Robber-like pollinators: overwintered queen bumblebees foraging on Corydalis ambigua

ABSTRACT.

• 1 The behaviour of nectar-collecting Bombus hypocrita sapporensis Cockerell queens was observed on a population of a spring ephemeral plant Corydalis ambigua Cham, et Schlecht.
• 2 Daily patterns of activity and behaviour changed with the progress of flowering. Activity peaked shortly before sunset early in the flowering season but approximately at noon towards the end of flowering. In the peak flowering period the queens tended to visit nearby plants and to change direction often, whereas early or late in the flowering period they flew further between visits and were less likely to change direction.
• 3 Each plant was visited 0 to 24 times (mean 9.4 ±SD 5.2) by the queens during the whole flowering season.
• 4 The queens collected nectar, rarely through the front of the flowers but mostly through the spurs perforated by themselves or predecessors. At the beginning of the flowering season the illegitimate foragers often visited the front of the flowers before moving to the spurs; later, most queens quickly learned to land directly on the spurs.
• 5 Even the 59.7% of plants that were visited only by illegitimate foragers set seeds. Close observation confirmed that the illegitimate foragers opened the inner petals enclosing anthers and stigma frequently when visiting the front of the flowers before robbing, or occasionally when walking about on the flowers or collecting nectar through the perforated spurs.

     

Additive apportioning of lepidopteran and coleopteran species diversity across spatial and temporal scales in a cool–temperate deciduous forest in Japan

Abstract.  1. Forest entomofauna retain high diversity, and examining beta diversity, or species turnover, among assemblages in a forest community is vital to elucidate the source of this diversity.
2. Under the DIVERSITAS in Western Pacific and Asia–International Biodiversity Observation Year (DIWPA–IBOY) project for simultaneously documenting biodiversity throughout the Western Pacific and Asian Region, 892 lepidopteran species (51 742 specimens) and 355 coleopteran species (11 633 specimens) were collected in 2001 by light traps in a cool–temperate forest in northern Japan.
3. This study evaluated the beta diversity of lepidopteran and coleopteran communities by ecological categories (i.e. trap location, forest strata, sampling days, and months), and assessed the habitat preferences of lepidopteran and coleopteran species.
4.  anova -like additive apportioning models were used to quantify the beta diversity among the categories. The models simultaneously provide assessments of whether species distributions are biased in favour of particular habitats.
5. Significantly high beta diversity was observed among months for both Lepidoptera and Coleoptera. The category of months corresponded fairly well to the number of specialist species detected in the category, although a remarkably large number of significant specialists in Coleoptera were observed on strata.
6. The high beta diversity and number of specialist species among strata in both communities indicate that stratification between canopy and ground, and seasonal variation, played major roles in species composition and the rich entomofauna in the forest. Highly mobile adults were influenced by the vertical spatial scale, as previously suggested for larvae.     

Demography and reproductive strategies of a polycarpic perennial, Trillium apetalon (Trilliaceae)

To investigate the connection between demographic strategies and reproductive strategies of a polycarpic perennial herb, Trillium apetalon Makino, we conducted three studies. First, we monitored the fate of individuals and the flowering behavior of T. apetalon for 12 years and used a transition matrix model to analyze the demography of the population. The analysis revealed that it takes a long time for individuals to go through one-leaf stage in juveniles. Elasticity analysis showed that the survival of flowering individuals was a decisive factor in the dynamics of the population. Furthermore, we found that the average remaining lifetime of flowering individuals was high relative to the other three stages. Second, to elucidate the demographic consequences of organ preformation, we investigated the development of flower buds for future years. We observed three to six flower buds per rhizome, suggesting that flower buds for the next 3–6 years were ready in advance in this plant. Third, the results of breeding experiments clarified that although this species appears to have a substantial capacity for both inbreeding and outbreeding, inbreeding plays an important role in seed production, and that crossing experiments (direct cross-pollination and self pollination) yielded similar seed-ovule ratios to those obtained from open-pollinated individuals. Our three studies suggest that the adult survival and continuous flowering strategies of T. apetalon obtained from demographic analysis are closely interlinked with breeding systems and preformation of flower buds.     

Temporal Hyperacuity in the Gymnotiform Electric Fish, Eigenmannia

SYNOPSIS. The gymnotiform electric fish, Eigenmannia, exhibitsextraordinary sensitivity to small timing differences betweensensory signals. The jamming avoidance response, gradual frequencyshifts of the electric organ discharges, requires the detectionof temporal disparities between sensory signals impinging upondifferent electroreceptors. This behavior occurs reliably evenwith temporal disparities being smaller than one microsecond.Since individual sensory receptors are not capable of encodingsuch minute timing with certainty, the high behavioral sensitivitymust, therefore, emerge from signal processing within the centralnervous system. Individual neurons, at the top of a well definedneuronal hierarchy have been found to be sensitive to temporaldisparities in the range of 1 microsecond. The response propertiesof these neurons as well as behavioral results suggest thatspatial convergence of sensory information plays a major rolein the emergence of this temporal hyperacuity.     

