Resource partitioning in a guild of aphid species associated with creeping thistle Cirsium arvense

Four aphid species (Aphis fabae cirsiiacanthoidis Scop., Brachycaudus cardui (L.), Capitophorus carduinus Walker and Uroleucon cirsii (L.)) feed on the creeping thistle Cirsium arvense. They utilize different parts of their host plant and at different times. A wide niche is typical of C. carduinus and U. cirsii, whereas A. f. crisiiacanthoidis and B. cardui, show narrower but overlapping niches. Morphological features such as stylet length and body size as well as colony size and density are associated with the choice of feeding site. C. carduinus, the smallest species with the shortest stylets was able to use leaf veins and lamina, while the other species mainly used the stem and peduncles. Within this group, A. f. cirsiiacanthoidis and B. cardui are restricted to the upper part of the stem because of their short stylets, but adult U. cirsii, the species with the longest stylets, can also feed at the base of the stem.

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Räumliche und zeitliche ressourcenaufteilung in der blattlausgilde an der ackerkratzdistel cirsium arvense

Zusammenfassung An der Ackerkratzdistel leben vier Blattlausarten (Aphis fabae cirsiiacanthoidis Scop., Brachycaudus cardui (L.), Capitophorus carduinus Walker und Uroleucon cirsii (L.)), die im Verlauf der Vegetationsperiode verschiedene Strukturen ihrer Wirtspflanze nutzen. Eine breite Nische ist für U. cirsii und C. carduinus typisch, während A. f. cirsiiacanthoidis und B. cardui engere Nischen besitzen, die sich nahezu überlappen. Die Nahrungsplatzwahl wird sowohl durch morphologische Parameter wie Stilettlänge und Körpergewicht als auch durch Koloniegröe und Dispersion innerhalb der Kolonie beeinflut. Die kleinste Art, C. carduinus, die auch das kürzeste Stilett besitzt, ist in der Lage, an Blattadern und auf der Blattspreite zu saugen. Die anderen Arten bevorzugen Stengel, Seitenstengel und Blütenstiele. Innerhalb dieser Gruppe können A. f. cirsiiacanthoidis und C. carduinus wegen ihrer kürzeren Stilette nur am oberen Teil des Stengels saugen, während adulte U. cirsii aufgrund ihrer längeren Stilette auch an der Stengelbasis leben können.

     

Differentiation of smooth muscle cells in the fetal rat testis and ovary: localization of alkaline phosphatase,smooth muscle myosin,F-actin,and desmin

Summary The histochemical demonstration of alkaline phosphatase (AP) activity and localization of smooth muscle myosin (SMM), F-actin, and desmin were carried out on frozen sections of testes and ovaries from 15-day-old fetal to newborn rats. The presence of immunocytochemically localized SMM and desmin was confirmed by Western blot analysis of proteins from isolated gonads. The development of smooth muscle cells was predominant in the testis. The first SMM-positive cells with an increasing intensity for F-actin and desmin appeared in the testicular tunica albuginea and around the testicular cords by the age of 16 days. A continuous layer of SMM- and F-actin-positive (but not uniformly desmin-positive) myoid cells was detected in the newborn testis. In the early gonads and in the newborn ovary, a majority of the interstitial cells expressed desmin, indicating that, in undifferentiated tissues, non-myogenic cells may also express desmin. During fetal development, male and female gonocytes showed a decrease in F-actin content but retained their high AP activity. In the cortex of the newborn rat ovary, the observed high AP activity and the presence of desmin may be associated with the postnatal histogenesis of the follicles. The presence of SMM-containing cells in the hilus of the ovary may be required for the demarcation of the ovary from the mesonephros by the constriction of the mesovarium. The occurrence of SMM-positive cells predominantly in male fetuses suggests that the development of the contractile cells in the fetal testis may be induced by testicular androgens.     

