Convergent Patterns of Body Shape Differentiation in Four Different Clades of Poeciliid Fishes Inhabiting Sulfide Springs

We investigated replicated differentiation in four lineages of livebearing fishes (two with the genus Poecilia and two within Gambusia), which inhabit freshwater habitats and have also colonized sulfide springs in Oklahoma, Mexico, and Venezuela. Sulfide springs are characterized by extreme hypoxia and high concentrations of toxic hydrogen sulfide, which provide a strong source of divergent selection compared to adjacent non-sulfidic habitats. Using geometric morphometric analysis of body shape, we found that sulfide spring populations significantly differ from relatives from regular freshwater habitats in all four lineages investigated. Differentiation is characterized by strong patterns of convergent evolution, with sulfide spring populations consistently exhibiting an increase in head size, even though the magnitude and nature differences varied across lineages. Head size is strongly correlated with an increase in gill size in sulfide spring populations of the genus Poecilia, which facilitates efficient oxygen acquisition in the hypoxic H₂S-environment and directly affects survival. The convergent patterns of differentiation support previous findings about the effects of sulfide on trait evolution.     

Phytotoxic effects of β-pinene on early growth and associated biochemical changes in rice

β-Pinene, an oxygenated monoterpene, is one of the major monoterpenes emitted into the atmosphere from forest areas and trees. Besides, it is a principal component of essential oils of a number of aromatic plants, which are involved in a variety of ecological interactions, including allelopathy, in the natural environment. However, studies pertaining to phytotoxicity and biochemical effect(s) of β-pinene are largely lacking. We investigated the effect of β-pinene (0.02, 0.04, 0.08, 0.20, 0.40 and 0.80 mg/ml) in a dose- and time-dependent manner on early seedling growth, dry weight accumulation, photosynthetic pigments and changes in macromolecule (protein and carbohydrate) content and activities of enzymes—proteases, α- and β-amylases, polyphenol oxidases and peroxidases- in rice (Oryza sativa) after 3rd, 5th and 7th day of exposure. β-pinene (≥0.04 mg/ml) significantly reduced the root (by 13–87%) and coleoptile (by 5–80%) length of rice. Exposure to β-pinene reduced total chlorophyll content in rice coleoptiles suggesting a negative impact on photosynthesis. The content of macromolecules (proteins and carbohydrates) enhanced significantly in response to β-pinene, whereas the activities of hydrolyzing enzymes—proteases, α-amylases, and β-amylases—declined (by 30–85, 26–84, 27–74%, respectively) in β-pinene-exposed seedlings. In contrast, the activities of peroxidases (POX) and polyphenol oxidases (PPO) enhanced significantly (by 16–152 and 53–290%, respectively) in rice roots in response to β-pinene in a dose- and time-dependent manner. Increased activities of POX and PPO indicate their involvement in providing protection and/or conferring resistance against β-pinene-induced stress. The study concludes that β-pinene inhibits the early growth of rice by altering the plant biochemical status and enhancing activities of POXs and PPOs involved in general plant defense.     

Anti-hemolytic and Peroxyl Radical Scavenging Activity of Organoselenium Compounds: An In Vitro Study

Selenium-containing amino acids, selenocystine (CysSeSeCys), methylselenocysteine (MeSeCys), and selenomethionine (SeMet) have been examined for anti-hemolytic and peroxyl radical scavenging ability. Effect of these compounds on membrane lipid peroxidation, release of hemoglobin, and loss of intracellular K⁺ ion as a consequence of peroxyl radicals-induced oxidation of human red blood cells were used to evaluate their anti-hemolytic ability. The peroxyl radicals were generated from thermal degradation of 2,2′-azobis(2-methylpropionamidine) dihydrochloride. Significant delay (t _eff) was observed in oxidative damage in the presence of the selenium compounds. From the IC₅₀ values for the inhibition of hemolysis, lipid peroxidation, and K⁺ ion leakage, the relative anti-hemolytic ability of the compounds were found to be in the order of CysSeSeCys > MeSeCys > SeMet. The anti-hemolytic abilities of the compounds, when compared with sodium selenite (Na₂SeO₃) under identical experimental conditions, were found to be better than Na₂SeO₃. Relative rate constants estimated for the reaction of MeSeCys and SeMet with peroxyl radicals by competition kinetics using ABTS²⁻ as a reference confirmed that all the compounds are efficient peroxyl radical scavengers. Comparison of the GPx-like activity of these compounds, by NADPH–GSH reductase coupled assay, indicated that CysSeSeCys exhibits the highest activity. Based on these results, it is concluded that among the compounds examined, CysSeSeCys, possessing the ability to reduce peroxyl radicals and hydroperoxides showed efficient anti-hemolytic activity.     

