Investigating the Link Between Visual Quality and Vision-Related Quality of Life in Patients With Keratoconus.

PURPOSE: The purpose of the study was to investigate the optical and visual determinants of vision-related quality of life (VR-QoL) in patients with keratoconus. METHODS: A cross-sectional case-control study was conducted at the Department of Ophthalmology, Antwerp University Hospital, Belgium. Patients previously diagnosed with keratoconus and healthy emmetropic or ametropic volunteers were included. Patients younger than 18 years, with ametropia of more than ±10 D, or with a history of corneal surgery or relevant ocular comorbidity limiting visual acuity were excluded. Assessment included autorefraction, high-contrast visual acuity testing, corneal imaging, intraocular straylight analysis, contrast sensitivity, aberrometry, and the National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25). The Rasch-modified visual functioning scale (VFS) and socio-emotional scale were used to quantify VR-QoL. Stepwise linear regression was used to investigate the association between the clinical variables and VR-QoL. RESULTS: Seventy-seven patients with keratoconus (77 pairs of eyes) and 77 age-matched and sex-matched controls were included in the study. The scores on the VFS and the SES were significantly lower in patients with keratoconus compared with controls ( P < 0.001). Higher-order and lower-order aberrations, high-contrast visual acuity, and contrast sensitivity were poorer in patients with keratoconus ( P < 0.001). Bivariate analyses showed that spectacle-corrected high-contrast visual acuity, higher spatial frequency contrast sensitivity, and higher-order aberration metrics were strong predictors of SES ( P < 0.001) and of VFS ( P < 0.001). Higher-order aberration of the worse eye was the strongest predictor for both SES (b = 0.310, P < 0.001) and VFS (b = 0.638, P < 0.001) on stepwise regression. Contrast sensitivity was not included in the stepwise regression because of insufficient data in the keratoconus group (33/77 patients; 42.9%). CONCLUSIONS: Both higher and lower aberration showed a strong correlation with VR-QoL, surpassing high-contrast visual acuity. These findings underline the importance of visual quality measures within keratoconus research and clinical care.

Are offspring begging levels exaggerated beyond the parental optimum? Evidence from a bidirectional selection experiment.

Parental care involves elaborate behavioural interactions between parents and their offspring, with offspring stimulating their parents via begging to provision resources. Thus, begging has direct fitness benefits as it enhances offspring growth and survival. It is nevertheless subject to a complex evolutionary trajectory, because begging may serve as a means for the offspring to manipulate parents in the context of evolutionary conflicts of interest. Furthermore, it has been hypothesized that begging is coadapted and potentially genetically correlated with parental care traits as a result of social selection. Further experiments on the causal processes that shape the evolution of begging are therefore essential. We applied bidirectional artificial selection on begging behaviour, using canaries (Serinus canaria) as a model species. We measured the response to selection, the consequences for offspring development, changes in parental care traits, here the rate of parental provisioning, as well as the effects on reproductive success. After three generations of selection, offspring differed in begging behaviour according to our artificial selection regime: nestlings of the high begging line begged significantly more than nestlings of the low begging line. Intriguingly, begging less benefitted the nestlings, as reflected by on average significantly higher growth rates, and increased reproductive success in terms of a higher number of fledglings in the low selected line. Begging could thus represent an exaggerated trait, possibly because parent-offspring conflict enhanced the selection on begging. We did not find evidence that we co-selected on parental provisioning, which may be due to the lack of power, but may also suggest that the evolution of begging is probably not constrained by a genetic correlation between parental provisioning and offspring begging.

Coadaptation of offspring begging and parental provisioning: A role for prenatal maternal effects?