Distribution of histamine in the rat kidney during pregnancy and development

Summary An antiserum against conjugated histamine and two oligonucleotide probes that detect the mRNA encoding L-histidine decarboxylase (HDC) involved in histamine synthesis were used to study the appearance of histamine and its location in the kidneys of fetal, newborn and young postnatal rats and in the kidneys of pregnant rats. On embryonic days 16 and 18 (E16 and E18), some HA-immunoreactive (HA-ir) cells were found within the largest S-shaped bodies. Histamine was found to appear rapidly between the 18th and 20th embryonic days in the convoluted tubules of the kidneys. On postnatal day 0 (P0), the distal convoluted tubules and collecting ducts exhibited bright fluorescence, the intensity of which decreased quickly so that it was faint on day P4 and absent at later stages. In kidneys of pregnant rats HA-ir was found in the epithelium of both the Bowman's capsule, collecting ducts and in a few cells within the tubules. Nonuniform HA-ir was also detected within glomeruli. No evidence for the presence of L-histidine decarboxylase mRNA in kidneys of fetuses or pregnant rats was seen. It is concluded that distinct structures in the developing rat kidney contain histamine during a period around birth from day E20 to day P4. In the pregnant rat, the epithelium that is in direct contact with the urine flow is immunoreactive for histamine from day 16 to 20 of pregnancy. The results suggest that histamine is not synthesized locally in the kidneys but rather originates from other tissues.     

Guild structure in solitary spider-hunting wasps (Hymenoptera: Pompilidae) compared with null model predictions

Abstract.

• 1 Three aspects of prey utilization are documented in a guild of spider-hunting pompilid wasps at a Breckland heath site: female phenology, size, and microhabitat utilization.
• 2 Twenty-four species were present at the site, 59% of the British fauna. Ten species individually represented more than 1% of the guild.
• 3 Pompilid abundance peaked in early July and mid-late August. Anoplius viaticus had a different life-history from other common guild members, making its inclusion in the guild questionable.
• 4 Most species represented by large samples occurred in all microhabitats and time intervals, and all species overlapped in size with all other species except A. viaticus. Arachnospila anceps was numerically dominant in all microhabitats and most time intervals.
• 5 Mean pair-wise overlaps in phenology and microhabitat utilization were significantly lower than predicted by null models, consistent with the idea that interspecific competition has been important in determining guild structure.
• 6 Female size is highly correlated with prey size, but the distribution of mean female sizes did not generally differ from null expectations.
• 7 Interpretation of comparisons with null models is problematic, particularly because it is difficult to quantify evolutionary ‘favourability’ of different resource states. Null models are currently of limited use because the patterns expected to result from key processes such as competition are uncertain in multi-dimensional systems.

     

神农架金丝猴的生态学观察

金丝猴(Rhinopithecus roxellanae)仅产于我国,属国家Ⅰ级保护动物,自然分布于四川、陕西、甘肃的部分地区和湖北省神农架自然保护区。1983年以来,笔者对神农架金丝猴生存环境生态习性等作了长期观察研究,结果报道如下。     

An ultrastructural study of embryonic chick retinal neurons in culture

Summary The differentiation of cells and synapses in explants of 9-day-old chick embryo retina has been studied by light and electron microscopy over a period of 35 days in vitro, and samples of retina from the 9-day chick foetus were directly fixed and prepared for study.At the time of explantation the retinae were poorly differentiated and no lamination was apparent. From day 14 onwards, (i) outer and inner nuclear layers (ONL, INL) separated by a layer of neuropil corresponding to the outer plexiform layer (OPL) and (ii) a layer of scattered large ganglion cells separated from the INL by a zone of neuropil resembling the inner plexiform layer (IPL) were apparent, and (iii) a well-differentiated outer limiting membrane was established close to the surface of the explants. In the oldest cultures some development of photoreceptor outer segments occurred but a distinct optic nerve fibre layer did not form.Although cell identification presented problems even in the oldest cultures, the major retinal cell types described in vivo could be identified. Photoreceptor cells developed pedicles in the OPL which became filled with synaptic vesicles and synaptic ribbons and established ribbon synapses (including triads) with and were commonly invaginated by processes from horizontal and bipolar cells. Processes of bipolar cells in the IPL formed simple and dyad synapses. At least two types of presynaptic amacrine cells were also identified in the INL, one of which contained large numbers of dense-core vesicles. The ganglion cells, though sparse, were large and well differentiated.These findings show that all the major neuronal types of the retina are capable of developing and differentiating in vitro, lagging behind the time-table of development and differentiation in vivo by approximately 7 days, but resulting in a histotypically organised retina with synaptic neuropil showing many similarities to the corresponding neuropil in vivo.     

