Social status and reproductive success of male Macaca fascicularis

Dominant males of nonseasonally breeding species should have more opportunity than seasonal breeders to monopolize access to estrous females and thus enhance their reproductive success. They may also use other strategies for maximizing reproductive success such as producing offspring by relatively high ranking females. To test these hypotheses, the paternity of 35 (80%) of 44 Macaca fascicularis offspring, born over a 28-month period, was established using electrophoretically and serologically defined genetic markers. The social ranks of each of the seven potential fathers and 26 potential mothers were determined by recording outcomes of dyadio agonistic interactions. No evidence could be found to support either hypothesis. Further, in view of previously reported significant, positive correlations between male social rank and sexual activity rates in this study group, sexual activity rates do not appear to predict the number of offspring a male sires in this species.     

BRE over-expression promotes growth of hepatocellular carcinoma

BRE, also known as TNFRSF1A modulator and BRCC45, is an evolutionarily highly conserved protein. It is a death receptor-associated protein in cytoplasm and a component of BRCA1/2-containing DNA repair complex in nucleus. BRE was found to have anti-apoptotic activity. Over-expression of BRE by transfection promoted survival of cell lines against apoptotic induction; whereas depletion of the protein by siRNA resulted in the opposite. In vivo anti-apoptotic activity of BRE was demonstrated by significant attenuation of Fas-induced acute fulminant hepatitis in transgenic mice expressing the human protein specifically in the liver. BRE was also implicated in tumor promotion by the accelerated tumor growth of Lewis Lung carcinoma transfected with human BRE; and by high expression of BRE specifically in the tumoral regions of human hepatocellular carcinoma (HCC). The present study was to test directly if transgenic expression of BRE in livers could promote HCC development in neonatal diethylnitrosamine model. By 8 months after tumor induction, the maximal sizes of tumor nodules of transgenic mice were significantly larger than those of the non-transgenic controls, although the numbers of tumor nodules between the two groups did not significantly differ. Importantly, as in human HCC, the mouse endogenous BRE level was up-regulated in mouse HCC nodules. These results show that BRE over-expression can indeed promote growth, though not initiation, of liver tumors. Furthermore, the common occurrence of BRE over-expression in human and mouse HCC suggests that up-regulation of BRE is functionally important in liver tumor development.     

Further results on the survival of a gene represented in a founder population

This paper is concerned with gene survival in a population which may increase without density dependence according to a generalization of the Moran model for haploid individuals. A selective advantage to one allele and the possibility of differential reproductive rates are allowed. Simple conditions are given for ultimate homozygosity to be certain and for the possibility of ultimate polymorphism. The results complement and extend those of Heyde (1981, 1982).     

Sexual advertisement and immune function in an arachnid species (Lycosidae)

A simple version of the immunocompetence handicap hypothesizesthat through condition-dependence, the size of the sexual traitmay be positively related to immune function at the populationlevel. In the present study, we investigated the relationshipbetween sexual advertisement and immune function in a naturalpopulation of male wolf spiders, Hygrolycosa rubrofasciata (Araneae:Lycosidae). Males of H. rubrofasciata have a costly and condition-dependentacoustic signal, courtship drumming. In the mating season, malesdrum against dry leaves while wandering around the habitat searchingfor receptive females. Males increase their mating success byincreasing their drumming rate and mobility. We used drummingrate and mobility measured without female proximity as estimatesof sexual advertisement. As estimates of male immune function,we used encapsulation rate and lytic activity. Encapsulationrate is a common challenging technique, which measures immuneresponse against multicellular parasites. Lytic activity isa monitoring technique, which measures immune response againstpathogens. Our results show that males with higher drummingrate had higher encapsulation rate. This suggests that femalesmight use drumming rate as a signal for choosing males withgood immunocompetence. Moreover, our results show that maleswith higher mobility had higher lytic activity. As females aremore likely to encounter those males that have higher mobility,this might also select males with better immune function. Ourresults suggest that the immunocompetence handicap might workalso among spiders, although we could not assess the causalityof the relationship between sexual selection and immune functionin this correlational study.     

EFFECTS OF MORTALITY RISK AND GROWTH ON A MODEL OF REPRODUCTIVE EFFORT: WHY THE SHINE AND SCHWARZKOPF MODEL IS NOT GENERAL

Using data and reanalysis of a model published by Shine and Schwarzkopf (1992) we reject the two unsubstantiated assertions made by Shine et al. (1996) about modeling the evolution of reproductive effort in squamate reptiles: (1) mortality schedules do not affect predictions of the Shine and Schwarzkopf (1992) model; and (2) growth rates that would affect the predictions of the original model are biologically unreasonable. On the basis of these two points alone, we strongly reject Shine et al.'s (1996) claim that a critique by Niewiarowski and Dunham (1994) actually reinforces the original conclusions of Shine and Schwarzkopf (1992). Furthermore, results and data presented here are strong enough to severely circumscribe the generality of the Shine and Schwarzkopf (1992) model. Though we do not provide data or new analyses of the potential effects of offspring size variation, we reaffirm the position of Niewiarowski and Dunham (1994) that the sensitivity of the Shine and Schwarzkopf (1992) model to such effects should be explored before using it as a basis for structuring future research on the evolution of reproductive effort in squamate reptiles.     

Age,growth and reproduction of Marcusenius pongolensis,Oreochromis mossambicus and Schilbe intermedius in an oligotrophic impoundment in Swaziland

The age, growth and reproductive biology of Marcusenius pongolensis, Oreochromis mossambicus and Schilbe intermedius were investigated in the Mnjoli Dam, Swaziland. Otolith annulus formation occurred in winter for M. pongolensis, and in spring/summer for O. mossambicus and S. intermedius. Maximum ages of 8, 6 and 8 years were recorded for M. pongolensis, O. mossambicus and S. intermedius, respectively. Growth was described by the von Bertalanffy growth model as L_t = 238.73(1 − exp^{−0.27(t+2.27}) mm fork length (FL) for M. pongolensis, L_t = 226.83(1 − exp^{−0.45(t+2.02)}) mm total length (TL) for O. mossambicus, and L_t = 214.59(1 − exp^{−0.60(t+1.20)}) mm FL for S. intermedius. Sexual maturity was estimated for male and female M. pongolensis at 134 mm FL and 119 mm FL, respectively. Marcusenius pongolensis matured within their first year. Female O. mossambicus and S. intermedius matured at 239 mm TL and 205 mm FL, corresponding to 2 and 4 years of age, respectively. Extended spawning periods, with two spawning peaks was observed for M. pongolensis, one in spring (September) and the second in autumn (March) and one peak over late‐summer for S. intermedius.