Biological data for the neotropical termite Nasutitermes globiceps (Isoptera: Termitidae: Nasutitermitinae)

Nasutitermes globiceps is a Neotropical termite, considered a pest in Brazil. It has been reported to cause damage to wood of buildings, transmission poles, fences, trees and stored material. Nest architecture of this arboreal Nasutitermes is described in a small area of natural vegetation of Sāo Paulo state. Polycalism and polygyny are reported as reproductive mechanisms present in the species.

Morphologically differentiated sex chromosomes in neotropical freshwater fish

A general survey of the occurrence of morphologically differentiated sex chromosomes in the neotropical freshwater fishes is presented. The total number of 32 occurrences involving simple XX-XY and ZZ-ZW, and multiple X1X2Y, XY1Y2 and ZW1W2 sex chromosome systems is described, with comments on the aspects of sex chromosome evolution in this fish fauna. The occurrence of different sex chromosome systems in related species of the same genus, or in different populations of the same nominal species, involving male and sometimes female heterogamety, and differences in the molecular composition of sex-linked heterochromatin, are considered as indicative of the early stage of sex chromosomes evolution in fish.

Dominance hierarchy in different stages of development in colonies of the primitively eusocial wasp Mischocyttarus cerberus styx (Hymenoptera, Vespidae)

In primitively eusocial insect societies, reproductive division of labor is established by dominance-submission interactions which determine a linear dominance hierarchy. As previously observed for other species, in Mischocyttarus cerberus styx (Hymenoptera, Vespidae), the dominant female is the main egg layer. Most of her attacks were to the females directly beneath in the rank establishing a hierarchy. During the pre-emergence stage, the hierarchy was already defined and in the post-emergence stage, pre-male substage, the frequency of dominance interactions were strong but the hierarchy was still maintained by the first-ranked female. In the decline stage there were many neutral individuals which could be the reproductives of a new colony.

A new rain-operated seed dispersal mechanism in Bertolonia mosenii (Melastomataceae), a Neotropical rainforest herb

Although widespread among fungi, lichens, liverworts, and mosses, seed dispersal mechanisms operated by rain are unusual among flowering plants. Generally speaking, two mechanisms are involved in seed dispersal by rains: the splash-cup and the springboard. Here we describe a new seed dispersal mechanism operated by rain in a Neotropical rainforest herb Bertolonia mosenii Cogniaux (Melastomataceae). The study was carried out at the lowland Atlantic rainforest, southeastern Brazil. We experimentally demonstrate that rain is necessary to release the seeds from the capsules through what we call squirt-corner seed dispersal mechanism: when a raindrop strikes the mature fruit, the water droplet forces the seeds outward to the angles (corners) of the triangular capsule and the seeds are released. As far as we know squirt-corner represents a new rain-operated seed dispersal mechanism, and a novel seed dispersal mode both for Melastomataceae and for flowering plants from Neotropical forests.

RAPD analysis in the Neotropical fish Brycon lundii: Genetic diversity and its implications for the conservation of the species

Random amplified polymorphic DNA (RAPD) technique was used to examine the genetic variability on an endangered Neotropical fish species, Brycon lundii, collected on two regions with distinct environmental conditions in the São Francisco River (Brazil), downstream from a hydroelectric station. Using decamer oligonucleotides as single primers in Polymerase Chain Reaction (PCR), genetic similarity index, mean allele frequency and mean heterozigosity were estimated, revealing variations between samples from the two regions. Moreover, a fragment of about 1200 base pairs was found in 100% of the examined animals collected at the region closer to the hydroelectric dam, while its frequency was much lower (27.3%) within the sample from the second collecting site, 30 km downstream from the dam, indicating a possible correlation between genetic variation and geographical area. A dendogram representing the relationships among genotypes was obtained, demonstrating at least two major clusters of animals. Based on the data, a model of population structuring in Brycon lundii is suggested. The described approach holds great promise for further analyses and gives support to biodiversity maintenance and recovery efforts of B. lundii.

