Danon Clemes Cardoso

Cytogenetic and molecular analyses reveal a divergence between Acromyrmex striatus (Roger, 1863) and other congeneric species: taxonomic implications.

The leafcutter ants, which consist of Acromyrmex and Atta genera, are restricted to the New World and they are considered the main herbivores in the neotropics. Cytogenetic studies of leafcutter ants are available for five species of Atta and 14 species of Acromyrmex, both including subspecies. These two ant genera have a constant karyotype with a diploid number of 22 and 38 chromosomes, respectively. The most distinct Acromyrmex species from Brazil is A. striatus, which is restricted to the southern states of Santa Catarina and Rio Grande do Sul. Several cytogenetic and phylogenetic studies have been conducted with ants, but the karyotypic characterization and phylogenetic position of this species relative to leafcutter ants remains unknown. In this study, we report a diploid number of 22 chromosomes for A. striatus. The phylogenetic relationship between A. striatus and other leafcutter ants was estimated based on the four nuclear genes. A. striatus shared the same chromosome number as Atta species and the majority of metacentric chromosomes. Nuclear data generated a phylogenetic tree with a well-supported cluster, where A. striatus formed a different clade from other Acromyrmex spp. This combination of cytogenetic and molecular approaches provided interesting insights into the phylogenetic position of A. striatus among the leafcutter ants and the tribe Attini.

Ant community composition and its relationship with phytophysiognomies in a Brazilian Restinga

In this study, the composition of ant communities was compared in four adjacent phytophysiognomies in Morro dos Conventos Restinga, Brazil. We tested our hypothesis that the ant community composition differs between habitats across a gradient from sea to inland continent. Ant species were sampled with pitfall traps. Overall, 71 ant species were collected. Ant species composition differed between phytophysiognomies. Our results suggest that environments were more similar in the adjacent than in the more distant phytophysiognomies, a pattern similar to the vegetation zonation and gradient sea–inland Restinga. Thirteen species determined more than 50% of the dissimilarity between phytophysiognomies. Solenopsis saevissima was the species that contributed more to ant species composition distinction between phytophysiognomies, followed by Pheidole and Camponotus species. The type of vegetation is one of the main factors affecting the composition of ant communities in Restinga. The role of plants is linked to the availability of resources and conditions and they may determine ant assemblage composition and different interactions occurring in Restinga.

The role of fusion in ant chromosome evolution: insights from cytogenetic analysis using a molecular phylogenetic approach in the genus mycetophylax.

Among insect taxa, ants exhibit one of the most variable chromosome numbers ranging from n = 1 to n = 60. This high karyotype diversity is suggested to be correlated to ants diversification. The karyotype evolution of ants is usually understood in terms of Robertsonian rearrangements towards an increase in chromosome numbers. The ant genus Mycetophylax is a small monogynous basal Attini ant (Formicidae: Myrmicinae), endemic to sand dunes along the Brazilian coastlines. A recent taxonomic revision validates three species, Mycetophylax morschi, M. conformis and M. simplex. In this paper, we cytogenetically characterized all species that belongs to the genus and analyzed the karyotypic evolution of Mycetophylax in the context of a molecular phylogeny and ancestral character state reconstruction. M. morschi showed a polymorphic number of chromosomes, with colonies showing 2n = 26 and 2n = 30 chromosomes. M. conformis presented a diploid chromosome number of 30 chromosomes, while M. simplex showed 36 chromosomes. The probabilistic models suggest that the ancestral haploid chromosome number of Mycetophylax was 17 (Likelihood framework) or 18 (Bayesian framework). The analysis also suggested that fusions were responsible for the evolutionary reduction in chromosome numbers of M. conformis and M. morschi karyotypes whereas fission may determines the M. simplex karyotype. These results obtained show the importance of fusions in chromosome changes towards a chromosome number reduction in Formicidae and how a phylogenetic background can be used to reconstruct hypotheses about chromosomes evolution.

