A revised polytomous key for the identification of species of the genus Xiphinema Cobb, 1913 (Nematoda: Longidoridae) with exclusion of the X. americanum-group

The species of the genus Xiphinema Cobb, 1913 are listed and their current status is indicated. A revised polytomous key to the 172 valid species (excluding the X. americanum-group) is presented. Because of the very large number of species the key is split into eight groups on the basis of development of the anterior female genital branch, uterine differentiation and tail shape. In accordance with the opinion of Cohn & Sher (1972) X. vulgare Tarjan, 1964 is considered a synonym of X. setariae Luc, 1968. X. cubense Razzhivin, 1973 is placed in species inquirendae. Longidorella chappuisi (Schneider, 1935) is transferred to Xiphinema and its possible identity with X. hygrophilum Southey & Luc, 1974 is discussed.     

EVOLUTIONARY POTENTIAL AND LOCAL GENETIC DIFFERENTIATION IN A PHENOTYPICALLY PLASTIC TRAIT OF A CYCLICAL PARTHENOGEN,DAPHNIA MAGNA

The frequent use of neutral markers to quantify genetic variation in natural populations emphasizes the role of stochastic events in explaining genetic differentiation between populations. Complementary studies on ecologically relevant traits are needed to assess the role of natural selection acting on adaptive variation in the development of local genetic differentiation. To test the hypothesis of local adaptation in the cyclical parthenogenetic species Daphnia magna, the phototactic behavior in the absence and presence of fish kairomone was assayed for 30 clones derived from resting eggs isolated from three habitats characterized by a different predation pressure by fish. Clones derived from populations in which fish are present were, on average, more negatively phototactic in and more responsive to the presence of fish kairomone than clones derived from a fishless habitat. In addition, the results show a high genetic diversity for the traits studied in all three gene pools investigated, indicating a high potential for microevolutionary changes in behavior of these Daphnia populations in the face of changes in predation pressure. The results of the present study indicate that working with large samples at the expense of having less precise estimates of genotypic values for specific genotypes may result in a loss of information with regard to the evolutionary potential of local populations.     

A revised polytomous key for the identification of species of the genusXiphinema Cobb, 1913 (Nematoda: Longidoridae) with exclusion of theX. americanum-group: Supplement 2

Thirty-one species and one subspecies have been described since publication of the first supplement to the polytomous key toXiphinema spp. (see Loof & Luc, 1993). Of these, 11 species belonging to the X. americanum-group are not considered here. Of the 20 remaining species, 13 are considered valid, for which identification codes are given. Three species were described earlier, but had not come to authors' notice; two of them,X. chothecolla andX. clavatus (sic) have already been synonymised withX. radicicola (see Luc & Loof, 1993); codes are given for the third species,X. codiaei. Xiphinema adenohystherum, X. cohni, X. macrogastrum, X. nuragicum andX. sphaerocephalum were considered junior synonyms ofX. pyrenaicum by Baujardet al. (1996);X. hunaniense is considered a junior synonym ofX. radicicola andX. hispanum ofX. aceri. Changes in the group and/or identification codes are made forX. aceri, X. barense, X. dentatum, X. diversicaudatum, X. filicaudatum filicaudatum, X. globosum, X. hardingi, X. paritaliae (= X. dolosum), X. paulistanum, X. pyrenaicum andX. transkeiense. The specific nameX. swarti is emended toX. swartae. Information is given for computerisation of the key.     

The hemoglobin concentration ofChironomus cf.Plumosus l. (Diptera: Chironomidae) larvae from two lentic habitats

Hemoglobin concentrations ofChironomus cf.plumosus larvae were measured in two different habitats of the same pond. Larger larvae have higher hemoglobin concentrations than small larvae. There is strong indication that the animals of poorly oxygenated deep water, have higher hemoglobin concentrations than the animals from the well-oxygenated littoral zone.     

