Multivariate study of lice (Insecta: Psocodea: Phthiraptera) assemblages hosted by hummingbirds (Aves: Trochilidae)

Lice were collected from 579 hummingbirds, representing 49 species, in 19 locations in Brazil, Costa Rica, Honduras, Paraguay and Peru, at elevations 0–3000 m above sea level. The following variables were included in an ecological analysis (1) host species' mean body mass, sexual size dimorphism, sexual dichromatism, migratory behaviour and dominance behaviour; (2) mean elevation, mean and predictability of temperature, mean and predictability of precipitation of the host species' geographic area; (3) prevalence and mean abundance of species of lice as measures of infestation. Ordination methods were applied to evaluate data structure. Since the traits are expressed at different scales (nominal, interval and ratio), a principal component analysis based on d-correlations for the traits and a principal coordinates analysis based on the Gower index for species were applied. Lice or louse eggs were found on 80 (13.8%) birds of 22 species. A total of 267 lice of 4 genera, Trochiloecetes, Trochiliphagus, Myrsidea and Leremenopon, were collected, with a total mean intensity of 4.6. There were positive interactions between migration behaviour and infestation indices, with elevational migrants having a higher prevalence and abundance of lice than resident birds. Further, we found weak negative correlations between host body mass and infestation indices and positive correlations between mean elevation and prevalence and abundance of Trochiliphagus. Thus, formerly unknown differences in the ecological characteristics and infestation measures of Trochiliphagus and Trochiloecetes lice were revealed, which allows a better understanding of these associations and their potential impacts on hummingbirds.

Coevolutionary stability of host-symbiont systems with mixed-mode transmission

The coevolution of hosts and symbionts based on virulence and mode of transmission is a complex and diverse biological phenomenon. We introduced a conceptual model to study the stable coexistence and coevolution of an obligate symbiont (mutualist or parasite) with mixed-mode transmission and its host. Using an age-structured Leslie model for the host, we demonstrated how the obligate symbiont could modify the host's life history traits (survival and fecundity) and the long-term growth rate of the infected lineage. When the symbiont is vertically transmitted, we found that the host and its symbiont could maximize the infected lineage's evolutionary success (multi-level selection). Our model showed that symbionts' effect on host longevity and reproduction might differ, even be opposing, and their net effect might often be counterintuitive. The evolutionary stability of the ecologically stable coexistence was analyzed in the framework of coevolutionary dynamics. Moreover, we found conditions for the ecological and evolutionary stability of the resident host-symbiont pair, which does not allow invasion by rare mutants (each mutant dies out by ecological selection). We concluded that, within the context of our simplified model conditions, a host-symbiont system with mixed-mode transmission is evolutionarily stable unconditionally only if the host can maximize the Malthusian parameters of the infected and non-infected lineages using the same strategy. Finally, we performed a game-theoretical analysis of our selection situation and compared two stability definitions.

Definitions of parasitism, considering its potentially opposing effects at different levels of hierarchical organization

An annotated synthesis of textbook definitions of parasitism is presented. Most definitions declare parasitism is a long-lasting relationship between individuals of different species harming the hosts. The infection-induced costs are interpreted as diseases in the medical-veterinary literature. Alternatively, evolutionary ecologists interpret it as a reduction of host's fitness (longevity, fertility or both). Authors often assume that such effects decrease host population growth and select for antiparasitic defences, which is not necessarily true because infections may simultaneously express opposite effects at different levels of biological organization. (i) At the cellular level, infection-induced cell growth, longevity and multiplication may yield tumours maladaptive at higher levels. (ii) At the individual level, reduced host longevity, fertility or both are interpreted as disease symptoms or reduced fitness. (iii) Contrary to common sense, the growth rate of infected host lineages may increase in parallel with the individuals' reduced survival and fertility. This is because selection favours not only the production of more offspring but also their faster production. (iv) Finally, infections that reduce host individuals' or lineages' fitness may still increase infected host populations' growth rate in the context of ecological competition. Therefore, differences between parasitism and mutualism may depend on which level of organization one focuses on.

Relationship between body size and sexual size dimorphism in syringophilid quill mites

A positive relationship of body size and sexual size dimorphism (males’ size relative to females), called Rensch’s rule, is often observed in comparisons within non-parasitic taxa. However, this allometric relationship has rarely been tested in comparisons across closely related parasite species. Since male sexual rivalry is often regarded as the main cause of this phenomenon, the present study tests this rule in a taxon where sexual selection is almost totally absent in males. Body size data of (non-physogastric) female and male quill mites (Acari: Syringophilidae) were gathered from the literature to investigate this relationship. The data set consisted of 113 species representing 8 genera. For the data set as a whole, increasing body size came together with decreasing relative body size of males (relative to females), a phenomenon known as converse Rensch’s rule. Repeating the same analysis for the 8 genera separately, similar patterns were found in 4 significant and 3 non-significant cases. There was a significant tendency to comply with Rensch’s rule only in one genus, the Neoaulonastus. Thus, converse Rensch’s rule is the primary trend in syringophilid quill mites that appears repeatedly and independently in several genera. This phenomenon is probably caused by their extreme inbreeding, which strongly reduces sexual competition among males in this taxon.

