants.

Leaf-cutter ants perform a series of specialized behaviors in preparing plant substrates for their symbiotic fungus. This process may be related to contamination of workers by substances such as insecticides, leading us to hypothesize that substances are spread among workers through behaviors they perform to grow the fungus. To test this hypothesis, we analyzed the behavioral acts of workers during the processing of the pellets by using a fat-soluble tracing dye, since the active ingredient that composes toxic baits, used for control of leaf-cutter ants, is fat-soluble. The frequencies of performed behaviors were recorded and the number of dyed workers was assessed after fungus cultivation. The most frequent behavior is allogrooming and corresponds to 45.87% of the contamination process in workers, followed by holding, licking, and cutting pellets, which account for 40.22% of the process. After pellet processing, the workers had their external and internal morphological structures marked by the tracing dye-93.75% and 79.25%, respectively. These results confirm that behaviors performed during fungus cultivation contribute to dispersing substances such as insecticides, causing the contamination of workers.

Contamination Route of Leaf-Cutting Worker Ants Analyzed Through a Fat-Soluble Tracer Dye in Toxic Bait.

Our study seeks to discover contamination routes of leaf-cutting worker ants during chemical control by formicide baits. To do so, toxic baits containing fat-soluble tracer dye were provided to colonies of three subspecies of Acromyrmex under laboratory conditions, in order to assess the proportion of dyed workers by size category, as well as dyed internal morphological structures. Results showed that nearly 50% of the workers come into contact with the active ingredient, since the internal structures of their bodies are dyed by the fat-soluble tracer dye within the first 24 h from contact with the toxic bait. In addition, the three subspecies of leaf-cutting ants present a similarity as to the contamination of their workers, probably due to their specialized behavior performed during the growth of the fungus garden with the baits. We conclude that the workers' pattern of behavior during fungus garden growth was the main means for dispersion of a fat-soluble substance among approximately half of the nest mates in our experiments, serving as a model for further studies on contamination of worker ants with insecticides.

Study on membrane fluidity and erythrocyte aggregation in equine, bovine and human species.

The aim of the present paper is to analyze whether membrane fluidity can be predicted from its lipid composition and to assay the possible relationship between such variable and the aggregating properties of erythrocytes from equine, bovine and human species due to the widely acknowledged differences in their tendency to form aggregates. The main difference between phospholipids from plasma membrane in these species lies in the concentration levels of sphyngomyelin (SM) and phosphatidilcoline (PC); more precisely, in the external hemilayer of the lipid bilayer. Membrane fluidity was estimated by the fluorescence polarization method, while erythrocyte aggregation was assessed by an optical method. According to our results, bovine erythrocytes containing high SM and low PC levels, presented the highest anisotropy value as well as an imperceptible aggregation value. Equine erythrocytes, which contain a considerable PC percentage and scarce SM levels, showed the lowest anisotropy value and the highest values of the aggregation parameters. Human erythrocytes presented intermediate values for both properties. Our hypothesis claims that the phospholipid composition would constitute one of the factors determining erythrocyte membrane fluidity and also taking part in the different aggregation tendency shown by equine, bovine and human species.

Acute training in racing horses at two different levels of effort: A haemorheological analysis.

During acute exercise several significant cardiovascular alterations take place, along with possible physiopathological consequences, such as Exercise Inducted Pulmonary Haemorrhage (EIPH). Given the relevance of blood rheology in the determination of flow resistance and its supposed participation in the stated events, the present paper focuses on the analysis of modifications in haematocrit, blood viscosity and erythrocyte deformability in Thoroughbred horses caused by two different levels of effort (6 to 9 m/s and 13 to 16 m/s), in the same track they train in and with their own jockeys. The results obtained show a deep modification in those parameters, as consequence of the exercise. However, no significant discrepancies were observed between the different levels of effort in which the training was performed.