Light‐induced damage to the dioptric apparatus of nephrops norvegicus (L.) and the quantitative assessment of the damage

In Nephrops norvegicus damage to the compound eye following exposure to excess light is not restricted to the photoreceptor layer, but is followed by morphological changes to the dioptric apparatus. Retinula cell damage results in the disruption of the cone cell processes leading to distal retraction of the crystalline tracts. The shape of the cones is also affected and there is a redistribution of the distal pigments. Within two months of exposure the reflective properties of subcorneal elements are changed and damage may be seen in the intact eye. A method based on external observations of the intact eye has been developed for quantitatively estimating the damage to the dioptric layer. The figures obtained were compared with estimates of retinula cell damage in the same eyes calculated using measurements from serially sectioned material. The estimation of ommatidial damage without recourse to sectioning should be of immediate practical benefit.     

Trickle or clumped infection process? A stochastic model for the infection process of the parasitic roundworm of humans, Ascaris lumbricoides

The importance of the mode of acquisition of infectious stages of directly-transmitted parasitic helminths has been acknowledged in population dynamics models; hosts may acquire eggs/larvae singly in a “trickle” type manner or in “clumps”. Such models have shown that the mode of acquisition influences the distribution and dynamics of parasite loads, the stability of host-parasite systems and the rate of emergence of anthelmintic resistance, yet very few field studies have allowed these questions to be explored with empirical data. We have analysed individual worm weight data for the parasitic roundworm of humans, Ascaris lumbricoides, collected from a three-round chemo-expulsion study in Dhaka, Bangladesh, with the aim of discerning whether a trickle or a clumped infection process predominates. We found that hosts tend to harbour female worms of a similar weight, indicative of a clumped infection process, but acknowledged that unmeasured host heterogeneities (random effects) could not be completely excluded as a cause. Here, we complement our previous statistical analyses using a stochastic infection model to simulate sizes of individual A. lumbricoides infecting a population of humans. We use the intraclass correlation coefficient (ICC) as a quantitative measure of similarity among simulated worm sizes and explore the behaviour of this statistic under assumptions corresponding to trickle or clumped infections and unmeasured host heterogeneities. We confirm that both mechanisms are capable of generating aggregates of similar-sized worms, but that the particular pattern of ICCs described pre- and post-anthelmintic treatment in the data is more consistent with aggregation generated by clumped infections than by host heterogeneities alone. This provides support to the notion that worms may be acquired in clumps. We discuss our results in terms of the population biology of A. lumbricoides and highlight the significance of our modelling approach for the study of the population dynamics of helminth parasites.     

The significance of chelae in the agonistic behaviour of the white‐clawed crayfish,a Ustropotamobius pallipes

As in other benthic decapods, crayfish have chelae that are important for intra‐specific agonistic encounters. In Austropotamobius pallipes, scars and mutilations are present mostly on the chelae, these being the main targets of agonistic contacts. Because males participate in more aggressive interactions than females do and compete with other males for acquiring females in escalating contests, selection for large chelae should be stronger in males. Thus, in A. pallipes (i) chelae are longer, wider and higher in males than in females; (ii) chelar size in males increases allometrically with cephalothorax length; (iii) male specimens are more often deprived of at least one cheliped and (iv) large males have the highest frequency of scars. Males with one regenerated cheliped, when opposed to a competitor with both large chelipeds, display the same motivation to fight, but perform less chelae threat displays than normal crayfish and immediately get a lower hierarchical rank. In these contests, Resource Holding Potential (= chelar size) is highly different between the crayfish and the information of this asymmetry is correctly transferred between the two opponents.     

‘Males second’ strategy in the allocation of sexes by the parasitic wasp,Gryon japonicum

Summary Patterns of the sex ratio allocation of Gryon japonicum (Ashmead) (Hymenoptera: Scelionidae), a solitary egg parasitoid of Riptortus clavatus (Thunberg) (Heteroptera: Alydidae), were investigated in the laboratory, and the result was checked against the field data on the sex composition of the parasitoid. When five host eggs were presented simultaneously to each of the females of G. japonicum in a laboratory experiment, they had a strong tendency to lay a male egg in second host egg and female eggs in the others. However, when four host eggs were presented to each female more than 3 h after the completion of oviposition on a host egg, most of the females laid male eggs in the third oviposition, i.e. the second host eggs after the experimental interruption of oviposition. These results indicated that there was a mechanism for G. japonicum to produce a male egg in the second host egg in consecutive ovipositions, and that the mechanism was reset by more than 3 h intervals of oviposition. By this mechanism, G. japonicum is thought to produce the precise sex ratio in response to the size of a host egg batch. Field data on the size of a host egg batch and the sex composition of the parasitoid in a host egg batch supported this view.     