Genetic status of lowland-type Racka sheep colour variants

Lowland-type Racka is an indigenous sheep breed that beside Hungarian Grey cattle and Mangalitza pig is one of the national symbols of Hungary. However, the genetic description of Racka sheep has not yet been conducted based on whole-genome screening. By using the Geneseek Ovine SNP50 BeadChip, we have sampled the genome of 126 Black and 128 White Racka sheep. For comparative purposes, we used 134 Hungarian Merinos and further 3345 animals from 81 different breeds have been included from an available database. Performance of a multidimensional scaling plot showed that White and Black Rackas represent well-separated groups among other sheep breeds and clustered separately from each other. However, the number and total length of Runs of Homozygosity was similar to other sheep breeds, except Soay. The inbreeding coefficients (method-of-moments relatedness F coefficient) of Black and White Racka were 0.147 and 0.133, respectively. Based on multidimensional scaling and admixture analyses and on comparisons of genetic distances of the investigated 84 populations, we suggest considering the colour variants of Racka as genetically differentiated breeds. The most differentiated markers between Black and White Racka highlight several candidate genes including 5-Hydroxytryptamine Receptor 5A, Insulin Induced Gene 1, Cyclin Dependent Kinase 5 and Melanocortin 1 Receptor. The results of this study help the recognition of Racka as a unique genetic resource among sheep and pave the way of application of genome screens to guide the resolution of questions arising among breeders.

Sex interacts with age-dependent change in the abundance of lice-infesting Amur Falcons (Falco amurensis)

Sex-biassed and age-biassed parasite infections are common in nature, including ectoparasites-vertebrate host systems. We investigated the effect of Amur Falcons’ sex, age and body size on the abundance of their lice at a migratory stopover site, where the falcons’ habitat use and behaviour are more homogeneous across sex and age categories than during the breeding season. We sampled Amur Falcons in Nagaland, India at major roosting sites in 2016. We applied generalized linear models (with negative binomial distribution and log-link) to model the abundance of their two most numerous lice (Colpocephalum subzerafae and Degeeriella rufa) using the host age category (juvenile or adult) and wing length, both in interaction with sex, as explanatory variables. The abundance of C. subzerafae was only affected by host age, being nearly four times higher on juveniles than on adults. Juveniles were also more infested with D. rufa than the adults. Additionally, the abundance of the latter species was lower on adult male Falcons as compared to adult females. A juvenile bias in ectoparasite infestations is common in nature, probably due to juveniles being immunologically naïve, more resource-limited and may be inexperienced in body maintenance behaviours like preening and grooming. On the other hand, female-biassed infestations are much rarer than male-biassed infestations. We briefly discuss the possible causes of female-biassed infestations on Amur Falcons reported here, and in the closely related Red-footed Falcon and Lesser Kestrel as reported in the literature.

Sex-dependent changes in the louse abundance of red-footed falcons (Falco vespertinus)

Permanent ectoparasites live in stable environments; thus, their population dynamics are mostly adapted to changes in the host life cycle. We aimed to investigate how static and dynamic traits of red-footed falcons interplay with the dynamics of their louse subpopulations during breeding and how they affect the colonisation of new hosts by lice. We sampled red-footed falcon (Falco vespertinus) nestlings (two breeding seasons) and adults (one breeding season) in southern Hungary. The mean abundance of Colpocephalum subzerafae and Degeeriella rufa lice on the nestlings was modelled with generalized linear mixed models using clutch size and host sex in interaction with wing length. For adults, we used wing length and the number of days after laying the first egg, both in interaction with sex. D. rufa abundances increased with the nestlings' wing length. In one year, this trend was steeper on females. In adult birds, both louse species exhibited higher abundances on females at the beginning, but it decreased subsequently through the breeding season. Contrarily, abundances were constantly low on adult males. Apparently, D. rufa postpones transmission until nestlings develop juvenile plumage and choose the more feathered individual among siblings. The sexual difference in the observed abundance could either be caused by the different plumage, or by the females' preference for less parasitized males. Moreover, females likely have more time to preen during the incubation period, lowering their louse burdens. Thus, sex-biased infestation levels likely arise due to parasite preferences in the nestlings and host behavioural processes in the adult falcons.

Rensch's rule in avian lice: contradictory allometric trends for sexual size dimorphism

Rensch’s rule (RR) postulates that in comparisons across closely related species, male body size relative to female size increases with the average size of the species. This holds true in several vertebrate and also in certain free-living invertebrate taxa. Here, we document the validity of RR in avian lice using three families (Philopteridae, Menoponidae, and Ricinidae). Using published data on the body length of 989 louse species, subspecies, or distinct intraspecific lineages, we applied phylogenetic reduced major axis regression to analyse the body size of females vs. males while accounting for phylogenetic non-independence. Our results indicate that philopterid and menoponid lice follow RR, while ricinids exhibit the opposite pattern. In the case of philopterids and menoponids, we argue that larger-bodied bird species tend to host lice that are both larger in size and more abundant. Thus, sexual selection acting on males makes them relatively larger, and this is stronger than fecundity selection acting on females. Ricinids exhibit converse RR, likely because fecundity selection is stronger in their case.

Biostatistics for Parasitologists - A Primer to Quantitative Parasitology

The aggregated distributions of host-parasite systems require several different infection parameters to characterize them. We advise readers how to choose infection indices with clear and distinct biological interpretations, and recommend statistical tests to compare them across samples. A user-friendly and free software is available online to overcome technical difficulties.

Co-infections in Visceral Pentastomiasis, Democratic Republic of the Congo

Results of PCR and histology indicate this infection is endemic to this country.

