Feralisation targets different genomic loci to domestication in the chicken.

Feralisation occurs when a domestic population recolonizes the wild, escaping its previous restricted environment, and has been considered as the reverse of domestication. We have previously shown that Kauai Island's feral chickens are a highly variable and admixed population. Here we map selective sweeps in feral Kauai chickens using whole-genome sequencing. The detected sweeps were mostly unique to feralisation and distinct to those selected for during domestication. To ascribe potential phenotypic functions to these genes we utilize a laboratory-controlled equivalent to the Kauai population-an advanced intercross between Red Junglefowl and domestic layer birds that has been used previously for both QTL and expression QTL studies. Certain sweep genes exhibit significant correlations with comb mass, maternal brooding behaviour and fecundity. Our analyses indicate that adaptations to feral and domestic environments involve different genomic regions and feral chickens show some evidence of adaptation at genes associated with sexual selection and reproduction.

Within-population Y-linked genetic variation for lifespan in Drosophila melanogaster.

The view that the Y chromosome is of little importance for phenotypic evolution stems from early studies of Drosophila melanogaster. This species' Y chromosome contains only 13 protein-coding genes, is almost entirely heterochromatic and is not necessary for male viability. Population genetic theory further suggests that non-neutral variation can only be maintained at the Y chromosome under special circumstances. Yet, recent studies suggest that the D. melanogaster Y chromosome trans-regulates hundreds to thousands of X and autosomal genes. This finding suggests that the Y chromosome may play a far more active role in adaptive evolution than has previously been assumed. To evaluate the potential for the Y chromosome to contribute to phenotypic evolution from standing genetic variation, we test for Y-linked variation in lifespan within a population of D. melanogaster. Assessing variation for lifespan provides a powerful test because lifespan (i) shows sexual dimorphism, which the Y is primarily predicted to contribute to, (ii) is influenced by many genes, which provides the Y with many potential regulatory targets and (iii) is sensitive to heterochromatin remodelling, a mechanism through which the Y chromosome is believed to regulate gene expression. Our results show a small but significant effect of the Y chromosome and thus suggest that the Y chromosome has the potential to respond to selection from standing genetic variation. Despite its small effect size, Y-linked variation may still be important, in particular when evolution of sexual dimorphism is genetically constrained elsewhere in the genome.

Applying the genetic theories of ageing to the cytoplasm: cytoplasmic genetic covariation for fitness and lifespan.

Two genetic models exist to explain the evolution of ageing - mutation accumulation (MA) and antagonistic pleiotropy (AP). Under MA, a reduced intensity of selection with age results in accumulation of late-acting deleterious mutations. Under AP, late-acting deleterious mutations accumulate because they confer beneficial effects early in life. Recent studies suggest that the mitochondrial genome is a major player in ageing. It therefore seems plausible that the MA and AP models will be relevant to genomes within the cytoplasm. This possibility has not been considered previously. We explore whether patterns of covariation between fitness and ageing across 25 cytoplasmic lines, sampled from a population of Drosophila melanogaster, are consistent with the genetic associations predicted under MA or AP. We find negative covariation for fitness and the rate of ageing, and positive covariation for fitness and lifespan. Notably, the direction of these associations is opposite to that typically predicted under AP.

The genetic architecture of fitness in a seed beetle: assessing the potential for indirect genetic benefits of female choice.

BACKGROUND: Quantifying the amount of standing genetic variation in fitness represents an empirical challenge. Unfortunately, the shortage of detailed studies of the genetic architecture of fitness has hampered progress in several domains of evolutionary biology. One such area is the study of sexual selection. In particular, the evolution of adaptive female choice by indirect genetic benefits relies on the presence of genetic variation for fitness. Female choice by genetic benefits fall broadly into good genes (additive) models and compatibility (non-additive) models where the strength of selection is dictated by the genetic architecture of fitness. To characterize the genetic architecture of fitness, we employed a quantitative genetic design (the diallel cross) in a population of the seed beetle Callosobruchus maculatus, which is known to exhibit post-copulatory female choice. From reciprocal crosses of inbred lines, we assayed egg production, egg-to-adult survival, and lifetime offspring production of the outbred F1 daughters (F1 productivity). RESULTS: We used the bio model to estimate six components of genetic and environmental variance in fitness. We found sizeable additive and non-additive genetic variance in F1 productivity, but lower genetic variance in egg-to-adult survival, which was strongly influenced by maternal and paternal effects. CONCLUSION: Our results show that, in order to gain a relevant understanding of the genetic architecture of fitness, measures of offspring fitness should be inclusive and should include quantifications of offspring reproductive success. We note that our estimate of additive genetic variance in F1 productivity (CVA=14%) is sufficient to generate indirect selection on female choice. However, our results also show that the major determinant of offspring fitness is the genetic interaction between parental genomes, as indicated by large amounts of non-additive genetic variance (dominance and/or epistasis) for F1 productivity. We discuss the processes that may maintain additive and non-additive genetic variance for fitness and how these relate to indirect selection for female choice.

