André Barbosa Vargas

Efeitos de fatores ambientais sobre a mirmecofauna em comunidade de restinga no Rio de Janeiro, RJ

The effects of environmental factors on the richness, diversity and abundance of ants were studied in the Restinga da Marambaia, south coast of Rio de Janeiro State, Brazil. The samples were taken using pitfall traps in August/2004 (winter) and March/2005 (summer) in three different vegetation types: (1) herbaceous ridge palmoid (homogeneous habitat); (2) shrub dune thicket and (3) ridge forest (heterogeneous habitats). At each habitat a range of environmental attributes was recorded: soil temperature and humidity, percentage of soil covering by litter and litter depth. Ninety-two ant species belonging to 36 genera and eight subfamilies were recorded. Density of ant species and abundance varied significantly between habitats and seasons; ant diversity varied only between habitats. Homogeneous habitat had lower ant species density, abundance and diversity than heterogeneous habitats. The two first variables were positively correlated with litter depth and both were higher in summer than in winter samples. There were more species of Ponerinae and Ectatomminae in heterogeneous than in the homogeneous habitat, whereas the Formicinae species were more abundant in the later.

A Triatoma maculata (Hemiptera, Reduviidae, Triatominae) population from Roraima, Amazon region, Brazil, has some bionomic characteristics of a potential Chagas disease vector

Even though Chagas disease is rare in the Brazilian Amazon, the conditions for the establishment of domiciliated cycles prevail in many areas where triatomines are of frequent occurrence. In Roraima, a previous serological and entomological survey in three agricultural settlements showed the existence of all transmission cycle elements, i.e., individuals infected by Trypanosoma cruzi, triatomine species previously found harboring T. cruzi in the broader Amazon region of neighboring countries and, domicile/ peridomicile conditions favorable to triatomine colonization. Triatoma maculata was the most frequent species, found in chicken houses in the peridomicile and sporadically within residences. Aiming to investigate the possibility of T. maculata to possess the potentiality to transmit T. cruzi in the area, bionomic characteristics were studied under laboratory conditions. These were feeding frequency, time for defecation after a blood meal, time elapsed in voluntary fasting pre- and pos-ecdysis, moulting time periods, pre-oviposition and oviposition periods and index of oviposition, incubation period, egg viability, longevity and mortality rate. Results show that the Passarão population of T. maculata should be considered a potential vector of T. cruzi since it shows a capacity to infest artificial ecotopes in the peridomicile, to carry out large number of meals during the nymphal cycle, to have a relatively short developmental cycle capable of producing 2.9 generations/year, to blood source eclecticism, to defecate immediately after the blood meal while still on the host and to the fact that has been previously found naturally infected by T. cruzi.

Teste da regra de equivalência energética para formigas de serapilheira: efeitos de diferentes métodos de estimativa de abundância em floresta ombrófila

The Energetic Equivalence Rule (EER) states that species tend to consume energy independent of their body size. Here, the EER was tested for litter ants using body size and abundance data. Rainforest ants were obtained using pitfall traps and Winkler extractor. The abundance data from the Winkler extractions confirmed the EER, while the pitfall traps rejected it. Combination of abundance from pitfall catches and Winkler extractions either confirmed or rejected the EER. Further studies should focus on the interaction between sampling techniques and habitat types in the test of EER for ant communities.

Two new tiny Nemesiidae species from Reserva Biológica do Tinguá, Rio de Janeiro, Brazil (Araneae: Mygalomorphae)

Two new Nemesiidae species from Reserva Biologica do Tingua, Rio de Janeiro, Brazil are described. Acanthogonatus minimussp. nov. differs from the remaining species of the genus by the male palpal bulb, which has very long and twisted embolus, ca. 2/3 the length of the palpal tibia, long and twisted spermathecae, anterior eye row recurved and fovea T-shaped. Chaco tinguasp. nov. differs from the remaining species of the genus by the retrolateral megaspine on tibia I, palpal embolus tip hook-shaped, inferior tarsal claw on all legs, absence of pubescence on the carapace and legs. Both species were collected with Winkler extractors in leaf litter. They are the smallest specimens in their respective genera and also among the world Nemesiidae described to date. The smallest male of A. minimussp. nov. measures 4.22 mm and of C. tinguasp. nov. measures 3.85 mm. Data on the phenology of C. tinguasp. nov. is presented.

Resposta da assembleia de formigas na interface solo-serapilheira a um gradiente de alteração ambiental

O estudo objetivou avaliar a resposta da assembleia de formigas que nidificam na interface solo-serapilheira a um gradiente de alteracao ambiental. O estudo foi realizado em tres ambientes com diferentes usos do solo: fragmento florestal, sistema agroflorestal (SAF) e pastagem situados em regiao de dominio da mata atlântica no sudeste do Brasil. Em cada ambiente foram demarcadas 10 parcelas de 1 m2 e todos os ninhos de formigas encontrados foram registrados. Foram encontrados 215 ninhos (103 no fragmento florestal, 64 no sistema agroflorestal e 48 na pastagem), de 31 especies. O numero acumulado de especies foi maior no fragmento florestal que na pastagem, mas nao diferiu do SAF. A composicao de especies foi diferente entre o fragmento florestal e os outros dois ambientes. A riqueza media de especies de formigas por parcela foi maior no fragmento florestal e menor na pastagem. A quantidade de serapilheira nao foi um fator importante para as diferencas na riqueza de especies. Atividades humanas que reduzam a heterogeneidade da vegetacao alteram a composicao e diminuem a riqueza de especies das assembleias de formigas.