Structure et dynamique d’un peuplement d’amphibiens en savane protégée du feu (Lamto, Côte-d’Ivoire)

Si les effets directs du feu sur la biologie des Amphibiens de la savane sont négligeables, tel n’est pas le cas de ses effets indirects, qui résultent de son impact sur la physionomie du bioto pe et sur son microclimat. L’analyse comparative des structures taxinomiques (spectre d’abondance relative des espèces) des peuplements de savane non brûlée avec, d’une part, ceux de savane brûlée, et d’autre part, ceux des galeries forestières qui morcèlent la savane, a été faite. Elle montre que les différences tranchées;*qui séparent, d’un côté les peuplement de savane brûlée et les peuplements de forêt, et d’un autre côté, en savane même, les peuplements des bas-fonds humides et celui du plateau, se réduisent sensiblement lorsque la savane a été protégée du feu pendant plusieurs années. Une telle transformation de la physionomie du peuplement d’Amphibiens en savane non brûlée, qui va de pair avec un accrois sement des effectifs — lesquels doublent ou triplent, selon les années — s’établit en fait dès le début de la première année sans incendie. Elle résulte pour l’essentiel de la prolifération d' Arthro leptis poecilonotus et de la quasi-disparition de Bufo regularis. Favorisé par la persistance de la strate herbeuse et le développe ment de la litière d’herbes et de feuilles, qui tamponnent les varia tions de température et d’humidité tout en maintenant élevée cette dernière, Arthroleptis poecilonotus représente 63 % de l’ef fectif annuel récolté en savane brûlée. A l’inverse, probablement entravé dans ses mouvements par la densité du tapis végétal, Bufo regularis, qui réunissait un peu plus de 30 % du peuplement an nuel de la savane brûlée, est représenté en savane non brûlée par moins de 4 % des effectifs. Cette espèce est une forme colonisa trice qui envahit chaque année, dès les premières pluies d’orage de février-mars, le plateau brûlé de la savane, encore inhospitalier aux autres espèces d’Amphibiens.The bush-fires which occur yearly in the Lamto savana, during the dry season, do not affect Amphibian populations directly, but rather through their action upon vegetation structure and micro climate. The population density and relative abundance of the various species were studied during 1964-1965 in two unburnt 30 X 30 m plots : one which had been protected from fire for two years and another which had remained unburned for five years. Compa risons were made with populations from burned plots and nearby gallery forests. The obvious differences of population densities and relative species abundance so far described between savanna and forest communities, as well as between « bottom » and « plateau » communities within the savanna, tend to disappear when bush- fires are prevented. However the seasonal cycle of population abundance remains basically the same in both cases. In unburnt savanna plots the density of Amphibian popula tions increases rapidly and is already noticeable during the second year. Population density may be increased 2 to 3 fold. This is mostly due to a proliferation of one species (Arthroleptis poecilo notus), which takes place simultaneously with the reduction in numbers of the toad Bufo regularis

Production annuelle des populations naturelles du lézard Mabuya Buttneri (Matschie)

Monthly counts were made of populations of the skink Mabuya büttneri during a four year period (1964-1968) in burnt savanna areas at Lamto in the Ivory Coast

Structure et dynamique d’un peuplement de lézards : les scincides de la savane de Lamto (Côte-d’Ivoire)

