EXOPHTHALMOS—From the Standpoint of the Otolaryngologist

Exophthalmos may be due to an inflammatory process or to tumor formation. Inflammatory processes are most likely to occur in children and young adults. Tumors are the most common cause of exophthalmos in adults.Since the advent of chemotherapy and the antibiotics, rarely does orbital cellulitis develop from sinal infection.Tumors causing exophthalmos are likely to be benign if they arise from the frontal sinus and malignant if they arise from the maxillary and ethmoid sinuses.     

Vocal and Facial Attractiveness Judgments of Children, Adolescents and Adults: the Ontogeny of Mate Choice

Physical traits are thought to be used as indicators of mate quality, allowing individuals to select mates most likely to help them bear the fittest offspring. As the capacity for human sexual behaviour emerges at puberty, we investigated whether adult‐like judgments of the relative attractiveness of opposite‐sex individuals also arise at puberty. Following previous research, we focussed on facial and vocal attractiveness, which are known to be used in human mate choice and to carry concordant information regarding mate quality. Here we show that males with more attractive faces have more attractive voices as judged by female adults and adolescents, but not by female children. This suggests that cues of facial and vocal attractiveness provide similar information, but that awareness of these cues does not develop fully until reproductive capability, when mate choice judgments become relevant. Adolescents’ judgments also mirrored those of adults in that, like adults, they preferred lower‐pitched male voices, and as a group made concordant judgments about facial attractiveness. However, they did not make similarly concordant judgments about vocal attractiveness, suggesting that a further period of maturation and learning is required to fully develop optimal judgments for mate choice.     

Antioxidants, showy males and sperm quality

The fertility of males sometimes correlates with their ornamental display, but we do not have a mechanistic explanation to universally link these traits. We suggest that both sperm quality (fertility; integrity of DNA), and the substrates responsible for male ornamentation, may be vulnerable to free radical attack, which can be mitigated by antioxidants. Support for these ideas is at present weak, and requires validation in ecological contexts. We hypothesize that a link between ornamentation and sperm quality could arise if antioxidants are in limited supply, and the showiest males may be preferred because they are most likely to be fertile, or to provide sperm with undamaged genotypes that could give rise to fit offspring.     

Alternative to Homo-oligomerisation: The Creation of Local Symmetry in Proteins by Internal Amplification

The biologically active state of many proteins requires their prior homo-oligomerisation. Such complexes are typically symmetrical, a feature that has been proposed to increase their stability and facilitate the evolution of allosteric regulation. We wished to examine the possibility that similar structures and properties could arise from genetic amplifications leading to internal symmetrical repeats. For this, we identified internal structural repeats in a nonredundant Protein Data Bank subset. While testing if repeats in proteins tend to be symmetrical, we found that about half of the large internal repeats are symmetrical, most frequently around a rotation axis of 180°. These repeats were most likely created by genetic amplification processes because they show significant sequence similarity. Symmetrical repeats tend to have a fixed number of copies corresponding to their rotational symmetry order, that is, two for 180° rotation axis, whereas asymmetrical repeats are in longer proteins and show copy number variability. When possible, we confirmed that proteins with symmetrical repeats folding as an n-mer have homologues lacking the repeat with a higher oligomerisation number corresponding to the rotation symmetry order of the repeat. Phylogenetic analyses of these protein families suggest that typically, but not always, symmetrical repeats arise in one single event from proteins that are homo-oligomers. These results suggest that oligomerisation and amplification of internal sequences can interplay in evolutionary terms because they result in functional analogues when the latter exhibit rotational symmetry.     

The influence of parasites on the retention of long-term partnerships in the Australian sleepy lizard, Tiliqua rugosa

Many studies have shown that potential partners are less likely to be chosen for mating if they are infected with parasites, although most of those studies have considered short-term choices. This paper shows that the Australian sleepy lizard, Tiliqua rugosa (Scincoidea), retains long-term pair fidelity for up to 21 years. However, in some cases pairs separate, and abandoned males have significantly higher tick loads in their last year with their previous female partner than did males that retained their partners from 1 year to the next. These data are consistent with the hypothesis that pair bonds are retained because individuals, both with low infection levels, are less likely to become infected if they remain with the same sexual partner.     

