Ontogenesis of auditory fovea representation in the inferior colliculus of the Sri Lankan rufous horseshoe bat,Rhinolophus rouxi

Summary This report describes the ontogenesis of tonotopy in the inferior colliculus (IC) of the rufous horseshoe bat (Rhinolophus rouxi). Horseshoe bats are deaf at birth, but consistent tonotopy with a low-to-high frequency gradient from dorsolateral to ventromedial develops from the 2nd up to the 5th week. The representation of the auditory fovea is established in ventro-mediocaudal parts of the IC during the 3rd postnatal week (Fig. 3). Then, a narrow frequency band 5 kHz in width, comprising 16% of the bat's auditory range, captures 50–60 vol% of the IC (Fig. 3c). However, foveal tuning is 10–12 kHz (1/3 octave) lower than in adults; foveal tuning in females (65–68 kHz) is 2–3 kHz higher than in males (62–65 kHz). Thereafter, foveal tuning increases by 1–1.5 kHz per day up to the 5th postnatal week, when the adult hearing range is established (Figs. 4, 5). The increase of sensitivity and of tuning sharpness of single units also follows a low-to-high frequency gradient (Fig. 6).Throughout this development the foveal tuning matches the second harmonic of the echolocation pulses vocalised by these young bats. The results confirm the hypothesis of developmental shifts in the frequency-place code for the foveal high frequency representation in the IC.Abbreviations BF best frequency - CF constant frequency - FM frequency modulation - IC inferior colliculus - IHC inner hair cell; - OHC outer hair cell - RR Rhinolophus rouxi     

Development of 19 polymorphic microsatellite loci for the intermediate horseshoe bat, Rhinolophus affinis (Rhinolophidae, Chiroptera)

The intermediate horseshoe bat (Rhinolophus affinis) is a widespread species in Southeast Asia. We developed 19 novel microsatellite loci from an enriched genomic library of the bat, and tested their polymorphism using a single population from Guangdong province, southern China. The number of alleles ranged from 3 to 15 per locus with the expected and observed heterozygosity ranging from 0.397 to 0.920 and 0.280–0.926, respectively. Three markers significantly deviated from the Hardy-Weinberg expectations after Bonferroni correction and no linkage disequilibrium was detected in any of loci. These microsatellite loci will be useful in studying the phylogeography of this species.     

Isolation and characterization of 13 microsatellite loci in Rhinolophus pusillus (least horseshoe bat) with cross-amplification in five related species

We used the enriched genomic library method to isolate and characterize dinucleotide microsatellite loci in the least horseshoe bat, Rhinolophus pusillus. Seventeen loci were obtained and tested on 31 individuals sampled from Guangxi Province in southern China. Thirteen of these markers were polymorphic with expected heterozygosity ranging from 0.821 to 0.909. A total of 164 alleles were detected and the number of alleles per locus ranged from 9 to 16 (mean 12.6). These polymorphic markers will be used to assess population structure in R. pusillus. In addition, successful cross-amplification in five congeneric bat species suggests most of these markers will also be useful for studying related species.     

The influence of the auditory cortex on acoustically evoked cerebellar responses in the CF-FM bat,Rhinolophus pearsonic chinesis