Trois espèces de Scincidés, Mabuya buettneri, Mabuya macu lilabris et Panaspis nimbaensis, représentent ensemble près de 98 % des effectifs de Lézards vivant dans les savanes de Lamto, non compris les Geckos strictement arboricoles. L’étude quantitative de ces populations a été effectuée de 1964 à 1968 à l’aide de défrichements de 900 m2 qui permirent le ramassage exhaustif des Lézards. Les densités ne sont jamais très élevées puisque, dans les meilleures conditions, celles de M. buettneri ne dépassent guère 60 individus par ha et celles de M. maculilabris 70 — y compris les individus cantonnés sur les arbustes et dans les Rôniers. Encore faut-il préciser qu’il s’agit là des populations totales, jeunes inclus ; les nombres d’adultes sont évidemment plus faibles. Les populations sont d’une manière générale plus nombreuses pendant la saison humide (avril-novembre) , mais il existe d’importantes différences dans le cycle saisonnier des espèces étudiées. Les effectifs augmentent dès le mois de février chez Mabuya maculilabris dont les jeunes éclosent toute l’année, pendant les mois de mars, avril et mai chez Mabuya buettneri, et entre juin et octobre chez Panaspis nimbaensis. Une telle chronologie des époques d’éclosion contribue évidemment à accroître la séparation écologique des espèces déjà largement assurée par le décalage de leurs rythmes nycthéméraux d’activité et la spécialisation de leurs domaines d’activité. Les trois espèces atteignent leur taille adulte vers l’âge de 6 mois. L’importance moyenne des pontes est de 8,4 œufs, 5,5 œufs et 2,5 œufs respectivement chez M. buettneri, M. maculilabris et P. nimbaensis ; les femelles peuvent produire plusieurs pontes successives, la fécondité annuelle moyenne par femelle étant égale, les espèces étant prises dans le même ordre, à 13,4, 30,4 et 12,8 œufs — soit, en moyenne, 1,5, 5,5 et 5 pontes. Ainsi, malgré une fécon dité presque triple, M. maculilabris ne supplante pas dans la savane les deux autres espèces qui ont des taux de mortalité pré natale et juvénile nettement inférieurs aux siens. La mortalité précoce, mesurée entre le stade œuf et l’âge moyen de 0,5 mois après l’éclosion, est en effet de 74 % chez M. maculilabris contre 42 % chez M. buettneri et 37 % chez P. nimbaensis ; à l’âge adulte, le nombre des survivants exprimé en % du nombre d’œufs pondus est égal respectivement à 8,5 %, 48,2 % et 25,1 %. A partir de la maturité sexuelle les individus de chaque sexe n’ont plus la même mortalité — et celle-ci varie toujours d’une espèce à l’autre. Dans le cas des femelles parvenues au stade adulte, l’espérance moyenne de vie est égale à 9,2 mois, 7,1 mois, et 2,2 mois, chez M. maculila bris, P. nimbaensis et M. buettneri respectivement ; elle est tou jours plus faible chez les mâles, pour lesquels on trouve, les espèces étant prises dans le même ordre : 6,2, 3,8 et 1,3 mois. En dépit d’un large éclectisme alimentaire, les divers Scin- cidés de la savane ne mangent pas tout à fait les mêmes proies, par suite de différences dans leur habitus, leur comportement, leurs domaine et rythme d’activité. La stabilité relative des peuplements de Lézards résulte en grande partie de la diversité de l’écosystème. Diversité et hétéro généité accroissent les chances de survie des individus, des popu lations et même des espèces, par l 'étalement des risques (Den Boer, 1968) et contribuent ainsi à niveler les fluctuations de densité de beaucoup d’espèces. C’est dans ce cadre que s’exercent certaines interactions régulatrices plus précises et les prédateurs, dans le cas des Lézards, y jouent le premier rôle, la nourriture paraissant toujours surabondante. Avec la trame que constitue l’analyse démographique des populations, le calcul de la production et de la consommation du peuplement de Lézards est une opération assez simple. Dans la savane brûlée peu boisée la production annuelle moyenne par ha est, en poids vif, égale à environ 200 g pour M. buettneri, 90 g pour M. maculilabris et 8 g pour P. nimbaensis. Ces trois espèces représentent près de 98 % des effectifs et de la biomasse des Lézards qui vivent dans la savane (Geckos exceptés, qui sont strictement inféodés à la strate ligneuse) et l’on peut considérer que la production annuelle du peuplement de Lézards terricoles est de l’ordre de 300 g par ha (en poids vif). La consommation moyenne totale des population de Lézards de savane brûlée peu boisée est égale, en poids vif, à 3 150 g par ha et par an, à raison d’une ration quotidienne par Lézard de 0,06 g/g à 0,13 g/g d’Araignées, Blattes ou Orthoptères — selon l’âge et l’état sexuel des individus. Inégalement répartie dans l’année, cette consommation est plus élevée pendant la saison humide. Pour calculer le rendement écologique de croissance des espèces, rapport de leur production à leur consommation, les poids vifs ont été transformés en poids secs puis en calories sur la base d’un équivalent moyen de 5 054 cal/g pour les proies (d’après Gillon, 1973), de 4 810 et 4 734 cal/g pour les Lézards M. buettneri et M. maculilabris, et de 6 400 et 6 500 cal /g pour leurs œufs. Le rendement écologique des populations naturelles de Lézards est, dans le cas des deux Mabuya de l’ordre de 0,10.Population densities of terrestrial lizards were estimated monthly, for five consecutive years, in the Lamto savanna (Ivory Coast), by collecting all individuals within 900 m2 quadrats. Although their breeding cycles were different, the three most numerous species Mabuya buettneri, M. maculilabris and Panaspis nimbaensis were more abundant during the wet season. These skinks require six months to reach a mature size ; their daily rate of growth is about 0.2 to 0.3 mm. The average reproductive potential of females of Mabuya buettneri, M. maculi labris and Panaspis nimbaensis were determined by counting yolked ovarian follicles and eggs in oviducts, and by estimating clutch size. The average annual egg production was 13.4, 30.4 and 12.8 eggs in the above three species, and the number of clutches 1.5, 5.5 and 5.0 per female per year. Mortality of eggs and hatchings is high and survivorship to maturity is low : 18.2 %, 8,5 % and 25.1 % of eggs laid respectively by Mabuya buettneri, M. maculilabris and Panaspis nimbaensis. From sexual maturity onwards, the death rate for females is lower than that of males in all species, but is fairly high for both sexes. The longest average life expectancy is about 9.0 months for females of Mabuya maculilabris, and the shortest 1.3 months for males of M. buettneri. Although they are opportunistic feeders, these sympatric lizards do not compete for the same preys because their activity patterns, their behaviours and their sizes are fairly different. The annual food consumption of the ground lizard community in Lamto savanna is about 3 kg/ha (live weight) and its average net production, calculated from life tables, is about 300 g/ha/year. Ecological efficiency of the Mabuya species is 10 %