Recent studies on birds have shown that offspring begging and parental provisioning covary at the phenotypic level, which is thought to reflect genetic correlations. However, prenatal maternal factors, like yolk testosterone, may also facilitate parent-offspring coadaptation via their effects on offspring begging and development. In fact, maternal effects are thought to adjust offspring phenotype to the environmental conditions they will experience after birth, which are in turn strongly dependent on the levels of parental provisioning. Using cross-fostering experiments in canaries, we tested the role of maternal effects on parent-offspring coadaptation from two different approaches. First, we analyzed whether females deposit yolk testosterone in relation to their own or their partner's prospective parental provisioning, measured as the rate of parental feeding to foster nestlings. Second, we investigated whether females deposit yolk testosterone in relation to costs they incurred when raising a previous brood, as this likely impinges on their capacity to provide parental care in the near future. However, from the results of both experiments we have no evidence that canary females deposit yolk testosterone in order to match offspring begging to the levels of care they and/or their partners provide. We therefore found no evidence that yolk testosterone facilitates parent-offspring coadaptation. In addition, our results suggest that the functional consequences of yolk testosterone deposition may relate to hatching asynchrony since it primarily varied with egg laying order.

Coadaptation of offspring begging and parental provisioning--an evolutionary ecological perspective on avian family life.

Offspring begging and parental provisioning are the two central social behaviours expressed during the period of parental care. Both behaviours influence each other and it is, therefore, hypothesized that they should ultimately become (genetically) correlated, stabilized by fitness costs to parents and/or offspring. By reciprocally exchanging entire clutches in canaries (Serinus canaria), we tested (1) whether there is covariation between these behaviours and (2) whether a mismatch--as introduced by cross-fostering--entails costs. Begging was scored in a standardized begging test and parental provisioning was measured via (a) the actual feeding rate and (b) using the growth rate of the foster nestlings as a proxy. Costs were established in terms of future reproductive investment in subsequent clutches and offspring growth. We found a positive and significant phenotypic covariation between offspring begging and parental feeding when using the growth rate as a proxy and, to a lesser extent, in case of the parental feeding rate. Female parents suffered no future reproductive costs when feeding foster nestlings that were more demanding than their own nestlings. Neither growth measured amongst all offspring nor the reproductive investment measured amongst the female offspring as adults was influenced by their begging behaviour. However, the reproductive investment of female offspring tended to depend on the parental qualities of their foster parents. Thus, offspring may only be able to extract resources within the limit of generosity of their foster parents. This suggests parental control of feeding, which is also supported by the positive covariation between offspring begging and parental feeding.

The male sex pheromone of the butterfly Bicyclus anynana: towards an evolutionary analysis.

BACKGROUND: Female sex pheromones attracting mating partners over long distances are a major determinant of reproductive isolation and speciation in Lepidoptera. Males can also produce sex pheromones but their study, particularly in butterflies, has received little attention. A detailed comparison of sex pheromones in male butterflies with those of female moths would reveal patterns of conservation versus novelty in the associated behaviours, biosynthetic pathways, compounds, scent-releasing structures and receiving systems. Here we assess whether the African butterfly Bicyclus anynana, for which genetic, genomic, phylogenetic, ecological and ethological tools are available, represents a relevant model to contribute to such comparative studies. METHODOLOGY/PRINCIPAL FINDINGS: Using a multidisciplinary approach, we determined the chemical composition of the male sex pheromone (MSP) in the African butterfly B. anynana, and demonstrated its behavioural activity. First, we identified three compounds forming the presumptive MSP, namely (Z)-9-tetradecenol (Z9-14:OH), hexadecanal (16:Ald ) and 6,10,14-trimethylpentadecan-2-ol (6,10,14-trime-15-2-ol), and produced by the male secondary sexual structures, the androconia. Second, we described the male courtship sequence and found that males with artificially reduced amounts of MSP have a reduced mating success in semi-field conditions. Finally, we could restore the mating success of these males by perfuming them with the synthetic MSP. CONCLUSIONS/SIGNIFICANCE: This study provides one of the first integrative analyses of a MSP in butterflies. The toolkit it has developed will enable the investigation of the type of information about male quality that is conveyed by the MSP in intraspecific communication. Interestingly, the chemical structure of B. anynana MSP is similar to some sex pheromones of female moths making a direct comparison of pheromone biosynthesis between male butterflies and female moths relevant to future research. Such a comparison will in turn contribute to understanding the evolution of sex pheromone production and reception in butterflies.