Site-specific selfish genes as tools for the control and genetic engineering of natural populations

Site-specific selfish genes exploit host functions to copy themselves into a defined target DNA sequence, and include homing endonuclease genes, group II introns and some LINE-like transposable elements. If such genes can be engineered to target new host sequences, then they can be used to manipulate natural populations, even if the number of individuals released is a small fraction of the entire population. For example, a genetic load sufficient to eradicate a population can be imposed in fewer than 20 generations, if the target is an essential host gene, the knockout is recessive and the selfish gene has an appropriate promoter. There will be selection for resistance, but several strategies are available for reducing the likelihood of it evolving. These genes may also be used to genetically engineer natural populations, by means of population-wide gene knockouts, gene replacements and genetic transformations. By targeting sex-linked loci just prior to meiosis one may skew the population sex ratio, and by changing the promoter one may limit the spread of the gene to neighbouring populations. The proposed constructs are evolutionarily stable in the face of the mutations most likely to arise during their spread, and strategies are also available for reversing the manipulations.     

Translocation for conservation: Neonates are less suitable than adults

Animal behaviour can affect the outcome of conservation translocations. It is important to understand the behaviour of the species being considered for translocation and how its behaviour varies over life stages. There may be uncertainty about what life stages are best as founders for release back into wild populations. A technique called head‐starting whereby juvenile life stages are raised in captivity and then released is one potential pre‐release strategy. However, juveniles of many species have a dispersive role in the life cycle, potentially raising difficulties for establishing new populations due to dispersal from the intended habitat following release. For this study, we compared aspects of the behaviour of captive adult and neonate pygmy bluetongue lizards (Tiliqua adelaidensis) – an endangered species for which translocation is likely to be an important management strategy – to determine if neonate behavioural characteristics are appropriate for their translocation. We filmed adult and neonate pygmy bluetongue lizards and compared their behaviour. We also filmed adults over an activity season to compare seasonal behaviour. Behavioural parameters measured included basking time, burrow exits, burrows occupied and walking the perimeter wall. Neonates basked significantly more than adults in summer and autumn. Neonates are likely to be basking more than adults because they are in a stage of rapid growth and need to gain body mass before the winter inactivity period. Neonates exited burrows more often than adults and used a greater number of burrows. These results indicate neonate lizards are actively exploring their habitat. Neonates are unlikely to be as suitable for translocation as they are actively moving about and more likely to be predated upon or disperse from the translocation site. Our finding can be applied to other species that have active juvenile life stages and are at particular risk of predation due to their small size.     

Using heterochrony to detect modularity in the evolution of stem diversity in the plant family moringaceae

Organisms are made up of semiautonomous parts or modules, but identifying the limits of modules is not straightforward. Covariation between morphological features across the adults of a clade can identify suites of characters as putative modules. We contrast such an approach for delimiting modules with one that includes inferences of heterochrony, evolutionary change in the timing of developmental events. That two features show differing types of heterochrony is a strong indication that they are ontogenetically dissociated and belong to differing modules even though these features may covary across adults. We focus on xylem vessels (wood water conduits) and phloem fibers (bark support cells) in the stems of the 13 species of the plant genus Moringa (Moringaceae), which vary from massive bottle trees to tiny tuberous shrubs. Across adults, vessel diameter and number of phloem fibers scale positively and significantly with stem size and with respect to one another. This covariation across adults suggests that these features may be members of the same ontogenetic module, a finding that might be expected given that these cells both derive from the same tissue ontogenetically and are tightly functionally integrated in the stem. In contrast, ontogenetic data in the context of a phylogenetic hypothesis suggest that vessel elements and phloem fibers have undergone different types of paedomorphosis, heterochronic alteration to ontogeny producing adults of descendant species that resemble the juveniles of their ancestors. Vessels and phloem fibers would be expected to show differing types of paedomorphosis only if they are not ontogenetically coupled, and therefore it is likely that they are part of different modules; this ontogenetic independence was invisible to inference based only on adult covariation. Finally, we show reasons to implicate paedomorphosis in the diversification in life form of Moringa across the Old World dry tropics.     

Vocal development in vervet monkeys

Observations and playback experiments were used to study the development of grunts and alarm calls among free-ranging vervet monkeys. Results indicate that the production of vocalizations, their use in appropriate circumstances, and the response to the vocalizations of others emerge gradually during an individual's first 4 years. Particularly in the case of grunts, different acoustic components develop at different rates. Immatures respond appropriately to the calls of others before they produce appropriate vocalizations themselves. Finally, immature vocal development may be aided by cues received from adults. If an infant gives an alarm call to a genuine predator (as opposed to a non-predator), adults respond more strongly. When infants hear a playback of an alarm, they are more likely to respond appropriately if they first look at an adult.     