Karyomorphology of Incarvillea (Bignoniaceae) and its implications in distribution and taxonomy

The karyomorphology of 11 species of the genus Incarvillea Juss. is reported. The chromosome numbers of all species studied are 2 n  = 22. The interphase nuclei and prophase chromosomes were found to be of the simple chromocentre type and the interstitial type, respectively. The asymmetry of the karyotype of I. arguta (two populations) in subgenus Amphicome is type 2A. The karyotypes of Incarvillea s inensis var. sinensis , I.  s inensis var. przewalskii, and I. olgae in subgenus Incarvillea are of asymmetry type 3A. The remaining nine species and one variety in subgenus Pteroscleris are also of asymmetry 3A. Data on three species and one variety studied are first reports. This study indicates that karyotype variation at the diploid level appears to be the predominant feature of chromosome evolution in the genus Incarvillea . According to this study of karyomorphology, morphological characteristics and geographical distribution, it seems that the three subgenera should be regarded as three independent genera. The geography of the genus is discussed.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 113–121.     

Development of catalase activity in yeast in relation to growth and respiration

1. 1) When yeast cells grown anaerobically were adapted to aerobicculture in a normal medium, catalase formation was markedlyenhanced after the earlier stage of exponential growth of thecells. The same thing occurred with cells transferred from ananaerobic culture into a nitrogen deficient medium.
2. 2) Thecatalase activity of aerobically grown cells declinedprogressivelyuntil glucose, which had been added to the mediumwas profoundlyexhausted. This decline was followed by a progressiverecoveryof activity to a normal level with the growth of thecells.Similar behavior of catalase was also seen at low concentrationsof glucose, except that an abrupt rise in activity was observedat the beginning of incubation. Even when cells which had declinedto a minimum of catalase activity were aerated in phosphatebuffer, they continued to synthesize catalase.
3. 3) The patternof alteration of catalase activity during cellgrowth was accompaniedby a comparable pattern of alterationin respiratory capacity.On the basis of this finding, togetherwith the fact that antimycinA causes intensive depression incatalase formation, it maybe inferred that the formation ofthe respiratory chain conductsthe formation of catalase.
4. 4) In the presence of ethyl alcoholas the carbon source inplace of glucose, a rise in both catalaseactivity and respiratorycapacity occurred from initiation ofincubation. This fact canbe interpreted to mean that the repressiveeffect of glucoseon catalase formation depends on the aerobiccharacter of thecells.

(Received February 26, 1968; )     

STUDIES ON NITELLA HAVING ARTIFICIAL CELL SAP I. REPLACEMENT OF THE CELL SAP WITH ARTIFICIAL SOLUTIONS

A method for replacing the cell sap of Nitella with an artificialsolution was introduced. The technique, which is a modificationof KAMIYA and KURODA'S (1, 2), is applicable not only for isotonicbut also for hypertonic or hypotonic solutions. Photometricdeterminations of K⁺, Na⁺, Ca⁺⁺ and Cl^– proved that thereplacement of the cell sap with the present method is satisfactory.The internodal cell of Nitella, whose cell sap was replacedwith an isotonic solution with a simple composition such asa mixture of KCl, NaCl and CaCl₂, can be kept living at leastfor several days, sometimes even for more than one month. (Received September 6, 1963; )     

STUDIES ON NITELLA HAVING ARTIFICIAL CELL SAP II. RATE OF CYCLOSIS AND ELECTRIC POTENTIAL

The rate of cyclosis, the value of resting potential and theexcitability were studied on the Nitella internode whose cellsap was replaced with artificial solutions. K⁺ to Ca⁺⁺ ratioin the cell sap should be within 2 to 50 in order to maintainthe normal rate of cyclosis and the resting and action potentialsat least for several days. Replacement of the cell sap witha solution containing Li⁺, Na⁺ or Rb⁺ in place of K⁺ had noappreciable effect on the activity of the internode for severaldays, while gradual but marked decrease in the rate of cyclosisand the resting potential was observed with Cs⁺. There was noappreciable difference between the effects of Cl^– andNO₃^– on cyclosis, resting and action potentials, whileSO₄^–– decreased them to some extent. The rate ofcyclosis was not affected appreciably by changes in osmoticconcentration between 0.17 and 0.30 M. (Received September 6, 1963; )