Main Peak Of Activity Research Articles

Let's wait for the evening: nocturnal copulation in a tropical damselfly Phylolestes ethelae (Odonata, Synlestidae)

Sexual selection is one of the main causes of the diversity of reproductive behaviours observed intra- and interspecifically. Here we study the reproductive behaviour of a unique species, Phylolestes ethelae, the only member of the family Synlestidae (Odonata) found in America. Our hypothesis was that the phylogenetic uniqueness of this species and the fact that it lives on an island would produce novel behaviours worth protecting as they are a part of the biodiversity. Between 2017 and 2019 we studied a population of P. ethelae in the National Park Armando Bermúdez in the Dominican Republic by means of mark-recapture techniques and focal observations. The survival rate was estimated as 0.953 ± 0.012 (SE), which translates into an expected lifespan of 20.6 days. We found that some males showed high site fidelity but very little activity, and territorial disputes were almost inexistent. Females, on the other hand, were rarely observed on the river, and were found mainly on the nearby paths and forest. We recorded 28 tandems and observed a total of 17 copulations, lasting an average of 18.6 min. Examination of sperm volumes in females interrupted during copulation indicated that males removed most of the sperm from the female bursa copulatrix during stage I of copula, but they could not remove sperm from the paired spermathecae. The duration of precopulatory tandem was highly variable (from 3 min to 7.8 h). In some cases, copulation was observed shortly (3 min) after tandem formation, mainly during the morning. However, some pairs formed during the morning, remained in tandem for several hours, and mated late, after dusk. Females laid eggs not accompanied by the male. Mating after the main peak of activity might be a strategy which protects sperm investment because females laying eggs after dusk are unlikely to be mated again that day. Further studies are needed to decipher phenotypic correlates of the males that mate after dusk.

Habitat partitioning among sympatric tinamous in semiarid woodlands of central Argentina.

Sympatric, phylogenetically related and morphologically similar species that overlap in their distributions at a regional scale display different patterns of co-occurrence at local assemblages. Occurrence of each species at local scales might be the result of interspecific competition for limiting resources. However, these patterns could also arise from species-specific habitat preferences along the abiotic or land use gradients. To assess the role of these mechanisms, we investigated niche partitioning among sympatric tinamou species occurring in semiarid woodlands of central Argentina. We used occupancy models incorporating habitat characteristics and interspecific interactions, while accounting for detectability, to examine the spatial overlap among elegant crested tinamous (Eudromia elegans), brushland tinamous (Nothoprocta cinerascens), and nothura tinamous (Nothura darwinii and N. maculosa) across a wide regional scale. In addition, we investigated time partitioning among these species by estimating the degree of overlap in their daily activity patterns. The regional distribution of the three species was influenced by the gradient in plant productivity and vegetation structure, in agreement with their broad habitat requirements. We also found that the occurrence of each species was presumably affected by the presence of one or two predator species. Models including interactions among tinamou species found weak negative and positive interactions among species pairs, suggesting that co-occurrence patterns were mainly driven by species-specific habitat use rather than interspecific competition. The three species were diurnal, showing two main peaks of activity, and overlapped widely in their overall diel activity, although subordinate species tended to shift their activity patterns to reduce encounters with the dominant tinamou species, suggesting some segregation in this niche dimension. Projected changes in rainfall seasonality and warmer conditions in this region could benefit elegant crested tinamous over the other two species, although climate and land use changes will likely have a negative impact on all tinamou species.

Wood feeding and social living: Draft genome of the subterranean termite Reticulitermes lucifugus (Blattodea; Termitoidae).