Estimation of Michaelis constant and maximum velocity from the direct linear plot

When estimates of Michaelis-Menten parameters are obtained from kinetic observations taken in pairs, as in the direct linear plot, bias can arise in the final estimates if any pairs lead to negative values of the maximum velocity V. This bias can be removed by treating such negative values as if they were large and positive, and by treating the corresponding values of Km in the same way.     

Relocation, reproduction and remaining alive in the orb-web spider

When mortality is high, animals run a risk if they wait to accumulate resources for improved reproduction so they may trade-off the time of reproduction with number and size of offspring. Animals may attempt to improve food acquisition by relocation, even in 'sit and wait' predators. We examine these factors in an isolated population of an orb-web spider Zygiella x-notata . The population was monitored for 200 days from first egg laying until all adults had died. Large females produced their first clutch earlier than did small females and there was a positive correlation between female size and the number and size of eggs produced. Many females, presumably without eggs, abandoned their web site and relocated their web position. This is presumed because female Zygiella typically guard their eggs. In total, c . 25% of females reproduced but those that relocated were less likely to do so, and if they did, they produced the clutch at a later date than those that remained. When the date of lay was controlled there was no effect of relocation on egg number but relocated females produced smaller eggs. The data are consistent with the idea that females in resource-poor sites are more likely to relocate. Relocation seems to be a gamble to find a more productive site but one that achieves only a late clutch of small eggs and few achieve that.     

Diversity and the maintenance of sex by parasites

The Red Queen hypothesis (RQH) predicts that parasite‐mediated selection will maintain sexual individuals in the face of competition from asexual lineages. The prediction is that sexual individuals will be difficult targets for coevolving parasites if they give rise to more genetically diverse offspring than asexual lineages. However, increasing host genetic diversity is known to suppress parasite spread, which could provide a short‐term advantage to clonal lineages and lead to the extinction of sex. We test these ideas using a stochastic individual‐based model. We find that if parasites are readily transmissible, then sex is most likely to be maintained when host diversity is high, in agreement with the RQH. If transmission rates are lower, however, we find that sexual populations are most likely to persist for intermediate levels of diversity. Our findings thus highlight the importance of genetic diversity and its impact on epidemiological dynamics for the maintenance of sex by parasites.     

Dynamics of the control of body pattern in the development of Xenopus laevis. IV. Timing and pattern in the development of twinned bodies after reorientation of eggs in gravity

The mesendodermal anatomy of twinned larval axes is described in relation to the normal single pattern, when twinning has been caused by experimental tilting of eggs before first cleavage. The formation of two origins for gastrulation movements (dorsal lips) and their relatively rapid spread and coalescence to give a circular blastopore, is a predictor of twin formation in individual embryos after treatment. The anatomy of twins where development has been disturbed from the outset in this way is appreciably different from that induced by the later operation of second dorsal lip implantation. It is also variable in a systematic way. The total sizes of cellular allocations to individual notochords and prechordal head patterns are enhanced above normal if they arise relatively close together in the tissue, but significantly reduced if they arise far apart. These and other features of twinned patterns due to precleavage disturbance are discussed in terms of what they might indicate about the physicochemical nature of the body positional system. The results confirm that by a variety of rather simple, nonsurgical manipulations the relative amounts of territory in the egg devoted to different parts of the body can be greatly influenced.     

Coalition formation: a game-theoretic analysis

There are many examples of individuals forming coalitions toobtain or protect a valuable resource. We present an analyticalmodel of coalition formation in which individuals seek alliancesif they judge themselves too weak to secure the resource alone.We allow coalition seeking to carry an investment cost () andlet contest outcomes depend probabilistically on the relativefighting strengths of contesting parties, with effective coalitionstrength directly proportional to combined partner strength.We identify the evolutionarily stable strength thresholds, belowwhich individuals within triads should seek a coalition. Weshow that if exceeds a critical value, then unilateral fightingover resources is an evolutionarily stable strategy (ESS). Universal(3-way) coalitions are also an ESS outcome if is less thana second critical value. Both of these extreme solutions areless likely to arise, the greater the variance in fighting strengthsand the greater the benefit from dominating opponents. Our analysisalso identifies intermediate solutions in which only the weakerindividuals seek coalitions: only then can a true coalition(2 vs. 1) form. We characterize these ESSs and show that truecoalitions are more likely to arise when the effective strengthof a coalition is less than the sum of its individual strengths(antergy). Alliances in primates are characterized by antergy,high reliability of strength as a predictor of contest outcome,and high variability in strengths. These are precisely the conditionsin which in our model most favors true coalition formation.     

