Cytochemistry and Ultrastructure of Hyphae and Haustoria of Peronospora parasitica (Pers. ex Fr.) Fr.

The uniform distribution of nuclei, mitochondria, lipid material,protein, and RNA in the hyphae and haustoria of Peronosporaparasitica was demonstrated by staining techniques. Glycogenwas not detected, the only insoluble carbohydrate material detectedby the periodic acid-Schiff reaction being in the fungal wall.The host cell walls reacted more intensely to this stain thanthe hyphal walls. The reaction of haustorial walls varied betweenthe slight staining reaction characteristic of the fungal walls,and the strong reaction of the host cell wall. Callose sheathswere occasionally seen. Fine structure was found to be similar to that of other Oomycetes.Welldeveloped sheaths of a vesicular nature, possibly synonymouswith callose sheaths, were occasionally seen partly surroundinghaustoria.     

The Hemiptera (Insecta) communities of tropical rain forest in Sulawesi

The structure and composition of Hemiptera communities of tropical rain forest in Dumoga-Bone National Park, Sulawesi, Indonesia were investigated over a 1-year period. The aim was to investigate the extent to which insect samples, obtained using six different techniques, were representative of the whole community, and to explore temporal and spatial variation in Hemiptera community composition. Sampling techniques employed were Rothamsted light trapping, canopy fogging, malaise trapping at both ground and canopy level, flight interception trapping and yellow water pan trapping. Overlap between faunas collected using different techniques was surprisingly low emphasizing the limitations of using any single method to sample and thereby describe the Hemiptera community. Differences were observed at the species, family and suborder levels. Similarly, there were major differences in faunal composition between sites and diversity appeared to peak at elevations between 600–1000 m. Seasonal changes were also significant but generally lower than between methods or sites. Results are discussed in relation to factors such as food availability and host specialization and the efficacy of each sampling method is reviewed in relation to the biology of the different Hemiptera groups and the composition of the samples obtained.     

Effects of temperature on phenological synchrony and altitudinal distribution of jumping plant lice (Hemiptera: Psylloidea) on dwarf willow (Salix lapponum) in Norway

Summary.

• 1 The geographical distributions of three species of jumping plant lice (psyllids) along an altitudinal transect (988–1300 m a.s.l.) in southern Norway were restricted within the range of their host plant Salix lapponum. One species, Cacopsylla propinqua, occurred at all sampling locations between 988 and 1222 m, whereas C.palmeni was confined to higher altitudes (1153–1222 m) and C.brunneipennis was more abundant at lower altitudes (988–1101 m).
• 2 C.brunneipennis and C.palmeni developed only on female catkins. Development times of catkins and psyllids were similar (approximately 50 days) and successful psyllid development depended on close phenological synchrony with catkins.
• 3 Thermal requirements for development of female catkins were greater at low altitude (988 m) compared with higher altitude (1222 m), showing local adaptation of S.lapponum to altitude. In general, thermal requirements of psyllids were less than those of catkins at the same location. C.brunneipennis had higher thermal requirements than C.palmeni.
• 4 Field experiments, using polythene enclosures to elevate temperatures at two sites at different altitudes (by 0.6–1.4 deg. C), showed that insects had an enhanced relative rate of development under elevated temperatures compared with their host plants.
• 5 Indices of phenological synchrony were calculated from thermal requirements of psyllids and catkins. Under elevated temperatures, phenological synchrony decreased at both sites. This resulted in the subsequent development of smaller adult insects at low altitude, although at higher altitude, insects developing under elevated temperatures were larger and had a higher survival rate compared with controls.
• 6 Effects of temperature on phenological synchrony may explain the limits to the geographical range of psyllids. The consequences of climate change on psyllid populations will depend on the effects of decreased phenological synchrony on insect development and this may differ within the insect's geographical range.

     

Kinetic Analysis of Chemokinesis of Paramecium1

Paramecia detect and accumulate in or disperse from some chemicals. Cells do this by changing frequency of turning and speed of swimming. There are at least two mechanisms by which cells respond: one dependent on ability to turn, one dependent on speed modulation. There are also two classes of chemicals: those that require the cells' ability to turn in order to cause accumulation and dispersal (type I), and those that apparently require only speed modulation (type II). Attractants of type I cause qualitatively similar changes in behavior to repellents of type II and the converse; therefore, assays are needed to distinguish between these two classes of chemicals, despite qualitatively similar behavior of some attractants and repellents. We examined two assays of paramecium chemoresponse, T-maze assay and well test, to understand how the T-maze distinguishes between attractants of type I and repellents of type II and why the well test does not.     

The distribution, abundance and host plant relationships of Salix- feeding psyllids (Homoptera: Psylloidea) in arctic Alaska

Abstract. 1. Five species of psyllid occurred on seven species of Salix at Meade River, Alaska. Studies were made on the two common species Psylla pclmeni Löw and P.phlebophyllae Hodkinson. The former feeds on the phanerophy tes Salix pulchra, S.lanata, S.alaxensis and S.glauca , the latter on the chamaephytes S.phlebophylla and S.reticulata.
2. Both P.palmeni and P.phlebophyllae had a 1-year life cycle and nymphal development took place on the female Salix catkin. The life cycle was generally closely synchronized with the period of catkin development. However, only a few eggs were laid on S.glauca
3. Seasonal perturbation of the host plant by flooding, ice movement and blown sand prevented psyllids breeding in certain areas colonized by the host plant.
4. In P.palmeni densities and 'feeding pressure', measured as biomass of psyllids per gram of catkin, on the different host plants followed the sequence S.pulchra>S.lanata> S.alaxensis > S.glauca. In P.phlebophyllae densities and feeding intensities were similar on S.phlebophylla and S.reticulata and grazing intensity was comparable with P.palmeni on S.pulchra.
5. A highly significant negative correlation was found between psyllid density and catkin dry weight in S.pulchra, S.phlebophylla and S.reticulata , suggesting that psyllid feeding is affecting catkin growth.
6. Predation of psyllid nymphs by syrphid larvae was heavy but there was no evidence of parasitism.
7. The life history strategies of the five psyllid species are discussed within the context of the constraints imposed by the arctic environment.     