Termites (Insecta, Blattodea, Termitoidae) are a widespread and diverse group of eusocial insects known for their ability to digest wood matter. Herein, we report the draft genome of the subterranean termite Reticulitermes lucifugus, an economically important species and among the most studied taxa with respect to eusocial organization and mating system. The final assembly (~813 Mb) covered up to 88% of the estimated genome size and, in agreement with the Asexual Queen Succession Mating System, it was found completely homozygous. We predicted 16,349 highly supported gene models and 42% of repetitive DNA content. Transposable elements of R. lucifugus show similar evolutionary dynamics compared to that of other termites, with two main peaks of activity localized at 25% and 8% of Kimura divergence driven by DNA, LINE and SINE elements. Gene family turnover analyses identified multiple instances of gene duplication associated with R. lucifugus diversification, with significant lineage-specific gene family expansions related to development, perception and nutrient metabolism pathways. Finally, we analysed P450 and odourant receptor gene repertoires in detail, highlighting the large diversity and dynamical evolutionary history of these proteins in the R. lucifugus genome. This newly assembled genome will provide a valuable resource for further understanding the molecular basis of termites biology as well as for pest control.

Risk Assessment of the Role of the Ecotones in the Transmission of Zoonotic Cutaneous Leishmaniasis in Central Tunisia.

Zoonotic cutaneous leishmaniasis (ZCL), endemic in Central and Southern Tunisia, is caused by Leishmania major (Kinetoplastida: Trypanosomatidae), which is transmitted by the sand fly Phlebotomus papatasi. In Tunisia, the fat sand rat Psammomys obesus and the desert jird Meriones shawi are the principal reservoir hosts of L. major. The presence of the P. papatasi vector of the L. major etiologic agent of ZCL was assessed in the vicinity of villages in endemic areas of Central Tunisia. The study was performed from September through October 2019, a period corresponding to the main peak of activity of P. papatasi. Sand flies were collected from rodent burrows located at the ecotone level, which is the transition zone between the natural environment and human settlement. Sand flies were identified to species level and tested for the presence of L. major by PCR. Our entomological survey showed that P. papatasi is the most abundant sand fly species associated with rodent burrows, and this abundance is even higher in ecotones primarily occupied by P. obesus in comparison to ecotones occupied by M. shawi. Infections with Leishmania major were detected only in P. papatasi, with an overall minimum infection rate (MIR) of 2.64%. No significant difference was observed between the MIRs in ecotones of P. obesus and of M. shawi. Incidence of ZCL in the studied areas ranged from 200 to 700 cases per 100,000 inhabitants, with a mean incidence of 385.41 per 100,000. Higher ZCL incidence was identified in ecotones of M. shawi compared to ecotones of P. obesus. ZCL cases are positively correlated with the MIRs. Considering the short flight range of P. papatasi, increases in its densities associated with burrows of P. obesus or M. shawi at the ecotone level expand the overlap of infected vectors with communities and subsequently increase ZCL incidence. Therefore, control measures should target P. papatasi populations at the ecotones.

Pest categorisation of Resseliella citrifrugis.

The EFSA Panel on Plant Health performed a pest categorisation of the citrus fruit midge, Resseliella citrifrugis Jiang (Diptera: Cecidomyiidae), for the territory of the EU. This species is not included in EU Commission Implementing Regulation 2019/2072. This oligophagous species, which feeds on Citrus spp. fruits, is known to occur in China (provinces of Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi and Sichuan). First‐generation adults emerge in April and oviposit on the peduncle and calyx of citrus fruits. Larvae feed on the albedo (the white layer between skin and pulp) of the fruit, which they tunnel. Infested fruit most often drop prematurely. Larvae pupate either within the fallen fruit or in the soil. This species has three main peaks of activity (May, June–July, August–September) and four generations per year in its native range. Mature larvae from the last generation are the overwintering stage. Potential entry pathways for R. citrifrugis, such as Citrus spp. plants for planting with foliage and soil/growing media, and soil/growing media can be considered as closed. The citrus fruit pathway remains open from countries where R. citrifrugis is known to occur. Indeed, this species was intercepted in fresh pomelos 11 times from December 2020 to January 2021 in the EU. Should R. citrifrugis enter the EU, the ample availability of hosts (Citrus spp.) and the climatic conditions in citrus‐growing areas of southern EU Member States would most probably allow this species to successfully establish and spread. Economic impact in citrus production is anticipated if establishment occurs. R. citrifrugis satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as a potential Union quarantine pest. There is uncertainty about the nomenclature of R. citrifrugis and its exact host range. However, because the name Resseliella citrifrugis is used in multiple sources reporting it as a pest of citrus in China, where symptoms, biology and impact are described, these uncertainties do not affect the conclusions of this categorisation.