Sperm competition mechanisms,confidence of paternity,and the evolution of paternal care in the golden egg bug (Phyllomorpha laciniata)

Theoretical models predict how paternal effort should vary depending on confidence of paternity and on the trade-offs between present and future reproduction. In this study we examine patterns of sperm precedence in Phyllomorpha laciniata and how confidence of paternity influences the willingness of males to carry eggs. Female golden egg bugs show a flexible pattern of oviposition behavior, which results in some eggs being carried by adults (mainly males) and some being laid on plants, where mortality rates are very high. Adults are more vulnerable to predators when carrying eggs; thus, it has been suggested that males should only accept eggs if there are chances that at least some of the eggs will be their true genetic offspring. We determined the confidence of paternity for naturally occurring individuals and its variation with the time. Paternity of eggs fertilized by the last males to mate with females previously mated in the field has been determined using amplified fragment length polymorphisms (AFLPs). The exclusion probability was 98%, showing that AFLP markers are suitable for paternity assignment. Sperm mixing seems the most likely mechanism of sperm competition, because the last male to copulate with field females sires an average of 43% of the eggs laid during the next five days. More importantly, the proportion of eggs sired does not change significantly during that period. We argue that intermediate levels of paternity can select for paternal care in this system because: (1) benefits of care in terms of offspring survival are very high; (2) males have nothing to gain from decreasing their parental effort in a given reproductive event because sperm mixing makes it difficult for males to reach high paternity levels and males are left with no cues to assess paternity; (3) males cannot chose to care for their offspring exclusively because they can neither discriminate their own eggs, nor can they predict when their own eggs will be produced; and (4) males suffer no loss of further matings with other females when they carry eggs. Thus, our findings do not support the traditional view that paternal investment is expected to arise only in species where confidence of paternity is high. The results suggest that females maximize the chances that several males will accept eggs at different times by promoting a mechanism of sperm mixing that ensures that all males that have copulated with a female have some chance of fathering offspring, that this probability remains constant with time, and that males have no cues as to when their own offspring will be produced.     

Migratory connectivity of Palaearctic–African migratory birds and their responses to environmental change: the serial residency hypothesis

In most long‐distance migratory birds, juveniles migrate without their parents and so are likely to lack detailed knowledge of where to go. This suggests the potential for stochasticity to affect their choice of wintering area at a large scale (> 1000 km). Adults, in contrast, may re‐use non‐breeding sites that promote their survival, so removing uncertainty from their subsequent migrations. I review the evidence for large‐scale stochastic juvenile site selection followed by adult site fidelity, and then develop a ‘serial‐residency’ hypothesis based on these two traits as a framework to explain both the migratory connectivity and the population dynamics of migrant birds and how these are affected by environmental change. Juvenile stochasticity is apparent in the age‐dependent effects of weather or experimental displacement on the outcome of migration and in the very wide variation in the destinations of individuals originating from the same area. Adults have been shown to be very faithful to their wintering grounds and even to staging sites. The serial residency hypothesis predicts that migrants that show these two traits will rely on an individually unique but fixed series of temporally and spatially linked sites to complete their annual cycle. As a consequence, migratory connectivity will be apparent at a very small scale for individuals, but only at a large scale for a population, and juveniles are predicted to occur more often at less suitable sites than adults, so that survival will be lower for juveniles. Migratory connectivity will arise only through spatial and temporal autocorrelation with local environmental constraints, particularly on passage, and the distribution and age structure of the population may reflect past environmental constraints. At least some juveniles will discover suitable habitat that they may re‐use as adults, thus promoting overall population‐level resilience to environmental change, and suggesting value in site‐based conservation. However, because migratory connectivity only acts on a large scale, any population of migrants will contain individuals that encounter a change in suitability somewhere in their non‐breeding range, so affecting average survival. Differences in population trends will therefore reflect variation in local breeding output added to average survival from wintering and staging areas. The latter is likely to be declining given increasing levels of environmental degradation throughout Africa. Large‐scale migratory connectivity also has implications for the evolutionary ecology of migrants, generally because this is likely to lead to selection for generalist traits.     

