Buccal floor of reptiles, a summary

A general survey of the information presently available on the osteology and myology of the hyobranchial apparatus. Included in the survey are examples of the hyobranchial skeleton of the major groups of reptiles, including the Chelonia, Crocodilia, Rhynchocephalia, and Squamata. The myology treats the muscles directly associated with the hyoid as well as those associated with the functioning of the apparatus, but not arising or inserted directly on or from the hyoid. The innervation of the hyobranchial apparatus is reviewed and briefly discussed based on the information available in a few major studies. An attempt is made to cite all pertinent literature references, and in Tables 1 and 2 the references to basic areas are indicated. Twenty - nine plates and figures are included, some of which represent original research.     

Exercise conditioning decreases downstream movement of pond-reared razorback suckers released into a stream environment

Despite augmentation stocking efforts, wild populations of razorback suckers ( Xyrauchen texanus ) continue to decline. Endangered razorback suckers are commonly raised in off-channel ponds until maturity (approximately 300 mm TL) and then stocked into the Colorado River or its tributaries. After fish are stocked, they commonly move large distances downstream. We conducted an experiment to determine if downstream dispersal could be reduced through exercise conditioning. Two groups of razorback suckers, exercised and nonexercised, were released into Fossil Creek, Arizona. Prior to release, a subsample from each treatment group was tested in a laboratory flow chamber. Razorback suckers that had been exercise conditioned were able to maintain a position in the flow chamber 2 times longer and at velocities 25 cm · s –1 higher than nonexercised fish. Although the intended method of field data collection via passive-integrated-transponder (PIT) antennas and a remote communication station failed because river otters ( Lontra canadensis ) preyed upon the released razorback suckers, implanted PIT tags were retained in otter scat. Recovered PIT tags enabled distributional analysis, which indicated that exercised razorback suckers did not move as far downstream from the point of release as nonexercised razorbacks. Exercise conditioning may increase overall fitness of pond-reared razorback suckers, and, consequently, increase the effectiveness of augmentation stocking. A pesar de los esfuerzos de repoblación, las poblaciones silvestres del matalote jorobado ( Xyrauchen texanus ) siguen en declive. Los matalotes jorobados, que están en peligro de extinción, se crían en estanques fuera del cauce hasta la etapa adulta (~300 mm) y después son liberados en el Río Colorado o uno de sus afluentes. Los peces suelen desplazarse largas distancias río abajo después de su introducción al río. Llevamos a cabo un experimento para determinar si la dispersión río abajo se podía reducir mediante el acondicionamiento por ejercicio. Dos grupos de matalotes fueron liberados en Fossil Creek, Arizona, uno que había sido acondicionado y otro que no. Antes de liberarlos, examinamos una submuestra de cada grupo en una cámara de flujo en el laboratorio. Los matalotes que habían sido acondicionados por ejercicio pudieron mantener sus posición en la cámara de flujo dos veces más tiempo y a velocidades de 25 cm · s –1 más altas que los peces no acondicionados. Aunque falló el método de colecta de datos mediante antenas de sistema PIT (passive integrated transponder) y una estación remota de comunicación, los matalotes liberados fueron depredados por nutrias de río ( Lontra canadensis ) y las marcas PIT implantadas se quedaron en las heces de las nutrias. La recuperación de estas etiquetas PIT permitió un análisis de distribución que indicó que los matalotes acondicionados no se desplazaron río abajo tan lejos del punto de liberación como los matalotes no acondicionados. El acondicionamiento por ejercicio podría mejorar la condición física de los matalotes jorobados criados en cautiverio y así aumentar la eficacia de la reintroducción.     

The God particle et al

The territory of the Large Hadron Collider might be populated not just by the Higgs particle but also by all manner of other exotic apparitions.     

Maize HapMap2 identifies extant variation from a genome in flux

Whereas breeders have exploited diversity in maize for yield improvements, there has been limited progress in using beneficial alleles in undomesticated varieties. Characterizing standing variation in this complex genome has been challenging, with only a small fraction of it described to date. Using a population genetics scoring model, we identified 55 million SNPs in 103 lines across pre-domestication and domesticated Zea mays varieties, including a representative from the sister genus Tripsacum. We find that structural variations are pervasive in the Z. mays genome and are enriched at loci associated with important traits. By investigating the drivers of genome size variation, we find that the larger Tripsacum genome can be explained by transposable element abundance rather than an allopolyploid origin. In contrast, intraspecies genome size variation seems to be controlled by chromosomal knob content. There is tremendous overlap in key gene content in maize and Tripsacum, suggesting that adaptations from Tripsacum (for example, perennialism and frost and drought tolerance) can likely be integrated into maize.     

Tetraethyl lead dose response curve for mortality in laboratory rats

Résumé On a donné à 96 rats mâles albinos six doses différentes de plomb tétra-éthyle par intubation intragastrique. Une courbe dose-réaction a été établie à partir des résultats obtenus et les calculs ont donné une valeur LD₅₀ de 12,3 mg/kg (11,50 à 13,15). Cette valeur diffère de celle qui a été obtenue précédemment. On croit que cette différence résulte du fait qu'un nombre plus grand d'échantillons a été utilisé dans cette série d'observations.     

Basic avian pulmonary design and flow-through ventilation in non-avian theropod dinosaurs

Birds are unique among living vertebrates in possessing pneumaticity of the postcranial skeleton, with invasion of bone by the pulmonary air-sac system. The avian respiratory system includes high-compliance air sacs that ventilate a dorsally fixed, non-expanding parabronchial lung. Caudally positioned abdominal and thoracic air sacs are critical components of the avian aspiration pump, facilitating flow-through ventilation of the lung and near-constant airflow during both inspiration and expiration, highlighting a design optimized for efficient gas exchange. Postcranial skeletal pneumaticity has also been reported in numerous extinct archosaurs including non-avian theropod dinosaurs and Archaeopteryx. However, the relationship between osseous pneumaticity and the evolution of the avian respiratory apparatus has long remained ambiguous. Here we report, on the basis of a comparative analysis of region-specific pneumaticity with extant birds, evidence for cervical and abdominal air-sac systems in non-avian theropods, along with thoracic skeletal prerequisites of an avian-style aspiration pump. The early acquisition of this system among theropods is demonstrated by examination of an exceptional new specimen of Majungatholus atopus, documenting these features in a taxon only distantly related to birds. Taken together, these specializations imply the existence of the basic avian pulmonary Bauplan in basal neotheropods, indicating that flow-through ventilation of the lung is not restricted to birds but is probably a general theropod characteristic.     

Methanotrophic symbionts provide carbon for photosynthesis in peat bogs

Wetlands are the largest natural source of atmospheric methane, the second most important greenhouse gas. Methane flux to the atmosphere depends strongly on the climate; however, by far the largest part of the methane formed in wetland ecosystems is recycled and does not reach the atmosphere. The biogeochemical controls on the efficient oxidation of methane are still poorly understood. Here we show that submerged Sphagnum mosses, the dominant plants in some of these habitats, consume methane through symbiosis with partly endophytic methanotrophic bacteria, leading to highly effective in situ methane recycling. Molecular probes revealed the presence of the bacteria in the hyaline cells of the plant and on stem leaves. Incubation with (13)C-methane showed rapid in situ oxidation by these bacteria to carbon dioxide, which was subsequently fixed by Sphagnum, as shown by incorporation of (13)C-methane into plant sterols. In this way, methane acts as a significant (10-15%) carbon source for Sphagnum. The symbiosis explains both the efficient recycling of methane and the high organic carbon burial in these wetland ecosystems.