Effects of salinity on ZOANTHUS SOCIATUS (Cnidaria: Anthozoa): Is low salinity a limiting factor?

Abiotic factors, such as variations on salinity, exert influence on the animal distribution in the intertidal zone, including zoanthids. This study evaluated the osmotic, morphological and ethological effects of salinity variations on tropical zoanthid Zoanthus sociatus. In order to analyze the hypothesis of osmotic conformation, the zoanthid was submitted to salinity stress. To estimate the osmotic capabilities of the species studied, specimens collected in beach rocks were taken alive to the laboratory and maintained in water collected from the site. The osmoregulatory ability of Z. sociatus was determined by measuring the hemolymph osmolality under various salinity conditions and comparing it to the medium osmolality. Zoanthid Z. sociatus is able to present osmotic conformation in hemolymph salinity in a wide range of external salinity values. The bleaching frequency was high in low salinities and the mortality rate was high after two days of experiment. This experiment shows for the first time the importance of osmotic conformation in a tropical zoanthid and discusses the role of low salinity as a limiting factor for survival and distribution of these important animals in tropical coastal reefs.

Duration of Protopolybia exigua exigua (de Saussure) nests and related aspects as influenced by phorid fly infestation (vespidae, polistinae, epiponini)

The main characteristics of 55 nests of Protopolybia exigua exigua were periodically evaluated in Ribeirão Preto, southeastern Brazil. Although the queens' life-span can eventually reach one year, nests barely thrive for six months because most of them are periodically invaded by the scavenger phorid fly, Megaselia aff. picta. Under heavy infestation the adult wasp population partially closes the nest entrance, migrates and constructs a new nest in the neighborhood. Afterwards the old-nest's entrance can be completely closed by the wasps which results in blocking the parasitoid flies inside. In the tropics, predation by ants is considered the main selective pressure which shaped most of the bionomic characteristics of Polistinae wasps. It is suggested that Megaselia can easily overcome the usual wasps defensive tactics just because they are so specialized against ants. Aerial raids, fast erratic-jerking movements, rapid and efficient oviposition behavior, etc. can eventually turn Megaselia into a very important enemy of some social wasps.

Multiple nymphoid reproductives in the nests of the neotropical termite, Armitermes euamignathus (Isoptera, Termitidae, Nasutitermitinae)

Armitermes euamignathus Silvestri (Termitidae, Nasutitermitinae) is a mound building termite that is common in Brazilian regions of the Cerrado vegetation. Multiple neotenic reproductives were found in three isolated nests of these species localized in other secondary habitats different from Cerrado vegetation. The number of second form queens was always higher than the number of secondary males. In two of these nests, the primary king was present along with the second form reproductives. Eggs and brood were found in the three nests but mature alates were present in only one. Multiple neotenic reproductives were never found in the studied Cerrado region where the nests contained only the primary pair. A study of oviposition rate between primary queens and nymphoid reproductives showed an increased number of eggs in the colony headed by neotenic reproductives.

A new species of Constrictotermes from central Brazil with notes on the mandibular glands of workers (Isoptera: Termitidae: Nasutitermitinae)

Constrictotermes rupestris, new species, is described from central Brazil, with illustrations of the imago, soldier, worker head, worker mandibles, worker mandibular gland, and nest. The new species lives in a dry forest, on rocky terrain, building its nest always on rocks. In the colonies examined, all castes showed a striking reddish coloration due to something accumulated in the fat tissues. Inquilinitermes microcerus was present in most examined nests. The worker of C. rupestris has an enlarged mandibular gland. Workers also show an aggressive behavior, which suggests that the mandibular glands may produce defensive secretions.

Notes on Eucryptotermes with a new species from central Amazonia (Isoptera: Kalotermitidae)

Eucryptotermes breviceps, new species, is described from central Amazonia. Both imagoes and soldiers of this new species have only two apical spurs on the foretibia, a condition previously unknown for Kalotermitidae. The soldier of E. breviceps has a peculiar and extremely phragmotic head. The geographical distribution of E. wheeleri is expanded with new records, and measurements of soldiers and imagoes of this species are presented for the first time. E. wheeleri is a native of the Atlantic forest of southeastern Brazil, from Santa Catarina to Rio de Janeiro, but it has been recorded in urban areas and may be an occasional minor pest.

