Über einige Vertreter der Eryopoidea (Amphibia: Temnospondyli) aus dem europäischen Rotliegend (? höchstes Karbon — Perm) 1.Sclerocephalus

The chronospeciesSclerocephalus bavaricus andSclerocephalus haeuseri, with the chronosubspeciesS. h. haeuseri andS. h. jeckenbachensis n. ssp., are redescribed based on material from the lower Rotliegend of the Saar-Nahe region (southern Germany). For the first time numerous features of the skull and postcranial skeleton as wellas the ontogenetic development of the skull are documented. The evolution of these species is discussed.     

Root Morphology and Nitrogen Uptake of Maize Simultaneously Supplied with Ammonium and Nitrate in a Split-root System

We studied the response of maize (Zea mays L. cv. Anjou 256)to a simultaneous, but separated supply of ammonium and nitrate(localized supply, LS). A split-root system was used to supplyhalf of the roots with ammonium and the other half with nitrate.A homogeneously distributed supply of both nitrogen forms (HS)was the control treatment. Seedlings were grown for 12 d fromthe two-leaf to the three-leaf stage in hydroponics at threepH levels (4, 5·5 and 7). The total N concentration was3 mol m^-3. The split-root system was established by removingthe seminal root system and using only four nodal roots perplant. Total root length and root surface area were recordedautomatically with a modified Delta- T area meter. Other morphologicalroot traits (such as main axis length and diameter, number,density, and length of laterals) were recorded manually. Uptakeof ammonium and nitrate was measured by the depletion of thenutrient solution. As compared with LS, HS was superior in shootand root DM, total root length and root surface area, ammoniumand nitrate uptake and shoot nitrogen concentration, irrespectiveof pH level. This indicates that, also under field conditions,mixed ammonium and nitrate fertilization is only beneficialto plant growth if both N forms are evenly distributed in thesoil. At both HS and LS, ascending pH increased the ammonium:nitrateuptake ratio. At LS, declining pH induced a considerable shiftin the distribution of root DM, root length, and root surfacearea the nitrate-fed compartment.Copyright 1993, 1999 AcademicPress Maize, Zea may L., ammonium, nitrate, pH, root morphology, split-root     

Scaling of limb joint surface areas in anthropoid primates and other mammals

Recently it was reported that limb joint surface areas scale positively allometrically with body weight in anthropoid primates. This was attributed to the biomechanics of weight bearing: larger animals must require relatively larger joint surfaces to withstand relatively greater weight-related stresses on the joints. Our data on humeral and femoral geometry and joint surface areas in 73 species belonging to six mammalian orders (including primates) demonstrate that positive allometry of joint surface areas is not a general phenomenon for mammals and cannot have its basis among Anthropoidea in the biomechanics of weight bearing. We argue that, to the extent that positive allometric scaling of joint surface areas occurs in anthropoid primates, it is an artifact of differences in positional behaviour among distinct taxonomic groups that also happen to differ widely in body weight. Furthermore, we argue that, among mammals ranging in body size from sportive lemurs to giant pandas, functionally similar groups tend to exhibit: (1) linear dimensions (especially diameters and shaft circumferences) that scale in direct proportion to each other; and (2) joint surface areas that scale in direct proportion to the squares of linear dimensions and to the 2/3 power of body mass. In other words, limb bones of functionally similar animals fit the theoretical model of geometric similarity (or skeletal isometry). Differences in relative sizes of joint surface areas are related to differences in force transmission and movement potential among functionally distinct groups of animals.     

The relA locus and the regulation of lysine biosynthesis in Escherichia coli

Summary The allelic state of relA influences the phenotype of Escherichia coli strains carrying the lysA22 mutation: lysA22 relA strains are Lys^– where lysA22 relA ⁺ strains grow (slowly) in the absence of lysine. This physiological effect has been related to an effect of the expression of the relA locus on the regulation of lysine biosynthesis. The fully derepressed levels of some lysine enzymes (aspartokinase III, aspartic semialdehyde dehydrogenase, dihydrodipicolinate reductase) are observed under lysine limitation only in rel ⁺ strains. And the induction of DAP-decarboxylase by DAP is much higher in rel ⁺ than in rel ^– strains when an amino acid limitation of growth is also realised. These results are in agreement with the hypothesis of Stephens et al. (1975) on a possible role of the stringent regulation as a general signal for amino acid deficiency.     