No evidence of mitochondrial genetic variation for sperm competition within a population of Drosophila melanogaster.

Recent studies have advocated a role for mitochondrial DNA (mtDNA) in sperm competition. This is controversial because earlier theory and empirical work suggested that mitochondrial genetic variation for fitness is low. Yet, such studies dealt only with females and did not consider that variation that is neutral when expressed in females, might be non-neutral in males as, in most species, mtDNA is never selected in males. We measured male ability to compete for fertilizations, at young and late ages, across 25 cytoplasms expressed in three different nuclear genetic backgrounds, within a population of Drosophila melanogaster. We found no cytoplasmic (thus no mtDNA) genetic variation for either male offence or offensive sperm competitiveness. This contrasts with previous findings demonstrating cytoplasmic genetic variation for female fitness and female ageing across these same lines. Taken together, this suggests that mitochondrial genes do not contribute to variation in sperm competition at the within-population level.

A comparison of nuclear and cytoplasmic genetic effects on sperm competitiveness and female remating in a seed beetle.

It is widely assumed that male sperm competitiveness evolves adaptively. However, recent studies have found a cytoplasmic genetic component to phenotypic variation in some sperm traits presumed important in sperm competition. As cytoplasmic genes are maternally transmitted, they cannot respond to selection on sperm and this constraint may affect the scope in which sperm competitiveness can evolve adaptively. We examined nuclear and cytoplasmic genetic contributions to sperm competitiveness, using populations of Callosobruchus maculatus carrying orthogonal combinations of nuclear and cytoplasmic lineages. Our design also enabled us to examine genetic contributions to female remating. We found that sperm competitiveness and remating are primarily encoded by nuclear genes. In particular, a male's sperm competitiveness phenotype was contingent on an interaction between the competing male genotypes. Furthermore, cytoplasmic effects were detected on remating but not sperm competitiveness, suggesting that cytoplasmic genes do not generally play a profound evolutionary role in sperm competition.

Fitness effects of female mate choice: preferred males are detrimental for Drosophila melanogaster females.

The evolution of female mate choice, broadly defined to include any female behaviour or morphology which biases matings towards certain male phenotypes, is traditionally thought to result from direct or indirect benefits which females acquire when mating with preferred males. In contrast, new models have shown that female mate choice can be generated by sexual conflict, where preferred males may cause a fitness depression in females. Several studies have shown that female Drosophila melanogaster bias matings towards large males. Here, we use male size as a proxy for male attractiveness and test how female fitness is affected by reproducing with large or small males, under two different male densities. Females housed with large males had reduced lifespan and aged at an accelerated rate compared with females housed with small males, and increased male density depressed female fitness further. These fitness differences were due to effects on several different fitness components. Female fitness covaried negatively with male courtship rate, which suggests a cost of courtship. Mating rate increased with male size, whereas female fitness peaked at an intermediate mating rate. Our results suggest that female mate choice in D. melanogaster is, at least in part, a by-product of sexual conflict over the mating rate.

The evolution of female mate choice by sexual conflict.

Although empirical evidence has shown that many male traits have evolved via sexual selection by female mate choice, our understanding of the adaptive value of female mating preferences is still very incomplete. It has recently been suggested that female mate choice may result from females evolving resistance rather than attraction to males, but this has been disputed. Here, we develop a quantitative genetic model showing that sexual conflict over mating indeed results in the joint evolution of costly female mate choice and exaggerated male traits under a wide range of circumstances. In contrast to tradition explanations of costly female mate choice, which rely on indirect genetic benefits, our model shows that mate choice can be generated as a side-effect of females evolving to reduce the direct costs of mating.

Ultrastructural analysis of 20 intraosseous endolymphatic sacs from patients with cerebello-pontine angle tumours. A surgically obtained control material for histopathological studies.