Observations sur la reproduction et la dynamique des populations de quelques Anoures tropicaux. I. Ptychadena maccarthyensis et Ptychadena oxyrhynchus

The populations of two frogs, Ptychadena maccarthyensis and P. oxyrhynchus, were studied over a four-year period in the Lamto savanna (Ivory Coast), where the climate is characterized by a dry season lasting from December to February, and a rainy season from March to November. P. oxyrhynchus breeds from February to May, while P. mac carthyensis does not breed before March but can continue to do so until October. Consideration of size-frequency histograms constructed from sequential samples in the two populations shows that the two species reach sexual maturity 8 to 9 months after metamorphosis, when the females attain a length of 43 mm for P. maccarthyensis and 59 mm for P. oxyrhynchus. There is very little overlap in adult size, either between sexes or species. Average clutch size is 1333 eggs in P. maccarthyensis and 3476 eggs in P. oxyrhynchus. The laying of a second clutch of eggs during the year has not been observed. However there is a strong probability that this does in fact occur, particularly in P. maccarthyensis which has a long breeding season. Fecundity is high in the two species studied. The mortality rate is high for eggs and young individuals, especially during dry years. Adult mortality is low

Treatment of advanced hepatocellular carcinoma with very low levels of amplitude-modulated electromagnetic fields

BACKGROUND: Therapeutic options for patients with advanced hepatocellular carcinoma (HCC) are limited. There is emerging evidence that the growth of cancer cells may be altered by very low levels of electromagnetic fields modulated at specific frequencies. METHODS: A single-group, open-label, phase I/II study was performed to assess the safety and effectiveness of the intrabuccal administration of very low levels of electromagnetic fields amplitude modulated at HCC-specific frequencies in 41 patients with advanced HCC and limited therapeutic options. Three-daily 60-min outpatient treatments were administered until disease progression or death. Imaging studies were performed every 8 weeks. The primary efficacy end point was progression-free survival >= 6 months. Secondary efficacy end points were progression-free survival and overall survival. RESULTS: Treatment was well tolerated and there were no NCI grade 2, 3 or 4 toxicities. In all, 14 patients (34.1%) had stable disease for more than 6 months. Median progression-free survival was 4.4 months (95% CI 2.1-5.3) and median overall survival was 6.7 months (95% CI 3.0-10.2). There were three partial and one near complete responses. CONCLUSION: Treatment with intrabuccally administered amplitude-modulated electromagnetic fields is safe, well tolerated, and shows evidence of antitumour effects in patients with advanced HCC. British Journal of Cancer (2011) 105, 640-648. doi:10.1038/bjc.2011.292 www.bjcancer.com Published online 9 August 2011 (C) 2011 Cancer Research U