Snakeborne Armillifer pentastomiasis is an emerging human parasitic infection in rural tropical areas where snake meat is eaten. After a series of severe ocular A. grandis larval infections and anecdotal abdominal infection in Sankuru District, Democratic Republic of the Congo, during 2014–2015, we systematically investigated possible pentastomid etiology in patients who underwent surgery in the region. Histologic and molecular analyses by established pentastomid 18S rDNA- and newly developed Armillifer-specific cytochrome oxidase PCRs revealed larval pentastomid lesions in 3.7% of patients. Some persons had A. armillatus and A. grandis co-infections. Another pentastomid larva, Raillietiella sp., was molecularly detected in 1 patient who had concomitant A. grandis and A. armillatus infection. The PCRs used were suitable for detecting pentastomid species even in highly necrotic tissues. Phylogenetic analyses of Armillifer cytochrome oxidase genes detected multiple local strains.

Armillifer-Infected Snakes Sold at Congolese Bushmeat Markets Represent an Emerging Zoonotic Threat

African pythons (Pythonidae) and large vipers (Bitis spp.) act as definitive hosts for Armillifer armillatus and Armillifer grandis parasites (Crustacea: Pentastomida) in the Congo Basin. Since the proportion of snakes in bushmeat gradually increases, human pentastomiasis is an emerging zoonotic disease. To substantiate the significance of this threat, we surveyed snakes offered for human consumption at bushmeat markets in the Kole district, Democratic Republic of the Congo, for the presence of adult pentastomids. In Bitis vipers (n = 40), Armillifer spp. infestations exhibited an 87.5% prevalence and 6.0 median intensity. Parasite abundance covaried positively with viper length, but not with body mass. In pythons (n = 13), Armillifer spp. exhibited a 92.3% prevalence and 3.5 median intensity. The positive correlations between parasite abundance and python length or mass were statistically nonsignificant. Ninety-one percent of A. grandis were discovered in vipers and 97% of infected vipers hosted A. grandis, whereas 81% of A. armillatus specimens were found in pythons and 63% of infected pythons hosted A. armillatus. Thus, challenging the widespread notion of strict host specificity, we found 'reversed' infections and even a case of coinfection. In this study, we also gathered information about the snake consumption habits of different tribal cultures in the area. Infective parasite ova likely transmit to humans directly by consumption of uncooked meat, or indirectly through contaminated hands, kitchen tools or washing water.

The evolutionary logic of sepsis

The recently proposed Microbiome Mutiny Hypothesis posits that members of the human microbiome obtain information about the host individuals' health status and, when host survival is compromised, switch to an intensive exploitation strategy to maximize residual transmission. In animals and humans, sepsis is an acute systemic reaction to microbes invading the normally sterile body compartments. When induced by formerly mutualistic or neutral microbes, possibly in response to declining host health, sepsis appears to fit the 'microbiome mutiny' scenario except for its apparent failure to enhance transmission of the causative organisms. We propose that the ability of certain species of the microbiome to induce sepsis is not a fortuitous side effect of within-host replication, but rather it might, in some cases, be the result of their adaptive evolution. Whenever host health declines, inducing sepsis can be adaptive for those members of the healthy human microbiome that are capable of colonizing the future cadaver and spread by cadaver-borne transmission. We hypothesize that such microbes might exhibit switches along the 'mutualist - lethal pathogen - decomposer - mutualist again' scenario, implicating a previously unsuspected, surprising level of phenotypic plasticity. This hypothesis predicts that those species of the healthy microbiome that are recurring causative agents of sepsis can participate in the decomposition of cadavers, and can be transmitted as soil-borne or water-borne infections. Furthermore, in individual sepsis cases, the same microbial clones that dominate the systemic infection that precipitates sepsis, should also be present in high concentration during decomposition following death: this prediction is testable by molecular fingerprinting in experimentally induced animal models. Sepsis is a leading cause of human death worldwide. If further research confirms that some cases of sepsis indeed involve the 'mutiny' (facultative phenotypic switching) of normal members of the microbiome, then new strategies could be devised to prevent or treat sepsis by interfering with this process.

Size matters for lice on birds: Coevolutionary allometry of host and parasite body size

Body size is one of the most fundamental characteristics of all organisms. It influences physiology, morphology, behavior, and even interspecific interactions such as those between parasites and their hosts. Host body size influences the magnitude and variability of parasite size according to Harrison's rule (HR: positive relationship between host and parasite body sizes) and Poulin's Increasing Variance Hypothesis (PIVH: positive relationship between host body size and the variability of parasite body size). We analyzed parasite-host body size allometry for 581 species of avian lice (∼15% of known diversity) and their hosts. We applied phylogenetic generalized least squares (PGLS) methods to account for phylogenetic nonindependence controlling for host and parasite phylogenies separately and variance heterogeneity. We tested HR and PIVH for the major families of avian lice (Ricinidae, Menoponidae, Philopteridae), and for distinct ecological guilds within Philopteridae. Our data indicate that most families and guilds of avian lice follow both HR and PIVH; however, ricinids did not follow PIVH and the "body lice" guild of philopterid lice did not follow HR or PIVH. We discuss mathematical and ecological factors that may be responsible for these patterns, and we discuss the potential pervasiveness of these relationships among all parasites on Earth.