Two Digestive Trypsins Occur in Three Species of Neotropical Anophelines

Trypsin activity increases in the midgut of Anopheles aquasalis, Anopheles albitarsis, and Anopheles darlingi after a bloodmeal. The activity returns to basal levels at the time the blood is completely digested. Affinity chromatography, reversed-phase high performance liquid chromatography (HPLC), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used to sequentially purify the mosquito trypsins found in the midguts at 24 h after feeding. Amino-terminal sequencing of the purified trypsins showed the occurrence of two distinct trypsins in the midgut of each of the mosquitoes studied. The sequences obtained are similar to those of the trypsins of other hematophagous insects.

Ultramorfologia e Histologia da Glândula Salivar do Tórax de Polistes versicolor (Olivier) (Vespidae), Comparada com a de Outros Hymenoptera

The salivary system of the Hymenoptera consists of the mandible, hypopharynx and thoracic salivary glands. It is very important because it is related to various aspects of the life of the insects, such as pheromone production, feeding the young, food digestion and nest building. Adult Polistes versicolor (Olivier) individuals were dissected, the thoracic salivary glands removed and processed for scanning electronic microscopy and histological examination. The P. versicolor thoracic salivary gland presents alveolar secretory units, consists of pseudoacines and does not have a reservoir. Four types of cells are present in the gland. The T1 and T2 cells make up the pseudoacines and differ mainly by the many secretory vessels in T2. There is a cluster of T3 cells at the base of the gland duct collectors, also with secretory characteristics. The secretion produced in the pseudoacines is conducted by canals and ducts to the outside, and the latter are made of T4 cells. The comparison of these characteristics with those of different Hymenoptera species, already studied, showed that the thoracic salivary gland cannot be used as a single comparison factor in evolutionary studies.

Male behavior in colonies of the social wasp Polistes lanio (Hymenoptera, Vespidae)

Sixteen post-emergent colonies of Polistes lanio were studied while producing males in the course of the colonial cycle. Individually, they remained in the nest only 10.5 days (5-31, n=165). Twelve different male behaviors were observed: remaining immobile on the nest (82,8%), giving alarm (4,8%), flying out from the nest (2,4%), copulating on the nest (2,4%), being dominated (1,6%), self-grooming (1,2%), checking cells (1,2%), adult-adult trophallaxis (receiving food) (0,8%), larva-adult trophallaxis (0,8%), chewing prey and giving it to the larvae (0,8%), returning to the nest without food (0,8%), and fanning the nest (0,4%). In comparison to the behavioral repertory of females (28 items), they performed fewer tasks and remained immobile most of the time on the nest. Their behavior was largely related to self maintenance, but also included giving chewed prey to the larvae, giving alarm signals and fanning the nest.

Conformation and lytic activity of eumenine mastoparan: A new antimicrobial peptide from wasp venom

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A new interpretation of the defense glands of neotropical Ruptitermes (Isoptera, Termitidae, Apicotermitinae)

Suicidal altruism has been reported for some species of eusocial insects, in which the individual dies in defense of the society. The termites of the genus Ruptitermes are known for the suicidal behavior of the workers which liberate a sticky defensive secretion by body bursting. In the present paper it is given a new interpretation of the defense glands of Neotropical Ruptitermes based on the morphological analysis of three species collected at Rio Claro, SP, Brazil. Before the current study, the suicidal defensive behavior was attributed to the dehiscence of the salivary gland reservoirs. The defense or dehiscent glands of Neotropical Ruptitermes are pair structures rounded in shape that are independent of the salivary glands. The dehiscent glands consist of multiple secretory units that are kept together by thin connective tissue. Each secretory unit is composed of one cell generally with one peripheral nucleus and characteristic secretion. The three species studied here present some histological differences in the secretory units, probably related to the chemical composition of the secretion.