Treatment of advanced hepatocellular carcinoma with very low levels of amplitude-modulated electromagnetic

BACKGROUND: Therapeutic options for patients with advanced hepatocellular carcinoma (HCC) are limited. There is emerging evidence that the growth of cancer cells may be altered by very low levels of electromagnetic fields modulated at specific frequencies. METHODS: A single-group, open-label, phase I/II study was performed to assess the safety and effectiveness of the intrabuccal administration of very low levels of electromagnetic fields amplitude modulated at HCC-specific frequencies in 41 patients with advanced HCC and limited therapeutic options. Three-daily 60-min outpatient treatments were administered until disease progression or death. Imaging studies were performed every 8 weeks. The primary efficacy end point was progression-free survival X6 months. Secondary efficacy end points were progression-free survival and overall survival. RESULTS: Treatment was well tolerated and there were no NCI grade 2, 3 or 4 toxicities. In all, 14 patients (34.1%) had stable disease for more than 6 months. Median progression-free survival was 4.4 months (95% CI 2.1 -5.3) and median overall survival was 6.7 months (95% CI 3.0 -10.2). There were three partial and one near complete responses. CONCLUSION: Treatment with intrabuccally administered amplitude-modulated electromagnetic fields is safe, well tolerated, and shows evidence of antitumour effects in patients with advanced HCC. British Journal of Cancer (2011Cancer ( ) 105, 640 -648. doi:10.1038Cancer ( /bjc.2011 Published online 9 August 2011 & 2011 Cancer Research UK Keywords: hepatocellular carcinoma; phase II study; radiofrequency electromagnetic fields; tumour-specific modulation frequencies; 27.12 MHz Treatment of inoperable or metastatic solid tumours is a major challenge in oncology, which is limited by the small number of therapeutic agents that are both well tolerated and capable of longterm control of tumour growth. Hepatocellular carcinoma (HCC) is the second most common cause of cancer death in men and the sixth in women worldwide Therapies for HCC are limited. Resections of the primary tumour or liver transplantation are the preferred therapeutic approaches in patients who are surgical candidates The intrabuccal administration of low and safe levels of electromagnetic fields, which are amplitude-modulated at disease-specific frequencies (RF AM EMF) PATIENTS AND METHODS Patients The study was aimed at offering treatment to patients with ChildPugh A or B advanced HCC and limited therapeutic options. Patients were classified as having advanced disease if they were not eligible for surgical resection or had disease progression after surgical or locoregional therapies or had disease progression after chemotherapy or sorafenib therapy. Patients with measurable, inoperable HCC were eligible for enrolment. Previous local or systemic treatments were allowed as long as they were discontinued at least 4 weeks before enrolment. Inclusion criteria included Eastern Cooperative Oncology Group performance status of 0, 1, or 2 and biopsy-confirmed HCC. Also allowed were patients with no pathological confirmation of HCC with a level of a-fetoprotein higher than 400 ng ml À1 and characteristic imaging findings as assessed by multislice computer tomography (CT) scan or intravenous contrast ultrasound (US). As per the University of São Paulo Department of Transplantation and Liver Surgery guidelines, liver biopsies are avoided in patients eligible for transplant or with severely impaired liver function. Exclusion criteria included confirmed or suspected brain metastasis, Child -Pugh C, previous liver transplant, and pregnancy. Study design This was an investigator-initiated, single centre, uncontrolled phase I/II trial in patients with advanced HCC. The trial was approved by the local human investigation committee and conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from each patient. The protocol was registered: clinicaltrial.gov identifier no. NCT00534664. Translational Therapeutics Administration of AM EMFs The generator of AM EMFs consists of a battery-driven radiofrequency (RF) EMF generator connected to a 1.5 m long 50 O coaxial cable, to the other end of which a stainless-steel spoonshaped mouthpiece is connected via an impedance transformer ( We have previously reported the discovery of HCC-specific modulation frequencies in 46 patients with HCC using a patientbased biofeedback approach and shown the feasibility of using AM EMFs for the treatment of patients with cancer The treatment method consists of the administration of AM EMFs by means of an electrically conducting mouthpiece, which is Translational Therapeutics in direct contact with the oral mucosa ( Efficacy