Cellular expression of bone-related proteins during in vitro osteogenesis in rat bone marrow stromal cell cultures

The regulation of cell surface fibroblast growth factor (FGF) receptors during the differentiation of F9 teratocarcinoma cells was investigated. The capacity of F9 cells to bind ¹²⁵I-basic FGF (FGF-2) increased upon induction of differentiation with dibutyryl cAMP and retinoic acid. No change in binding capacity was observed in the first 24 h after addition of differentiating agents, but a sixfold increase in binding capacity was observed after 48 h and a fivefold increase after 72 h. Scatchard analysis of the binding data indicated that the increased binding of ¹²⁵I-FGF-2 was due to an increase in the number of receptors with no change in their affinity. When ¹²⁵I-FGF-2 was cross-linked to cell surface receptors, an increase in FGF-2-receptor complexes with molecular weights of 140,000–160,000 was also observed in the differentiated F9 cells. Undifferentiated F9 cells are known to secrete FGF-4 and cease expression of this molecule upon differentiation. To determine whether the low level of receptors in undifferentiated cells might be related to their production of FGF ligands, the ability of suramin, a drug that can disrupt FGF-receptor interactions, to modulate receptor number on F9 cells was investigated. Suramin treatment increased ¹²⁵I-FGF-2 binding capacity of undifferentiated F9 cells threefold but had little effect on the binding capacity of differentiated cells. In addition, antibodies to FGF-4 increased the ¹²⁵I-FGF-2 binding capacity of undifferentiated F9 cells by 58%. These results suggest that undifferentiated F9 cells might be responding in an autocrine manner to their own FGF ligands resulting in downregulation of cell surface FGF receptors. The increased number of receptors observed in differentiated cells may partly result from the decreased production of FGF ligands by these cells. © 1994 Wiley-Liss, Inc.     

Life histories and habitat selection in Daphnia: divergent life histories of D. magna clones differing in phototactic behaviour

To test the hypothesis of co-adaptation of life histories and daytime vertical distribution (vertical migration behaviour) in Daphnia, life history characteristics were analysed for two positively, three negatively, and four intermediately phototactic Daphnia magna clones. Clones with different phototactic behaviour were found to have divergent life history strategies, with positively phototactic clones being good exploiters under the non-limiting conditions provided in the laboratory, i.e. low density (1 ind./1), high food concentration (6,5–7 10⁵ Scenedesmus cells/ml, restored daily) and high temperature (20° C). They realized a high intrinsic rate of increase at a small adult body size through rapid development, at a cost of producing small neonates. Negatively and intermediately phototactic clones had larger adult body sizes, and produced larger neonates that were more starvation-resistant than those of positively phototactic clones. Selection for high intrinsic rate of increase in intermediately phototactic clones was mediated through the production of large clutches.     

Selectively 13C-enriched DNA: 13C and 1H assignments of a triple helix by two-dimensional relayed HMQC experiments

Summary We present NMR studies of an intramolecular triple helix, the three strands of which have been linked by a hexaethylene glycol chain. To overcome the generally encountered difficulties of assignment in the homopyrimidine strands, the carbon C1 of the pyrimidines were selectively ¹³C-enriched. Assignments of the aromatic and sugar protons were obtained from NOESY-HMQC and TOCSY-HMQC spectra. We show that the recognition of a DNA duplex by a third strand via triplex formation is easily carried out in solution by observing the changes of the ¹H1–¹³C1 connectivities as a function of pH. Furthermore, the conformation of the sugars has been found to be C2-endo, on the basis of the coupling constant values directly measured in an HSQC spectrum.     

The effect of nutrient supplementation on the biofiltration removal of butanal in contaminated air

Butanal is one of the odorous compounds produced in the animal-rendering and food-processing industries and also in sewage-treatment plants. It shows the necessity for complementing such plants with systems for off-gas treatment. Biofiltration using simple packing material was tested for the removal of butanal. Excellent results were obtained when the filters operated at optimal humidity and were supplemented with inorganic nutrients. Without nutrients, butyric acid was detected in the effluent gas, which may explain the lower efficiency of filters without nutrients. Under optimal conditions an elimination of around 90 g·m^–3·h^–1 was reached.