Contextual analysis and epidemiology of spider bite in southern Santa Catarina State, Brazil

The aim of this work was to conduct an epidemiological and clinical review of 1126 cases of envenoming by spider recorded in the national notifiable diseases information system (SINAN) files of the Municipal Health Secretary of the Criciúma region, Santa Catarina State, Brazil from 1994 to 2006. This work presents a critical analysis carried out by the application of the chi(2) test, with different regional contextual parameters, including the incidence coefficient. Spider envenoming accounts for more than 50% of all cases recorded in the SINAN files for poisonous animals and is the main cause of human envenomation in the Criciúma region. The majority of the spider bites (57.4%) were reported in the hottest months, from December to May. The anatomic region that suffered the most bites was the hand. Nearly 50% of the accidents were recorded in the group aged 20-49 years. The spiders most frequently involved in accidents for all age groups were of the Loxosceles genus. Although the data collected lack further epidemiological and, especially, clinical details, this does not affect the conclusions of the study, which could be used in the planning of actions aimed at improving environmental health.

Epidemiology and injuries (1994–2005) resulting from poisonous animals in southern Santa Catarina State, Brazil

Accidents involving poisonous animals in southern Santa Catarina State, Brazil, from 1994 to 2005 were evaluated with the aim of verifying their frequency through the analysis of 2,625 victim’s reports involving poisonous animals from the SINAN (System of Injury Notification Information) files of the Municipal Health Secretary of the AMESC and AMREC microregions, formed by 27 municipalities. Statistical analysis was performed using the chi-square exact test to verify similarities between the AMREC and AMESC microregions, where p values ≤0.05 were considered significant. The results demonstrated that: 52.95% (n = 1,390) of occurrences involved spiders, 18.13% (n = 476) snakes, 5.00% (n = 131) bees, 2.29% (n = 60) caterpillars, 1.41% (n = 37) scorpions, 5.45% (n = 143) other animals and 14.78% (n = 388) unknown. The anatomic region that suffered the most bites was the feet 16.11% (n = 444). Accidents were more frequent in men 54.64% (n = 1.437) than in women 45.25% (n = 1,188). In only 1.18% (n = 31) of cases did recovery present sequelae. The months presenting the highest number of recorded cases were October through March, spring and summer in Brazil. The high frequency of victim recuperation suggests that the public health system is efficient, and the low frequency of recovered victims with sequelae also suggests that this system is fast and well-adjusted. However, there may have been deficiencies in the epidemiologic information system.

Estimation of nuclear genome size of the genus Mycetophylax Emery, 1913: Evidence of no whole-genome duplication in Neoattini

Genome size estimates and their evolution can be useful for studying the phylogenetic relationships and taxonomy of a particular group. In the present study, the genome sizes of the three species that comprise the Mycetophylax genus were estimated by flow cytometry (FCM). There was little variation in genome size among them. The mean haploid genome size value of male and female individuals of Mycetophylax morschi was 312.96 Mbp (0.32 pg) and that of Mycetophylax conformis and Mycetophylax simplex females were 312.96 Mbp (0.32 pg) and 381.42 Mbp (0.39 pg), respectively. At first glance, this variation could be related with the heterochromatin content. Our results, together with other previous reports, have contributed to our knowledge about Attini genome size and will be useful to improve the understanding of the evolution of this tribe. It will help select potential model species in Attini for future genomic and sequencing projects.

Antinociceptive effect of a ruthenium complex in mice.

1. The ruthenium complexes are important tools in inorganic chemistry. Different biological properties are found in the presence of distinct coordinate ligands, which offer a variety of potential clinical and pharmacological uses. 2. The aim of this work was to evaluate the antinociceptive and behavioural effects of the ruthenium complex, trans-[RuCl(2)(i-dinic)(4)]Cl, in mice. 3. The potential analgesic activity was tested using the formalin and hot plate tests and the behavioural effect was evaluated using the rotarod and spontaneous locomotor tests. The complex was administered at concentrations of 1.3, 4.5 and 18.0 mumol kg(-1) i.p. Morphine (6.0 mg kg(-1), i.p.) and diclofenac sodium (20.0 mg kg(-1), i.p.) were used as reference drugs. 4. The compound had no sedative activity on motor ataxia in the behavioural and analgesic tests. No significant effect was observed in the first phase of the formalin test, however, an effect was observed in the second phase. 5. The complex studied was probably more powerful than the reference drugs as an antinociceptive agent, as this mechanism also involved the nitric oxide (NO) pathway. From this perspective, further experimental studies will be useful to understand the effect of these compounds on NO and the relationship between prostaglandin and NO biosynthesis.