Mantled Howler (<Emphasis Type=Italic>Alouatta palliata</Emphasis>) Arboreal Pathway Networks: Relative Impacts of Resource Availability and Forest Structure

Numerous studies have concluded that primates move about their environments in a nonrandom manner, frequently traveling between consecutive foraging sites along relatively straight-line paths. However, primates do not always take the most direct path between resources, and a number of species have been observed to travel repeatedly along a network of the same arboreal pathways. In this study, I used spatially explicit techniques to examine quantitatively what mantled howler monkey groups on Barro Colorado Island, Panama, accomplish by selecting nonlinear paths between resources and by repeatedly using the same paths within an arboreal network. Results show that chosen arboreal paths between sites where foraging occurred have higher levels of resource availability and canopy connectivity than comparable straight-line paths between the same sites. When comparing the relative importance of these factors, autologistic models of pathway choice indicate that though canopy connectivity is related to the location of repeatedly used arboreal pathway networks, the most statistically significant predictor is resource availability (both on a path and within a visual detection distance of a path). These results provide support for the hypothesis that repeated use of arboreal pathway networks aids in resource monitoring and acquisition. In addition, statistical models developed from 1 primary focal group’s travel patterns had high predictive value when employed to generate likely locations for arboreal pathways in the home ranges of 3 neighboring groups. This finding has important implications for studies of primate habitat use and seed dispersal, as it suggests that different groups consistently use similar characteristics when deciding on travel paths.     

An efficient protocol for stimulating cell development in protoplast culture of S<Emphasis Type=Italic>caevola</Emphasis>

Scaevola, characterised by unique fan-shaped flowers, is an Australian endemic ornamental having a great commercial potential. The breeding of Scaevola however is limited due to poor seed germination, therefore it is critical to understand the embryogenesis in Scaevola so as to facilitate its breeding improvement programs. Direct differentiation of embryo structures was first reported here in mesophyll protoplast cultures of Scaevola aemula. The isolated protoplasts initiated cell division when cultured in KM or MS medium. Higher plating efficiencies were observed in the medium containing a combination of NAA and BAP in contrast to 2,4-D and BAP. The formation of globular embryo structures was successfully achieved. This protoplast culture system can be utilized as an experimental platform for the study of embryogenic differentiation of cells. It may open new vistas to investigate the seed development at molecular and cellular levels in Scaevola and related Australian native plants that are well known for their low seed viability and germination.     

Jurassic mountain building and Mesozoic-Cenozoic geodynamic evolution of the Northern Calcareous Alps as proven in the Berchtesgaden Alps (Germany)

New data from the Berchtesgaden Alps result in a reconstruction of the Mesozoic-Cenozoic geodynamic history of the Northern Calcareous Alps. The closure of the western part of the Neotethys Ocean started in the late Early Jurassic and is evidenced by the onset of thick clay-rich sediments in the outer shelf area (=Hallstatt realm). The Middle to early Late Jurassic contraction is documented by the migration of trench-like basins formed in front of a propagating thrust belt. Due to ophiolite obduction, these basins propagated from the outer shelf area, forming there the Bajocian to Oxfordian Hallstatt Mélange, to the Hauptdolomit/Dachstein platform area, where the Oxfordian Rofan and Tauglboden Mélanges were formed. The basins were separated by nappe fronts forming structural highs. This scenario mirrors syn-orogenic erosion and deposition in an evolving thrust belt. Active basin formation and nappe thrusting ended around the Oxfordian/Kimmeridgian boundary, which was followed by the onset of carbonate platforms on structural highs prograding towards the former basins in latest Oxfordian to Early Tithonian time. Underfilled basins remained between the platforms. Rapid deepening around the Early/Late Tithonian boundary was induced by extension due to mountain uplift and resulted in the reconfiguration of the platforms and basins related to normal and probably strike-slip faults. Erosion of the uplifted nappe stack including obducted ophiolites caused final drowning and demise of the platforms in the Berriasian. The remaining Early Cretaceous basins were filled up with molasse sediments including siliciclastics until Aptian. Around the Early/Late Cretaceous boundary again extension and strike-slip movements started, followed by Eocene thrusting and Miocene strike-slip movements with block rotations. These younger tectonic movements destroyed the Triassic to Early Cretaceous palaeogeography and arranged the modern block configuration. The described Jurassic to Early Cretaceous history corresponds with that of the Western Carpathians, the Dinarides, and the Albanides, where (1) age dating of the metamorphic soles prove late Early to Middle Jurassic inneroceanic thrusting followed by late Middle to early Late Jurassic ophiolite obduction, (2) Kimmeridgian to Tithonian shallow-water platforms formed on top of the obducted ophiolites, and (3) latest Jurassic to Early Cretaceous sediments show postorogenic character. Therefore, we correlate the Jurassic geodynamic evolution of the Northern Calcareous Alps with the closure of the western part of the Neotethys Ocean.     