Late Cretaceous to early Eocene magmatic evolution of the Laramide arc in the Nacozari quadrangle, northeastern Sonora, Mexico and its regional implications

Late Cretaceous to early Eocene volcanic and plutonic rocks that crop out in the Nacozari quadrangle compose the Laramide magmatic arc in northeastern Sonora, northwestern Mexico. The purpose of this work is to characterize the arc rocks based on new cartography, stratigraphy, U-Pb and K-Ar geochronology, and major, trace and isotope geochemical data and interpret them in the regional context of evolution of the arc. The study area lies within the Proterozoic Mazatzal crustal block which is limited to the south by the Caborca block. The volcanic rocks regionally correlate with the Tarahumara Formation and consist of volcanic flows, breccias, tuffs and volcaniclastic sandstones with an estimated thickness of 4km. They range in composition from andesite to rhyolite and have isotopic ages from 76.8±0.4 to 57.1±0.4Ma. The granitic plutons and rhyolitic domes that intrude them yielded ages from 59.3±0.8 to 53.3±1.6Ma. Initial 87Sr/86Sr and epsilon Nd values for these rocks vary from 0.70553 to 0.70841 and −3.7 to −8.5, respectively, and have 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb isotope ratios that range from 18.05 to 19.05, 15.52 to 15.63, and 38.25 to 39.07, respectively. Regional integration of our U-Pb ages suggests that the volcanic activity lasted between ca. 81 and 57Ma, with two main peaks of activity at 74.5 and 61Ma. Similarly, regional magmatic activity indicated by dated plutons initiated at ca.91 and ended by 50Ma, after main peaks of activity at 71 and 60–55Ma. The plutonism between 91 and 80Ma was subordinate and regionally restricted to coastal and central Sonora and might represent an older event unrelated to the Laramide arc. Two K-Ar cooling ages of 55.4±0.7 and 48.5±0.7Ma obtained from La Púrica granite dated at ca. 59Ma (U-Pb) in the study area, correlate regionally with a possible event of rapid uplift between 68 and 50Ma. The geochemical composition of the studied rocks indicate high-K, calc-alkaline, metaluminous to weakly peraluminous compositions, typical of subduction arc-related magmas which characterize the Laramide magmatic belt in northwestern Mexico. The Nd, Sr and Pb isotope compositions of these and other samples documented for northeastern Sonora, closely correlate with isotope signatures of the Mazatzal crustal block in southeastern Arizona and differ from those in the Caborca block, which display affinity with the Mojave-Yavapai province. The data also allow to best constrain the location of the boundary between the Mazatzal and Caborca crustal blocks in east-central Sonora.

Unimodal activity pattern in forest-dwelling chamois: typical behaviour or interspecific avoidance?

Daily activity rhythms in mammals are influenced by a range of biotic and abiotic factors. During warm periods, mountain ungulates living in open areas typically show a bimodal pattern of activity rhythms, with peaks at dawn and dusk. To date, however, little is known about the activity patterns of mountain ungulates living in forested habitats and in areas where large predators are present. Using camera traps over a 6-month period between May and October of 2012, we investigated the activity pattern of a chamois population dwelling in the forests of the northern Mount Velebit region (Croatia) and its overlap with the activity patterns of potential predators (brown bear, grey wolf) and competitors (wild boar). Chamois showed a peak of activity between 5:00 a.m. and 7:00 a.m., when 65 % of individuals were photographed. Contrary to previous literature on chamois, we found evidence for a unimodal pattern of activity with a peak in the early morning hours: At a seasonal level, this pattern remained fairly consistent, though the activity at dusk increased in the warmest months. The main peak of activity occurred during periods of decreased activity of potential predators and competitors, and chamois exhibited the least tolerance for overlap with grey wolf. Further studies are needed to clarify whether this pattern is typical of forest-dwelling populations or if it reflects a temporal niche shift, possibly as a strategy to avoid predators.