A nuclear DNA based phylogeny of endemic sand dune ants of the genus Mycetophylax (Emery, 1913) : how morphology is reflected in molecular data.

Molecular methods have substantially advanced our knowledge about ant systematics in the past few years. Here, we infer the molecular phylogeny of sand dune ants of the genus Mycetophylax, Emery 1913 (Formicidae: Myrmicinae: Attini) using 730 base pairs of DNA sequences of the two nuclear genes longwave rhodopsin and wingless. Our analyses indicate that Mycetophylax is monophyletic, as suggested by its morphological characters. M. morschi, previously considered a species of Cyphomyrmex due to a scrobe-like impressed area on the head, forms a well-supported cluster with the two other species of Mycetophylax, M. conformis and M. simplex. Our analysis yields the first comprehensive phylogeny of Mycetophylax based on molecular data and includes specimens from localities within a wide distributional range as well as all species belonging to the genus following the recent taxonomic revision.

Molecular phylogenetic reconstruction and localization of the (TTAGG)n telomeric repeats in the chromosomes of Acromyrmex striatus (Roger, 1863) suggests a lower ancestral karyotype for leafcutter ants (Hymenoptera)

Abstract Chromosome counts and karyotype characterization have proved to be important features of a genome. Chromosome changes during the diversification of ants might play an important role, given the diversity and success of Formicidae. Comparative karyotype analyses on ants have enriched and helped ant systematics. Among leafcutter ants, two major chromosome counts have been described, one frequent in Atta Fabricius, 1804 (2n = 22 in all Atta spp. whose karyotype is known) and the other frequent in Acromyrmex Mayr, 1865 (2n = 38 in the majority of species whose karyotype is known). The main exception is Acromyrmex striatus (Roger, 1863), which harbors a diploid chromosome set of 22. Here we describe the use of fluorescence in situ hybridization (FISH) with telomeric probes with (TTAGG)6 repeats to describe the telomere composition of A. striatus and to recover potential interstitial non-telomeric signals that may reflect fusion events during the evolution of leafcutter lineage from 38 to 22 chromosomes. Further, we reconstruct the ancestral chromosome numbers of the leafcutter clade based on a recently proposed molecular phylogenetic hypothesis and phylogenomic tree. Distinct signals have been observed in both extremities on the telomere chromosomes of A. striatus. Non-telomeric signals have not been retrieved in our analysis. It could be supposed that the low-numbered karyotype indeed represents the ancestral chromosome number of leafcutters. The phylogenetic reconstruction also recovered a low chromosome number from the diverse approaches implemented, suggesting that n = 11 is the most likely ancestral karyotype of the leafcutter ants and is a plesiomorphic feature shared between A. striatus and Atta spp.

Agro-predation by Megalomyrmex ants on Mycetophylax fungus-growing ants

Fungus-growing ants are a remarkable taxon of New World ants that engage in a mutualistic symbiosis with basidiomycete fungi. Their fungus-gardens are valuable resources and are exploited in countless ways by parasites and other beneficiaries outside of the ant-fungi mutualism. Here, for the first time, we report on the agro-predatory behavior of the ant Megalomyrmex incisus on Mycetophylax conformis and Mycetophylax morschi fungus-growers from sand dunes near Ilhéus, Brazil. Me. incisus workers raided colonies of My. conformis and My. morschi and aggressively antennated, pulled, bit, and stung the fungus-growers, which played dead or retreated on the fungus. Me. incisus quickly usurped the fungus-garden and expelled all Mycetophylax workers. The usurpation closely resembled that described for raids of Me. wettereri on Cyphomyrmex longiscapus, in that the fungus-growers remained passive and avoided confrontation. This passive behavior suggests that Me. incisus uses chemical weapons that facilitate the exploitation of the host colony resources.