The feeding ecology of elaterid larvae in central European arable land: New perspectives based on naturally occurring stable isotopes

To understand soil food webs, empirically generated data on the trophic connections and the feeding ecology of the major below-ground animal taxa are needed. Here we used stable isotope analysis to assess the trophic ecology of wireworms, the larvae of click beetles, in Central European arable land. Wireworms are amongst the major soil macroinvertebrates and are of practical importance in arable soils. Besides feeding on crops, they are thought to feed on weeds, soil organic matter (SOM), and even animal prey, but their feeding ecology is poorly studied under natural conditions. Elaterid larvae and their putative feeding substrates—plant roots, SOM, and litter—were sampled at 17 locations in Austria, Germany, and Italy and their isotope ratios of carbon (¹²C/¹³C) and nitrogen (¹⁴N/¹⁵N) measured to determine the wireworms’ trophic level, the importance of SOM and weeds within the diet of Agriotes larvae, as well as the individual diet variation in Agriotes obscurus larvae. δ¹⁵N signatures suggested that Agriotes larvae are predominately herbivorous, whereas the other wireworm species primarily fed on animal prey. In contrast to SOM, weeds were readily eaten by Agriotes larvae: their dietary contribution ranged between 28% and 67% in weedy maize fields. Most A. obscurus larvae fed on a mixed diet of weeds and maize, although ～15% of the larvae fed primarily on one of the two food sources only. δ¹⁵N signatures indicated that ～10% of the “herbivorous” A. obscurus larvae fed primarily on animal prey, revealing high intraspecific trophic plasticity in these soil insects. Wireworm feeding behaviour is apparently complex at the individual level: the population consists of types A and B generalists, a phenomenon which needs further assessment.     

Diversity of arbuscular mycorrhizal fungi associated with the rhizosphere of tea growing in ‘natural’ and ‘cultivated’ ecosites

The colonization and diversity of arbuscular mycorrhizal fungi (AMF) associated with the rhizosphere of tea [Camellia sinensis (L.) O. Kuntze] growing under ‘natural’ as well as ‘cultivated’ conditions in the Kumaun region of Uttaranchal Himalaya (India), during the periods of active growth and dormancy were investigated. Root and rhizosphere soil samples, collected from both the ecosites (natural and cultivated), were monitored for root colonization. While the percent root colonization was quite high (77.66 ± 4.40 and 86.40 ± 3.02%, in the natural and cultivated tea, respectively) during the period of active growth in both the ecosites, relatively higher colonization (97.33 ± 0.78 and 98.13 ± 0.80%, in the natural and cultivated tea, respectively) was recorded during the period of dormancy. The rhizosphere of cultivated tea bushes was found to be dominated by Glomus morhpotypes (88.89% of the total isolates) along with three morphotypes of Acaulospora; occurrence of 35 morphotypes belonging to four genera viz. Acaulospora (11.43%), Gigaspora (11.43%), Glomus (68.57%) and Scutellospora (8.57%) was recorded in the rhizosphere of tea plants from the natural ecosite. A total of 51 AMF morphotypes were detected. Shannon–Weaver index of diversity was higher (1.80 ± 0.13 and 2.05 ± 0.10 during periods of active growth and dormancy, respectively) at the species level for the natural ecosite over its counterparts from the cultivated ecosite. Values for the diversity indices of natural and cultivated ecosites did not show much variation in the period of dormancy. These data suggest that collectively, various cultural practices negatively affect AMF diversity at the genus level in tea plantations of the colder regions.     

Formation of furan and methylfuran by maillard-type reactions in model systems and food

The formation of furan and 2-methylfuran was studied in model systems based on sugars and selected amino acids. Both compounds were preferably formed under roasting conditions in closed systems yielding up to 330 micromol of furan and 260 micromol of 2-methylfuran per mol of precursor. The amounts obtained under pressure cooking conditions were much lower, usually below 20 micromol/mol, except for 2-furaldehyde, which yielded 70-100 micromol/mol of furan. Labeling studies indicated two major formation pathways for both furans: (i) from the intact sugar skeleton and (ii) by recombination of reactive C(2) and/or C(3) fragments. Under roasting conditions in the absence of amino acids, furan was mainly formed from the intact sugar skeleton. Formic and acetic acid were identified as byproducts of sugar degradation, indicating the split off of C(1) and/or C(2) units from hexoses. The presence of alanine, threonine, or serine promoted furan formation by the recombination of C(2) fragments, such as acetaldehyde and glycolaldehyde, which may originate from both sugars and amino acids. In aqueous solution, about half of furan was generated by the recombination of sugar fragments. 2-Methylfuran was preferably formed in the presence of amino acids by aldol-type reactions of C(2) and C(3) fragments with lactaldehyde as a key intermediate, the Strecker aldehyde of threonine. The total furan levels in cooked vegetables were increased by spiking with hexoses. However, in pumpkin puree, only about 20% of furan was formed from sugars, preferably from the intact carbon skeleton.     

