Movement and dispersal patterns in the bush cricket Pholidoptera griseoaptera: the role of developmental stage and sex

Abstract.  1. To persist in a highly fragmented environment, such as the intensively used agricultural landscapes of Europe, species may need to successfully disperse between sub-populations. This paper describes a capture – mark – resight experiment to investigate movement and dispersal patterns of the flightless bush cricket species Pholidoptera griseoaptera .
2. Movement parameters showed little difference between juveniles and imagos as well as between males and females. Both developmental stages and sexes moved considerable distances, were cap\able of crossing habitat boundaries, and showed successful inter-patch dispersal through the agricultural matrix.
3. The results suggest that P. griseoaptera exhibits movement behaviours that compensate for its inability to fly. It was concluded that the good dispersal ability exhibited by animals of both sexes and developmental stage is an important factor allowing P. griseoaptera to persist in fragmented agricultural landscapes.     

EVALUATION OF THE PETRIFILMTM AND REDIGELTM AS RAPID METHODS TO THE STANDARD PLATE COUNT METHOD FOR THE ENUMERATION OF PROCESSED MEATS AND ENVIRONMENTAL SAMPLES

Aerobic plate counts (APC) are used by the food industry to help determine the sanitary state of equipment and bacterial load of finished product. Conventional aerobic count methods for processed meats require approximately 72 h incubation before results are available. Food processing plants with in-house analytical laboratories require methods that are simple, reliable and rapid. New test methods using Petrifilm^TM (PF) and Redigel^TM (RG) have been developed for determining APC. These methods are faster and easier than culturing in a standard agar medium. A variety of raw, cooked; cured and noncured meat products, cooling brine and environmental surface swabs were collected and analyzed for APC using PF, RG and plate count agar (PCA). Data analyses from over 200 samples indicated that the sensitivity of rapid testing methods for aerobic bacteria can vary depending on sample type.     

Plastid terminal oxidase (PTOX) has the potential to act as a safety valve for excess excitation energy in the alpine plant species Ranunculus glacialis L.

Ranunculus glacialis leaves were tested for their plastid terminal oxidase (PTOX) content and electron flow to photorespiration and to alternative acceptors. In shade‐leaves, the PTOX and NAD(P)H dehydrogenase (NDH) content were markedly lower than in sun‐leaves. Carbon assimilation/light and C_i response curves were not different in sun‐ and shade‐leaves, but photosynthetic capacity was the highest in sun‐leaves. Based on calculation of the apparent specificity factor of ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco), the magnitude of alternative electron flow unrelated to carboxylation and oxygenation of Rubisco correlated to the PTOX content in sun‐, shade‐ and growth chamber‐leaves. Similarly, fluorescence induction kinetics indicated more complete and more rapid reoxidation of the plastoquinone (PQ) pool in sun‐ than in shade‐leaves. Blocking electron flow to assimilation, photorespiration and the Mehler reaction with appropriate inhibitors showed that sun‐leaves were able to maintain higher electron flow and PQ oxidation. The results suggest that PTOX can act as a safety valve in R. glacialis leaves under conditions where incident photon flux density (PFD) exceeds the growth PFD and under conditions where the plastoquinone pool is highly reduced. Such conditions can occur frequently in alpine climates due to rapid light and temperature changes.     

Hydrological connectivity structures concordant plant and animal assemblages according to niche rather than dispersal processes

1. Understanding the processes that structure community assembly across landscapes is fundamental to ecology and for predicting and managing the consequences of anthropogenically induced changes to ecosystems. 2. We assessed the community similarity of fish, macroinvertebrate and vegetation communities against geographic distances ranging from 4 to 480 km (i.e. distance–decay relationships) to determine the balance between local environmental factors and regional dispersal processes, and thus whether species‐sorting (niche processes) or dispersal limitation (neutral processes) was more important in structuring these assemblages in Australia’s wet‐dry tropics. We investigated whether the balance between niche and dispersal processes depended on the degree of hydrological connectivity, predicting that dispersal processes would be more important at connected sites, and also whether there was spatial concordance among these three assemblage types. 3. There was significant but weak spatial concordance among the study communities, suggesting limited potential for surrogacy among them. Distance–decay in community similarity was not observed for any study assemblage at perennial sites, suggesting dispersal was not limiting and assemblages were structured more strongly by local niche processes at these connected sites. At intermittent sites, weak distance–decay relationships for each assemblage type were confounded by significant relationships with environmental dissimilarity, suggesting that dispersal limitation contributed, albeit weakly, to niche processes in structuring our three study assemblages at disconnected sites. 4. Two environmental factors, flow regime and channel width, explained significant proportions of variation in all three assemblages, potentially contributing to the observed spatial concordance between them and representing local environmental gradients along which these communities re‐assemble after the wet season, according to niche rather than dispersal processes.     