Mid-Holocene cluster of large-scale landslides revealed in the Southwestern Alps by 36Cl dating. Insight on an Alpine-scale landslide activity

Although it is generally assumed that the internal structure of a slope (e.g. lithology and rock mass properties, inherited faults and heterogeneities, etc.) is preponderant for the progressive development of large-scale landslides, the ability to identify triggering factors responsible for final slope failures such as glacial debuttressing, seismic activities or climatic changes, especially when considering landslide cluster at an orogen-scale, is still debated. Highlighting in this study the spatial and temporal concordant clustering of deep-seated slope failures in the external Southwestern Alps, we discuss and review the possible causes for such wide-spread slope instabilities at both local and larger (Alpine) scale.High resolution field mapping coupled with electrical resistivity tomography first allows establishing an inventory of large landslides in the Southwestern Alps, determining their structural model, precising their depth limit (100–200 m) as well as the involved rock volumes (>107 m3). We show that they developed in the same geostructural context of thick mudstone layers overlain by faulted limestone and followed a block-spread model of deformation that could evolve in rock-collapse events.Cosmic ray exposure dating (CRE), using both 36Cl and 10Be in coexisting limestone and chert, respectively, has been carried out from the main scarps of six Deep Seated Landslides (DSL) and leads to landslide-failure CRE ages ranging from 3.7 to 4.7 ka. They highlighted: (i) mainly single and fast ruptures and (ii) a possible concomitant initiation with a main peak of activity between 3.3 and 5.1 ka, centered at ca 4.2 ka.Because this region was not affected by historical glaciations events, landslide triggering by glacial unloading can be excluded. The presented data combined with field observations preferentially suggest that these failures were climatically driven and were most likely controlled by high pressure changes in the karstic medium. In effect, the chronicle of failure-ages is concomitant to a well-known climatic pulse, the “4.2 ka” climate event characterized by intense hydrological perturbations associated to the heaviest rainfall period of the entire Holocene. Despite requiring further investigations and discussions, the dating of numerous events across the entire Alps during the middle Holocene period suggests a potential synchronous triggering of several large-scale gravitational-failures induced by the mid-Holocene climatic transition.

Notes on the blood-feeding behavior of Aedes albopictus (Diptera: Culicidae) in Cameroon.

BackgroundThe invasive mosquito Aedes albopictus is often considered a poor vector of human pathogens, owing to its catholic feeding behavior. However, it was recently incriminated as a major vector in several Chikungunya epidemics, outside of its native range. Here we assessed two key elements of feeding behavior by Ae. albopictus females in Yaoundé, Cameroon, Central Africa. Host preference was explored and the human-biting activity of females was monitored over 24 h to determine periods of maximum bite exposure.FindingsAnalysis of ingested blood in outdoor-resting females showed that Ae. albopictus preferentially fed on humans rather than on available domestic animals (95% of the blood meals contained human blood). Our results further showed that Ae. albopictus is a day-biting species in Yaoundé, with a main peak of activity in the late afternoon.ConclusionThis is the first report on the feeding behavior of Ae. albopictus in Central Africa. The species is highly aggressive to humans and might therefore be involved in human-human virus transmission in this setting.