Avian Haemosporidian blood parasite infections at a migration hotspot in Eilat, Israel

Haemosporidian blood parasites are frequent amongst passerines. Though they often do not cause detectable consequences to host health, however, their presence or absence and also their prevalence across host populations may potentially carry meaningful information about the health, stress, body condition and viability of bird individuals or populations. The study of migratory birds captured in Eilat, Israel, allowed us to evaluate the prevalence of blood parasite infections in a wide range of both migrant and resident species in spring (N = 1,950) and autumn (N = 538) of 2004 and 2005. According to blood film microscopy, Haemoproteus spp. and Leucocytozoon spp. were more prevalent in the spring than in the autumn (0.289, 0.082 vs. 0.132, 0.033, respectively), whilst Plasmodium spp. exhibited a slight opposite trend (0.034, 0.056). All other parasites (such as trypanosomes, microfilaria and haemococcidians) were rare. During the spring seasons, prevalences were significantly higher in migrant than in resident species, whilst this difference was only marginally significant in the autumn. Given that Eilat is a migration hotspot for several Palearctic passerine species, the present descriptive study may hopefully serve to set the baseline values for future long-term epidemiological monitoring.

Distribution of the myrmecoparasitic fungus Rickia wasmannii (Ascomycota: Laboulbeniales) across colonies, individuals, and body parts of Myrmica scabrinodis

The ant species Myrmica scabrinodis plays a markedly important ecological role through much of the humid grasslands of Eurasia. It hosts a species-rich community of pathogens and parasites, including Rickia wasmannii, an enigmatic member of entomoparasitic laboulbenialean fungi. This study provides a descriptive ecology of R. wasmannii by characterizing its prevalence and distribution across several hierarchical levels: colonies, individuals, and anatomic body parts. Infections were restricted to a single ant species, M. scabrinodis, and infected colonies occurred predominantly in wet habitats. Infections tended to be highly prevalent within infected colonies, often reaching 100% sample prevalence among workers. Individual infections exhibited an aggregated distribution typical to host-parasite systems. Workers from the aboveground part of nests (presumably older ones acting as foragers) were more infected than those from the belowground part. Fungal thalli could be found all over the body of the hosts, the head and the abdomen being the most infected parts of the body. The fungi's distribution among host body parts statistically differed between low versus high-intensity infections: the initial dominance of the head decreased with advancing infection. These findings may provide baseline data for future comparative or monitoring studies.

Comparing radio-tracking and visual detection methods to quantify group size measures

1. Average values of animal group sizes are prone to be overestimated in traditional field studies because small groups and singletons are easier to overlook than large ones. This kind of bias also applies for the method of locating groups by tracking previously radio-collared individuals in the wild. If the researcher randomly chooses a collared animal to locate a group to visit, a large group has higher probability to be selected than a small one, simply because it has more members.

2. The question arises whether location of groups by means of finding collared animals has smaller or greater bias than searching for groups by visual observation. If the bias is smaller or same, this method can be recommended for finding groups. However, such a comparison cannot be made by speculation, only by empirical investigation.

3. The present study compares the two methods empirically, by statistically comparing group size measures (mean, median, quantiles, frequency distribution, and ‘typical group size’) between two data sets. These data sets comprise of Rocky Mountain mule deer group size values collected in the same area during the same period of time, referring either to groups located by the traditional ‘search and observe method’ or located by tracking formerly collared individuals.

4. All group size measures are statistically similar in the two samples, thus we conclude that the two methods yielded similar biases. Although the true group size measures are not known, we presume that both methods have overestimated them. We propose that these results do not necessary apply to other species, thus cannot be generalized. The reason for this is that bias may depend on factors specific to the species: bias of visual observation may depend on how well the species conceals itself in the existing habitat, and the bias associated with finding groups using collared animals is likely dependent on group size distribution and also on the proportion of collared animals in the population.

The microbiome mutiny hypothesis: can our microbiome turn against us when we are old or seriously ill?

Background

The symbiotic organisms of the healthy microbiome tend to be harmless or even beneficial for the host; however, some symbionts are able to adjust their virulence in response to external stimuli. Evolutionary theory suggests that optimal virulence might increase if the mortality of the host (from unrelated causes) increases.

Presentation of the hypothesis

We hypothesize that microorganisms of the human microbiome may be capable of a coordinated phenotypic switch to higher virulence (“microbiome mutiny”) in old or seriously ill people, to optimize their transmission under the conditions of increased background mortality. This proposed virulence shift might contribute to the death of old or seriously ill people even in the absence of apparent disease.

Testing the hypothesis

Testable predictions of the hypothesis include increased expression of virulence factors in isolates of the same species of the microbiome obtained from ailing/old versus healthy/young individuals, and the existence of microbial mechanisms to assess the general condition (background mortality) of the host. Such tests are going to be important to distinguish the cases of “microbiome mutiny” from the situation where opportunistic infections or increased effective virulence arise from relaxed immune control in ailing or old individuals in the absence of changes in the symbionts/pathogens.

Implications of the hypothesis

Elucidating this potential mechanism might open up new possibilities for the clinical management of age related health issues and critical injuries or disease. Targeted prophylaxis against the microbes capable of virulence shifts could break the harmful feedback loop between deteriorating health and the “mutiny” of the microbiome.

Reviewers

This article was reviewed by Eugene V Koonin, Neil Greenspan and Michael Gilchrist.