Trail‐following and trail‐searching behaviour in homing of the intertidal gastropod mollusc,Onchidium verruculatum

When uncovered by the tide, Onchidium verruculatum leaves its place of hiding, grazes on the rock surface, and thèn returns to its own home. Onchidium will follow its own mucus trail, most frequently towards the origin. This behaviour explains homing when the outward path is partly or completely retraced. Sometimes, however, homing occurs without contact with the outward trail. It was observed that trails were followed more closely at low humidities than at high humidities. No evidence was found for any method of orientation other than detection of chemical trials: when displaced onto sand Onchidium tend simply to crawl in a spiral until they contact their own trail. In addition to being a safe retreat, the home provides a fixed starting point to feeding excursions : this may facilitate re‐location of preferred feeding areas.     

Trickle or clumped infection process? An analysis of aggregation in the weights of the parasitic roundworm of humans, Ascaris lumbricoides

Studying the distribution of parasitic helminth body size across a population of definitive hosts can advance our understanding of parasite population biology. Body size is typically correlated with egg production. Consequently, inequalities in body size have been frequently measured to infer variation in reproductive success (VRS). Body size is also related to parasite age (time since entering the definitive host) and potentially provides valuable information on the mode of acquisition and establishment of immature (larval) parasites within the host: whether parasites tend to establish singly or in aggregates. The mode of acquisition of soil-transmitted helminths has been a theoretical consideration in the parasitological literature but has eluded data-driven investigation. In this paper, we analyse individual Ascaris lumbricoides weight data collected from a cohort of human hosts before and after re-infection following curative treatment, and explore its distribution within and among individuals in the population. Lorenz curves and Gini coefficients indicate that levels of weight inequality (a proxy for VRS) in A. lumbricoides are lower than other published estimates from animal-helminth systems. We explore levels of intra-host weight aggregation using statistical models to estimate the intraclass correlation coefficient (ICC) while adjusting for covariates using a flexible fractional polynomial transformation approach capable of handling non-linear functional relationships. The estimated ICCs indicate that weights are aggregated within hosts both at equilibrium and after re-infection, suggesting that parasites may establish within the host in clumps. The implications of a clumped infection process are discussed in terms of ascariasis transmission dynamics, control and anthelmintic resistance.     

Avian predation on a parasitic fly of cervids during winter: can host‐related cues increase the predation risk?

The deer ked (Lipoptena cervi) is an ectoparasitic fly on cervids that has expanded its distribution rapidly in Northern Europe. However, the regulating biotic factors such as predation remain unknown. The host‐independent pupal stage of the fly lasts for several months. Blackish pupae are visible against snow, especially on the bedding sites of hosts, and are thus exposed to predators. To evaluate the role of predation on the invasion dynamics and evolution of L. cervi, we monitored pupal predation on artificial bedding sites in three geographical areas in Finland during winter. We explored: (1) possible predators; (2) magnitude of predation; and (3) whether predation risk is affected by host‐derived cues. We demonstrate that pupae are predated by a number of tit species. Any reddish brown snow discoloration on bedding sites, indicating heavy infestation of the host, serves as an exploitable cue for avian predators, thereby increasing the risk of pupal predation. The ability of tits to use this host‐derived cue seems to be dependent on the prevalence of L. cervi and the period of invasion history, which suggests that it may be a learned behavioural response. Predation by tits may potentially affect the L. cervi population dynamics locally. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 275–286.     

Role of oil‐seed cakes for the management of plant‐parasitic nematodes and soil‐inhabiting fungi on lentil and mungben

The oil‐seed cakes of neem (Azadirachta indica), castor (Ricinus communis), linseed (Linum usitatissimum), groundnut (Arachis hypogaea), mustard (Brassica campestris) and duan (Eruca sativa) were tested for their efficacious nature against plant‐parasitic nematodes and soil‐inhabiting fungi infesting lentil and also on the subsequent crop, mungbean in field trials. The population of plant‐parasitic nematodes such as Meloidogyne incognita, Rotylenchulus reniformis, Tylenchorhynchus brassicae, Helicoty‐lenchus indicus etc., and the frequency of pathogenic fungi Macrophomina phaseolina, Fusarium oxysporum f. lentis, Rhizoctonia solarii, Septoria leguminum, Sclerotium rolfsii, etc., were significantly reduced by the incorporation of oil‐seed cakes, however, the frequency of saprophytic fungi Aspergillus niger, Trichoderma viridae, Penicillium degetatum, etc., was increased. A several‐fold improvement was observed in plant‐growth parameters such as plant weight, percent pollen fertility, pod numbers, chlorophyll content, nitrate reducíase activity in leaves and root‐nodulation. The residual effects of different oil‐seed cakes were also noted in the subsequent crop, mungbean, in the next growing season. The population of plant‐parasitic nematodes and frequency of soil‐inhabiting fungi also influenced by the depth of ploughing.     

