Systematic reinstatement of Schilbe depressirostris (Peters, 1852), based on differences in DNA barcoding and morphology,from Schilbe intermedius Rüppell, 1832 (Siluriformes,Schilbeidae)

Climate change poses an unprecedented threat to biodiversity worldwide. Consequently, unrecognised taxa may not receive adequate conservation attention to survive. We used molecular and morphological data to address the challenge of species delimitation within the genus Schilbe. The presence or absence of an adipose fin and distribution based on east-flowing, conceivably faster-flowing, or west-flowing, probably more slow-flowing, river systems were considered. Distinctive geographic patterns in genetic variation within southern, eastern, and western African populations were revealed. Particularly, the South African population is distinct from those of Namibia, Botswana and Nigeria. No individuals with rudimentary adipose fins were found at any locality, but specimens from three localities either had or did not have adipose fins. These mixed occurrences are suspected to be a result of human interventions, and that the presence of rudimentary adipose fins in the east African species could be an adaptive feature that serves to stabilise these fish in faster currents. In addition, the genetic divergence observed among African silver catfish from geographically isolated river systems is conceivably the result of micro-evolutionary adaptive responses to different environmental conditions. Collectively, these results distinguish S. depressirostris from S. intermedius.     

Living enantiosymmetric and enantioasymmetric polymerization of methylthiirane in homogeneous phase

The polymerization of racemic methylthiirane in homogeneous phase, initiated by bis(isopropyl-S-cysteinato) cadmium is a living process. The resulting polymers are isotactic and optically active at partial conversion. The optical purity of the residual monomer may reach 27% at half conversion. The propagation occurs mainly on one valency of Cd, however oligomers grow slowly on the second valency. The stereoregularity of the polymer chain appears only when the length of the oligomer becomes high enough, making possible a bicoordination of the Cd counterions. The stereoregularity of the polymer is characterized by the molar fraction σ of isotactic diads which varies from 0.5 for atactic chains—formed at the beginning—to about one for isotactic segments formed for longer chains. The stereospecifictity also depends on temperature of propagation and on initiator concentration. The kinetics observed (zero order in monomer and one-half in Cd) are explained by monomer coordination before insertion and dimeric association of the thiolate end groups. The enantioasymmetric process observed results from an unbalance in the number of the two different types of active sites and possibly from a difference in their reactivities. Enantioasymmetry has been found to decrease significantly when the dielectric constant ε of the medium increases.     

THE EFFECT OF ASSOCIATED SOIL MICROFLORA ON FUSARIUM UDUM BUTL., THE FUNGUS CAUSING WILT OF PIGEON-PEA (CAJANUS CAJAN (L.) MILLSP.)

Inoculation with Fusarium udum Butl. produced more wilt of pigeon-pea in sterilized than in unsterilized soils at the same pH. From unsterilized soils with low disease incidence, nine fungi, Bacillus subtilis and an Actinomyces were isolated. The number of isolations of a particular organism varied from month to month during the cropping season of pigeon-pea in Delhi. Interaction of Fusarium udum and other organisms isolated was studied. Aspergillus niger and A. terreus secreted inhibitory substances in potato-dextrose broth: Bacillus subtilis inhibited growth on solid medium and also produced a toxic substance in potato-dextrose broth. The nature of the medium employed and period of growth were important factors in the production of the inhibitory principle, which is thermostable. The low incidence of pigeon-pea wilt in unsterilized soils may result from the inhibitory activity of the associated microflora in the soil.     

Tritiated Water Vapour Exchange Method for the Evaluation of Whole Plant Diffusion Resistance

Water vapour exchange between plant and atmosphere was studiedby using THO as a tracer. Pulses of THO vapour were brieflyinjected into the airflow of an open circuit plant chamber.Water vapour exchange was calculated from the difference intotal quantity of THO escaping from the plant chamber with andwithout a plant The amount of THO exchanged was closely dependenton the product of total leaf area x mean leaf conductance. Themethod is suitable for measuring on the same plant short termvariations in leaf conductance following changes in environmentalconditions.     

ZONE LINES IN PLANT TISSUES

The black lines of Polyporus squamosus have been found in the wood of elms. Isolations were made from these lines and an account of the development of P. squamosus in artificial culture is given. Particular mention is made of the formation of black plates, or lines as they appear in section, in culture media and of the appearance of abnormal fructifications. Pure cultures of the fungus on sterilized wood blocks have produced black lines in the wood, similar to those occurring in nature.
From a consideration of the structure and formation of the black plates, the suggestion is made that they form the limiting layer or rind of sclerotium-like bodies buried in the attacked wood.
A review is given of sclerotium formation and structure in several species of Polyporus, and analogies are made between these sclerotia and the sclerotium-like body of P. squamosus. It is decided to distinguish the P. squamosus body from these sclerotia by naming it a pseudo-sclerotium, on the criteria previously advanced for Armillaria mellea (8).     

IVF for premature ovarian failure: first reported births using oocytes donated from a twin sister

Background  

Premature ovarian failure (POF) remains a clinically challenging entity because in vitro fertilisation (IVF) with donor oocytes is currently the only treatment known to be effective.