The Ultrastructure of the Daughter Sporocyst Tegument of Cercaria vaullegeardi Pelseneer (Digenea, Hemiuridae)

The body wall of the daughter sporocyst of Cercaria vaullegeardi Pelseneer, 1906 is unusual for a species without a birth pore in consisting of an outer anucleated, microvillous syncytial tegument and a cellular subtegument which lacks secretory cells. In contrast, most other known daughter sporocysts without birth pores have a nucleated region above the microvillous region of the tegument. The significance and functional aspects of this structure are discussed.     

Growth Hormones and the Creeping Thistle Rust

A re-examination of the life cycle of the rust fungus Puccimapunctiformis (Str.) Rohl. (syn. P. suaveolens (Pers.) Rostr.,P. obtegens Tul. ex Fuckel) on the creeping thistle Cirsiumarvense (L) Scop, has led to the development of a method forgrowing comparable healthy and diseased thistle plants in thegreenhouse. These were used to define the developmental changeswhich result from systemic infection. Closely similar changesare produced by the exogenous application of gibberellic acid(GA₃). The endogenous gibberellin content of systemically diseasedthistle plants is consistently higher than that of healthy plantsduring the earlier part of the season when they are growingfaster. Evidence is given for the presence of two gibberellinswhose relative proportions change during development. The firsthas not been characterized but there is some evidence that thesecond may be GA₃. These results support the hypothesis thatsome of the characteristic features of systemic infection ofthe host are due to the excess production of gibberellins.     

The importance of terrestrial resource subsidies for shredders in open‐canopy streams revealed by stable isotope analysis

1. Allochthonous detritus is the major source of energy in forested streams, but less is known of the importance of terrestrial subsidies to open‐canopy streams. Here, we used stable isotope analysis to assess the importance of allochthonous versus autochthonous energy sources to invertebrate shredders in four open‐canopy streams in Sweden. Shredders and potential food sources were analysed at both open sites and those with deciduous trees in the riparian zone. 2. Mixing models showed that allochthonous coarse particulate organic matter was the most important energy source to shredders at both the open and wooded sites, suggesting that terrestrial subsidies may be an important process in open‐canopy streams, just as they are in forested streams. 3. However, shredders at open sites had a larger proportion of biofilm in their diet than at wooded sites, indicating an ability of shredders to adjust their diet with food availability. 4. We also used the carbon and nitrogen stable isotope signatures to assess the size of the feeding niche of shredders. Feeding on both allochthonous and autochthonous sources at open sites was reflected in a larger feeding niche than at wooded sites for one of the three species analysed. There was substantial overlap of the feeding niche among shredder species, indicating a high functional redundancy within this guild.     

The Extrafloral Nectaries of Sambucus nigra

The structure and ultrastructure of the extrafloral nectariesof Sambucus nigra L. were studied. These nectaries are stalk-likeand occur at the bases of the leaves and leaflets. The nectariferoustissue occurs at the top of the nectary and is continuous withthe single central vascular bundle. The nectariferous cellshave a dense cytoplasm and contain a well developed endoplasmicreticulum. With the commencement of nectar secretion disintegrationof the nectariferous cells takes place. This process startsat the summit of the nectary and proceeds downwards. The questionas to whether the process of secretion is holocrine or merocrineis discussed. Sambucus nigra, Extrafloral nectary, nectariferous cells, disintegration of cells     

Palaeolimnological insights for biodiversity science: an emerging field

1. Decreases in biodiversity are so widespread that they are now considered a form of global change in their own right. Given the grave nature of this issue, rapid advances in understanding are needed to mitigate further impacts. In this Opinion paper, we argue that palaeolimnological studies have important contributions to make to biodiversity science. 2. Given that long‐term community data are sparse in their geographic coverage and tend to span no more than 5 years, greater insight into biodiversity dynamics can be obtained from palaeoecological analyses. One such approach is palaeolimnology, which is a field that can provide long‐term data on changes in both physico‐chemical and biological components of lake ecosystems. 3. To date, a handful of quantitative palaeolimnological studies have addressed biodiversity questions, focussing primarily on defining the drivers of change in species richness or identifying functional traits that best capture ecosystem processes. Several studies have also quantified the role of spatial variables in determining assemblage structure, a necessary first step in addressing how metacommunity interactions influence biodiversity–ecosystem processes. Overall, these early studies show that palaeolimnological approaches can address both similar and novel questions compared with contemporary ecological studies. However, palaeolimnology allows for a great expansion of the temporal scale of investigation, the quantification of rates of change to stressors and the possibility of conducting experiments by applying resurrection techniques. 4. As an emerging field, there are numerous exciting applications of palaeolimnology to biodiversity science. It is an opportune time to create synergy between contemporary aquatic ecologists and palaeolimnologists.     

Genomic dissection of drought resistance in durum wheat × wild emmer wheat recombinant inbreed line population

Drought is the major factor limiting wheat productivity worldwide. The gene pool of wild emmer wheat, Triticum turgidum ssp. dicoccoides , harbours a rich allelic repertoire for morpho-physiological traits conferring drought resistance. The genetic and physiological bases of drought responses were studied here in a tetraploid wheat population of 152 recombinant inbreed lines (RILs), derived from a cross between durum wheat (cv. Langdon) and wild emmer (acc# G18-16), under contrasting water availabilities. Wide genetic variation was found among RILs for all studied traits. A total of 110 quantitative trait loci (QTLs) were mapped for 11 traits, with LOD score range of 3.0–35.4. Several QTLs showed environmental specificity, accounting for productivity and related traits under water-limited (20 QTLs) or well-watered conditions (15 QTLs), and in terms of drought susceptibility index (22 QTLs). Major genomic regions controlling productivity and related traits were identified on chromosomes 2B, 4A, 5A and 7B. QTLs for productivity were associated with QTLs for drought-adaptive traits, suggesting the involvement of several strategies in wheat adaptation to drought stress. Fifteen pairs of QTLs for the same trait were mapped to seemingly homoeologous positions, reflecting synteny between the A and B genomes. The identified QTLs may facilitate the use of wild alleles for improvement of drought resistance in elite wheat cultivars.     

Protecting wildlife from predation by owned domestic cats: Application of a precautionary approach to the acceptability of proposed cat regulations

Abstract While it is undeniable that owned domestic cats Felis catus (Mammalia: Felidae) kill large numbers of wildlife, it is contentious if this has significant impacts on wildlife populations. Under the precautionary principle such uncertainty does not preclude measures to reduce putative risk, but action should follow consultation with stakeholders. To initiate such consultation for the City of Armadale, Western Australia, we surveyed urban and rural residents to determine their opinions regarding putative impacts of owned cats on wildlife and the acceptability of proposed regulations. Key statements accepted by 70% or more of respondents, irrespective of their residence, gender or cat ownership status, included: (i) there is a need to regulate owned domestic cats; (ii) the presence of cats in nature reserves is harmful to wildlife; (iii) cats not owned by licensed breeders should be desexed; and (iv) local councils should be empowered to restrict the maximum number of cats per household. Seventy per cent or more of owners agreed to keep their cats on their property from sunset to sunrise and to register them if these measures became compulsory. All groups except urban men also indicated 70% or greater willingness to keep their cats on their property constantly if required. However, fewer than 40% of owners supported empowering local councils to enforce cat‐free zones. In this community, cat regulation excluding cat‐free zones should enjoy support. Similar approaches should be effective wherever the environmental impacts of owned domestic cats are debated, because compliance with such regulations should be high.