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We review the extent and nature of scientific knowledge of the Big-headed Amazon River Turtle, Peltocephalus dumerilianus, covering distribution, morphology, taxonomy, diet, behaviour, reproduction, and ecology. We discuss the phylogenetic position of the species and its evolutionary relationships with the other podocnemidids, comparing morphological, karyological and molecular information. Also, we describe the importance of this species and its relationship with traditional Amazonian communities, including capture techniques, uses, beliefs and taboos. Finally, we comment on the conservation status of the species and the urgent need for additional studies. Besides discussing and reinterpreting published data, we provide new information from recent genetic studies, field activities and captive observations.

Abstract Background Convalescent plasma has been used for numerous viral diseases including influenza, severe acute respiratory syndrome, Middle East respiratory syndrome and Ebola virus; however, evidence to support its use is weak. SARS-CoV-2 is a novel coronavirus responsible for the 2019 global pandemic of COVID-19 community acquired pneumonia. We have undertaken a randomized controlled trial to assess the efficacy and safety of COVID-19 convalescent plasma (CCP) in patients with SARS-CoV-2 infection. Methods CONCOR-1 is an open-label, multicentre, randomized trial. Inclusion criteria include the following: patients > 16 years, admitted to hospital with COVID-19 infection, receiving supplemental oxygen for respiratory complications of COVID-19, and availability of blood group compatible CCP. Exclusion criteria are : onset of respiratory symptoms more than 12 days prior to randomization, intubated or imminent plan for intubation, and previous severe reactions to plasma. Consenting patients are randomized 2:1 to receive either approximately 500 mL of CCP or standard of care. CCP is collected from donors who have recovered from COVID-19 and who have detectable anti-SARS-CoV-2 antibodies quantified serologically. The primary outcome is intubation or death at day 30. Secondary outcomes include ventilator-free days, length of stay in intensive care or hospital, transfusion reactions, serious adverse events, and reduction in SARS-CoV-2 viral load. Exploratory analyses include patients who received CCP containing high titre antibodies. A sample size of 1200 patients gives 80% power to detect a 25% relative risk reduction assuming a 30% baseline risk of intubation or death at 30 days (two-sided test; α = 0.05). An interim analysis and sample size re-estimation will be done by an unblinded independent biostatistician after primary outcome data are available for 50% of the target recruitment (n = 600). Discussion This trial will determine whether CCP will reduce intubation or death non-intubated adults with COVID-19. The trial will also provide information on the role of and thresholds for SARS-CoV-2 antibody titres and neutralization assays for donor qualification. Trial registration Clinicaltrials.gov NCT04348656 . Registered on 16 April 2020.

Chelonians represent an important resource in the Amazon, either as a source of protein at the base of the food chain of aquatic and transition ecosystems, or in the dispersion of seeds of plants from floodplains and flooded forests. The consumption and predatory exploitation of their meat and eggs by local populations has been, and still is, one of the main threats to these animals. Community-based conservation projects allied to official protection programs have been restoring populations of chelonians of the genus Podocnemis throughout the Amazon since 1974. In this study, we analyzed the historical time series of protection data of Podocnemis expansa, P. unifilis, P. sextuberculata and P. erythrocephala in areas protected by the government and communities in the Amazonas state and northwest of Pará state. Between 1974 and 2019, 230,444 nests and 21,350,201 hatchlings of P. expansa, 170,076 nests and 3,229,821 hatchlings of P. unifilis, 647,715 nests and 6,410,092 hatchlings of P. sextuberculata and 24,617 nests and 168,856 hatchlings of P. erythrocephala were protected. Community protection schemes emerged in 1990, and covered 80.7% of the areas and produced 64.2% of P. unifilis hatchlings and 44.6% of P. sextuberculata hatchlings. The areas with the highest production of P. expansa remain under government protection (57.4%). Using the time series of production of nests and hatchlings per beach, logistic growth curves were estimated, and the values of r and K were compared between the two protection systems (government and community). Beaches controlled by the government showed higher support capacity in the production of nests (1,910.7 ± 1,035) and hatchlings (211,513 ± 93,031) of P. expansa and P. sextuberculata (81,160 ± 34,924 hatchlings). However, the communities were more efficient in protecting nests (r = 0.102 ± 0.2315) and hatchlings (r = 0.282 ± 0.166) of P. unifilis. Community-based protection and monitoring programs are an important component that should be incorporated by the government’s environmental agencies for the management and conservation of turtles in the Amazon.

