THE “BIOTYPES” OF THE RICE BROWN PLANTHOPPER,NILAPARVATA LUGENS

From previous studies, the biological nature of the so-called biotypes of N. lugens is obscure. Experiments on biotypes 1, 2 and 3 from the Philippines demonstrated that they lacked significant breeding barriers. Inbred biotype cultures showed considerable variation and overlap between each other in virulence. A field population from the Philippines was similarly variable and included individuals which could be attributed to different biotypes. It is concluded that the use of the term biotype in this species is biologically misleading and undesirable.

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Résumé La nature biologique de ce qui a été appelé des biotypes de Nilaparvata lugens, paraît obscure si l'on se réfère aux études antérieures. Des expériences sur les biotypes 1, 2 et 3 des Philippines révèlent qu'ils ne présentent pas de barrières sexuelles significatives. Les élevages consanguins de biotypes présentent une variabilité considérable, et les virulances des biotypes se chevauchent les unes les autres. De même une population récoltée dans les çhamps aux Philippines était hétérogène et comprenait des individus qui auraient pu être rattachés à différents biotypes. On peut en conclure que le terme de biotype est, pour cette espèce, inapproprié et indésirable.

     

Seasonal changes and alternation of food plant preference in some mesophyll-feeding leafhoppers

Summary The life histories of two bivoltine mesophyll-feeding leafhoppers, Lindbergina aurovittata (Douglas) and Edwardsiana rosae (L.), in South Wales are described. L. aurovittata alternates between evergreen Rubus and Quercus in the first generation and various deciduous broad-leaved trees in the second. Experiments on nymphal food preferences and adult oviposition behaviour show that nymphs of both generations tend to prefer older to younger leaves, but show little species specificity. However, adults are discriminating in oviposition preferences, which change regularly and completely in alternating generations. Similar results were obtained with E. rosae. Such obligate seasonal changes in host preferences and utilization are well known amongst aphids, but previously have not been reported in leafhoppers.     

Management of coastal ecosystems in eastern Sumatra: the case of Berbak Wildlife Reserve,Jambi Province

The eastern lowlands of Sumatra comprise about 88 000 square kilometres, or approximately eighteen percent of the island's total area. Most of these lowlands were originally peatswamp forest, freshwater swamp forest and mangrove. A significant proportion of the area is subject to tidal influence.The lowlands have experienced a variety of land uses, firstly by the native people, who were mainly hunter-gatherers, later by the Buginese and Banjarese immigrants from Sulawesi and Kalimantan respectively, and more recently by transmigrants from Java, Bali and Madura.Land uses have involved principally agriculture, logging and fishing, and a wide range of associated activities. As in most attempts to settle and convert wetlands to other uses, there have been many problems. The Berbak Wildlife Reserve located on the southeast coast of the Province of Jambi provides a microcosm of these problems. The issues and impacts evident in Berbak include nearly all of the issues and impacts affecting wetland areas elsewhere in the eastern lowlands and provide a useful case study.The Asian Wetland Bureau and the Indonesian Directorate General of Forest Protection and Nature Conservation have carried out a two-year project which includes development of management of the Reserve and the preparation of an Environmental Profile for the lowland wetlands of Jambi Province as a background for regional planning. These components of the project are aimed at investigating and resolving management problems affecting the Reserve, and may be extrapolated to the solution of similar problems in other parts of the Sumatran lowlands.     

Biotransformation of benzonitrile to benzohydroxamic acid by Rhodococcus rhodochrous in the presence of hydroxylamine

Whole cells of the bacterium Rhodococcus rhodochrous LL100-21, which had been grown on benzonitrile to induce the nitrilase enzyme, converted benzonitrile to benzohydroxamic acid in the presence of hydroxylamine.     

Chromosome variation in British populations of Oncopsis (Hemiptera:Cicadellidae)

The British species of Oncopsis fall into two groups with respect to male karyotype. Four species—O. avallanae, O. carpini and O. subangulata, together with an undescribed new species close to carpini—consistently show ten autosome pairs and a single X-chromosome (2n=10AII+XO). In O. tristis too the XO state predominates but single neo-sex chromosome variants with nine and eight autosome pairs respectively have also been found. The two remaining species-O. alni and O. flavicollis—both regularly include derived neo-XY states involving the incorporation of autosomal material onto the X(2n=9AII+XY). The single population of O. alni studied was entirely neo-XY but the situation in O. flavicollis proved more complex. Montane populations which occur on Betula pubescens are XO-monomorphic whereas populations in lowland woodlands are polymorphic, including both XO and neo-XY types. In such situations the XO forms are found predominantly on B. pubescens whereas the XY morphs predominate on a second species of birch, B. pendula, which is absent from montane woodlands. In all three species where the neo-XY state is present, different autosomes have been involved in the fusion process.     

Heart Ratios at Different Stages in the Life Cycle of Lampreys

Heart ratios (heart weight/body weight. ×100) have been obtained for freshly killed and preserved (10% formalin) specimens of the lampreys Petromyzon marinus, Lampetra fluviatilis and L. planeri. Values for comparable stages were significantly higher in the preserved material, probably as a result of retention and fixation of blood in the heart chambers. The regression slope for the logarithmic relationship between heart and body weights was close to one in all stages of the three species investigated. A marked increase was observed in the heart ratio during metamorphosis, apparently attributable to an increase in the number and density of myocardial fibres. Heart ratios in the lamprey were generally higher than for most other fishes, with values of 0.1 and 0.3 being obtained for example in the case of freshly killed ammocoete and sexually mature adult stages of L. fluviatilis.     

Compensation and Plasticity in an Invasive Plant Species

Plant plasticity under varying resources is one character that contributes to competitiveness and invasibility. The plasticity of plant modules of the invasive Japanese stilt grass (Microstegium vimineum) was examined under different light and nutrient levels using a balanced field and greenhouse study. Ample light and nutrients resulted in the greatest biomass accumulation in all plant modules. However, M. vimineum showed extreme plasticity, producing stolons and flowers (reproductive structures) under a wide range of environmental conditions except infertile, low light. The addition of nutrients under various shading regimes compensated for lower light levels, rendering little change in the allocation of carbon to reproductive structures. Data from the field study corroborate the greenhouse results, but also suggest plasticity in response to competition.     

An unsaturated peptidomimetic assembly derived from a carbohydrate.

A strategy has been established for the synthesis of peptidomimetics derived from unsaturated carbohydrates, and exemplified by the use of methyl 2,6-anhydro-7-azido-3,7-deoxy-4,5-O-isopropylidene-D-lyxo-hept-2-enonate 9 as a dipeptide 'monomer' which can be elaborated from either end. Selective reduction of 9 gives a protected pseudodipeptide ester suitable for use as an amino component, and saponification gives an azido acid suitable for use as a carboxyl component. The 'dimer' product of coupling these two components with TBTU can be similarly elaborated at either end to give a 'trimer' and a further cycle of selective reduction and coupling gave a 'tetramer', 17, a pseudo-octapeptide.