Biogeochemical behaviour of Cd, Cu, Pb and Zn in the Scheldt estuary during the period 1981–1983

Cu, Zn, Cd and Pb have been analysed in suspendedmatter and water samples from the Scheldt estuary,collected during five cruises between May 1982 and May1983. In order to evaluate the overall metal behaviourin the estuary, continuous longitudinal profiles ofthe total, the particulate and the dissolved metalconcentrations are discussed in relation to variousspecific physico-chemical parameters. By means ofcorrelation and multi-regression techniques, severalestuarine processes could be identified which dominateand/or control the behaviour of the individual tracemetals in three distinct areas of the Scheldt estuary. The behaviour of the four selected metals was foundto show some common features, but is besides this alsocharacterised by many individual and specificproperties. The total metal concentrations seem toco-vary well with the turbidity in the maximumturbidity zone between salinities 2 and 10 psu. In thedownstream area a dilution profile is observed for thetotal metal concentrations of Cu and Cd as well as forthe dissolved concentrations of all metals. Dissolved metal production rates are high for Cu andCd, but much lower for Zn and Pb, confirming thedifferent longitudinal dissolved metal profiles. ForCu and Cd these dissolved metal profiles arecharacterised by a broad mobilisation area, coveringthe whole middle estuary. Pb on the other hand, showsa more confined mobilisation area, and for Zn no sucharea was found. During winter the dissolved metalproduction rates seem to be controlled, predominantly,by desorption processes. During summer dissolved metalproduction is correlated mainly to the dissolvedoxygen content, suggesting the domination of redoxprocesses solely or in combination with desorptionprocesses. In some cases, co-existent with nearly zerooxygen concentrations, removal of dissolved metals wasobserved, possibly reflecting precipitation reactions. Longitudinal particulate metal profiles all show anegative deviation versus the dilution profile. Cu andCd provide the higher deviations, characterised by anarrow enrichment zone preceding a broad mobilisationarea. Finally, all particulate metal profiles appearedto correlate well with POC, when expressed involumetric units. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hidden diversity in the non‐caryophyllaceous plant‐parasitic members of Microbotryum (Pucciniomycotina: Microbotryales)

Abstract

Members of the fungal genus Microbotryum are well‐known parasites on eudicotyledonous plant hosts. However, recent studies focused exclusively on Microbotryum species being parasites in the anthers of Caryophyllaceae in which strong host‐specificity was confirmed by molecular analyses. Consequently, species numbers have risen considerably as multi‐host parasites were split up in so‐called cryptic species. We subjected three non‐caryophyllaceous Microbotryum groups to molecular phylogenetic analyses to see whether we would confirm multi‐host morphospecies or if host‐specific cryptic species in these selected groups could be revealed as well (i.e. a group of non‐caryophyllaceous anther smuts, parasites on different Fallopia species, and parasites on Polygonum bistorta and Polygonum vi‐viparum). We applied a multiple analysis strategy to correct for varying alignment effects on a two‐locus dataset (ITS and LSU rDNA). The results obtained by the different approaches are uniform; high host‐specificity exists in the non‐ caryophyllaceous anther smuts, but overlapping host ranges occur in the parasites of Fallopia species. Results for the parasites of Polygonum are similar, with Microbotryum bistortarum being separated into three lineages and M. marginale forming a lineage on P. bistorta which apparently is conspecific with M. bistortarum p.p. Our study shows that phylogenetic patterns within Microbotryum are much more complicated than deduced from morphological observations alone. Even though Microbotryum species are highly host‐specific, it is impossible to identify species based solely on host taxa affiliation. Species status is reinstated for the anther smut on Salvia pratensis.     

A comparison of crayfish burrow morphologies: Triassic and Holocene fossil,paleo‐ and neo‐ichnological evidence,and the identification of their burrowing signatures

The architectural and surficial morphologies of crayfish burrows from the Upper Triassic Chinle Formation and Holocene sediments were compared in order to determine: 1) if Triassic burrows could truly be attributed to crayfish activity; 2) how comparable the burrowing mechanisms are; and 3) whether or not a common set of burrowing signatures could be identified for both ancient and modern freshwater crayfish. Materials used in this study include burrows from the members of the Upper Triassic Chinle Formation, casts of modern burrows constructed by Procambarus clarkii Hobbs and Procambarus acutus acutus (Girard) in the laboratory, and casts of naturally constructed modern burrows of Cambarus diogenes di‐ogenes (Girard).