Se analizaron cuarenta pares de ovarios de hembras adultas de Peltocephalus dumerilianus (Schweigger 1812), para establecer los cambios morfológicos mensuales producidos durante un año. Se llevaron a cabo exámenes macroscópicos de los oviductos y de los ovarios de especímenes que los habitantes ribereños del municipio de Barcelos, Amazonas, Brasil, utilizaron para su consumo, usando metodológicamente la medida del diámetro y conteo de los folículos ováricos y de los cuerpos lúteos. Los resultados muestran la presencia gradual de folículos acorde con la época reproductiva, resaltando que durante el último tercio del proceso, justo antes de la postura se hacen más evidentes; se analiza la relación existente entre el tamaño de la hembra y la masa ovárica, la cual es estadísticamente significativa (F (10,29)=3,655, p < 0,05). Se hace evidente la existencia de una jerarquía ovario folicular que demuestra que para esta especie solo es posible fisiológicamente una postura por año.Forty pairs of ovaries of mature female Peltocephalus dumerilianus (Schweigger 1812) were analyzed, to establish the morphologic monthly changes that take place during one year; we examined macroscopically the oviducts and the ovaries of specimens that the riverside inhabitants of the municipality of Barcelos, Amazons, Brazil, used for their consumption. We measured the diameter and recorded the number of enlarged ovarian follicles and corpora lutea. The results show the gradual enlargement of follicles in agreement with the reproductive period, observing that during the last third of the process; just before oviposition they become more evident. The positive relationship between the size of the female and the ovarian mass, is statistically significant (F (10.29)=3.655, p < 0.05). Follicullar sizes suggest that this species nests only once a year.

Excitable media such as the myocardium or the brain consist of arrays of coupled excitable elements, in which the local excitation of a single element can propagate to its neighbors in the form of a non-linear autowave. Since each element has to pass through a refractory period immediately after excitation, the frequency of autowaves is self-limiting. In this work, we consider the case where each element is spontaneously excited at a fixed average rate and thereby initiates a new autowave. Although these spontaneous self-excitation events are modelled as independent Poisson point processes with exponentially distributed waiting times, the travelling autowaves lead collectively to a non-exponential, unimodal waiting time distribution for the individual elements. With increasing system size, a global 'clock' period T emerges as the most probable waiting time for each element, which fluctuates around T with an increasingly small but non-zero variance. This apparent synchronization between asynchronous, temporally uncorrelated point processes differs from synchronization effects between perfect oscillators interacting in a phase-aligning manner. Finally, we demonstrate that asynchronous local clocks also emerge in non-homogeneous systems in which the rates of self-excitation are different for all individuals, suggesting that this novel mechanism can occur in a wide range of excitable media.

La alimentación es uno de los aspectos más importantes en la vida de los organismos. En el grupo de los quelonios acuáticos amazónicos del género Podocnemis este aspecto es descuidado para P. sextuberculata. En este trabajo se presentan los resultados de una investigación sobre la alimentación de esta especie en la Reserva de Desarrollo Sustentable Mamirauá-RDSM. Se analizaron 235 muestras de contenidos estomacales, 117 machos y 118 hembras. Para obtener muestras de contenido estomacal, se utilizó el método de lavado con agua. Los contenidos estomacales también fueron colectados por disecación de tracto digestivo. Materia vegetal fue el ítem predominante en la alimentación de P. sextuberculata. No hubo diferencia en la frecuencia de semillas en las temporadas de aguas bajas y altas de los ríos. En todos los hábitat el volumen total de las semillas fue muy alto. La especie está adaptada a los cambios de estación, siendo las áreas inundables el hábitat más apropiado, en relación a la abundancia de las especies de la familia Poaceae. La información obtenida destaca la importancia de proteger las especies vegetales y los hábitat usados por P. sextuberculata en la RDSM.

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