end points and disease assessment The primary end point of this trial was the proportion of patients progression-free at 6 months. Secondary end points were progression-free survival (PFS) (first day of treatment until progression of disease or death) and overall survival (OS) (first day of receiving treatment to death). Objective response was assessed using the Response Evaluation Criteria in Solid Tumours group classification for patients with disease assessed by either helical multiphasic CT (Therasse et al, 2000). Whenever contrastenhanced US radiological assessment was used, it was performed and reviewed by the same radiologist specialised in HCC (MCC) as this imaging modality is investigator dependent. Tumour measurements were performed at baseline and every 8 weeks. Only patients with at least one repeat tumour measurement during therapy were considered for response analysis. Throughout the study, lesions measured at baseline were evaluated using the same technique (CT or contrast-enhanced US). Overall tumour response was scored as a complete response (CR), partial response (PR), or stable disease (SD) if the response was confirmed at least 4 weeks later. Alpha-fetoprotein (AFP) levels were measured every 8 weeks in all patients throughout the study, but changes in AFP were not an end point for assessment of response. Pain was assessed according to the NCI-CTCAE v.3.0 (http://ctep.cancer.gov/protocolDevelopment/electronic_applications/docs/ctcaev3.pdf). Statistical analyses and efficacy assessment All eligible patients who began treatment were considered assessable for the primary and secondary end points. A Simon two-stage phase II minimax design was used (Simon, 1989) to evaluate the rate of progression-free survival at 6 months. The interim analysis was performed once enrolment into the first stage was completed. In the first stage, 23 patients were observed. If two or fewer patients had progression-free survival X6 months, the trial would be terminated early for lack of efficacy. If the progression-free survival of 3 or more of the first 23 patients was equal or greater than 6 months, then an additional 18 patients would be enrolled to a maximum of 41 patients. If eight or more of the 41 had PFS of at least 6 months, we would conclude that the treatment was efficacious. This design had a Type I error rate of 5% and a Type II error rate of 10% for the null hypothesis of a 6-month PFS rate of 10% vs the alternative of 27.5%. KaplanMeier estimates of survival, PFS, and duration of response were calculated with standard errors based on Greenwood's formula. These calculations were performed using the Proc Lifetest in SAS 9.2 (SAS Institute Inc., Cary, NC, USA). RESULTS Patient recruitment and follow-up From October 2005 to July 2007, 267 patients were assessed for eligibility ( Translational Therapeutics A total of 31 patients (75.6%) had radiological evidence of disease progression at the time of enrolment as defined by comparison of baseline imaging studies, with imaging studies obtained within the previous 6 months; 34 (82.9%) patients had received therapy before enrolment, five (14.6%) of them systemic chemotherapy or sorafenib Treatment efficacy Six of the first 23 patients (26.1%) had progression-free survival X6 months, which led us to continue enrolling patients up to the preplanned total of 41 patients A total of 28 patients were evaluable for tumour response Translational Therapeutics patients without biopsy-proven disease subsequently withdrew consent after 4.9 months to undergo liver transplantation. The patient died of progression of disease 9.4 months later before undergoing liver transplantation. One patient with Child -Pugh B disease had a partial response lasting 11.7 months and died of gastrointestinal bleeding. One patient died of disease progression at 44.6 months. Overall, there were six long-term survivors with an OS greater than 24 months and four long-term survivors with an OS greater than 3 years. Importantly, five of the six (83%) long-term survivors had radiological evidence of disease progression at the time of study enrolment In all, 11 patients reported pain before treatment initiation, 3 patients reported grade 3, 5 patients reported grade 2, and 3 patients grade 1. Five patients reported complete disappearance of pain and two patients reported decreased pain shortly after treatment initiation. Two patients reported no changes and two patients reported increased pain. There were no treatment-related grade 2, 3, or 4 toxicities. The only treatment-related adverse events were grade 1 mucositis (one patient) and grade 1 somnolence (one patient) over a total of 266.8 treatment months. DISCUSSION Treatment with AM EMFs did not show any significant toxicity despite long-term treatment. The