Utilisation des données de la Caisse générale de Sécurité sociale de la Réunion dans le cadre de la surveillance non spécifique

Background In Reunion Island, non-specific surveillance developed mainly in 2009 and was based on the activity of hospital emergency department, emergency calls and mortality. From March 2010, a new surveillance was implemented in collaboration between the Indian Ocean regional epidemiology unit and the regional office of the National Health Insurance. The system is based on the weekly number of general practitioner consultations and home visits by municipality. This article presents methods of using these data for non-specific monitoring in Reunion Island. Materials and methods Data analyzed cover consultations and visits to general practitioners and pediatricians for each of the 24 municipalities. Data were received in week S + 1 and were updated week by week following the flow of repayments. To perform weekly monitoring, determine monitoring impact and detect any unusual health event, a correction factor was thus calculated and applied for the overall data set and for each municipality. Received data covered 72% of the population of the island. Results Over the study period from 2005 to 2009, the monthly average of consultations was 80,000 (min: 58,000 – max 12,0000). Two main peaks of activity were noticed throughout the island during the study period, the first one from weeks 4 to 9 of 2006 with a peak of 105,000 consultations in week 8 and the second one from weeks 34 to 41 of 2009 with a peak of 120,000 consultations in week 35. Conclusion The two peaks described in 2006 and 2009 respectively correspond to outbreaks of chikungunya and influenza A(H1N1) 2009. This monitoring study has two main advantages: an almost exhaustive data set corresponding to three-quarters of the Reunion Island population and the geographic analysis by municipality. Positioned alongside other monitoring networks, this system expands the indicators monitored reflecting varying uses of care.

Superoxide dismutase, catalase, and glutathione peroxidase in the testis of the Mexican big-eared bat (Corynorhinus mexicanus) during its annual reproductive cycle

The reproductive physiology of Corynorhinus mexicanus includes a testes growth-involution cycle. Testis recrudescence begins in May-June, peaks in August and then undergoes a profound involution being totally regressed in November. Adult, male individuals were captured monthly during one year and ROS scavenging enzyme activities were measured in testes and expressed per total wet-weight and per mg protein. SOD total activity is very low from October to February; increases sharply one full month before testes recrudescence starts, and in August, when testis activity was at its peak, SOD is 3-4 times lower than in July. Catalase total activity is bimodal. The main peak of activity occurs during testicular recrudescence with an additional smaller peak, two months before the onset of recrudescence. Glutathione peroxidase total activity parallels almost exactly the testis growth cycle, increases in July, reaches a peak in August and decreases through September to almost disappear in October. SOD specific activity shows a pre-testicular increase of activity, maintains its activity from March to July and then descends drastically to almost nil in August, maintaining these low values until February. Catalase specific activity is particularly important during the period of testicular regression. GPX specific activity is low from March to July, months of testicular recrudescence; whereas its activity increases in August and peaks in November, when testes regression occurs. Our data show that ROS-scavenging enzymes may play a very important role during testes involution-recrudescence in C. mexicanus, and we believe their participation could be equally important in all seasonally breeding mammals.

Bovine γ‐Glutamylamine cyclotransferase purification

γ-Glutamylamine cyclotransferase (γ GACT) from bovine kidney is a soluble enzyme believed to be involved in the metabolism of transglutaminase products. This enzyme catalyses the cleavage of Nε-(γ-glutamyl)lysine with intramolecular cyclization of the glutamyl moiety into 5-oxoproline and release of free lysine. Fluorescence derivatization of the lysine produced and SDS-PAGE are used to monitor the enzyme during the purification. In the initial purification of γ GACT from kidney tissue ultracentrifugation, anion exchange chromatography on DEAE-Sepharose, ammonium sulfate fractionation, and size exclusion chromatography on Sephacryl S-100 are employed. Size exclusion chromatography on Superdex-S75 using reducing conditions gives a single peak of enzyme activity with a molecular mass of ~ 20 KDa. In chromatography with strong anion exchange on a Mono Q column several peaks of activity are observed; the relative concentration of the two main peaks of activity depends on the reducing conditions. Heterogeneity of the enzyme activity is also observed in isoelectric focusing (IEF). This research is supported by a grant from the Baylor University Research Committee.

