Fabíola da Silva Albuquerque

Body weight of wild and captive common marmosets (callithrix jacchus)

Captive studies and occasional trappings of wild individuals indicate that callitrichids have small size and body weight and lack sexual dimorphism. We compared body weights of captive and wild Callithrix jacchus obtained by repeatedly weighing subjects from two populations in Brazil. We obtained captive data by routinely weighing 138 individuals from the Universidade Federal do Rio Grande do Norte colony and wild data via regular trapping of 243 individuals in 15 free-ranging groups from IBAMAs field site in Nísia Floresta. We assigned all subjects to one of four age classes—infant, juvenile, subadult, and adult—according to their birth dates or size, reproductive status, and dental development. There is no significant difference between males and females in any of the four age classes, but captive subjects were heavier than wild ones in all age classes but infant. Reproductive and nonreproductive adult females showed no statistical difference in weight. These results accord with previous reports of lack of body size sexual dimorphism in common marmosets and suggest that differences between wild and captive common marmosets are not constitutional, but are instead a consequence of diet and physical activity. The absence of weight difference between reproductive and nonreproductive females suggests that any possible advantage from high rank is outweighed by the costs of reproduction in common marmosets.

Two Breeding Females within Free-Living Groups May Not Always Indicate Polygyny: Alternative Subordinate Female Strategies in Common Marmosets (Callithrix jacchus)

The mating system of callitrichids has been reported to be monogamous, polygynous and polyandrous. In Callithrix jacchus, groups with 2 breeding females and groups with 1 breeding female have been reported. Our purpose was to evaluate the occurrence of occasional reproduction by subordinate females in free-ranging C. jacchus groups characterized as monogamous. Four groups were monitored at a field site of IBAMA-Brazil for between 20 and 72 months. We recorded the birth of 7 sets of twins to subordinate females that had never reproduced before. Sexual activities were recorded opportunistically: dominant females copulated with only the resident male, while subordinates copulated with extra-group males. We suggest these were essentially monogamous groups that occasionally had 2 reproductive females. Between-group copulations seem to be an alternative strategy used by the subordinates. Despite the costs, there would probably be benefits as a result of scanning for vacancies for reproductive positionsin neighbouring groups and the establishment of ties with extra-group males that might become a reproductive partner in the future.

Carrying Behaviour in Captive and Wild Marmosets (Callithrix jacchus) : A Comparison Between Two Colonies and a Field Site

Data on callitrichids infant carrying is highly variable, and there is some disagreement over the relative involvement of different group members. Considering that variation may result from different social and environmental conditions it is important to compare data from different environments. The purpose of this study was to compare infant carrying in 11Callithrix jacchus groups living in two colonies, in the UK and Brazil, or in a field site in the northeastern Brazil. No differences were found in the amount of time that infants were carried, in the three environmental conditions, during weeks 1 to 4, 7, and 10. Fathers and mothers carried infants for equivalent amounts of time in the three conditions, but helpers from natural groups carried infants more than their captive counterparts. In general, adult helpers carried infants more than subadults and juveniles. The results suggest that carrying is a stable feature inCallithrix jacchus groups, but there is a trend suggestive of an extended carrying period in natural groups. Mothers behaviour were remarkably stable, but fathers behaviour, although comparable, was more conspicuous in captivity than in the field, what may be attributed to paternity certainty. Finally, the greater participation of field helpers in carrying is considered as deriving mostly to age of helpers than to group size.

Differential infant carrying in captive and wild common marmosets (Callithrix jacchus)

Callitrichids are communal breeders that lack sexual dimorphism, and only a few studies have examined behavioral gender differences among them. The purpose of this study was to investigate gender differences in infant carrying in 16 captive and seven wild common marmoset groups. Our results showed that female–female twin pairs were carried significantly more often by fathers than were male–male and male–female pairs both in the wild and in captivity. We suggest these differences may be related to different reproductive potentials of male and female Callithrix jacchus and possibly to future breeding competition among females.

A amígdala e a tênue fronteira entre memória e emoção

Embora os mecanismos neurobiologicos envolvidos na memoria para situacoes aversivas nao estejam completamente esclarecidos, o complexo basolateral da amigdala parece exercer um papel fundamental nesse tipo de memoria. O presente trabalho tem como objetivo revisar os principais estudos acerca da participacao da amigdala na memoria e discutir os aspectos teoricos dos modelos utilizados. Foi realizada uma revisao dos estudos em humanos e em modelos animais que visam investigar e discutir a participacao da amigdala na memoria. Duas hipoteses norteiam as investigacoes aqui revisadas: 1) a amigdala seria o local dos processos plasticos envolvidos na aquisicao e consolidacao de informacoes de conteudo aversivo e 2) essa estrutura modularia os processos de aquisicao e consolidacao que ocorreriam em outras estruturas. Os resultados que embasam a primeira hipotese foram obtidos em um modelo de resposta de medo condicionada em ratos, enquanto que a segunda hipotese provem de estudos que utilizam um modelo experimental que envolve aspectos mais declarativos da informacao aversiva. Apesar de os trabalhos aqui revisados fornecerem fortes evidencias de que a amigdala modula as estruturas relacionadas com a consolidacao da memoria, novos estudos poderao esclarecer melhor essa relacao, principalmente com novos paradigmas de investigacao.