Male mate choice scales female ornament allometry in a cichlid fish

<p>Abstract</p> <p>Background</p> <p>Studies addressing the adaptive significance of female ornamentation have gained ground recently. However, the expression of female ornaments in relation to body size, known as trait allometry, still remains unexplored. Here, we investigated the allometry of a conspicuous female ornament in <it>Pelvicachromis taeniatus</it>, a biparental cichlid that shows mutual mate choice and ornamentation. Females feature an eye-catching pelvic fin greatly differing from that of males.</p> <p>Results</p> <p>We show that allometry of the female pelvic fin is scaled more positively in comparison to other fins. The pelvic fin exhibits isometry, whereas the other fins (except the caudal fin) show negative allometry. The size of the pelvic fin might be exaggerated by male choice because males prefer female stimuli that show a larger extension of the trait. Female pelvic fin size is correlated with individual condition, suggesting that males can assess direct and indirect benefits.</p> <p>Conclusions</p> <p>The absence of positive ornament allometry might be a result of sexual selection constricted by natural selection: fins are related to locomotion and thus may be subject to viability selection. Our study provides evidence that male mate choice might scale the expression of a female sexual ornament, and therefore has implications for the understanding of the relationship of female sexual traits with body size in species with conventional sex-roles.</p

Interaction between the obesity-risk gene FTO and the dopamine D2 receptor gene ANKK1/TaqIA on insulin sensitivity

Variations in FTO are the strongest common genetic determinants of adiposity, and may partly act by influencing dopaminergic signalling in the brain leading to altered reward processing that promotes increased food intake. Therefore, we investigated the impact of such an interaction on body composition, and peripheral and brain insulin sensitivity. Participants from the Tubingen Family study (n = 2245) and the Malmo Diet and Cancer study (n = 2921) were genotyped for FTO SNP rs8050136 and ANKK1 SNP rs1800497. Insulin sensitivity in the caudate nucleus, an important reward area in the brain, was assessed by fMRI in 45 participants combined with intranasal insulin administration. We found evidence of an interaction between variations in FTO and an ANKK1 polymorphism that associates with dopamine (D2) receptor density. In cases of reduced D2 receptor availability, as indicated by the ANKK1 polymorphism, FTO variation was associated with increased body fat and waist circumference and reduced peripheral insulin sensitivity. Similarly, altered central insulin sensitivity was observed in the caudate nucleus in individuals with the FTO obesity-risk allele and diminished D2 receptors. The effects of variations in FTO are dependent on dopamine D2 receptor density (determined by the ANKK1 polymorphism). Carriers of both risk alleles might, therefore, be at increased risk of obesity and diabetes.Peer reviewe

Plasticity of Astrocytic Coverage and Glutamate Transporter Expression in Adult Mouse Cortex

Astrocytes play a major role in the removal of glutamate from the extracellular compartment. This clearance limits the glutamate receptor activation and affects the synaptic response. This function of the astrocyte is dependent on its positioning around the synapse, as well as on the level of expression of its high-affinity glutamate transporters, GLT1 and GLAST. Using Western blot analysis and serial section electron microscopy, we studied how a change in sensory activity affected these parameters in the adult cortex. Using mice, we found that 24 h of whisker stimulation elicited a 2-fold increase in the expression of GLT1 and GLAST in the corresponding cortical column of the barrel cortex. This returns to basal levels 4 d after the stimulation was stopped, whereas the expression of the neuronal glutamate transporter EAAC1 remained unaltered throughout. Ultrastructural analysis from the same region showed that sensory stimulation also causes a significant increase in the astrocytic envelopment of excitatory synapses on dendritic spines. We conclude that a period of modified neuronal activity and synaptic release of glutamate leads to an increased astrocytic coverage of the bouton–spine interface and an increase in glutamate transporter expression in astrocytic processes

Dose-Dependent Effects of Endotoxin on Neurobehavioral Functions in Humans

Clinical and experimental evidence document that inflammation and increased peripheral cytokine levels are associated with depression-like symptoms and neuropsychological disturbances in humans. However, it remains unclear whether and to what extent cognitive functions like memory and attention are affected by and related to the dose of the inflammatory stimulus. Thus, in a cross-over, double-blind, experimental approach, healthy male volunteers were administered with either placebo or bacterial lipopolysaccharide (LPS) at doses of 0.4 (n = 18) or 0.8 ng/kg of body weight (n = 16). Pro- and anti-inflammatory cytokines, norephinephrine and cortisol concentrations were analyzed before and 1, 1.75, 3, 4, 6, and 24 h after injection. In addition, changes in mood and anxiety levels were determined together with working memory (n-back task) and long term memory performance (recall of emotional and neutral pictures of the International Affective Picture System). Endotoxin administration caused a profound transient physiological response with dose-related elevations in body temperature and heart rate, increases in plasma interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α and IL-1 receptor antagonist (IL-1ra), salivary and plasma cortisol, and plasma norepinephrine. These changes were accompanied by dose-related decreased mood and increased anxiety levels. LPS administration did not affect accuracy in working memory performance but improved reaction time in the high-dose LPS condition compared to the control conditon. In contrast, long-term memory performance was impaired selectively for emotional stimuli after administration of the lower but not of the higher dose of LPS. These data suggest the existence of at least two counter-acting mechanisms, one promoting and one inhibiting cognitive performance during acute systemic inflammation