HdaA, a Major Class 2 Histone Deacetylase of Aspergillus nidulans , Affects Growth under Conditions of Oxidative Stress

Histone deacetylases (HDACs) catalyze the removal of acetyl groups from the epsilon-amino group of distinct lysine residues in the amino-terminal tail of core histones. Since the acetylation status of core histones plays a crucial role in fundamental processes in eukaryotic organisms, such as replication and regulation of transcription, recent research has focused on the enzymes responsible for the acetylation/deacetylation of core histones. Very recently, we showed that HdaA, a member of the Saccharomyces cerevisiae HDA1-type histone deacetylases, is a substantial contributor to total HDAC activity in the filamentous fungus Aspergillus nidulans. Now we demonstrate that deletion of the hdaA gene indeed results in the loss of the main activity peak and in a dramatic reduction of total HDAC activity. In contrast to its orthologs in yeast and higher eukaryotes, HdaA has strong intrinsic activity as a protein monomer when expressed as a recombinant protein in a prokaryotic expression system. In vivo, HdaA is involved in the regulation of enzymes which are of vital importance for the cellular antioxidant response in A. nidulans. Consequently, deltahdaA strains exhibit significantly reduced growth on substrates whose catabolism generates molecules responsible for oxidative stress conditions in the fungus. Our analysis revealed that reduced expression of the fungal catalase CatB is jointly responsible for the significant growth reduction of the hdaA mutant strains.

Interactions between a blue‐green reversible photoreceptor and a separate UV‐B receptor in stomatal guard cells

Stomatal opening exhibits two main peaks of activity in the visible range-a red peak, mediated by photosynthesis, and a blue peak, mediated by one or more blue light (BL) photoreceptors. In addition, a pronounced peak in the UV-B region has been characterized, as has a smaller UV-A peak. The BL-induced stomatal opening can be reversed by green light (GL). Here we report that UV-B-induced opening is also antagonized by GL. To determine whether UV-B is being absorbed by the BL photoreceptor or by a separate UV-B receptor, the UV-B responses of two different Arabidopsis mutants, npq1 and phot1/phot2, were tested. Both putative BL-photoreceptor mutants exhibited normal stomatal opening in response to UV-B, consistent with the existence of a separate UV-B photoreceptor. Moreover, GL failed to antagonize UV-B-induced stomatal opening in the phot1/phot2 double mutant and only partially antagonized UV-B opening in npq1. Thus, both phot1 and phot 2, as well as zeaxanthin, are required for the normal GL inhibition of UV-B. A model for a photoreceptor network that regulates stomatal opening is presented. Unlike the situation in guard cells, the UV-B bending response of Arabidopsis hypocotyls during phototropism appears to be mediated by phototropins.

Immunisation against Theileria parva in eastern Zambia: influence of maternal antibodies and demonstration of the carrier status.

Immunisation of calves by the infection and treatment method (I & T) has been extensively used in the eastern province of Zambia to control East Coast fever (ECF), a protozoan tick-borne disease. This paper presents the results of a field longitudinal study, which included a total of 148 Angoni calves. After immunisation against ECF, they were monitored for a full rainy season, coinciding with the main peak of activity of the vector of Theileria parva, the tick Rhipicephalus appendiculatus. Dysimmunisation (acute reaction generated by I & T immunisation), seroconversion and mortality are among the parameters recorded. The effect of maternal antibodies on these parameters was analysed and also studied in experimental conditions on two calves. Before immunisation, young calves had a higher seroprevalence than older animals (maternal antibodies) but their post-immunisation seroprevalence was lower. There was no evidence that their immunoprotection was weaker but this indicates that the post-immunisation seroconversion is probably not a reliable tool to monitor the efficacy of calf immunisation. The carrier state of cattle after immunisation was investigated in experimental conditions on three bovines whereas in the field, the infection prevalence in the ticks was estimated using the relation between the tick burden and the T. parva contacts with the calves. The ability of larval and nymphal R. appendiculatus ticks to pick-up T. parva from carriers and to transmit it to naïve animals after moulting was assessed. It was found that both instars are able to transmit clinical and lethal ECF but that the prevalence of T. parva infection in nymphs is much lower than in adults, confirming the primary role of adults in the transmission of ECF in endemic conditions. Similar results were obtained from the field whereby the ECF peak corresponds with the peak of adult R. appendiculatus activity. The infection prevalence in the ticks was however much lower in the field than in experimental conditions indicating that an important proportion of them feed on alternative hosts. Old ticks seemed to have lost part of their infectivity.