Characteristics of Agrobacterium tumefaciens auxotrophic mutant infectivity

Lippincott, Barbara B. (Northwestern University, Evanston, Ill.), and James A. Lippincott. Characteristics of Agrobacterium tumefaciens auxotrophic mutant infectivity. J. Bacteriol. 92:937-945. 166.-Mutants of Agrobacterium tumefaciens auxotrophic for adenine, methionine, or asparagine are less infectious than the wild-type strain B6 from which they were derived and show increased infectivity on pinto bean leaves when the specific compounds required for growth of the mutants are added to the infected leaf. Reversion to a prototrophic form of nutrition is accompanied by increased infectivity. Tumors initiated by these auxotrophic mutants are shown to arise only at large wound sites where nutritional conditions may be less restricting. The data indicate that, after inoculation, the bacteria pass through a phase in which host-supplied nutrients are utilized for the production of one or more factors necessary for successful tumor initiation.     

Determination of an optimal potential window for catalysis by E. coli dimethyl sulfoxide reductase and hypothesis on the role of Mo(V) in the reaction pathway

Protein film voltammetry (PFV) of Escherichia coli dimethyl sulfoxide (DMSO) reductase (DmsABC) adsorbed at a graphite electrode reveals that the catalytic activity of this complex Mo-pterin/Fe-S enzyme is optimized within a narrow window of electrode potential. The upper and lower limits of this window are determined from the potential dependences of catalytic activity in reducing and oxidizing directions; i.e., for reduction of DMSO (or trimethylamine-N-oxide) and oxidation of trimethylphosphine (PMe(3)). At either limit, the catalytic activity drops despite the increase in driving force: as the potential is lowered below -200 mV (pH 7.0-8.9), the rate of reduction of DMSO decreases abruptly, while for PMe(3), an oxidative current is observed that vanishes as the potential is raised above +20 mV (pH 9.0). Analysis of the waveshapes reveals that both activity thresholds result from one-electron redox reactions that arise, most likely, from groups within the enzyme; if so, they represent "switches" that reflect the catalytic mechanism and may be of physiological relevance. The potential window of activity coincides approximately with the appearance of the Mo(V) EPR signal observed in potentiometric titrations, suggesting that crucial stages of catalysis are facilitated while the active site is in the intermediate Mo(V) oxidation state.     

Ecological studies on algal-lysing bacteria in fresh waters

Algal-iysing bacteria are present in five lochs, two reservoirs, one sewage works and five alkaline soils whieh were examined. Nine out of thirty-six isolates have been studied in detail and all are gram-negative non-fruiting myxobaeteria. All are aero-philic, require a neutral or alkaline pH (optimum 7.0–9.0) for good growth, have temperature optima of 28–37°C, require contact with the host for lysis to oecur, and are so similar in morphology and host range that they all appear to be strains of a single genus. They lyse all bloom-forming Cyanophyeeae on whieh they have been tested, including species of Anabaena, Aphanizomenon, Gloeotrichia, Microcystis and Oscillatoria. Their abundance is usually correlated direetly with the abundance of Cyanophyeeae in eutrophic waters and it is probable that in most ecosystems the algae and the bacteria co-exist, although if the equilibrium changes markedly as a result of change in environmental conditions situations may arise where the bacteria may play an important role in the lysis of algal blooms. The available evidence suggests, however, that this is likely to be a rare occurrence in natural ecosystems.     

The challenge of pollen analysis in palaeoenvironmental studies of hominid beds: the record from Sterkfontein caves

The search for pollen in carbonate-rich sediments from the hominid site Sterkfontein has been justified because previous investigations suggested that although pollen contamination is a problem, speleothems (e.g. travertines and stalagmites) are most likely to contain reliable assemblages. The new results confirm that, although they have some potential, most sediment types from the site, even speleothems, are usually not suitable for analysis and that they contain very low concentrations of pollen, if any. The extraction of pollen from them is complicated by the problem of contamination from the modern environment. Such contamination has shown up in many previous investigations at this and similar sites and judging from published literature, its significance has not been fully appreciated. Cave palynology can be a very valuable tool in palaeoenvironmental research but the caveats associated with palynology of different sediment types especially carbonate impregnated sediments must be emphasized.