Ocular pentastomiasis in the Democratic Republic of the Congo

Ocular pentastomiasis is a rare infection caused by the larval stage of pentastomids, an unusual group of crustacean-related parasites. Zoonotic pentastomids have a distinct geographical distribution and utilize reptiles or canids as final hosts. Recently, an increasing number of human abdominal infections have been reported in Africa, where pentastomiasis is an emerging, though severely neglected, tropical disease. Here we describe four ocular infections caused by pentastomids from the Democratic Republic of the Congo. Two cases underwent surgery and an Armillifer grandis infection was detected by morphological and molecular approaches. Thus far, 15 other cases of ocular pentastomiasis have been reported worldwide. Twelve cases were caused by Armillifer sp., recorded almost exclusively in Africa, where such infections occur as a consequence of hunting and consuming snakes, their final hosts. Seven further cases were caused by Linguatula serrata, a cosmopolitan pentastomid whose final hosts are usually canids. Intraocular infections caused permanent visual damage in 69% and a total loss of vision in 31% of reported cases. In contrast, ocular adnexal cases had a benign clinical course. Further research is required to estimate the burden, therapeutic options and pathogenesis of this neglected disease.

Langevin spin dynamics based on ab initio calculations: numerical schemes and applications

A method is proposed to study the finite-temperature behaviour of small magnetic clusters based on solving the stochastic Landau-Lifshitz-Gilbert equations, where the effective magnetic field is calculated directly during the solution of the dynamical equations from first principles instead of relying on an effective spin Hamiltonian. Different numerical solvers are discussed in the case of a one-dimensional Heisenberg chain with nearest-neighbour interactions. We performed detailed investigations for a monatomic chain of ten Co atoms on top of a Au(0 0 1) surface. We found a spiral-like ground state of the spins due to Dzyaloshinsky-Moriya interactions, while the finite-temperature magnetic behaviour of the system was well described by a nearest-neighbour Heisenberg model including easy-axis anisotropy.

Relativistic and thermal effects on the magnon spectrum of a ferromagnetic monolayer

A spin model including magnetic anisotropy terms and Dzyaloshinsky-Moriya interactions is studied for the case of a ferromagnetic monolayer with C2v symmetry like Fe/W(110). Using the quasiclassical stochastic Landau-Lifshitz-Gilbert equations, the magnon spectrum of the system is derived using linear response theory. The Dzyaloshinsky-Moriya interaction leads to asymmetry in the spectrum, while the anisotropy terms induce a gap. It is shown that, in the presence of lattice defects, both the Dzyaloshinsky-Moriya interactions and the two-site anisotropy lead to a softening of the magnon energies. Two methods are developed to investigate the magnon spectrum at finite temperatures. The theoretical results are compared to atomistic spin dynamics simulations and good agreement is found between them.

Avian brood parasitism and ectoparasite richness-scale-dependent diversity interactions in a three-level host-parasite system

Brood parasitic birds, their foster species and their ectoparasites form a complex coevolving system composed of three hierarchical levels. However, effects of hosts' brood parasitic life-style on the evolution of their louse (Phthiraptera: Amblycera, Ischnocera) lineages have never been tested. We present two phylogenetic analyses of ectoparasite richness of brood parasitic clades. Our hypothesis was that brood parasitic life-style affects louse richness negatively across all avian clades due to the lack of vertical transmission routes. Then, narrowing our scope to brood parasitic cuckoos, we explored macroevolutionary factors responsible for the variability of their louse richness. Our results show that taxonomic richness of lice is lower on brood parasitic clades than on their nonparasitic sister clades. However, we found a positive covariation between the richness of cuckoos' Ischnoceran lice and the number of their foster species, possibly due to the complex and dynamic subpopulation structure of cuckoo species that utilize several host species. We documented diversity interactions across a three-level host parasite system and we found evidence that brood parasitism has opposing effects on louse richness at two slightly differing macroevolutionary scales, namely the species richness and the genera richness.

Clever birds are lousy: co-variation between avian innovation and the taxonomic richness of their amblyceran lice

Lice (Insecta: Phthiraptera) are ectoparasites that reduce host life expectancy and sexual attractiveness. Their taxonomic richness varies considerably among their hosts. Previous studies have already explored some important factors shaping louse diversity. An unexplored potential correlate of louse taxonomic richness is host behavioural flexibility. In this comparative study, we examine the relationship between louse generic richness, innovative capabilities (as a proxy for behavioural flexibility), and brain size while controlling for host species diversity, phylogeny, body size and research effort. Using data for 108 avian families, we found a highly significant positive relationship between host innovative capabilities and the taxonomic richness of amblyceran lice, but a lack of a similar relationship in ischnoceran lice. Host brain size had only a marginal impact on amblyceran diversity and no correlation with ischnoceran diversity. This suggests that the effect in Amblycera is not mediated by metabolic limitations due to the energetic costs of brain size and maintenance, rather directly caused by the ecological differences between hosts with differing cognitive capabilities. We propose four alternative and mutually non-exclusive hypotheses that may explain this phenomenon.