Non-allometric caste differences in Agelaia vicina (Hymenoptera, Vespidae, Epiponini)

Non-allometric and clear-cut caste dimorphism were found in two colonies of the social wasp Agelaia vicina. Such type of allometry was previously recorded in the Epiponini and its origin is pre-imaginally determined as in the other analysed species which present caste dimorphism. Multivariate analyses evidenced that the most intercastes discriminant characters were found in the metasoma and mesosoma while head differences were slight. Although queens were characterized by marked ovary development and insemination, the presence of some uninseminated queens was detected in one of the analysed colonies.

Karyotype evolution in the Termitidae (Isoptera)

The karyotypes of 15 species of Termitidae were analyzed. All of them are X1X2Y1Y2 (male) and X1X1X2X2 (female). With the exception of Neocapritermes opacus with 2n=40, the remaining species are 2n=42 in both sexes, a karyotype similar to those described for African species by other authors. The sex determining mechanism probably originated before the split up of Gondwanaland, in a single event, early during the karyotype evolution of the family Termitidae by means of a reciprocal translocation that involved the primitive Y and a chromosome from an autosomal pair.

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.

Agonistic behavior of Nasutitermes sp. (Isoptera: Termitidae)

The possible existence of agonistic, intraspecific behavior, and polycalic nests was investigated for Nasutitermes sp. Aggressive tests among soldiers, workers and between soldiers and workers of different nests were carried out, and later, injury percentage was analyzed from the results of such tests. Agonistic behavior was observed in the majority of the experiments performed between individuals from different colonies. In the light of such results, it was assumed that polycalism does not exist among the nests of this species.

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.

Experimental control of the effect of extra doses of juvenile hormone on bee development: The case of the wax glands of Apis mellifera (Hymenoptera: Apidae)

Experiments on the effect of topical application of the synthetic juvenile hormone (JH-III) and of the solvent used to dissolve the hormone on the development of the wax glands of workers of Apis mellifera, were made. The results show that it was impossible to determine the effect of the juvenile hormone (JH) apart from its solvent (acetone), which also alters the developmental pattern of the gland. Most of the experiments reported in scientific literature do not consider the effect of the solvent, analyzing the results by only comparing the treatment with the hormone plus solvent to a control without any treatment. The data presented suggests that this kind of procedure compromises the evaluation of the real JH effect.

Growth patterns of incipient colonies of Coptotermes havilandi (Isoptera, Rhinotermitidae) initiated in the laboratory from swarming alates

Fifty two colonies of Coptotermes havilandi were set up under laboratory conditions using alates collected from an urban area during a period of swarming. The first artificial nest used for each royal couple was a 6cm diameter Petri dish (22ml) filled with a moistened matrix of decayed pine sawdust. After 6 months, these colonies were transferred to 250ml plastic containers with the same culturing matrix. After 24 months a census of all colonies was performed. Each young colony had a live royal pair and the population size of all colonies indicated a nonlinear development. The total population (workers + soldiers + immatures + reproductives) of these incipient colonies ranged from 64 to 1, 164, with a mean of 345 individuals. The number of workers ranged from 53 to 830 individuals, and the number of soldiers ranged from 6 to 83. The present data showed a higher population of incipient colonies than our previous record for the species. We also compared the development of 12 transferred colonies to that of 12 untransferred incipient colonies. The results showed a higher population in transferred colonies, but in both incipient colonies (transferred and untransferred) there was a wide variation in total population. The correlation between queen weight and population size was positive in all 24 colonies.

Nest architecture and population dynamics of the ponerine ant Ectatomma edentatum (Hymenoptera, Formicidae)

Twelve nests of Ectatomma edentatum (Hymenoptera, Formicidae) were collected from January to December 1996, in Rio Claro, SP, southeastern Brazil. This species excavates their nests up to 1, 10m deep, containing 2, 3, or 4 chambers with an entrance hole of up to 5mm diameter. Colonies with 104, 79, and 82 adult ants respectively were found in February, October, and November. These numbers decreased from March. Colonies with 21 and 16 adult ants were observed in May and July. The colonies' populations increased again in August. Immature stages were not seen January, February, and July, but there were many between March-April and September-November. There was no significant correlation between the number of individuals per colony and temperature or between the number of colonies and relative humidity and rainfall.