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.     

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.     

Coevolution of daily activity timing in a host–parasite system

Coevolutionary theories applied in the study of host–parasite systems indicate that lineages exhibit progressive trends in response to reciprocal selective pressures. Avian brood parasites have generated intense interest as models for coevolutionary processes. Similar to avian cuckoos, Polistes wasp social parasites usurp a nest and exploit the parental care of a congeneric species to rear their own brood. In the present study, we show a coevolutionary arms race in the daily activity pattern in a Polistes host–parasite pair. We measured the daily activity rate, in constant laboratory conditions, of both host and parasite females during the period in which nest usurpations occur. The parasites showed a hyperkinesis in the middle of the day. As the field observations suggested, this mid-day activity is used to perform host nest usurpation attempts. Timing the usurpations allows the parasite to maximize its usurpation attempts during daytime when the host defence is lower. A field comparison of host presence on the nest in two populations with different parasitism rates showed that populations under strong parasitic pressure exhibit timing counteradaptations to optimize nest defence. This study provides the first example of a mutual coadaptation in timing activity in a parasite–host system.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 399–405.     

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.     

Feasibility Study of Using Centrifuge for Investigating LNAPL Migration in Unsaturated Soils

Centrifuge modeling appears potentially useful for studying geo-environmental problems such as pollutant migration in subsurface systems. In this study, the “modeling of models” technique was used to validate the feasibility of using a geotechnical centrifuge to model the transport behavior of light non-aqueous phase liquids (LNAPLs) in unsaturated soils. All the experiments were conducted to simulate a gasoline spill from a leaking underground storage tank (UST) and the subsequent subsurface migration of the gasoline. When the gravity in the centrifuge reached the desired g-level, the gasoline was released from the UST and then it migrated in the unsaturated soil corresponding to a prototype time equivalent of one year. After the centrifuge tests, soil samples were collected using sampling tubes and the concentrations of individual constituent in the LNAPL were directly measured by means of gas chromatograph analysis. Results obtained from the centrifuge tests at different g-levels show that similar migration patterns are found for LNAPL transport in unsaturated porous media. The location of the peak concentration and the behavior of lateral spreading can be adequately described. In addition, centrifuge test data show that the migration pattern of LNAPLs is related to the soil type and the physical properties of individual constituents in the LNAPLs.     

Nutritional versus genetic correlates of caste differentiation in a desert ant

1. In many ant species, caste differentiation stems from trophic differences at the larval stage. Adult workers that feed larvae have great control over the allocation of colony resources to growth (production of workers) versus reproduction (production of queens). However, larval caste fate may also be constrained very early on through direct genetic effects or non‐genetic maternal effects. 2. Here, we combined isotopic and genetic analyses to study the developmental origin of queens and workers in a desert‐dwelling ant, Cataglyphis tartessica (Amor & Ortega, 2014). Queens do not found new colonies alone but rather disperse with workers. As the latter are always wingless, selection pressures on specific queen traits such as flight ability have become relaxed. Though the phylogenetically related species, C. emmae (Forel, 1909) only produces winged queens much larger than workers, C. tartessica produces two types of small queens relative to workers: brachypterous (short‐winged) queens and permanently apterous ergatoid (wingless and worker‐like) queens. 3. Upon emergence, workers and ergatoids have similar δ15N isotopic values, which were lower than those of brachypters, suggesting the latter are fed more protein as larvae. Microsatellite analyses indicated that: (i) colonies are mostly monogynous and monandrous; (ii) both ergatoids and brachypters are equally related to workers; and (iii) in the few polyandrous colonies, patrilines were evenly represented across workers, brachypters and ergatoids. 4. Overall, there was no evidence of genetic caste determination. We suggest that, in contrast to brachypters, ergatoids are selfish individuals that escape the nutritional castration carried out by workers and develop into queens in spite of the colony's collective interests.     

Kinetic changes with temperature of phosphoenolpyruvate carboxylase from a CAM plant

Abstract. Purified and crude phosphoenolpyruvate carboxylase from the CAM plant Kalanchoë daigremontiana Hamet et Perrier ( Bryophyllum diagremontianum ) was assayed at temperatures between 10 and 45° C. The optimum temperature of the enzyme activity changed with substrate availability and effector concentration in the assay. l -malate inhibited the enzyme activity and lowered the optimum temperature. Glucose-6-phosphate raised the optimum temperature to 43°C. K _m values for phosphoenolpyruvate increased with assay temperature from 0.12 mol m^-3 at 15° C to 0.36 mol^m−3 at 35° C. Inhibition by malate increased with temperature and acidity of the assay. In the crude enzyme 50% of control activity was inhibited by 1.65 mol m^-3 malate at 15° C and by 0.5 mol m^-3 at 35° C (at pH 7.0). With purification malate sensitivity was lost ( K _i values for malate at least 10 times higher). The shift in optimum temperatures for PEP-carboxylase activity thus results from changes in the kinetic parameters with temperature and allosteric effectors. The often low optimum temperatures for CO₂ fixation observed in nature may thus be the result of substrate and effector concentrations in the cytoplasm and the antagonistic effect of temperature on substrate affinity and effector efficiency on phosphoenolpyruvate carboxylase.