Demographic correlates of sexual size dimorphism and male genital size in the lice Philopterus coarctatus

Sexual selection is an influential agent of evolution, often shaping the sex ratio, sexual size dimorphism (SSD), and genital size in animals. To explore its effects in ectoparasites, we quantified SSD and male genital size in relation to intensity and sex ratio across subpopulations of Philopterus coarctatus, a philopterid louse of the great grey shrike. SSD was calculated separately for the width and length of the head and abdomen. Presuming that sexual selection affects the evolution of avian lice, we would expect that infestation intensities should covary with sex ratio, relative male size, and relative male genital size, either positively or negatively depending upon presumptions. Contrary to former studies, there was a weak negative relationship between infestation intensity and sex ratio. The relative width of male abdomens exhibited a highly significant negative interaction with the intensity of infestations. In contrast, sex ratio did not predict any of the dimorphism measures. Similarly, male genital size did not covary with the intensity of infestations or sex ratios. These findings may indicate that intensity covaries positively with levels of inbreeding in this species, suggesting that more-inbred subpopulations, wasting less energy for sexual rivalry, can multiply more intensively. Thus, small subpopulations have more frequent males which also possess larger abdomens. Alternatively, however, the same pattern may also arise due to male-biased starvation in overcrowded habitats; thus, males are rarer and have smaller abdomens in larger infrapopulations.

A psychochemical weapon considered by the Warsaw Pact: a research note

Contrary to widespread rumours during the Cold War era, little, if any, evidence existed in the scientific literature to support the view that the Soviet Union or its Warsaw Pact allies considered the use of psychochemical weapons militarily. The Hungarian State Archives have recently opened up declassified records of Hungary's State Defence Council meetings held between 1962 and 1978. Materials submitted to the Council include reports about the coordinative meetings of the Warsaw Pact military medical services. Research into possible countermeasures against psychotropic drugs is listed as a research priority assigned to Hungary in 1962. Hungary rejected this task in 1963, but joined the ongoing project again in 1965. Methylamphetamine was produced in Budapest for use as an experimental model of such weapons. Within the context of contemporary western research, this drug was considered to be an effective interrogation tool. Similarly to the CIA, Hungary also failed to develop an antidote against it and the project was terminated, fruitlessly, in 1972. These documents serve as evidence that a Warsaw Pact forum had, in fact, been considering a psychochemical weapon as a "warfare agent."

The rise of non-adaptive intelligence in humans under pathogen pressure

Cleverness made our species the most successful primate on Earth, thus claiming that human intelligence is adaptive sounds to be a triviality. Not surprisingly, when establishing long-lasting pair-bonds, humans exhibit mate preferences in favour of clever partners, apparently to increase the chance that their offspring will be as clever as possible. Contrary to this well-established view, here I argue that the adaptive nature of human intelligence has never been proven in a strict evolutionary sense. Furthermore, the exceptional rise of intelligence in our species (and the lack of comparable phenomena in other apes) is best explained within the context of the Hamilton-Zuk Hypothesis. Apparently, humans have been subjected to an exceptionally strong selection pressure exerted by pathogens and parasites, and the human brain is particularly vulnerable to infections, thus cleverness is an ideal character to signal heritable genetic resistance against infections. In this scenario, human preference for intelligent mates is to increase the offspring's resistance against pathogens. Among other phenomena, this hypothesis can explain why humans enjoy wasting most of their intellectual capabilities for totally useless purposes, why prehistoric humans developed brains that made them potentially far more intelligent than required by their physical environment, and why we experience a continuous increase of human intelligence even in modern societies. Briefly, I argue that (1) human sexual selection favours intelligence as a signal of genetic resistance against pathogens, and (2) that intelligence enabled the rise of our species (in terms of population size and distribution) as an accidental side-effect.

Reduced Taxonomic Richness of Lice (Insecta: Phthiraptera) in Diving Birds

Avian lice occupy different habitats in the host plumage that the physical environment outside the host body may affect in several ways. Interactions between host plumage and water may be an important source of such effects. Here, we use a comparative approach to examine the effect of a host's diving behavior on the taxonomic richness of its lice. Louse genera richness was significantly lower in clades of diving birds than on their nondiving sister clades. Species richness of host and body mass did not differ significantly between these clades; thus, these factors did not bias our results. This study suggests that the hosts' diving behavior can effectively influence ectoparasite communities.

Deal in the womb: Fetal opiates, parent-offspring conflict, and the future of midwifery

This paper argues that parent-offspring conflict is mediated by placental beta-endorphins in placental mammals, i.e., foetuses make their mothers endorphin-dependent then manipulate them to increase nutrient allocation to the placenta. This hypothesis predicts that: (1) anatomic position of endorphin production should mirror its presumed role in fetal-maternal conflict; (2) endorphin levels should co-vary positively with nutrient carrying capacity of maternal blood system; (3) postpartum psychological symptoms (postpartum blues, depression and psychosis) in humans are side-effects of this mechanism that can be interpreted as endorphin-deprivation symptoms; (4) shortly after parturition, placentophagia could play an adaptive role in decreasing the negative side-effects of fetal manipulation; (5) later, breast-feeding induced endorphin excretion of the maternal pituitary saves mother from further deprivation symptoms. Finally, whatever the molecular mechanism of fetal manipulation is, widespread and intense medical care (such as caesarean section and use of antidepressants) affects the present and future evolution of mother-foetus conflict in the human species (and also in domestic animals) to increase 'fetal aggressiveness' and thus technology-dependency of reproduction.

PROPERTIES OF CROWDING INDICES AND STATISTICAL TOOLS TO ANALYZE PARASITE CROWDING DATA

Crowding, i.e., the size of the infrapopulation inhabiting an individual host, is a major component of parasites' environment, which often influences both morphological and life-history characters (the so-called density-dependent characters) in different parasite taxa. Although crowding equals intensity in case of a single parasite individual, mean intensity of the host population does not define mean crowding of the parasite population. Crowding indices are notoriously hard to handle statistically because of the inherently large number of nonindependent values in data. In this study, we aim to investigate the apparently paradox features of crowding indices and to make some proposals and also to introduce statistical methods to calculate confidence intervals and 1-sample and 2-sample tests for mean crowding. All methods described in this study are supported by the freely distributed statistical software Quantitative Parasitology.

