Fitness benefits of prolonged post-reproductive lifespan in women

Most animals reproduce until they die, but in humans, females can survive long after ceasing reproduction. In theory, a prolonged post-reproductive lifespan will evolve when females can gain greater fitness by increasing the success of their offspring than by continuing to breed themselves. Although reproductive success is known to decline in old age, it is unknown whether women gain fitness by prolonging lifespan post-reproduction. Using complete multi-generational demographic records, we show that women with a prolonged post-reproductive lifespan have more grandchildren, and hence greater fitness, in pre-modern populations of both Finns and Canadians. This fitness benefit arises because post-reproductive mothers enhance the lifetime reproductive success of their offspring by allowing them to breed earlier, more frequently and more successfully. Finally, the fitness benefits of prolonged lifespan diminish as the reproductive output of offspring declines. This suggests that in female humans, selection for deferred ageing should wane when one's own offspring become post-reproductive and, correspondingly, we show that rates of female mortality accelerate as their offspring terminate reproduction

Middleborns disadvantaged? testing birth-order effects on fitness in pre-industrial finns

Parental investment is a limited resource for which offspring compete in order to increase their own survival and reproductive success. However, parents might be selected to influence the outcome of sibling competition through differential investment. While evidence for this is widespread in egg-laying species, whether or not this may also be the case in viviparous species is more difficult to determine. We use pre-industrial Finns as our model system and an equal investment model as our null hypothesis, which predicts that (all else being equal) middleborns should be disadvantaged through competition. We found no overall evidence to suggest that middleborns in a family are disadvantaged in terms of their survival, age at first reproduction or lifetime reproductive success. However, when considering birth-order only among same-sexed siblings, first-, middle-and lastborn sons significantly differed in the number of offspring they were able to rear to adulthood, although there was no similar effect among females. Middleborn sons appeared to produce significantly less offspring than first-or lastborn sons, but they did not significantly differ from lastborn sons in the number of offspring reared to adulthood. Our results thus show that taking sex differences into account is important when modelling birth-order effects. We found clear evidence of firstborn sons being advantaged over other sons in the family, and over firstborn daughters. Therefore, our results suggest that parents invest differentially in their offspring in order to both preferentially favour particular offspring or reduce offspring inequalities arising from sibling competition

Development of mandibular, hyoid and hypobranchial muscles in the zebrafish: homologies and evolution of these muscles within bony fishes and tetrapods

<p>Abstract</p> <p>Background</p> <p>During vertebrate head evolution, muscle changes accompanied radical modification of the skeleton. Recent studies have suggested that muscles and their innervation evolve less rapidly than cartilage. The freshwater teleostean zebrafish (<it>Danio rerio</it>) is the most studied actinopterygian model organism, and is sometimes taken to represent osteichthyans as a whole, which include bony fishes and tetrapods. Most work concerning zebrafish cranial muscles has focused on larval stages. We set out to describe the later development of zebrafish head muscles and compare muscle homologies across the Osteichthyes.</p> <p>Results</p> <p>We describe one new muscle and show that the number of mandibular, hyoid and hypobranchial muscles found in four day-old zebrafish larvae is similar to that found in the adult. However, the overall configuration and/or the number of divisions of these muscles change during development. For example, the undivided adductor mandibulae of early larvae gives rise to the adductor mandibulae sections A0, A1-OST, A2 and Aω, and the protractor hyoideus becomes divided into dorsal and ventral portions in adults. There is not always a correspondence between the ontogeny of these muscles in the zebrafish and their evolution within the Osteichthyes. All of the 13 mandibular, hyoid and hypobranchial muscles present in the adult zebrafish are found in at least some other living teleosts, and all except the protractor hyoideus are found in at least some extant non-teleost actinopterygians. Of these muscles, about a quarter (intermandibularis anterior, adductor mandibulae, sternohyoideus) are found in at least some living tetrapods, and a further quarter (levator arcus palatini, adductor arcus palatini, adductor operculi) in at least some extant sarcopterygian fish.</p> <p>Conclusion</p> <p>Although the zebrafish occupies a rather derived phylogenetic position within actinopterygians and even within teleosts, with respect to the mandibular, hyoid and hypobranchial muscles it seems justified to consider it an appropriate representative of these two groups. Among these muscles, the three with clear homologues in tetrapods and the further three identified in sarcopterygian fish are particularly appropriate for comparisons of results between the actinopterygian zebrafish and the sarcopterygians.</p

Hepatitis C Virus Induced a Novel Apoptosis-Like Death of Pancreatic Beta Cells through a Caspase 3-Dependent Pathway