Feeding and growth responses of sea bass ( Dicentrarchus labrax) reared by four feeding methods

As they grew from approximately 2.8 to 260 g, sea bass were fed according to four feeding methods: self- (SF), automatic (AF), hand (HF, two meals per day), and combined (CF, automatic and to satiation by hand) feeding. The experiment, which lasted 79 weeks, was conducted under ambient environmental conditions. Feed supply to SF and HF fish was similar ( P>0.05), except during the last period when an increased feed input was recorded in the SF group. The AF fish were always overfed. Hand-fed (HF) sea bass consumed 52–61% of their daily ration during the afternoon feeding. AF-fed juveniles did not grow well initially but weight gain was higher later, resulting in a similar mean individual weight to the other methods. The weight of adults was lowest in SF-fed fish (in AF and HF fish weight was significantly better). Mortality (0.4–1.1%) occurred only amongst juveniles and was independent of feeding method. Juveniles fed according to the SF method had diurnal feeding activity which changed progressively to increased nocturnal feeding, with a main peak of activity at mid-day and a secondary one around dawn or dusk. From an aquaculture viewpoint, SF has the advantages of good feed conversion and lower labour costs as compared to the other feeding methods.

Effects of memory load on event-related patterns of 40-Hz EEG during cognitive and motor tasks

The present study describes a phasic event-related synchronization (ERS) in the gamma band (36–44 Hz) induced by the onset of probe visual stimuli. The experiment consisted of two experimental tasks with high and low memory-load in which a geometrical figure (S1) was held in memory for comparison with a subsequent stimulus (S2). In each task a Go–NoGo paradigm was used with a Same–Different discrimination task. The aim of the study was to examine the influence on 40-Hz ERS of stimulus type (`Same–Different') and of response (Go–NoGo) task as moderated by activation or effort level (high/low memory-load). The investigation was carried out in 27 women. The EEG was recorded from FP1, FP2, F3, F4, P3, P4, O1 and O2 scalp sites referenced to linked earlobes. As a manipulation check for activation level, we recorded heart rate (HR) during the S1–S2 period. A main peak of activity was found around 160 ms with a maximum at occipital sites. The amplitude of this peak was higher in the high memory-load as compared to the low memory-load condition. This difference was manifested mainly at F3 and O2 scalp sites. A larger 40-Hz peak at F3 was also found in the Go compared to the NoGo condition. No 40-Hz ERS differences between Same and Different trials were observed. The HR was found sensitive to the stimulus type showing a greater HR deceleration response to S2 for Same trials, as compared to Different ones. In parallel with 40-Hz ERS response, the HR deceleration was more pronounced for the high memory-load as compared to the low memory-load condition. The results indicate that the 40-Hz ERS is dependent upon both memory-load and motor responding. The influence of memory load on cognitive (Same–Different) and motor response (Go–NoGo) variables is discussed.

Acclimation of Cyanobacterial Communities in Rice Fields and Response of Nitrogenase Activity to Light Regime