1. Acoustically evoked responses of 284 neurons isolated from the cerebellar vermis, hemispheres and paraflocculus of Rhinolophus pearsonic chinesis were studied under free field acoustic stimulation conditions. 2. The BFs of these cerebellar auditory neurons ranged from 24 to 76 kHz but they mostly fall either between 48 and 64 kHz or between 65 and 76 kHz. However, the BF distribution varies among vermal, hemispheric and parafloccular neurons. 3. Threshold curves of cerebellar neurons are generally broad but those tuned to the frequency of the predominant CF component are extremely narrow. 4. Response latencies of cerebellar neurons ranged from 2 to 48 ms suggesting multiple auditory cerebellar pathways. The latency distribution also varies among vermal, hemispheric and parafloccular neurons. 5. Although both the vermis and hemispheres contain a disproportionate number of 65-74 kHz neurons, the response latencies of those neurons isolated from the vermis are scattered over a wide range of 2.2-28 ms while those neurons isolated from the hemispheres are generally stabilized between 5 and 12 ms. 6. Electrical stimulation of the auditory cortex evokes discharges from a recorded cerebellar auditory neuron. Cortical stimulation also facilitates the response of an acoustically evoked cerebellar neuron by increasing its number of impulses. The degree of facilitation is dependent upon the amplitude of the acoustic stimulus. 7. For a given electrical and acoustic stimulation condition, the facilitative latency and the degree of facilitation varied with the interstimulus interval. Among 23 neurons studied, most of them (19 neurons, 82.6%) had a maximal facilitative latency between 2 and 10 ms. 8. By examining the difference in the facilitative effect in each isolated cerebellar auditory neuron before and after a topical application of local anesthetic, procaine, onto the point of electrical stimulation in the auditory cortex, we found that the facilitative pathways to vermal and hemispheric neurons may be different from the pathway to parafloccular neurons. 9. Possible auditory pathways to different parts of the cerebellum are discussed in relation to the wide range of recorded response latencies. 10. The facilitative influence of the auditory cortex on the cerebellar auditory neurons is assumed to enhance the cerebellar role in acoustic motor orientation.     

Interpulse interval modulation by echolocating big brown bats (<Emphasis Type="Italic">Eptesicus fuscus</Emphasis>) in different densities of obstacle clutter

Big brown bats (Eptesicus fuscus) use biosonar to find insect prey in open areas, but they also find prey near vegetation and even fly through vegetation when in transit from roosts to feeding sites. To evaluate their reactions to dense, distributed clutter, bats were tested in an obstacle array consisting of rows of vertically hanging chains. Chains were removed from the array to create a curved corridor of three clutter densities (high, medium, low). Bats flew along this path to receive a food reward after landing on the far wall. Interpulse intervals (IPIs) varied across clutter densities to reflect different compromises between using short IPIs for gathering echoes rapidly enough to maneuver past the nearest chains and using longer IPIs so that all echoes from one sound can be received before the next sound is emitted. In high-clutter density, IPIs were uniformly shorter (20–65 ms) than in medium and low densities (40–100 ms) and arranged in “strobe groups,” with some overlap of echo streams from different broadcasts, causing pulse-echo ambiguity. As previously proposed, alternating short and long IPIs in strobe groups may allow bats to focus on large-scale pathfinding tasks as well as close-in obstacle avoidance.     

Spatial unmasking in the echolocating Big Brown Bat, <Emphasis Type="Italic">Eptesicus fuscus</Emphasis>

Masking affects the ability of echolocating bats to detect a target in the presence of clutter targets. It can be reduced by spatially separating the targets. Spatial unmasking was measured in a two-alternative-forced-choice detection experiment with four Big Brown Bats detecting a wire at 1 m distance. Depth dependent spatial unmasking was investigated by the bats detecting a wire with a diameter of 1.2 mm in front of a masker with a threshold distance of 11 cm behind the wire. For angle dependent spatial unmasking the masker was turned laterally, starting from its threshold position at 11 cm. With increasing masker angles the bats could detect thinner wires with diameters decreasing from 1.2 mm (target strength −36.8 dB) at 0° to 0.2 mm (target strength −63.0 dB) at 22°. Without masker, the bats detected wire diameters of 0.16 mm (target strength −66.2 dB), reached with masker positions beyond 23° (complete masking release). Analysis of the sonar signals indicated strategies in the echolocation behavior. The bats enhanced the second harmonics of their signals. This may improve the spatial separation between wire and masker due to frequency-dependent directionality increase of sound emission and echo reception.     