Parasite biodiversity and host defenses: chewing lice and immune response of their avian hosts

Antagonistic host-parasite interactions lead to coevolution of host defenses and parasite virulence. Such adaptation by parasites to host defenses may occur to the detriment of the ability of parasites to exploit alternative hosts, causing parasite specialization and speciation. We investigated the relationship between level of anti-parasite defense in hosts and taxonomic richness of two chewing louse suborders (Phthiraptera: Amblycera, Ischnocera) on birds. While Amblyceran lice tend to occur in contact with host skin, feed on host skin and chew emerging tips of developing feathers to obtain blood, Ischnoceran lice live on feathers and feed on the non-living keratin of feather barbules. We hypothesized that Amblyceran abundance and richness would have evolved in response to interaction with the immune system of the host, while Ischnoceran taxonomic richness would have evolved independently of immunological constraints. In an interspecific comparison, the abundance of Ischnocerans was positively related to host body size, while host body mass and Ischnoceran taxonomic richness accounted for the abundance of Amblycerans. Amblyceran taxonomic richness was predicted by the intensity of T-cell mediated immune response of nestling hosts, while the T-cell response of adults had no significant effect. In contrast, Ischnoceran taxonomic richness was not predicted by host T-cell responses. These results suggest that the taxonomic richness of different parasite taxa is influenced by different host defenses, and they are consistent with the hypothesis that increasing host allocation to immune defense increases Amblyceran biodiversity.

Distribution of Carnus hemapterus in a starling colony

The distribution of the haematophagous fly Carnus hemapterus among starling (Sturnus vulgaris) broods was investigated in a nest-box colony. Prevalence of infection was 94% among broods and 69% among individual nestlings, while median abundance was 54 flies per brood (range 0–284 flies; n = 33) and 8 flies per individual nestling (range 0–117 flies; n = 140). Parasites exhibited an aggregated distribution among starling broods. Carnus hemapterus populations changed significantly during the development of nestlings: fly abundance increased rapidly after nestlings hatched, peaked 5–8 days after hatching, and decreased thereafter. The proportion of winged flies (assumed to be the transmissive form) and the proportion of male flies decreased with increasing nestling mass. Measures of within-colony spatial position of nests were not related to mean brood abundance, proportion of winged flies, or sex ratio of the flies. Parasite abundance did not correlate with mortality rate or growth rate of nestlings. In conclusion, nestling developmental stage was the only significant predictor of variation in C. hemapterus populations in this starling colony.

Correlation between central somatosensory conduction time, blood flow velocity, and delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

In this retrospective study of 67 aneurysmal patients, the predictive role of central conduction time (CCT) on vasospasm occurrence evaluated by means of transcranial Doppler sonography (TCD) and the correlation of CCT to blood flow velocity measured simultaneously in postoperative course were studied. Data about the clinical state of patients at the time of admission (Hunt Hess scale), severity of subarachnoidal hemorrhage on initial CT scan (Fisher grade), timing of surgery (acute or delayed), outcome (Glasgow Outcome Scale), severity of vasospasm graded by highest mean blood flow velocity (BFV) during the entire clinical course and CCT values measured at admission (preoperatively), then postoperatively (one day after surgery) and simultaneously with later TCD investigations were collected from the files. Interhemispheric difference of CCT was also calculated. The results showed that CCT at admission was not predictive for vasospasm. CCT measured either at admission or on the first postoperative day did not differ significantly in the different grades of vasospasm. Similar results were obtained in the acute and in the late operated group of patients. The results also suggest that increased CCT and interhemispheric difference at the time of admission indicate a worse prognosis, but this can be related to higher surgical risk rather than to a higher incidence of late ischemic deterioration. Simultaneous CCT and TCD examinations demonstrated that coincident and statistically significant (p < 0.01) increase of actual CCT (6.7 msec) was found only in the severe grade of vasospasm (BFV 200 cm/s). The authors discuss the role of CCT and TCD monitoring in the management of aneurysmal subarachnoid hemorrhage.

Quantifying parasites in samples of hosts

Whereas terminological recommendations require authors to use mean intensity or mean abundance to quantify parasites in a sample of hosts, awkward statistical limitations also force them to use either the median or the geometric mean of these measures when making comparisons across different samples. Here, we propose to reconsider this inconsistent practice by giving priority to biological realism in the interpretation of different statistical descriptors and choosing the statistical tools appropriate to our decisions. Prevalence, mean intensity, and indices of parasite distribution (such as median intensity) are suitable descriptors to quantify parasites in a sample of hosts. These measures have different biological interpretations and need different statistical methods to be compared between samples.