Epidemiological and experimental studies have suggested that Hepatitis C virus (HCV) infection is associated with the development of type 2 diabetes. Pancreatic beta cell failure is central to the progression of type 2 diabetes. Using virus infection system, we investigate the influence of HCV infection on the fate of the insulinoma cell line, MIN6. Our experiments demonstrate that the HCV virion itself is indispensable and has a dose- and time-dependent cytopathic effect on the cells. HCV infection inhibits cell proliferation and induces death of MIN6 cells with apoptotic characteristics, including cell surface exposure of phosphatidylserine, decreased mitochondrial membrane potential, activation of caspase 3 and poly (ADP-ribose) polymerase, and DNA fragmentation in the nucleus. However, the fact that HCV-infected cells exhibit a dilated, low-density nucleus with intact plasma and nuclear membrane indicates that a novel apoptosis-like death occurs. HCV infection also causes endoplasmic reticulum (ER) stress. Further, HCV RNA replication was detected in MIN6 cells, although the infection efficiency is very low and no progeny virus particle generates. Taken together, our data suggest that HCV infection induces death of pancreatic beta cells through an ER stress-involved, caspase 3-dependent, special pathway

Anthropogenic noise is associated with changes in acoustic but not visual signals in red-winged blackbirds

Some birds in noisy areas produce songs with higher frequency and/or amplitude and altered timing compared to individuals in quiet areas. These changes may function to increase the efficacy of acoustic signals by reducing masking by noise. We collected audio recordings of red-winged blackbirds and measured noise levels. We found that males in noisier places produced songs with fewer syllables and slower repeat rate of elements in some components (rattles). Birds may also improve the efficacy of communication in noise by increasing usage of other signaling modalities. Red-winged blackbirds also perform a visual display in different intensities while singing. We also tested whether this species performs the visual display in different intensities according to current noise levels, and predicted that if the efficacy of songs is impaired in noisy places, males would compensate by performing a more intense visual display. For this, we also collected visual recordings from the same males from which we obtained acoustic recordings. We found no association between acoustic noise and the intensity of the visual display; thus, our results do not support the idea that males are using the visual display as a backup signal to communicate under acoustic noise. We discuss some possible explanations of this negative finding and for the observed noise-related changes in song length and rattle rate in the context of communication under noise

Capability of Forficula auricularia linnaeus (Dermaptera : Forficulidae) to prey on Aphis craccivora koch (Homoptera : Aphididae) in eastern and Central Africa.

Aphis craccivora Koch (Homoptera : Aphididae) is an economic pest of cowpea in eastern Uganda and in eastern Democratic Republic of the Congo (DRC). The earwig Forficula auricularia (Dermaptera : Forficulidae) is a predatory species frequently observed on farms in eastern and central Africa. To determine the predation capability of F. auricularia on A. craccivora, laboratory and field cage experiments were set up in Uganda and the DRC during the rainy seasons of 2004 and 2005, with various predator-prey ratios as treatments. In the laboratory, F. auricularia consumed a range of 1.27 to 7.82 A. craccivora per day, while in the field the range was 3.66 to 7.24. Although this earwig did not demonstrate high predation levels, it is contributing to natural control of insect pests and therefore its populations should be encouraged.Les pucerons, Aphis craccivora Koch (Homoptera : Aphididae) compte parmi les ravageurs d\'importance économique du niébé à l\'Est de l\'Uganda et à l\'Est de la République Démocratique du Congo. Le perce-oreille commun, Forficula auricularia (Dermaptera : Forficulidae) est un prédateur fréquemment rencontré dans les agro-écosystèmes intégrant le niébé en Afrique centrale et orientale. L\'action prédatrice (la capacité de prédation) exercée sur les pucerons par le perce-oreille commun, a été évaluée en conditions de laboratoire et de champs. Les essais de cage en champs ont été installés dans les terrains expérimentaux en Uganda et en République Démocratique du Congo, durant la petite et la grande saison pluvieuses des années 2004 et 2005. Dans ces essais, différents traitements de prédateur-proie ont été évalués. Les résultats montrent que F. auricularia est capable de consommer environs 1,27 à 7,82 pucerons par jour en conditions de laboratoire. En milieu réel (champ), F.auricularia consomme 3,66 à 7,24 pucerons par jour. Malgré le fait que l\'insecte n\'a pas démontré un taux élevé de consommation journalière des pucerons, il pourrait néanmoins contribuer à la réduction de l\'augmentation des colonies du ravageur (Aphis craccivora) en milieu paysan. Les perce-oreilles peuvent jouer un rôle important en lutte biologique contre les pucerons puisque ils sont potentiellement important agents de contrôle naturel de ces ravageurs. Ainsi, une forte densité, de ce prédateur dans les agro-écosystèmes intégrant le niébé et cultures céréalières, est à encourager en Afrique centrale et orientale Keywords: Predation capability, Forficula auricularia, Aphis craccivora, Uganda, D. R. CongoAgronomie Africaine Vol. 20 (1) 2008: pp. 49-5