Triassic and Holocene crayfish burrow morphologies exhibit simple to complex architectures, varying degrees of branching, chamber, and chimney development. They also exhibit relatively textured surficial morphologies (bioglyphs) such as scrape and scratch marks, mud‐ and lag‐liners, knobby and hummocky surfaces, pleopod striae, and body impressions. Holocene crayfish construct distinctive burrows due to their conservative limb arrangement, functional morphology, and behavior with respect to environmental stimuli. Similarities between Holocene and Triassic crayfish burrows suggest that extant and Triassic crayfish employed identical burrowing mechanisms. Features of the surficial and architectural morphologies impart a distinctive signature to burrows of both ancient and modern freshwater burrowing crayfish.

Burrowing signatures of crayfish can be used to identify new and previously misinterpreted continental trace fossils. These are useful in studies of the paleohydrogeology, paleoclimatology and paleoecol‐ogy of burrow‐bearing deposits.     

Who is the puppet master? Replication of a parasitic wasp-associated virus correlates with host behaviour manipulation

Many parasites modify their host behaviour to improve their own transmission and survival, but the proximate mechanisms remain poorly understood. An original model consists of the parasitoid Dinocampus coccinellae and its coccinellid host, Coleomegilla maculata; during the behaviour manipulation, the parasitoid is not in contact with its host anymore. We report herein the discovery and characterization of a new RNA virus of the parasitoid (D. coccinellae paralysis virus, DcPV). Using a combination of RT-qPCR and transmission electron microscopy, we demonstrate that DcPV is stored in the oviduct of parasitoid females, replicates in parasitoid larvae and is transmitted to the host during larval development. Next, DcPV replication in the host''s nervous tissue induces a severe neuropathy and antiviral immune response that correlate with the paralytic symptoms characterizing the behaviour manipulation. Remarkably, virus clearance correlates with recovery of normal coccinellid behaviour. These results provide evidence that changes in ladybeetle behaviour most likely result from DcPV replication in the cerebral ganglia rather than by manipulation by the parasitoid. This offers stimulating prospects for research on parasitic manipulation by suggesting for the first time that behaviour manipulation could be symbiont-mediated.     

Age‐related Changes in the Circadian and Homeostatic Regulation of Human Sleep

The reduction of electroencephalographic (EEG) slow‐wave activity (SWA) (EEG power density between 0.75–4.5 Hz) and spindle frequency activity, together with an increase in involuntary awakenings during sleep, represent the hallmarks of human sleep alterations with age. It has been assumed that this decrease in non‐rapid eye movement (NREM) sleep consolidation reflects an age‐related attenuation of the sleep homeostatic drive. To test this hypothesis, we measured sleep EEG characteristics (i.e., SWA, sleep spindles) in healthy older volunteers in response to high (sleep deprivation protocol) and low sleep pressure (nap protocol) conditions. Despite the fact that the older volunteers had impaired sleep consolidation and reduced SWA levels, their relative SWA response to both high and low sleep pressure conditions was similar to that of younger persons. Only in frontal brain regions did we find an age‐related diminished SWA response to high sleep pressure. On the other hand, we have clear evidence that the circadian regulation of sleep during the 40 h nap protocol was changed such that the circadian arousal signal in the evening was weaker in the older study participants. More sleep occurred during the wake maintenance zone, and subjective sleepiness ratings in the late afternoon and evening were higher than in younger participants. In addition, we found a diminished melatonin secretion and a reduced circadian modulation of REM sleep and spindle frequency—the latter was phase‐advanced relative to the circadian melatonin profile. Therefore, we favor the hypothesis that age‐related changes in sleep are due to weaker circadian regulation of sleep and wakefulness. Our data suggest that manipulations of the circadian timing system, rather than the sleep homeostat, may offer a potential strategy to alleviate age‐related decrements in sleep and daytime alertness levels.     

Self‐reported activation during the premenstrual and menstrual phases of the menstrual cycle

Abstract

A total of 171 female subjects completed a self‐report questionnaire dealing with activation (AD‐ACL) during the premenstrual and menstrual phases of their cycles. Significant variation between the two phases was found for all four activation factors: activation was highest premenstrually. Contraceptive use interacted significantly with cycle phase for the General Activation factor. Subjects taking oral contraceptive preparations also had lower scores on the Deactivation‐Sleep factor.     