Microsatellite Support for Active Inbreeding in a Cichlid Fish

In wild animal populations, the degree of inbreeding differs between species and within species between populations. Because mating with kin often results in inbreeding depression, observed inbreeding is usually regarded to be caused by limited outbreeding opportunities due to demographic factors like small population size or population substructuring. However, theory predicts inclusive benefits from mating with kin, and thus part of the observed variation in inbreeding might be due to active inbreeding preferences. Although some recent studies indeed report kin mating preferences, the evidence is still highly ambiguous. Here, we investigate inbreeding in a natural population of the West African cichlid fish Pelvicachromis taeniatus which showed clear kin mating preferences in standardized laboratory experiments but no inbreeding depression. The presented microsatellite analysis reveals that the natural population has, in comparison to two reference populations, a reduced allelic diversity (A = 3) resulting in a low heterozygosity (Ho = 0.167) pointing to a highly inbred population. Furthermore, we found a significant heterozygote deficit not only at population (Fis = 0.116) but also at subpopulation level (Fis = 0.081) suggesting that inbreeding is not only a by-product of population substructuring but possibly a consequence of behavioral kin preferences

Seismic performance evaluation of concentrically braced and fiction damped braced frames through full-scale testing

The study describes the analyses of a six storey concentrically braced frame (CBF) and an equivalent frame retrofitted with friction-damped bracing (FDBF). The CBF was designed according to the ductile braced frame requirements of the Canadian steel building standard CAN/CSA-S16.1-M89 (S16.1) and the National Building Code of Canada 1990. The optimum slip load for the friction dampers in the FDBF was determined on the basis of energy principles and its distribution was assumed to be uniform throughout the structure. Full-scale quasi-static cyclic and earthquake simulation testing was conducted on the storey predicted with the most severe damage. The analytical predictions of these two systems show that their overall response, in terms of peak interstorey drift, is similar. Full-scale tests conducted on the CBF using hollow steel structural sections for the cross-bracing show that the bracing may develop twice the energy dissipation ability predicted by computer analysis. This appears to be due to the coplanar interaction of the braces. Significant additional stresses are induced in the bracing due to this interaction, which the computer cannot model. Hollow structural section cross-bracing appears to provide significantly better energy dissipating properties than HSS single diagonal bracing or multilevel cross-bracing; however, this may be at the expense of early fatigue failure. The tests show that, when compared to other bracing configurations, significantly fewer load cycles can be carried by such braces prior to fatigue fracture. The test results indicate that the slenderness requirements set out in S16.1 appear to be adequate for the design of cross-bracing if based on the half length, as opposed to the full length of the brace diagonal. The width-to-thickness ratio requirements were inadequate to effectively delay fatigue fracture of the braces. The optimum slip-load study using the optimizing program FDBFAP for the six storey FDBF under investigation shows that the best response is obtainable with a frame shear resistance of 80 kN. A more detailed analysis using the program DRAIN-2D showed that a local optimum existed at 80kN, but that the global optimum was 320kN. The testing of the FDBF showed that the friction damper can be a reliable method of dissipating energy. The locally installed friction pads used in the damper were, however, unreliable for the slip-load level required. Significant fade in the slip-load occurred during cyclic loading. The friction pads failed on two occasions, and at a panel shear slip-load (base shear) of approximately 130 kN. The tests show that the compression brace remains in compression during an entire half cycle of loading. This implies that a buckled brace is not restraightened with the initiation of slip, but rather with load reversal, resulting in a slack in the hysteresis during loading and unloading, and therefore a reduction in the energy dissipation. Out-of-plane vibrations occurred during the testing. These vibrations appeared to be the result of a prestress which is induced in the system in the deformed position. The tests also indicated that significant brace bending occurred. This bending was found to be a function of the ratio of the frame panel size to damper size. It is expected that the combination of bending and tensile forces due to the prestressing effect can lead to brace yielding.Applied Science, Faculty ofCivil Engineering, Department ofGraduat

Parental investment in relation to offspring quality in the biparental cichlid fish Pelvicachromis taeniatus

Thünken T, Meuthen D, Bakker TCM, Kullmann H. Parental investment in relation to offspring quality in the biparental cichlid fish Pelvicachromis taeniatus. Animal Behaviour. 2010;80(1):69-74.Theory predicts that parents should adjust their parental investment to the reproductive value of the brood. Previous studies have mainly investigated the relationship between brood size, brood age and the intensity of care. However, the impact of brood quality traits such as the offspring’s average body size on parental investment has received relatively little attention. We examined the parental response to brood quality in the biparentally brood-caring cichlid fish Pelvicachromis taeniatus. We manipulated offspring quality by manipulating the food availability for the free-swimming fry and measured the parental response over 4 weeks. Generally, care decreased over the 4 weeks suggesting that parents adjust care to decreasing offspring vulnerability. However, parents of relatively low-quality broods, that is, of broods with relatively small average individual body size, showed a greater reduction in care than parents of high-quality broods resulting in a significant difference in care provided in the fourth week. The result suggests that parents adjust their care to brood quality and supports the predictions of the parental investment theory. Furthermore, mothers of high-quality fry were significantly more aggressive towards their partner than mothers of low-quality fry. This result is discussed in the context of parental response to brood value. Generally, females invested more in brood care than males