Makes a Difference

Michael Strevens has produced an ambitious and comprehensive new account of scientific explanation. This review discusses its main themes, focusing on regularity explanation and a number of methodological concerns.     

Homochiral Selectivity in RNA Synthesis: Montmorillonite-catalyzed Quaternary Reactions of D,L-Purine with D,L- Pyrimidine Nucleotides

Selective adsorption of D, L-ImpA with D, L-ImpU on the platelets of montmorillonite demonstrates an important reaction pathway for the origin of homochirality in RNA synthesis. Our earlier studies have shown that the individual reactions of D, L-ImpA or D, L-ImpU on montmorillonite catalyst produced oligomers which were only partially inhibited by the incorporation of both D- and L-enantiomers. Homochirality in these reactions was largely due to the formation of cyclic dimers that cannot elongate. We investigated the quaternary reactions of D, L-ImpA with D, L-ImpU on montmorillonite. The chain length of these oligomers increased from 9-mer to 11-mer as observed by HPLC, with a concominant increase in the yield of linear dimers and higher oligomers in the reactions involving D, L-ImpA with D, L-ImpU as compared to the similar reactions carried out with D-enantiomers only. The formation of cyclic dimers of U was completely inhibited in the quaternary reactions. The yield of cyclic dimers of A was reduced from 60% to 10% within the dimer fraction. 12 linear dimers and 3 cyclic dimers were isolated and characterized from the quaternary reaction. The homochirality and regioselectivity of dimers were 64.1% and 71.7%, respectively. Their sequence selectivity was shown by the formation of purine-pyrimidine (54–59%) linkages, followed by purine-purine (29–32%) linkages and pyrimidine-pyrimidine (9–13%) linkages. Of the 16 trimers detected, 10 were homochiral with an overall homochirality of 73–76%. In view of the greater homochirality, sequence- and regio- selectivity, the quaternary reactions on montmorillonite demonstrate an unexpectedly favorable route for the prebiotic synthesis of homochiral RNA compared with the separate reactions of enantiomeric activated mononucleotides.     

Late Cretaceous sedimentary evolution of a northern sector of the Adriatic Carbonate Platform (Matarsko Podolje,SW Slovenia)

Cretaceous shallow-marine carbonate rocks of SW Slovenia were deposited in the northern part of the Adriatic Carbonate Platform. A 560-m-thick continuous Upper Cenomanian to Santonian carbonate succession has been studied near Hru?ica Village in Matarsko Podolje. With regard to lithological, sedimentological, and stratigraphical characteristics, the succession has been divided into nine lithostratigraphic units, mainly reflecting regressive and transgressive intervals of larger scale. During the latest Cenomanian and Early Turonian, hemipelagic limestones were deposited on top of shallow-marine lagoon and peritidal Upper Cenomanian deposits indicating relative sea-level rise. Subsequently, the deeper marine depositional setting was gradually filled by clinoform bioclastic sand bodies overlain by peritidal and shallow-marine low-energy mainly lagoonal lithofacies. Similar lithofacies of predominately inner ramp/shelf depositional settings prevail over the upper part (i.e., Coniacian to Santonian) of the succession. In the area, the Upper Cetaceous carbonate rocks are separated from the overlying Lower Eocene (Upper Paleocene?) carbonate sequence by regional unconformity denoted by distinct paleokarstic features. On the Adriatic Carbonate Platform the deeper marine carbonate setting, developed at the Cenomanian/Turonian boundary, is usually correlated with OAE2 and related eustatic sea-level rise. Similarly, subsequent reestablished shallow-marine conditions are related to Late Turonian long- and short-term sea-level fall. However, we are suggesting that deeper marine deposits were deposited in a tectonically induced intraplatform basin formed simultaneously with the uplift of the northern and northeastern marginal parts of the Adriatic Carbonate Platform.