Types of sesquiterpene-coumarin ethers from Achillea ochroleuca and Artemisia tripartita

In addition to known derivatives, four new sesquiterpene-coumarin ethers were isolated from the roots of Achillea ochroleuca and Artemisia tripartita and identified by ¹H and ¹³C NMR spectroscopy, including lanthanide induced shifts. The new compounds are isofraxidin derived ethers which differ from the previously described derivatives by ring cleavage and methyl migration within the terpenoid unit. The chemosystematic importance of sesquiterpene-coumarin ether accumulation within the two genera is briefly discussed.     

Responses of the Circadian Locomotor Activity Rhythm of Mus Booduga to Shifts in LD Schedules

The responses of the field mouse Mus booduga to shifts in schedules of LD cycles were monitored and the results were interpreted with the help of a PRC constructed for the same species. The results reveal that, M. booduga reentrained faster with a lesser number of transients after delay shifts than advance shifts, thus exhibiting “asymmetry effect.” A positive correlation was observed between the number of transients and the number of hours of shift. In most of the shifts, the sign of the transients (negative for delaying transients and positive for advancing transients) coincided with the direction of the shift. Interestingly, 11 and 12 h of advance shifting resulted in delaying transients. An 11-h advance shift can also be interpreted as a 13-h delay. Reentrainment through delaying transients is faster as compared to reentrainment through advancing transients. Thus, this animal might have taken a “shorter route,” as proved by the fact that an 11-h advance shift has evoked delaying transients. But a 13-h advance shift evoked only advancing transients. This prompts us to speculate that there may be a “phase jump” in M. booduga. Further, irrespective of whether L or D has been doubled in a 12-h shift, both evoked only delaying transients.     

Responses to recent climatewarming of Pinus sylvestris and Pinus cembra within their montane transition zone in the Swiss Alps

Abstract. Altitudinal and latitudinal distribution limits of trees are mainly controlled by temperature. Therefore climate warming is expected to induce upslope or poleward migrations. In the Swiss Central Alps, summers in the period 1982-1991 were on average 0.8 °C warmer than those of the period 30 yr before. We investigated whether populations of conifers at the montane Pinus sylvestris-Pinus cembra ecocline exhibit demographic trends in response to that warming. We found no evidence for this. Young seedlings of Pinus sylvestris, the species which is expected to expand its range upward in a warmer climate, were virtually absent from all sites, whereas large fractions of Pinus cembra populations were observed in the seedling and juvenile categories even below the present lower distribution limit of adult trees. This suggests that there are no major altitudinal shifts in response to the recent sequence of warmer summers. Germination and seedling survival trials with Pinus sylvestris suggest that temperature per se would not exclude this species even from establishing at the current treeline in the Swiss Central Alps. Similar results were found at the polar treeline. Phytotron tests of seedling survival showed much less drought resistance in Pinus sylvestris than in Pinus cembra which is in contrast to their phytogeographic distributions. Thus, the montane pine ecocline in the Swiss Central Alps seems to be stabilized by species interactions and may not be directly responsive to moderate climatic change, which needs to be taken into account in predictive attempts.