OBJECTIVE: The purpose of this work was to collect a surgically obtained, freshly fixed material of the human intraosseous endolymphatic sac. This biopsy material was used to describe the normal ultrastructure as well as to serve as a control material for histopathological studies on Ménière's disease in particular. METHOD: The specimens, obtained during surgery for cerebello-pontine angle tumours, were fixed by immersion and then prepared by routine methods for transmission electron microscopy. The ultrastructural analysis was focused on intraluminal content, epithelial cell layer, subepithelial space, and morphological signs of immunological activity. The ultrastructure was analysed in relation to inner ear sensory function, tumour diagnosis, and patient's age and sex. RESULTS: As it was possible to obtain numerous specimens with an intact bony shell, the intraluminal substance could be analysed. Two separate epithelial cell types are described: one less abundant, often lighter and mitochondria-rich cell type; the other, often darker, epithelial cell with fever mitochondrias. Some of the latter cell types showed signs of active secretion. The subepithelial space was characterized by loose connective tissue adjacent to the epithelial lining, being more dense toward the bone. Elastic fibres were seen surrounding the entire endolymphatic sac. Macrophages in the intraluminal space and lymphocytes in the epithelial and subepithelial layers are described. No distinct morphology correlating to inner ear sensory function, tumour diagnosis, or patient's age and sex was revealed. CONCLUSIONS: This study confirms previously described, extensive variations in form and structure of the human endolymphatic sac. Various factors, such as surgical trauma, previous treatment, and processing method, can affect the ultrastructure and must be taken into consideration. The specimens described in this work appear to constitute a good control material for histopathological study of the human endolymphatic sac. It is still necessary to obtain large control materials such as this, as surgical specimens from patients with Ménière's disease are uncommon.

Sexual conflict promotes speciation in insects.

Speciation rates among extant lineages of organisms vary extensively, but our understanding of the causes of this variation and, therefore, the processes of speciation is still remarkably incomplete. Both theoretical and empirical studies have indicated that sexual selection is important in speciation, but earlier discussions have focused almost exclusively on the potential role of female mate choice. Recent findings of postmating reproductive conflicts of interest between the sexes suggest a quite different route to speciation. Such conflicts may lead to perpetual antagonistic coevolution between males and females and may thus generate rapid evolutionary divergence of traits involved in reproduction. Here, we assess this hypothesis by contrasting pairs of related groups of insect species differing in the opportunity for postmating sexual conflict. Groups where females mate with many males exhibited speciation rates four times as high as in related groups where females mate only once. Our results not only highlight the general importance of postmating sexual selection in speciation, but also support the recent suggestion that sexual conflict is a key engine of speciation.

Embryonic and postnatal accumulation of homogeneous substance in the endolymphatic sac in the guinea pig.

OBJECTIVE: The endolymphatic sac (ES) of vertebrates contains varying amounts of a homogeneous substance (HS) that stains deeply with basic aniline dyes. Histochemically, HS is characterized as a carbohydrate-protein complex, being both neutral and acidic in nature. In the present study, deposition of HS in the ES was studied in the guinea pig from the 3rd week of gestation to 104 weeks postnatally in order to find out if HS accumulates with age, at which point during embryonic development this substance appears, if its presence is correlated to the sense of hearing and if the amount of substance in the left versus right ear of one and the same animal is correlated to any degree. METHODS: Sixty-nine endolymphatic sacs were evaluated in 38 guinea pigs. The ES specimens were sectioned for light and transmission electron microscopy and the amount of HS filling was categorized in four groups: none, low, medium and a high level of substance. RESULTS: The substance was not discerned until after 7 weeks of gestation, when it filled only a minor part of the distal ES lumen. At 9 weeks gestation the nature of the substance altered, becoming homogeneous, as visualized by osmium-toluidine blue staining and approximately filling the distal half of the luminal space. In the postnatal period, 65% of ES specimens were filled with HS to the intermediate or proximal ES, whereas only 6.5% of the ES specimens were devoid of the substance. The extent of filling of the ES in the prenatal temporal bones was significantly less than postnatally (P < 0.0001, chi2-test). The extent of postnatal filling was not correlated with age. Left and right ears were closely correlated in one and the same animal. Phagocytic cells were often found at the border between clear endolymph and stainable substance. CONCLUSION: The appearance of HS seemed to coincide temporally with the onset of hearing during the prenatal period indicating that it could play a part in normal inner ear functioning in the guinea pig. The close correlation regarding the level of the HS in the left and right ear, both pre- and postnatally could reflect a general symmetry in endolymph pressure-volume conditions within the inner ear fluid systems, as well as in the environmental hydrostatic pressure in the posterior cranial fossa.

Stereocilia-like structures in the endolymphatic sac in Ménière's disease and acoustic neuroma.

The vestibular aqueduct was surgically removed in 3 patients undergoing labyrinthectomy due to severe Ménière's disease (MD). Stereocilia-like structures were found in the luminal contents of the endolymphatic sac (ES) in all of these patients. The ES from 18 patients with acoustic neuroma were used as controls. In 1 of these, numerous stereocilia-like structures were found in the ES and in 3 additional patients, a few isolated cilia-like structures were disclosed. The findings may suggest an ongoing hair cell degeneration in the inner ear that is more advanced in patients with MD. The data also suggest that the endolymphatic duct is patent and that a longitudinal flow of endolymph also occurs in patients with MD.