Does parasitic infection by the body cavity dwelling Philometra ovata (Nematoda) impair swimming performance of male European minnow (Phoxinus phoxinus)?

The influence of trophically transmitted parasite infection on fitness-related locomotor performance in fish as definite hosts has been studied relatively rarely and is thus mostly unknown. In this study, we examined the effect of body cavity dwelling nematode Philometra ovata on the swimming performance, fitness-related traits (male body quality) and male sexual ornamentation of their definitive host, European minnow (Phoxinus phoxinus). Despite the fact that P. ovata is relatively large in body size and thus presumably costly for their host minnows, we found that the abundance of the parasite did not correlate with the swimming performance of the male minnows. Neither did the infection of P. ovata impair the male sexual ornamentation or the male body quality. These partly unexpected results highlight the fact that the P. ovata induced impairment on fitness-related traits of host male minnows is not straightforward, and thus additional physiological studies in infected minnows are needed before final conclusions about the actual harmfulness of the parasite can be made.     

Natural infection of the anal glands of the opossum (Didelphis albiventris) by Trypanosoma cruzi in the municipality of Bambuí--MG, Brazil

Out of 87 opossums, Didelphis albiventris, captured in the Bambuí area (Minas Gerais State), 32 (36.7%) were found infected by Trypanosoma cruzi; the rates varied according to whether the specimens originated from sylvan, rural peridomiciliar or urban surroundings, being 34.9, 81.8 and 7.7 respectively. From 20 of the infected opossums the anal glands were repeatedly examined and found positive in only one (5%) specimen (GA 9), with 7 positive examinations out of 17 performed through an 18-months periods. Material from these glands produced patent parasitemia in opossums and sub-patent infections in mice. Isolates from the opossum GA 9, obtained through xenodiagnoses and hemocultures and from cultures of the infected anal glands fitted into zymodeme Z1.     

Why no feeding frenzy? Mechanisms of nutrient acquisition and utilization during infection by the rice blast fungus Magnaporthe oryzae

Magnaporthe oryzae is a devastating pathogen of rice and wheat. It is a hemibiotroph that exhibits symptomless biotrophic growth for the first 4 to 5 days of infection of susceptible cultivars before becoming necrotrophic. Here, we review recent advances in our understanding of how M. oryzae is able to grow, acquire nutrients, and interact with the plant cell during infection. In particular, we describe direct mechanisms (such as the integration of carbon and nitrogen metabolism by trehalose-6-phosphate synthase 1) and indirect mechanisms (such as the suppression of host responses) that allow M. oryzae to utilize available host nutrient. We contrast the ability of M. oryzae to voraciously metabolize a wide range of carbon and nitrogen sources in vitro with the carefully orchestrated development it displays during the biotrophic phase of in planta growth and ask how the two observations can be reconciled. We also look at how nutrient acquisition and effector biology might be linked in order to facilitate rapid colonization of the plant host.     

Is branch damage by xylophages related to the presence of epiphytes?

Host identity influences the guilds (epiphytes and xylophages) that interact within canopies. Host species can be categorized as either limiting or preferred hosts based on epiphyte load. It is possible that, depending on the host category (limiting or preferred), galleries bored by xylophages would affect the quality and availability of space for epiphytes. The objective of this study was to determine, among and within limiting and preferred hosts, the relationship between the damage inflicted by insects to branches and epiphytic bromeliads. We collected two branches each (with and without epiphytes, respectively) from limiting hosts (Bursera fagaroides, Ipomoea murucoides and I. pauciflora) and preferred hosts (Bursera copallifera and B. glabrifolia). The variables measured were: number and species of epiphytes, number of holes, number and taxonomical group of insects, percentage of epiphyte cover and percentage of area damaged by insects. These variables were compared among and within hosts and the significant correlations, where present, determined. We identified five bromeliad species and six taxonomical groups of insects. I. murucoides showed a higher proportion of damage and a larger number of insects. For the three limiting hosts, there was a negative relationship between (1) epiphyte cover and damaged area, (2) number of epiphyte individuals and number of xylophages and (3) number of epiphyte individuals and damaged area. Within species, B. copallifera, B. glabrifolia and I. pauciflora had more holes in branches that supported epiphytes than in branches without. We hypothesized that, inter-specifically, xylophages would interfere with the establishment of epiphytes by facilitating the release of allelopathics, but this possibility needs to be examined in more detail. Intra-specifically, it is possible that holes made by xylophages do not cause sufficient damage in hosts and, consequently, a possible repercussion on epiphytes is not reflected.