Influencing random transmission is a neutral character in hosts

This study introduces an individual-based model on a host-parasite assemblage to investigate whether hosts are necessarily selected for obstructing the transmission of virulent parasites to conspecifics. Contrary to the widespread notion, a host's ability to influence parasite transmission within the host population is a neutral character provided that parasite transmission routes are random, with no reference to genetic relatedness. Due to a lack of selection pressure under such circumstances, hosts may fail to evolve counteradaptations against manipulations by parasites to enhance transmission. However, vertically biased transmission (biased toward kin) selects hosts for a decrease of parasite transmission, while it is also known to select parasites to decrease virulence. Horizontally biased transmission routes (biased toward nonrelated conspecifics) select hosts to increase parasite transmission. In this case, their interests coincide with that of their virulent parasites in enhancing transmission to conspecifics. This finding yields the predictions that hosts infected by virulent pathogens, but unable to recover from disease, should be prone to emigrate from their natal territories and also to enhance transmission at a distance from their natal ranges. These results may considerably improve our understanding of the epidemiology of contagious pathogens and the evolution of social and sexual behavior in host species.

Host-mediated site segregation of ectoparasites: an individual-based simulation study

Site segregation of coexisting ectoparasite species may result either from a direct interaction such as resource competition between them or from a host-mediated interaction. Here we present an individual-based model for the coevolution of 1 host and 2 parasite species to study this latter hypothesis. Parasite species are generalists at the start of the simulation and develop site specificities under the following assumptions. Parasite populations are not subject to resource limitations but are limited directly by host defense as predation. Hosts have 2 sites that need different defensive abilities to reduce their parasite burden. Parasites need to exhibit different evasive abilities to survive on different sites. Host grooming selects parasites for an increasing capability for evasion, whereas parasites select hosts for an increasing efficiency of grooming. Two trade-offs are incorporated into the model: one between host defensive abilities on the 2 sites, and another between parasite evasive abilities on the 2 sites. We conclude that, under these assumptions, the optimization of host defense and parasite evasion strategies may select ectoparasites for site segregation and this may stabilize the coexistence of parasite species.

Wing-feather mite (Acari: Proctophyllodidae) abundance correlates with body mass of passerine hosts: a comparative study

Data from a 4-year study of wing-feather mites on passerines in Portugal (Behnke et al. 1995. Exp. Appl. Acarol. 19: 443–458) were used to investigate whether avian body mass influences the abundance of mites. When 17 host species were used as statistically independent observations, the mite infestation score correlated positively with avian body mass. This correlation is not a phylogenetic artefact, having been also found when avian phylogeny was controlled for. Three non-exclusive hypotheses might explain this finding: (1) larger birds may provide larger "habitat islands," enabling more mites to coexist; (2) larger birds may provide more topographic refugia for mites to evade host preening; (3) larger birds may provide greater longevity of habitat islands, thus reducing the decimating effects of transmission.

Adaptive sex-ratio manipulation in Pediculus humanus capitis: possible interpretations of Buxton's data

The sex-ratio pattern of an exceptional population of human head lice (collected in the Colombo Prison, Ceylon, in 1934 to 1936) was found to be consistent with a current hypothesis on adaptive sex-ratio manipulation. Data suggest that the louse burdens were isolated and, therefore, small burdens were inbred. Thus, local mate competition favored females that produced offspring with a female bias. This is the first report to suggest that anopluran lice are capable of adaptive sex-ratio manipulation.

Comparison of fullfat soybean, sunflower seed and protected fat as fat supplements for their effect on the performance of growing-finishing bulls and carcass fatty acid composition

One hundred and twelve Holstein bulls (179-203 kg) were allotted to four dietary treatment groups (I: control; II: fullfat soybean diet; III: sunflower seed diet, and IV: protected fat diet) and used in a 120-day comparative feedlot trial to evaluate the effect of toasted fullfat soybean, whole sunflower seed and protected fat (calcium soap) on their weight gain, feed conversion and carcass fatty acid composition. The diets consisted of 45-46% concentrate and 55-54% corn silage. Digestibility, nutritive value as well as degradability were also determined. The apparent digestibility of dry matter, organic matter, N-free extract and crude protein as well as nutritive value were almost similar for the four diets. However, crude fibre, acid detergent fibre (ADF) and neutral detergent fibre (NDF) digestibilities decreased with increasing fat level but the differences were not significant. The inclusion of fullfat soybean or whole sunflower seed significantly (P < 0.05) increased the digestion of fat. Ruminal degradability of protein and dry matter were significantly (P < 0.01) lower for toasted fullfat soybean mixture compared to whole sunflower mixture. The inclusion of toasted fullfat soybean, whole sunflower seed and calcium soap in the diets was not effective in improving the bulls' weight gain or feed conversion in this trial. As both toasted fullfat soybean and whole sunflower seed increased the proportions of C18:1, C18:2 and C18:3 in adipose fat tissue and decreased the proportion of C16:0, they consequently significantly (P < 0.01) increased the ratio of unsaturated fatty acids. Whole sunflower seed was more effective than fullfat soybean. However, inclusion of the calcium soap had no effect on the fatty acid profiles in the present study.

An experimental test of the site specificity of preening to control lice in feral pigeons

Site specificities of ectoparasites on the host may have evolved due to the selective pressure exerted by host grooming. The present study demonstrates that the efficiency of avian preening varies among sites on the host. The study relies on the simple idea that the effectiveness of preening behavior to control lice can be quantified by the removal rate of dead lice glued onto the feathers of living birds. Two treatments were done to document site-specific differences in the efficiency of preening for louse control. The first treatment showed that lice disappear from the underwing covert feathers significantly more than from the tail feathers. A second treatment showed that preening was responsible for the differential removal of lice. There seems to be some correspondence in the site specificity of the louse species Columbicola columbae and that of the efficiency of preening by the host, which is the feral pigeon (Columba livia).