Flexible responses of insects to changing environmental temperature – early season development of Craspedolepta species on fireweed

Developmental response to temperature during the critical early season growing period was investigated in two congeneric species of Craspedolepta feeding on Epilobium angustifolium at three sites at different altitudes in Norway and the UK. The larval development reaction norm to temperature, measured as accumulated day degrees, was not significantly different between Craspedolepta nebulosa and Craspedolepta subpunctata at sites where they co‐occurred but C. nebulosa development was consistently more advanced at any site. For individual species the reaction norms at the lowest site (Ainsdale, UK) were similar to the intermediate site (Geilo, Norway): and there were no differences between years. Insect size remained relatively constant. However, at the highest site (Haugastøl, Norway), where C. subpunctata is unable to complete its development, the reaction norm for C. nebulosa was significantly higher than at Geilo and the individual insects produced were smaller. These adaptations allow life‐history completion under limiting temperature conditions. An experiment at Ainsdale, to raise the mean temperature by around 2.5°C during the early growing season, resulted in accelerated development in both C. nebulosa and C. subpunctata but development in C. nebulosa was accelerated proportionately more. C. nebulosa thus displays the greater plasticity in developmental response to environmental temperature that allows it to occupy a greater altitudinal and latitudinal range than C. subpunctata, in which the response is less plastic and more canalized. The likely individualistic responses of the two species to climate warming are considered.     

Using space‐for‐time substitution and time sequence approaches in invasion ecology

1. Invasion biologists use two main approaches to evaluate the effects of non‐native species (NNS) on diversity of native species (DNS), namely space‐for‐time and time approaches. These approaches have pitfalls related to lack of controls: the former lacks pre‐invasion data, while the latter often lacks data from non‐invaded sites. 2. We propose a framework that combines space‐for‐time and time approaches and which should result in more focused mechanistic hypotheses and experiments to test the causes of invasibility and the effects of NNS on DNS. We illustrate the usefulness of our framework using two case studies: one with the submersed macrophyte, Hydrilla verticillata, in reservoir and the other with the fish, Geophagus proximus, in a large river–floodplain system. 3. Hydrilla verticillata invaded sites with DNS similar to that found in non‐invaded sites, indicating that biotic and/or abiotic factors did not influence invasion success; however, DNS increased over time in invaded sites compared with non‐invaded sites, suggesting that H. verticillata facilitated natives. In contrast, G. proximus invaded sites with higher DNS than non‐invaded sites, suggesting that biotic and/or abiotic factors favouring natives were important for invasion success, but DNS increased in invaded and non‐invaded sites over time, indicating that an independent factor contributed to DNS increases. 4. Conclusions from both studies would have been inaccurate or incomplete if the space‐for‐time and time approaches had not been used in combination as proposed in our framework.     

Drilling by Octopus vulgaris(Mollusca: Cephalopoda) in the Mediterranean

Octopus vulgaris drills holes in the shells of a variety of molluscs. The walls of the cavities drilled exhibit dissolution of mineral and organic material. The features which characterize the cavities have been described. The composition and structure of the shell itself is important in determining the size, shape and form of the cavity drilled, and not the size of the octopus. Capture, drilling the shell, and eating the occupant may take less than one hour.     

Callitriche Stem Elongation is controlled by Ethylene and Gibberellin

Callitriche platycarpa is a freshwater plant characterized by floating rosettes of leaves connected to the water-bed by threadlike (diameter < 1 mm) stems. The internodes within the rosettes are immature and short (< 2 mm). If they mature at the water surface, they become 10 to 30 mm long, but if the rosette is submerged the internodes elongate faster and to a greater extent (25–60 mm). This method of growth rate control is of interest.     

PRIMARY PEPTIDE SEQUENCES FROM SQUID MUSCLE AND OPTIC LOBE MYOSIN IIs: A STRATEGY TO IDENTIFY AN ORGANELLE MYOSIN

The squid giant axon provides an excellent model system for the study of actin-based organelle transport likely to be mediated by myosins, but the identification of these motors has proven to be difficult. Here the authors purified and obtained primary peptide sequence of squid muscle myosin as a first step in a strategy designed to identify myosins in the squid nervous system. Limited digestion yielded fourteen peptides derived from the muscle myosin which possess high amino acid sequence identities to myosin II from scallop (60–95%) and chick pectoralis muscle (31–83%). Antibodies generated to this purified muscle myosin were used to isolate a potential myosin from squid optic lobe which yielded 11 peptide fragments. Sequences from six of these fragments identified this protein as a myosin II. The other five sequences matched myosin II (50–60%, identities), and some also matched unconventional myosins (33–50%). A single band that has a molecular weight similar to the myosin purified from optic lobe copurifies with axoplasmic organelles, and, like the optic lobe myosin, this band is also recognized by the antibodies raised against squid muscle myosin II. Hence, this strategy provides an approach to the identification of a myosin associated with motile axoplasmic organelles.