Dominance hierarchy in different stages of development in colonies of the primitively eusocial wasp Mischocyttarus cassununga (Hymenoptera, Vespidae)

Seven colonies of Mischocyttarus cassununga were studied under field conditions at Universidade Federal de Juiz de Fora, MG, in southeastern Brazil: in pre-emergence, post-emergence and decline stages, during 145.8 hours. Dominance interactions among the females were quantified to verify the dynamics of succession in the social hierarchy of the colonies. Early pre-emergence colonies present more intense aggressive interactions than late pre-emergence ones, because the females are engaged in securing the role of main egg layer in the nest. In post-emergence (pre-male) colonies the dominance hierarchy is more defined and the frequency of dominance and subordination behaviors were lower than in pre-emergence stages: most of the agonistic behaviors are restricted to the first ranked females (potentially queens) and the subordinate individuals play the role of workers in the nests. In the post-emergence, post-male, and decline stages the hierarchy is still maintained by the aggressive behaviors of the 1st-ranked female but because the presence of males and future nest foundresses these interactions are not well defined in a linear way.

Effects of deltamethrin pyrethroid on the respiratory metabolism of the neotropical spirostreptid millipedes Gymnostreptus olivaceus and Plusioporus setiger

The effects of deltamethrin on the respiratory metabolism of Gymnostreptus olivaceus and Plusioporus setiger were investigated. Acetone solutions corresponding to half the LD50 values, i.e., 20 μg.g-1g for G. olivaceus and 4.40 μg.g-1 for P. setiger, were used. Metabolism was determined with a Warburg respirometer at 25°C. Respirometric measurements were performed 1, 3 and 6 hours after administration of the pyrethroid to the same groups of millipedes. After 24 hours, daily respirometric measurements lasting 1 hour each were made on different millipede groups for a period of 10 days. Significant differences were detected only between the groups treated with the pyrethroid and the two control groups. In G. olivaceus, respiratory rates increased by about 1.65-fold compared to normal immediately after administration of the pyrethroid, followed by a gradual decrease up to 72 hours and a return to normal levels thereafter. In P. setiger the increase was about 1.1-fold compared to normal, with a decrease up to 96 hours and a return to normal thereafter. Although increased oxygen consumption was observed, a detoxification process occurred in both species, so that the possible metabolism of the pyrethroid may justify the low toxicity of deltamethrin for G. olivaceus and P. setiger.

First chromosome characterization in the neotropical eel, Gymnothorax ocellatus (Pisces, Muraenidae)

Cytogenetics studies in 12 specimens of Gymnothorax ocellatus reveled a diploid chromosome number of 2n=42 (16 metacentrics, 18 submetacentrics and 8 acrocentrics). The nucleolar organizer regions were located in a terminal position on the long arm of the chromosome pair number fifteen. Conspicuous blocks of constitutive heterochromatin were observed in the centromeric and pericentromeric regions of some chromosome pairs. The results obtained are similar to those previously described for others species of this family. However, the cytogenetic informations may be useful in the identification of a possible variety of this species in Brazilian coast and contribute to the understanding of relationships among the species and the process of diversification which occurred in this group. © 2005 The Japan Mendel Society.

Histochemical characterization and secretory activity of the hypopharyngeal glands in the primitive social wasp Polistes versicolor (Hymenoptera: Vespidae)

Using histochemical techniques, the present work describes the basic histochemical characteristics of the secretion in hypopharyngeal glands of Polistes versicolor (Olivier) and estimates the secretory activity in specimens of different ages. The secretory activity was determined by glandular cell diameter and by the amount of secretion present in the glands. The results did not reveal a relationship between these parameters and the age of the wasps, not allowing us to determine the development cycle of these glands throughout the wasps' life. Also, a relationship between glandular cell diameter and amount of secretion present in the glands was not observed.

Characterization of the social wasp guild (Hymenoptera: Vespidae) visiting flowers in the Caatinga (Itatim, Bahia, Brazil)

Thirteen species of flower-visiting social wasps were collected from 41 plant species. The number of wasp species did not vary significantly. On the other hand, the number of individuals varied significantly during the data collection period. Four of the wasp species (Mischocyttarus lanei, Polybia ignobilis, Polybia occidentalis, and Polybia sericea) showed changes in body size over the year. The total wasp biomass and the number of plants monthly visited by wasps had a positive significant correlation. The structure of this social wasp community is characterized by a small number of dominant species, a large number species that are not frequently present and several plant species visited by few wasps. Social wasp species are differently affected by seasonal changes in the 'caatinga'.