Editorial

No abstract available for this article.     

Acremonium strictum pulmonary infection in a horse

A 10-year-old Thoroughbred gelding was admitted to the Veterinary Medical Teaching Hospital of the University of California-Davis with a 2-week history of intermittent fever and acute onset of lethargy, anorexia, and ataxia. Although the clinical signs were nonspecific, the results of initial hematologic and biochemical analysis were consistent with a chronic inflammatory process. Thoracic radiographs revealed an increased fine reticulonodular interstitial opacity throughout the dorsal caudal lung fields. Cytologic examination of bronchoalveolar lavage (BAL) fluid showed mixed inflammation with many mononuclear phagocytes containing single, spherical, intracytoplasmic fungal organisms. Four mold species were cultured in low numbers from the BAL fluid. One of the fungal elements observed on the culture plates was identified as Acremonium strictum by real-time polymerase chain reaction (PCR). A diagnosis of fungal pneumonia due to A strictum was made based on the results of thoracic imaging, cytologic evaluation, culture, and PCR testing. The horse made an uneventful recovery with supportive treatment and was disease-free based on normal physical, radiographic, and cytologic findings at 21 days after presentation. To our knowledge, this is the first report of isolation of A strictum from the BAL fluid of a horse with interstitial pneumonia.     

Environmental control of growth and flowering of Rubus idaeus L. cv. Glen Ample

Environmental control of the annual growth cycle of ‘Glen Ample’ raspberry has been studied in order to facilitate crop manipulation for out-of-season production. Plants propagated from root buds were raised in long days (LD) at 21 °C and then exposed to different temperature and daylength conditions at varying ages. Shoot growth was monitored by weekly measurements and floral initiation by regular sampling and examination of axillary bud #5. Under natural summer daylight conditions at 60°N shoot growth was nearly doubled at 21 °C compared with 15 °C, while at 9 °C one half of the plants ceased growing and formed flower buds at midsummer. Developing shoots have a juvenile phase and could not be induced to flower before the 15-leaf stage. No significant reduction in induction requirements was found in larger plants. Plants exposed to natural light conditions from 10th August, had an immediate growth suppression at 9 and 12 °C with complete cessation after 4 weeks (by September 7). This coincided with the first appearance of floral primordia. At 15 °C both growth cessation and floral initiation occurred 2 weeks later (by September 21), while at 18 °C continuous growth with no floral initiation was maintained until early November when the photoperiod had fallen below 9 h. The critical photoperiod for growth cessation and floral initiation at 15 °C was 15 h. Plants exposed to 10-h photoperiods at 9 °C for 2–4 weeks had a transient growth suppression followed by resumed growth under subsequent high temperature and LD conditions, while exposure for 5 or 6 weeks resulted in complete growth cessation and dormancy induction. The critical induction period for floral initiation was 3 weeks although no transitional changes were visible in the bud before week 4. When exposed to inductive conditions for marginal periods of 3 or 4 weeks, an increasing proportion of the plants (20% and 67%, respectively), behaved as primocane flowering cultivars with recurrent growth and terminal flowering. It is concluded that growth cessation and floral initiation in raspberry are jointly controlled by low temperature and short day conditions and coincide in time as parallel outputs from the same internal induction mechanism.     