lack of toxicity experienced by the 41 patients presented in this report as well as the 28 patients from our previous report These data are comparable to recent phase II studies evaluating the effectiveness of standard chemotherapy as well as novel targeted therapies in HCC The majority of patients enrolled in this study had either failed standard treatment options or had severely impaired liver function that limited their ability to tolerate any form of systemic or intrahepatic therapy. Indeed, 16 patients (39.0%) had Child -Pugh B8 or B9 disease. Among these patients, the median progressionfree survival was 4.4 months (95% CI 1.6 -7.6 months), which is identical to that of the entire group. Five of these 16 patients (31.3%) received therapy for more than 7.5 months, which indicates that this therapy is well tolerated even in patients with severely impaired liver function. Previous treatment with standard chemotherapy or sorafenib does not seem to impact the effectiveness of AM EMFs in the treatment of HCC. Indeed, three of the four patients who had a Translational Therapeutics partial response while receiving AM EMFs had received previous systemic therapies (chemotherapy and sorafenib) and one had received intrahepatic therapy with 131 I-lipiodol. Tumour shrinkage as assessed by radiological imaging as well as changes in AFP levels were documented in patients with advanced HCC receiving RF EMF modulated at HCC-specific frequencies administered by an intrabuccal probe. Antitumour activity in patients with advanced HCC was exemplified by partial responses observed in four patients (9.8%) and decreases in AFP levels greater than 20% in four patients. A total of 18 patients (43.9%) either had objective response or SD X6 months. Importantly, this therapeutic approach has long-lasting therapeutic effects in several patients with metastatic cancer. Two of these patients, one with recurrent thyroid cancer metastatic to the lungs Our phase I/II study has several limitations. First, only 19 of the 41 patients had biopsy-proven HCC, and the others were diagnosed by clinical criteria, an approach similar to that used in a recently reported phase II trial evaluating the clinical and biological effects of bevacizumab in unresectable HCC (Siegel et al, 2008). Importantly, analysis restricted to these 19 patients shows rates of progression-free survival at 6 months, median progression-free survival and OS that are similar to those without biopsyproven HCC Antitumour response is considered the primary end point for phase II studies to proceed to further investigations. Studies applying Cox proportional hazards analysis indicate that this end point is consistently associated with survival in trials of locoregional therapies for HCC (Llovet et al, 2002) and a recent consensus article suggests that randomised studies are necessary to capture the true efficacy of novel therapies in HCC (Llovet et al, 2008a). In summary, the encouraging findings from this study warrant a randomised study to determine the impact of AM EMFs on OS and time to symptomatic progression. ACKNOWLEDGEMENTS We thank Drs Al B Benson III, Northwestern University and Leonard B Saltz, Memorial Sloan-Kettering Cancer Center for reviewing the manuscript. There is clinical evidence that very low and safe levels of amplitude-modulated electromagnetic fields administered via an intrabuccal spoon-shaped probe may elicit therapeutic responses in patients with cancer. However, there is no known mechanism explaining the anti-proliferative effect of very low intensity electromagnetic fields. METHODS: To understand the mechanism of this novel approach, hepatocellular carcinoma (HCC) cells were exposed to 27.12 MHz radiofrequency electromagnetic fields using in vitro exposure systems designed to replicate in vivo conditions. Cancer cells were exposed to tumour-specific modulation frequencies, previously identified by biofeedback methods in patients with a diagnosis of cancer. Control modulation frequencies consisted of randomly chosen modulation frequencies within the same 100 Hz -21 kHz range as cancer-specific frequencies. RESULTS: The growth of HCC and breast cancer cells was significantly decreased by HCC-specific and breast cancer-specific modulation frequencies, respectively. However, the same frequencies did not affect proliferation of nonmalignant hepatocytes or breast epithelial cells. Inhibition of HCC cell proliferation was associated with downregulation of XCL2 and PLP2. Furthermore, HCC-specific modulation frequencies disrupted the mitotic spindle. CONCLUSION: These findings uncover a novel mechanism controlling the growth of cancer cells at specific modulation frequencies without affecting normal tissues, which may have broad implications in oncology. Conflict of interes