Regulation of the lysine biosynthetic pathway in Escherichia coli K-12: isolation of a cis-dominant constitutive mutant for AK III synthesis.

A method for isolating regulatory mutants for the synthesis of lysine biosynthetic enzymes in Escherichia coli is described. One of them is identified as a cis-dominant constitutive mutant for the synthesis of the lysine-sensitive asportokinase AK III (lysC gene).     

Phenotypic and genetic differentiation between diadromous and landlocked puyen Galaxias maculatus

This study reports the phenotypic and genetic differences between individuals of puyen Galaxias maculatus from two sites in the same river basin in Tierra del Fuego National Park, southern South America. Individuals from the two sampling sites presented morphometric and genetic differences. The morphometric differences indicated that individuals from Laguna Negra (LN) were short and more robust and had large eyes, whereas those from Arroyo Negro (AN) were thin and elongated and had small eyes. Genetic differences showed that AN individuals had a greater genetic structuration and an older demographic history than LN individuals. The results of this study affirmed that the individuals from the two sampling sites belong to different populations with a high degree of isolation. The demographic history could indicate that the individuals of G. maculatus which migrated to northern areas during the last glaciation settled in the Beagle Channel after its formation. The LN population could have originated after the retreat of the glaciers, migrating from AN.     

Effect of starvation on growth rate,muscle growth and energy density of puyen,Galaxias maculatus

Seasonal growth of Galaxias maculatus in Tierra del Fuego, at the southern limit of its distribution, can be explained by the variation in extrinsic factors, and experiments with fasting in summer conditions would allow researchers to focus on the potential feeding/fasting conditions independent of other seasonal cues, and thus distinguish the effect of fasting from other winter factors influencing fish growth. The study presents information on muscle growth in G. maculatus as well as the results of an experiment evaluating the effect of fasting on the growth rate, total muscle growth and energy density in this species under summer‐like conditions. A uniform pattern of muscle fibres suggests the absence of mosaic hyperplastic growth in G. maculatus. Hyperplasic growth was completed before puyen reached 65 mm total length, and hyperplasia cessation was correlated to the transition from the juvenile to the adult stage. In the experimental fish, where hypertrophic growth was the unique process responsible for adult muscle growth, fasting decreased mass, condition and energy density of the individuals, and stopped hypertrophic growth. These results are proof that reduced food consumption in southerly puyen populations during winter might contribute to the seasonality of the growth previously reported for this species. A provisional summer growth rate of 2–3 mm/month is suggested for populations inhabiting the southern limits of this species' distribution. G. maculatus is thus proposed as a useful model species to study hypertrophic muscle growth.     

Soil organic carbon stocks in estuarine and marine mangrove ecosystems are driven by nutrient colimitation of P and N

Mangroves play an important role in carbon sequestration, but soil organic carbon (SOC) stocks differ between marine and estuarine mangroves, suggesting differing processes and drivers of SOC accumulation. Here, we compared undegraded and degraded marine and estuarine mangroves in a regional approach across the Indonesian archipelago for their SOC stocks and evaluated possible drivers imposed by nutrient limitations along the land‐to‐sea gradients. SOC stocks in natural marine mangroves (271–572 Mg ha^?1 m^?1) were much higher than under estuarine mangroves (100–315 Mg ha^?1 m^?1) with a further decrease caused by degradation to 80–132 Mg ha^?1 m^?1. Soils differed in C/N ratio (marine: 29–64; estuarine: 9–28), δ¹⁵N (marine: ?0.6 to 0.7‰; estuarine: 2.5 to 7.2‰), and plant‐available P (marine: 2.3–6.3 mg kg^?1; estuarine: 0.16–1.8 mg kg^?1). We found N and P supply of sea‐oriented mangroves primarily met by dominating symbiotic N₂ fixation from air and P import from sea, while mangroves on the landward gradient increasingly covered their demand in N and P from allochthonous sources and SOM recycling. Pioneer plants favored by degradation further increased nutrient recycling from soil resulting in smaller SOC stocks in the topsoil. These processes explained the differences in SOC stocks along the land‐to‐sea gradient in each mangrove type as well as the SOC stock differences observed between estuarine and marine mangrove ecosystems. This first large‐scale evaluation of drivers of SOC stocks under mangroves thus suggests a continuum in mangrove functioning across scales and ecotypes and additionally provides viable proxies for carbon stock estimations in PES or REDD schemes.