Small urban woodlands as biodiversity conservation hot-spot: a multi-taxon approach

To evaluate the importance of urban woodlands to serve as potential sites for biodiversity conservation, we analysed bird, carabid beetle and small mammal community responses to urbanisation at different spatial scales. We analysed the relationships between the variations of the structure (species richness S, diversity H′ and dominance D) of animal communities of woodlands distributed along a rural–urban gradient, and the variations along this same gradient of (1) the vegetation within woodlands, (2) the landscape at 100 m and (3) 600 m around the woodlands. We identified the spatial scales whose variations along the gradient most affected each animal community structure, and characterised community responses to these variations. Our results showed that urbanisation affected taxa differently according to their dispersal ability. Carabid beetles, less mobile, seem to be sensitive to increasing fragmentation and built surfaces from periurban to town centre which could make their movement within the urban landscape difficult. Birds, mobile species, seem to be more sensitive to variations of the vegetation structure within woodlands from periurban to town centre that could affect their capacity to maintain in habitat patches. Although our study did not allow relating the small mammal community structure to urbanisation, it suggests that this taxa is sensitive to urban local disturbances. A relevant management scale of woodlands can be specified for each taxa conservation. Urban woodlands accommodate over 50% of the species present in periurban woodlands, and effective management could enhance this number. Woodlands seem to be a good choice for promoting biodiversity conservation in towns.     

Comparing four mitochondrial genes in earthworms – Implications for identification,phylogenetics, and discovery of cryptic species

Earthworms play a key role in soil ecology as they can reach high densities, are well known as soil engineers, and occupy a central position in soil food-webs. The identification of earthworms, however, is notoriously difficult and morphologically only possible for well-preserved adult specimens. Molecular markers could facilitate earthworm identification and would be a huge advantage in studies where it is important to species-specifically identify juveniles or where badly preserved specimens and remains of earthworms need to be identified. The aim of this study was to compare four mitochondrial genes (12S rRNA, 16S rRNA, COI, and COII) with respect to their value for identifying earthworms, calculating earthworm phylogenies, and discovering cryptic species. Our results indicate that all four genes are suitable for species identification. However, the genetic distances were approximately twice as high for the protein coding genes than for RNA coding ones. High genetic distances and deep genetic lineages, e.g. for Octolasion lacteum, Lumbricus rubellus and Aporrectodea rosea, indicate the possible presence of cryptic species and hamper molecular identification. The Bayesian analysis based on concatenated sequence data resulted in a phylogenetic tree with high posterior probabilities. The con-specific relationship of Aporrectodea spp. and Allolobophora spp. was not confirmed, underlining the ongoing discussion about the revision of these two genera. In conclusion, our findings suggest using 12S and 16S rRNA sequences as molecular markers for species identification whereas the COI gene is better suited to address genetic lineages and to explore possible cryptic species. Taxonomy and the identification of species are essential for most ecological studies. This study provides the needed molecular sequence information to develop molecular tools that can overcome many hurdles in studies on earthworms, their relationship and their ecology.     

Riverine status and genetic structure of Chilika buffalo of eastern India as inferred from cytogenetic and molecular marker-based analysis

The present study aimed at assessing the status of the Chilika buffalo population of eastern India employing cytogenetic and molecular markers. The Chilika buffaloes investigated cytogenetically possess a somatic chromosome count of 50, identical to that of typical riverine buffaloes. Various diversity estimates, viz. observed number of alleles (4.68), effective number of alleles (2.79), and observed (0.487) and expected (0.602) heterozygosity across 25 heterologous microsatellite markers indicated the presence of a moderate level of genetic diversity in Chilika buffaloes, comparable with three other prominent Indian riverine buffalo breeds (Murrah, Nagpuri and Toda) included in this study. Across the four buffalo populations, mean estimates of F -statistics from Jackknifing over loci were significantly different from zero (p < 0.05), with F _IT (total inbreeding estimate) = 0.315 ± 0.038, F _IS (within-population inbreeding estimate) = 0.178 ± 0.038, and F _ST (population differentiation) = 0.166 ± 0.025. Inter-breed analysis reflected Chilika buffaloes to be genetically close to Nagpuri followed by Murrah and Toda buffaloes. Factorial correspondence analysis (FCA) revealed low breed-specific clustering of Chilika and Nagpuri buffaloes. Additionally, the neighbour-joining tree structure of mitochondrial DNA D-loop haplotypes indicated clear grouping of the Chilika haplotypes with the riverine buffalo. Thus the cytogenetic, microsatellite and mitochondrial data analysed in the present study classify Chilika buffalo of eastern India to be of the riverine type and not swamp-type buffalo.