Diferenças de nichos entre duas espécies simpátricas de lagartos (Cnemidophorus abaetensis e C. ocellifer) em habitat de restinga no nordeste do Brasil

Differences among sympatric lizard species usually result from differences in the use of three resources: space, time and food or some combination of these three. However, differences in resource utilization among sympatric species may simply reflect their specific ecological needs rather than competitive pressures. In this study, we analyzed the temporal, spatial and food niche of two congeneric teiids (Cnemidophorus abaetensis and C. ocellifer) living sympatrically in the "restinga" habitat of Abaeté in the Salvador Municipality, Bahia State, Brazil to assess the degree of niche differentiation among them. The whiptail species overlapped considerably in an hourly activity (Ojk = 0.93), in microhabitat use (Ojk = 0.97) and in the prey items consumed (Ojk = 0.89). Differences in amount of vegetation in the microhabitats used by both lizard species may have contributed to differences in the activity period and in the distribution of the main prey eaten by these lizards which may, in turn, facilitate their coexistence in Abaeté. Although sympatric C. ocellifer and C. abaetensis in Abaeté differed only slightly in their use of microhabitats, period of activity and diet, the most important niche dimension segregating the two species seemed to be the food niche._____________________________________________________________________________________ RESUMO: As diferenças entre espécies simpátricas geralmente podem ser atribuídas às variações na utilização de três dimensões primárias de recurso: o período de atividade, o microhabitat e o alimento ou a alguma combinação das três. No entanto, tais diferenças na utilização de recursos entre espécies simpátricas têm sido sugeridas mais como um reflexo de suas necessidades ecológicas específicas do que resultado de pressão competitiva. Neste estudo, avaliou-se o nicho temporal, o espacial e o alimentar de dois teídeos cogenéricos (Cnemidophorus abaetensis e C. ocellifer) vivendo em simpatria na restinga de Abaeté em Salvador, Bahia. As duas espécies de lagartos sobrepõem-se consideravelmente no período de atividade (Ojk = 0,93), no uso dos microhabitats (Ojk = 0,97) e nos tipos de presas consumidas (Ojk = 0,89). As diferenças na quantidade de vegetação nos microhabitats utilizadas pelas duas espécies podem ter contribuído para as diferenças no período de atividade e na distribuição dos principais tipos de presas consumidas por estas duas espécies de lagartos, o que pode ter favorecido a coexistência entre elas na restinga do Abaeté. No entanto, as diferenças na dieta são as mais significativas para a segregação

Free energy estimation of short DNA duplex hybridizations

<p>Abstract</p> <p>Background</p> <p>Estimation of DNA duplex hybridization free energy is widely used for predicting cross-hybridizations in DNA computing and microarray experiments. A number of software programs based on different methods and parametrizations are available for the theoretical estimation of duplex free energies. However, significant differences in free energy values are sometimes observed among estimations obtained with various methods, thus being difficult to decide what value is the accurate one.</p> <p>Results</p> <p>We present in this study a quantitative comparison of the similarities and differences among four published DNA/DNA duplex free energy calculation methods and an extended Nearest-Neighbour Model for perfect matches based on triplet interactions. The comparison was performed on a benchmark data set with 695 pairs of short oligos that we collected and manually curated from 29 publications. Sequence lengths range from 4 to 30 nucleotides and span a large GC-content percentage range. For perfect matches, we propose an extension of the Nearest-Neighbour Model that matches or exceeds the performance of the existing ones, both in terms of correlations and root mean squared errors. The proposed model was trained on experimental data with temperature, sodium and sequence concentration characteristics that span a wide range of values, thus conferring the model a higher power of generalization when used for free energy estimations of DNA duplexes under non-standard experimental conditions.</p> <p>Conclusions</p> <p>Based on our preliminary results, we conclude that no statistically significant differences exist among free energy approximations obtained with 4 publicly available and widely used programs, when benchmarked against a collection of 695 pairs of short oligos collected and curated by the authors of this work based on 29 publications. The extended Nearest-Neighbour Model based on triplet interactions presented in this work is capable of performing accurate estimations of free energies for perfect match duplexes under both standard and non-standard experimental conditions and may serve as a baseline for further developments in this area of research.</p

