Nothobranchius cooperi (Teleostei: Cyprinodontiformes): a new species of annual killifish from the Luapula River drainage,northern Zambia

Nothobranchius cooperi, Nagy, Watters and Bellstedt, new species, is described from seasonal streams and ephemeral pools associated with the upper Mansa River system in the middle Luapula drainage and systems draining into the low-lying area marginal to the southwestern part of Lake Bangweulu, in the Luapula province of northern Zambia. It belongs to the N. brieni species group. Males of Nothobranchius cooperi are distinguished from congeners by the following unique combination of characters: body scales with broad orange posterior margin, forming a highly irregular cross-barred pattern; anal fin fairly uniform orange-red with irregular to regular, light blue-green zone close to the base; caudal peduncle length 1.2–1.3 times its depth; prepelvic length 48.8–51.9% SL; and head depth 75–77% of head length. Genetic divergence of the mitochondrial COI and ND2 genes and nuclear S7 gene support the distinction of the new species from its closest known relative, N. rosenstocki and confirms its position in the N. brieni species group.     

Growth of Aeromonas spp. at 4°C and related toxin production

Over the last few years Aeromonas spp. have been considered to be potential intestinal pathogens (Altwegg & Geiss 1989). Recently, detailed evidence has linked a strain from contaminated shrimp with a clinical isolate from a patient with diarrhoea and found them to be the same (Altwegg et al. 1991). It is now known that Aeromonas spp. are present in many foods, especially those of animal origin (Palumbo et al. 1989). Furthermore, previous studies have shown that these organisms are quite capable of growing at refrigeration temperatures. For example, Palumbo et al. (1985) found that seven out of 14 strains showed significant growth within 14 d at 5°C. However, most studies have only examined a relatively small number of strains, which were not speciated and were simply called A. hydrophila.
In this paper we examine the growth of 36 strains of aeromonas (divided into A. hydrophila, A. sobria and A. caviae ) at 4°C, and their ability to produce cyotoxins at 4°C, 30°C and 37°C.     

A Note on Testing Hypotheses about Trimmed Means

A well known result is that skewness can cause problems when testing hypotheses about measures of location, particulary when a one-sided test is of interest. Wilcox (1994) reports both theoretical and simulation results showing that when testing hypotheses about trimmed means, control over Type I error probabilities can be substantially better than methods for means. However, at least in some situations, control over the probability of a Type I error might still be judged to be inadequate. One way of adressing this concern is to combine trimmed means with the bootsrap method advocated by Westfall and Yuong (1993). This note reports simulation results indicating that there are situations where substantial improvements over Type I error probabilities are indeed obtained.     

Application of glucose at low concentrations to grass swards in waste-derived compost can significantly increase long-term yields

Carbohydrates have a range of effects on soil, dependent on the frequency and concentration of the application. Small quantities of glucose have the effect of accelerating the removal of available N (NH₄ ⁺, NO₃ ^–) through incorporation into the bodies of microorganisms. This reduces plant growth (Jenkinson, 1985), the rate of which depends largely on the presence of available N (Addiscott et al., 1991). However, in theory, if appropriate soil glucose concentrations are maintained, asymbiotic N₂-fixation will occur, supplying extra nitrogen nutrition to plants over an extended period. Here, it is demonstrated that the use of 0.028 M glucose and an appropriate source of N₂-fixing bacteria (green waste-derived compost) can result in increased grass dry matter yields of over 50% in a glasshouse experiment.