Potassium-dependent,bipolar gating of K+ channels in guard cells

Summary Guard cells of higher plants control transpirational water loss and gas exchange for photosynthesis by opening and closing pores in the epidermis of the leaf. To power these turgordriven movements, guard cells accumulate (and lose) 200 to 400mm (1 to 3 pmol/cell) K⁺, fluxes thought to pass through K⁺ channels in the guard cells plasma membrane. Steady-state current-voltage (I–V) relations of intactVicia guard cells frequently show large, outward-going currents at potentials approaching 0 mV. Since this current could be carried by K⁺ channels, its pharmacology and dependence on external K⁺ (K _v ⁺ ) has been examined under voltage clamp over an extended potential range. Measurements were carried out on cells which showed little evidence of primary electrogenic transport, thus simplifying analyses. Clamping these cells away from the free-running membrane potential (V _m ) revealed an outward-rectifying current with instantaneous and time-dependent components, and sensitive to the K⁺ channel blocker tetraethylammonium chloride. The current declined also under metabolic blockade with NaCN and in the presence of diethylstilbesterol, responses which were attributed to secondary effects of these inhibitors. The putative K⁺ current rose with voltage positive toV _m but it decayed over two voltage ranges, one negative toV _m and one near +100 mV, to give steady-stateI–V relations with two regions of negative (slope) conductance. Voltage-dependent and kinetic characteristics of the current were affected by K _v ⁺ and followed the K⁺ equilibrium potential. Against a (presumably) low background of primary ion transport, the K⁺ current contributed appreciably to charge balance atV _m in 0.1mm as well as in 1 to 10mm K _v ⁺ . Thus, gating of these K⁺ channels compensates for the prevailing K⁺ conditions to ensure net K⁺ movement out of the cell.     

Ectomycorrhizas associated with a relict population of Dryas octopetala in the Burren, western Ireland II. Composition, structure and temporal variation in the ectomycorrhizal community

The composition, structure and temporal variation of ectomycorrhizal (EM) communities associated with mountain avens (Dryas octopetala) in grass heaths of the Burren, western Ireland were assessed by using soil core sampling in two permanent plots and 30 other sites (196 cores in total). Of the 34 different EM types observed, 11 were common and constituted over 80% of the EM biomass. Four EM types, Craterellus lutescens, Tomentella sp., Dryadirhiza fulgens and Cenococcum geophilum were the most abundant as measured by EM length and frequency of occurrence in cores. The species profile and relative abundances were very similar in cores from the permanent plots and different sites in the Burren, indicating that they were all representative of the same EM community. The below-ground EM community in both plots was compared with production of basidiomes, and the latter was found to be an unreliable indicator of EM community structure. Temporal variation in the EM community was assessed by repeated core sampling of the two permanent plots over a 14-month period (between March 1998 and May 1999). No statistically significant shifts in EM abundance were found between sampling dates, probably as a consequence of the large variation in EM abundance between core samples over the sampling period. No significant relationship was found between rainfall, soil moisture or soil temperature and fluctuations in EM abundance. Patterns of total EM abundance and fluctuations in EM diversity were strongly correlated between the two permanent plots over the sampling period. Temporal fluctuations in the dominant EM type, Craterellus lutescens, were similar in both plots with respect to mycorrhizal length, biomass and relative abundance, and the patterns between both plots were positively correlated. EM diversity was negatively correlated with biomass of ectomycorrhizas of Craterellus lutescens in both plots, but it was significant only in plot 1.     

Separation of temporal control and trans-acting modulation of flagellin and chemotaxis genes in Caulobacter

Summary The genes involved in the biogenesis of the flagellum and the chemotaxis machinery are temporally regulated during the Caulobacter crescentus cell cycle. Using plasmid complementation, we have mapped the extent of the flaY and flaE genes. These genes function in trans to regulate the expression of the flagellin genes and the chemotaxis genes. We have found that the trans regulation that modulates the amounts of the flagellins and the chemotaxis proteins can be separated from the temporal control of fla and che gene expression. This conclusion is based on two observations: (1) the low level of synthesis of flagellins and chemotaxis proteins in flaY and flaE mutant strains occurred at the correct time in the cell cycle, and (2) complementation with plasmids containing intact flaY and flaE genes resulted in the synthesis of normal levels of flagellins and chemotaxis gene products with the maintenance of temporal cell cycle control.     