The short-term and long-term effects of light regime on nitrogenase activity (NA) and cyanobacterial communities in rice fields (Valencia, Spain) were examined. Daily variation in nitrogen fixation was measured during three periods of the crop cycle: tillering (formation of secondary stems in the rice plants), heading (formation of reproductive structures), and maturity. Two locations were examined over two consecutive years (1994 and 1995). Despite differences in the crop-cycle periods, location, and year, a consistent pattern of nitrogen fixation was observed, with a main activity peak in the morning and another in the late evening. Short-term experiments, performed on two cyanobacterial blooms (Nostoc sp. and Anabaena sp.) exposed to natural light under plant canopy (7% incidence irradiance), and to different light intensities under neutral density screens without plant cover (full sunlight, 43%, 26%, and 13% of incident irradiance), indicated that nitrogenase activity (NA) was dependent on both light intensity and quality. In long-term experiments, where natural communities of cyanobacteria were exposed to one month of different light intensities, changes in the species composition of the three main genera of heterocystous cyanobacteria (Nostoc, Anabaena, and Calothrix) were observed. The light intensity at which communities were exposed for one month became the optimum irradiance for NA for each cyanobacterial community. Assays performed at higher or lower irradiances showed lower NA. Nitrogen fixation followed a pattern of seasonal variation along the crop cycle. Values were low at the beginning of the crop (May), reached a maximum value at the end of the tillering stage (June), and declined thereafter until the end of the cultivation cycle (September).

Induction of cyclic AMP and cyclic GMP 3′:5′-cyclic nucleotide phosphodiesterase activities in neuroblastoma lines under differentiating conditions

It is now widely accepted that cyclic nucleotide phosphodiesterases (PDEs) play fundamental roles in signal transduction pathways; they show a remarkable molecular complexity, different tissue distribution and complex regulatory mechanisms. Here we report PDE isoforms expression in two dibutyryl cyclic AMP differentiated murine cell lines: the hybrid neuroblastoma-glioma 108CC15 and the parental neuroblastoma N18TG2. They differ for the ability to establish functional synapses, a feature present only in the former. Ionic exchange chromatography elution profiles of N18TG2 and 108CC15 undifferentiated cell extracts show two main peaks of activity. The first one hydrolyzes cyclic GMP and is specifically inhibited by Zaprinast, thus representing a member of the PDE5 family. The second peak hydrolyzes cyclic AMP and is significantly inhibited by rolipram, as all the PDE4 family members. The induction of differentiation by dibutyryl cyclic AMP in both clonal lines results in an increase of PDE activities only after 3hr of treatment, suggesting that protein neosynthesis is involved. Interestingly in both clones, besides the increase in cyclic AMP hydrolyzing specific activity (3.1 folds in 108CC15 and 2.5 folds in N18TG2), we also observed an increase in cyclic GMP hydrolyzing activity (1.7 folds in 108CC15 and 4.3 folds in N18TG2). While the induction of PDE4, previously reported also in other cellular systems, could be considered as a feedback response to the higher cyclic AMP levels, this is not true for the isoform that hydrolyzes cyclic GMP. These data suggest that the induction of PDE isoforms in neuroblastoma cells could be related to the activation of neuronal differentiative pathway.

Hawkmoth pollination in Cereus peruvianus, a columnar cactus from southeastern Brazil

Summary Pollination by hawkmoths (Sphingidae) is described for Cereus peruvianus (Cactaceae) in southeastern Brazil. The flower presents a dish to bowl-shaped perianth with whitish tepals and a long floral tube. The stamens, arranged like a brush, produce abundant pollen and the long, tube-like style ends in a multi-lobed stigma. Start of anthesis is crepuscular. Anthesis lasts one night. Only little nectar is produced, with ca. 27 % sugar concentration. Odour is weak, sweetish and persists throughout the night. Handpollination tests indicate that seed production is dependent on cross-pollination. Honeybees, scarabid beetles, and hawkmoths were observed visiting the flowers, but only the latter seem to be effective pollinators. The sphingids, Agrius cingulatus and Manduca rustica, showed similar visiting behavior, which consisted of hovering, alighting on the perianth, and partially introducing the body into the nectar chamber. Both floral attributes and the morphological/behavioral characteristics of sphingids point to an adaptive trend toward sphingophily in C. peruvianus. This trend is also reflected in the flowering season, which matches the main peak of activity for sphingids at the study areas, and in the steady state flowering pattern, which promotes cross-pollination visits by these insects.