Aphids acquired symbiotic genes via lateral gene transfer

<p>Abstract</p> <p>Background</p> <p>Aphids possess bacteriocytes, which are cells specifically differentiated to harbour the obligate mutualist <it>Buchnera aphidicola </it>(γ-Proteobacteria). <it>Buchnera </it>has lost many of the genes that appear to be essential for bacterial life. From the bacteriocyte of the pea aphid <it>Acyrthosiphon pisum</it>, we previously identified two clusters of expressed sequence tags that display similarity only to bacterial genes. Southern blot analysis demonstrated that they are encoded in the aphid genome. In this study, in order to assess the possibility of lateral gene transfer, we determined the full-length sequences of these transcripts, and performed detailed structural and phylogenetic analyses. We further examined their expression levels in the bacteriocyte using real-time quantitative RT-PCR.</p> <p>Results</p> <p>Sequence similarity searches demonstrated that these fully sequenced transcripts are significantly similar to the bacterial genes <it>ldcA </it>(product, LD-carboxypeptidase) and <it>rlpA </it>(product, rare lipoprotein A), respectively. <it>Buchnera </it>lacks these genes, whereas many other bacteria, including <it>Escherichia coli</it>, a close relative of <it>Buchnera</it>, possess both <it>ldcA </it>and <it>rlpA</it>. Molecular phylogenetic analysis clearly demonstrated that the aphid <it>ldcA </it>was derived from a rickettsial bacterium closely related to the extant <it>Wolbachia </it>spp. (α-Proteobacteria, Rickettsiales), which are intracellular symbionts of various lineages of arthropods. The evolutionary origin of <it>rlpA </it>was not fully resolved, but it was clearly demonstrated that its double-ψ β-barrel domain is of bacterial origin. Real-time quantitative RT-PCR demonstrated that <it>ldcA </it>and <it>rlpA </it>are expressed 11.6 and 154-fold higher in the bacteriocyte than in the whole body, respectively. LdcA is an enzyme required for recycling murein (peptidoglycan), which is a component of the bacterial cell wall. As <it>Buchnera </it>possesses a cell wall composed of murein but lacks <it>ldcA</it>, a high level of expression of the aphid <it>ldcA </it>in the bacteriocyte may be essential to maintain <it>Buchnera</it>. Although the function of RlpA is not well known, conspicuous up-regulation of the aphid <it>rlpA </it>in the bacteriocyte implies that this gene is also essential for <it>Buchnera</it>.</p> <p>Conclusion</p> <p>In this study, we obtained several lines of evidence indicating that aphids acquired genes from bacteria via lateral gene transfer and that these genes are used to maintain the obligately mutualistic bacterium, <it>Buchnera</it>.</p

Life-History Evolution on Tropidurinae Lizards: Influence of Lineage, Body Size and Climate

The study of life history variation is central to the evolutionary theory. In many ectothermic lineages, including lizards, life history traits are plastic and relate to several sources of variation including body size, which is both a factor and a life history trait likely to modulate reproductive parameters. Larger species within a lineage, for example tend to be more fecund and have larger clutch size, but clutch size may also be influenced by climate, independently of body size. Thus, the study of climatic effects on lizard fecundity is mandatory on the current scenario of global climatic change. We asked how body and clutch size have responded to climate through time in a group of tropical lizards, the Tropidurinae, and how these two variables relate to each other. We used both traditional and phylogenetic comparative methods. Body and clutch size are variable within Tropidurinae, and both traits are influenced by phylogenetic position. Across the lineage, species which evolved larger size produce more eggs and neither trait is influenced by temperature components. A climatic component of precipitation, however, relates to larger female body size, and therefore seems to exert an indirect relationship on clutch size. This effect of precipitation on body size is likely a correlate of primary production. A decrease in fecundity is expected for Tropidurinae species on continental landmasses, which are predicted to undergo a decrease in summer rainfall