Spectral sensitivity of the compound eyes in two day-active fireflies (Coleoptera: Lampyridae: Lucidota)

Summary The electroretinographic visual spectral sensitivity functions in day-active fireflies Lucidota luteicollis and Lucidota atra show a broad green sensitivity and a shoulder in the near-ultraviolet region of the spectrum (Figs. 1, 2) as is commonly found among day-active insects. The nomogram for P530 visual pigment matches the spectral sensitivity curves in the green. The adult L. luteicollis retains its larval bioluminescent light organ which has a peak emission at 562 nm. The _max of the ERG spectral sensitivity does not match the bioluminescent peak (Fig. 1B) as it does in twilight- and dark-active fireflies. Some relevant behavioural observations with respect to mating are presented.     

Maternal rejection and infant play in rhesus monkey infants

In five-minute records in which they were rejected by their mothers, passive preventions of nipple access, 11- to 15-week-old group-living rhesus monkey infants (Macaca mulatta) initiated fewer playful conctacts with others relative to the other kinds of social contact they initiated, while their overall rates of initiating social contacts may not have been reduced. Whether acts of maternal rejection are costly and distressing to the infant may depend on the nature of the social companions available for it and until more is known of the context of such acts, hypothesis about weaning conflict will be difficult to test in detail.     

Effects of D2O on permeation and gating in the Ca2+-activated potassium channel fromChara

We studied the effects of H₂O/D₂O substitution on the permeation and gating of the large conductance Ca²⁺-activated K⁺ channels inChara gymnophylla droplet membrane using the patchclamp technique. The selectivity sequence of the channel was: K⁺>Rb⁺≫Li⁺, Na⁺, Cs⁺ and Cl⁻. The conductance of this channel in symmetric 100mm KCl was found to be 130 pS. The single channel conductance was decreased by 15% in D₂O as compared to H₂O. The blockade of channel conductance by cytosolic Ca²⁺ weakened in D₂O as a result of a decrease in zero voltage Ca²⁺ binding affinity by a factor of 1.4. Voltage-dependent channel gating was affected by D₂O primarily due to the change in Ca²⁺ binding to the channel during the activation step. The Hill coefficient for Ca²⁺ binding was 3 in D₂O and around 1 in H₂O. The values of the Ca²⁺ binding constant in the open channel conformation were 0.6 and 6 μm in H₂O and D₂O, respectively, while the binding in the closed conformation was much less affected by D₂O. The H₂O/D₂O substitution did not produce a significant change in the slope of channel voltage dependence but caused a shift as large as 60 mV with 1mm internal Ca²⁺.     

Intra-individual variation in the vocalized frequency of the Taiwanese leaf-nosed bat, Hipposideros terasensis, influenced by conspecific colony members

We examined the intra-individual variation in resting frequency of the constant-frequency component of the second harmonic of the pulse (F _rest) over 4 years in a laboratory colony of the Taiwanese leaf-nosed bat (Hipposideros terasensis). Patterns of change in F _rest were observed when individuals were added to or removed from the colony so that we investigated whether F _rest was affected by neighboring colony members. F _rest of each bat continually showed a long-term gradual change throughout the year, and all bats in the colony increased or decreased their F _rest in the same direction as a group non-seasonally. The greatest short-term changes were observed when new bats with a relatively low F _rest joined the colony and F _rest of new bats converged with those of the original colony members around 8 –16 days after their introduction. Conversely, a single individual showed sudden short-term decrease in F _rest after its isolation from other colony members. These findings strongly indicate that F _rest is flexible according to the presence of neighboring conspecific bats. We suggest that the audio-vocal feedback for conspecific pulses appears to be involved in the short- or long-term intra-individual variation in F _rest other than factors previously thought such as age or season.     