"Endolymphatic sacitis" in a case of active Menière's disease. An ultrastructural histopathologic investigation.

An ultrastructural analysis of an entire intraosseous endolymphatic sac (ES) from a patient with active, well-documented Menière's disease was performed for the first time. The results were compared with those obtained from ES biopsy material from patients with acoustic neuromas. The ES was small in size and showed signs of focal inflammation with intraepithelial invasion by mononuclear cells. At these places the normal fine structure, including the vascular anatomy, was altered. The possible relationship between these changes and Meniere's disease is discussed.

Adrenergic innervation of the human endolymphatic sac.

Adrenergic innervation of the human endolymphatic sac (ES) has not been verified previously. To investigate this question a sensitive histofluorescence method for visualization of catecholamines and serotonin, using a solution composed of sucrose-potassium phosphate-glyoxylic acid (SPG) in cryostat sections, was employed. Three human ES specimens were obtained during surgery for acoustic neuroma. Distinct fluorescence in the subepithelial tissue, indicating the presence of monoaminergic neurones and their axonal varicosities, was observed. SPG-positive terminal nerve fibres around small ES capillaries and subendothelially were also seen. Like the effects of sympathetic stimulation elsewhere in the human body, the ES might respond to such stimulation with, for example, vasoconstriction and increased transepithelial water transport. Since the ES is thought to be responsible for maintaining inner ear fluid homeostasis, adrenergic influence could be important for it to function properly.

Localization of hyaluronan in the human endolymphatic sac. A study using the affinity hyaluronan binding protein.

This study was undertaken with the aim of localizing hyaluronan (hyaluronic acid, HYA) in tissue sections of the human endolymphatic sac by use of a hyaluronan-binding affinity protein and the avidin-biotin/peroxidase staining procedure. Five human endolymphatic sacs were removed during surgery for acoustic neuroma. After microwave-aided fixation and decalcification, paraffin-embedded sections were prepared by routine histological methods. HYA was detected in some of the intraluminal substance as well as in parts of the epithelial lining, mainly in the rugose portions of the endolymphatic sac. HYA was observed intracellularly in epithelial cells. It was also found in the subepithelial tissue near the epithelia and close to the bony aqueduct. The distribution of HYA was uneven at all locations. The finding of HYA within the human endolymphatic sac may imply that this substance has important functions in the control of inner ear fluid homeostasis.

Ultrasound treatment of Ménière's disease.

This article reviews the technical data about ultrasonography devices, the mode of action of ultrasound waves on vestibular structures, when to use this technique, and the surgical procedure. It also presents the results of this treatment obtained during the last 10 years in the authors' various institutions.

Endolymphatic sac morphology after instillation of hyperosmolar hyaluronan in the round window niche.

One hundred and sixty-eight mice were injected with hyaluronan (HA) of varying tonicity in the middle ear and compared with 81 control animals to study the effects of hypertonic solutions in the middle ear on inner ear fluid homeostasis and endolymphatic sac (ES) response. Six hours after 1.9% HA and 4, 6 and 8 h after 4% HA deposition there was a significant increase in the proportion of granule-containing light epithelial cells in the ES as compared with controls indicating an enhanced secretory activity from the epithelial lining. Six, 8 and 10 h after deposition of 4% HA, the ES volume was significantly reduced. The secretory activity and the ability of the ES to vary its volume could be specific responses to dehydration of the inner ear resulting from the high colloid osmotic pressure exerted by concentrated HA. The secretion of high-molecular substances into the ES may serve to keep the ES lumen patent and thus ensure a proper ES function and/or to regulate the intralabyrinthine volume and fluid pressure. Whether the findings may have clinical relevance for Ménière's patients remains to be elucidated.

Origin of sympathetic and sensory innervation of the endolymphatic sac. A retrograde axonal tracing study in the guinea pig.

Lectin-conjugated horseradish peroxidase (WGA-HRP) was used as a retrograde axonal tracer to determine endolymphatic sac (ES) innervation and the nature of such a nervous supply. WGA-HRP placed into the ES of the guinea pig resulted in labelling of neurons in the ipsilateral sympathetic superior cervical ganglion and the sensory trigeminal ganglion. The number of labelled neurons in the cervical superior ganglion varied according to the survival time with peak labelling occurring after 48 h. Sparse labelling of the sensory trigeminal ganglion was also present after 48 h. The results indicate that sympathetic neurons from the superior cervical ganglion and to a certain extent trigeminal somatosensory neurons innervate the ES or perisaccular tissue. If these findings reflect the existence of a sympathetic functional reflex unit remains to be elucidated.