Effects of changes in the driving forces on water quality and plankton dynamics in three Swiss lakes – long‐term simulations with BELAMO

1. With a modified version of the lake model BELAMO, we were able to describe the essential features of the dynamics of nutrients, dissolved oxygen, phyto‐ and zooplankton in three lakes of different trophic status over periods of 19–30 years, with essentially the same model parameters for all three lakes. This is remarkable, as the measured nutrient inputs decreased considerably during the simulated time period. 2. Despite having done this before for a period of 4 years with an earlier version of the model, a considerable effort was required that led to a series of model modifications without which the data could not be matched. This demonstrates that long‐term calibration of a model that combines processes in the water column with mineralisation in the sediment can be difficult. 3. Due to the necessarily simplified processes within the model, there is a bias in its output. We applied a recently developed technique for model calibration and uncertainty analysis to address bias and multiple calibration criteria. To account for the demanding long‐term simulations, a simplified numerical implementation of this technique was used. 4. Our results demonstrate good understanding of the chemical state of the lake during the calibration period but less of the biological variables. The credibility intervals used to visualise this knowledge widen substantially during the prediction period (consisting of the last 10 years of the simulation). 5. The joint calibration of the model with long‐term data from lakes of different trophic status is possible but only with considerable prediction uncertainty. Due to the explicit consideration of bias in our calibration technique, we are able to estimate quantitatively the uncertainty of our knowledge about chemical and biological variables in the lake.     

Serotonergic mechanisms mediating spawning and oocyte maturation in the zebra mussel,Dreissena polymorpha

Summary

The zebra mussel, Dreissena polymorpha, is a freshwater biofouling bivalve unintentionally introduced in the 1980s into North America from Europe. Oocyte maturation (germinal vesicle breakdown, GVBD) and spawning of the zebra mussel can be triggered with serotonin (5-hydroxytryptamine, 5-HT). In pharmacological experiments to characterize the receptor mediating spawning, the serotonin receptor agonists 8-OH-DPAT, TFMPP, and 1-(1-naphthyl)piperazine were effective at stimulating spawning; whereas, 2-methylserotonin and alpha-methylserotonin had no effect. In experiments with antagonists of serotonin receptors ketanserin and propranolol had no effect; mianserin, NAN-190, and cyproheptadine had partial inhibitory effects; and methiothepin was a very effective antagonist. Metergoline had mixed agonist/antagonist properties. Ergotamine was the most effective activator of spawning in females. Compared to serotonergic receptors in other organisms, the receptors that activate spawning in zebra mussels resemble 5HTlym, 5HTdro2 and human 5HT1Dβ, which are receptors that may act both by inhibiting adenylyl cyclase and by activating phospholipase C. In zebra mussels, 5-HT and 8-OH-DPAT activate GVBD in gonad fragments, a process also initiated by manual dissection of gonad fragments. GVBD can be inhibited by pre-treatment of ovaries with forskolin and theophylline, suggesting an inhibitory role for cyclic AMP. The Ca²⁺ ionophore A23187 can trigger GVBD and polar body formation. Thus, oocyte maturation in zebra mussels may be initiated via serotonergic receptors simultaneously inhibiting adenylyl cyclase and activating Ca²⁺ mechanisms.     

Seasonal differences in methyl farnesoate esterase activity in tissues of the spider crab Libinia emarginata

Summary

Methyl farnesoate (MF), an unepoxidated form of insect JH III, is present in Crustacea. MF is synthesized by the mandibular organs and is degraded to fomesoic acid (FA) by peripheral tissues. In this study we investigated MF degradation by esterases in hepatopancreas, ovary, testes and hemolymph of the spider crab Libinia emarginata collected at different times of the year to determine seasonal differences. The conversion of MF to FA varied among the tissues. In the summer, the hepatopancreas showed the greatest esterase activity (52.8% conversion in females and 59.16% in males), and it was twice as high (28.86%) in ovaries than in the testes (12.16%), but was low in the hemolymph of both sexes (10.84% in males, and 6.97% in females). In the fall, the conversion of MF to FA was significantly reduced in all tissues (ovary 8.55%, testes 6.21%, hepatopancreas 10.22%, hemolymph 3.96%). Eyestalk ablation of animals in the fall restored MF esterase activity to summer levels. When tissues from these animals were incubated with OTFP, a specific inhibitor of JH esterase, MF metabolism was significantly reduced. These results suggest that MF esterase activity depends on direct induction by MF, and its degradation is by a specific esterase(s).     

Tarsal contact chemoreceptors of the black swallowtail butterfly Papilio polyxenes: responses to phytochemicals from host- and non-host plants

Abstract Tarsal contact chemoreceptors of the black swallowtail butterfly Papilio polyxenes (Lepidoptera: Papilionidae) were stimulated with leaf-surface extracts and ethanolic extracts of whole leaves of a host-plant (Daucus carota) and a non-host (Brassica oleracea). Both leaf extracts evoked large numbers of spikes but stimulated different receptor neurones. It is concluded that a large difference exists between the sensory responses to host and non-host extracts. Two chemicals, luteolin 7-0-(6"-0-malonyl)-β-D-glucopyranoside and trans- chlorogenic acid, known to be present in the host and known oviposi-tion stimulants for P.polyxenes , were also tested and shown to be active. No responses were found to luteolin 7-O-β-D-glucoside or to luteolin 7-O-β-D-glucuronide. These flavonoids occur in D.carota foliage, but do not stimulate oviposition.