Spectral composition of irradiation regulates the cell growth and flavonoids biosynthesis in callus cultures of Saussurea medusa Maxim

Cell growth, flavonoids biosynthesis and L-phenylalanine ammonia-lyase (PAL) activity were studied in callus cultures of Saussurea medusa Maxim. under different types of spectral radiance. After 21 days, red light significantly improved the callus growth, but inhibited the biosynthesis of flavonoids in callus cultures. However, blue light was found to enhance the biosynthesis of flavonoids, although callus growth under this spectrum was comparable with that under white and other coloured spectra, such as green and yellow. The accumulation of flavonoids in callus cultures was related to the PAL activity, which was found to be stimulated by the spectral composition of irradiation.     

The karyotype and 5S rRNA genes from Spanish individuals of the bat species <Emphasis Type="Italic">Rhinolophus</Emphasis><Emphasis Type="Italic">hipposideros</Emphasis> (Rhinolophidae; Chiroptera)

The karyotype of individuals of the species Rhinolophus hipposideros from Spain present a chromosome number of 2n = 54 (NFa = 62). The described karyotype for these specimens is very similar to another previously described in individual from Bulgaria. However, the presence of one additional pair of autosomal acrocentric chromosomes in the Bulgarian karyotype and the differences in X chromosome morphology indicated that we have described a new karyotype variant in this species. In addition, we have analyzed several clones of 1.4 and 1 kb of a PstI repeated DNA sequence from the genome of R. hipposideros. The repeated sequence included a region with high identity with the 5S rDNA genes and flanking regions, with no homology with GenBank sequences. Search for polymerase III regulatory elements demonstrated the presence of type I promoter elements (A-box, Intermediate Element and C-box) in the 5S rDNA region. In addition, upstream regulatory elements, as a D-box and Sp1 binding sequences, were present in flanking regions. All data indicated that the cloned repeated sequences are the functional rDNA genes from this species. Finally, FISH demonstrated the presence of rDNA in nine chromosome pairs, which is surprising as most mammals have only one carrier chromosome pair.     

The spatial and temporal distribution of predatory and phytophagous mites in field-grown strawberry in the UK

Extensive sampling of strawberry plants in everbearing and June-bearing strawberry plantations and on potted plants showed that different species of mites were spatially separated. Of the two phytophagous species recorded, Tetranychus urticae was most abundant on old leaves and Phytonemus pallidus on folded leaves and flower/fruit clusters. Predatory phytoseiid mites were found on all plant parts but different species were spatially separated; Neoseiulus cucumeris and N. aurescens were found mostly on folded leaves and clusters, and N. californicus and Phytoseiulus persimilis on old and medium aged leaves. No Typhlodromus pyri were found in the field plantations. These patterns of distribution did not change over sampling dates in summer and early autumn. An understanding of this within-plant zonation of mite species is important when studying predator–prey interactions and when designing sampling strategies for strawberry. A programme to sample the entire mite system on strawberry should be stratified to include all the above mentioned parts of the plant. Different sampling protocols, as appropriate, are required for sampling different pest species and their associated predators.     

Spectral Filters and Temperature Effects on the Growth and Development of Chrysanthemums under Low Light Integral

The influence of altered light quality on the growth and development of chrysanthemum (cvs. Snowdon and Bright Golden Ann), was investigated in three different glasshouse temperatures i.e. 15, 20 or 24°C under low light levels. Five different colour filters i.e. blue and red absorbing (088), Blue absorbing (101), two partially blue absorbing (109 and 110) and Red absorbing (117) were tested, with clear polythene as a control. As in high light conditions, filters as well as temperature under low light levels significantly affected different growth parameters. Filters and temperatures significantly affected plant height and internode length, indicating that in chrysanthemum these were regulated by the action of phytochrome as well as a blue acting photoreceptor (cryptochrome). Time to flowering was affected by a combined action of phytochrome and cryptochrome since filters with blue transmission and high phytochrome photoequilibrium resulted in early flowering. The data were subjected to multiple regression and simple models were constructed to predict the influence of spectral quality on plant height, internode length and time to flowering in chrysanthemum. The models were then applied to simulate the potential benefits spectral filters used for green house cladding and regulation of plant growth under them.