Rotationally resolved fluorescence-dip and ion-dip spectra of single rovibronic states of benzene

We report fluorescence-dip as well as ion-dip spectra of single rovibronic one-photon states of benzene with a linewidth as narrow as 0.14 cm'1. The selective excitation of the rovibronic states was achieved through the combination of a frequency-doubled pulsed amplified cw dye laser (Avuv 100 MHz) and a collimated molecu-lar beam. The detailed analysis of the dip spectra shows that the observed spectral features correspond to single rovibronic transitions if suitable states are excited. From the spectra, precise harmonic frequencies and anharmonic constants for the So state are determined. A hitherto unknown Darling-Dennison resonance of the overtones of v, with the 52 state is found. 1

Sub-Doppler UV spectroscopy by resonance-enhanced two-photon ionization: the structure of the benzene20,22Ne cluster

In this work it is demonstrated that mass selected multiphoton ionization is a powerful technique for high resolution spectroscopy, isotope cluster separation and investigation of the structure of van der Waals clusters. The rotationally resolved UV spectra of the benzene-20Ne and benzene-22Ne clusters are selectively measured in a natural isotopic mixture of benzene and benzene-Ne clusters in a cooled supersonic jet. The analysis of these spectra yields accurate values for the rotational constants of both species. From this data it is found that the Ne atom is located on the C6 rotational axis of the benzene ring at an average distance of 3.46 Å with a slight difference for the two isotopes. This distance decreases by 40 mÅ when benzene is electronically excited. The influence of the large amplitude van der Waals vibrations on the average bond length is discussed

Rotationally resolved ultraviolet spectra of benzene-noble gas van der Waals clusters

Sub-Doppler electronic spectra with hundreds of resolved rotational lines are now available for benzene-Ar dimers and trimers. From their analysis the structure of these clusters is precisely determined. The analysis of two bands, 6 0 1 and 16 0 2 , of C6H6 · Ar is presented in detail. It leads to accurate values of the van der Waals bond length in the electronic ground and excited state. The change in frequency upon clustering is found to be a factor of 17 larger for the overtone of the out-of-plane modev 16 than for the in-plane vibrationv 1. This can be tentatively explained by an interaction of the low frequency out-of-plane motion of the ring with the van-der-Waals motion of the Ar atom

Acid water tolerance in a New Zealand native freshwater fish

Physiological experiments were conducted to measure the effects of low pH water upon Na⁺ fluxes and swimming performance in east coast neutral water banded kokopu, and west coast banded kokopu living in naturally acid water. This allowed comparisons to be made regarding the relative acid tolerance between the two population stocks. A morphological study of the gills using scanning electron microscopy and transmission electron microscopy was carried out on a limited number of fish to compare gill structures of east coast acid and non acid exposed fish with west coast fish. East coast kokopu from neutral water showed a reduced sodium influx on the first day of exposure to pH4 water. This was accompanied by a reduction in passive loss or efflux. After 4 days at pH4 influx recovered allowing the fish to approach sodium balance. West coast fish showed no significant change in influx upon introduction to pH7 water and maintained influx values in pH4 water near those measured for control fish. For east coast fish, swimming performance was significantly impaired on the 2nd swimming trial when pH was lowered from 7 to 4. On the third swim with the pH returned to 7, Ucrit was similar to the initial value. West coast banded kokopu showed a significant increase in performance between trial one and three and were unaffected by pH7 water, matching performances measured in control fish. Gills from east coast acid exposed fish resembled west coast fish in that the trailing edges of the lamellae were swollen due to the large numbers of chloride cells which were present to a point approximately half way up the lamellar edge. Microridges were present on the apical surfaces of the chloride cells of east coast control fish which contrasted with the microvilli structures observed in west coast and acid exposed east coast fish. The microvilli structures present on the chloride cells of west coast and east coast acid exposed banded kokopu appeared to assist in the anchorage of mucus to the apical surface of the cell

How Did the Spider Cross the River? Behavioral Adaptations for River-Bridging Webs in Caerostris darwini (Araneae: Araneidae)

Interspecific coevolution is well described, but we know significantly less about how multiple traits coevolve within a species, particularly between behavioral traits and biomechanical properties of animals' "extended phenotypes". In orb weaving spiders, coevolution of spider behavior with ecological and physical traits of their webs is expected. Darwin's bark spider (Caerostris darwini) bridges large water bodies, building the largest known orb webs utilizing the toughest known silk. Here, we examine C. darwini web building behaviors to establish how bridge lines are formed over water. We also test the prediction that this spider's unique web ecology and architecture coevolved with new web building behaviors.We observed C. darwini in its natural habitat and filmed web building. We observed 90 web building events, and compared web building behaviors to other species of orb web spiders.Caerostris darwini uses a unique set of behaviors, some unknown in other spiders, to construct its enormous webs. First, the spiders release unusually large amounts of bridging silk into the air, which is then carried downwind, across the water body, establishing bridge lines. Second, the spiders perform almost no web site exploration. Third, they construct the orb capture area below the initial bridge line. In contrast to all known orb-weavers, the web hub is therefore not part of the initial bridge line but is instead built de novo. Fourth, the orb contains two types of radial threads, with those in the upper half of the web doubled. These unique behaviors result in a giant, yet rather simplified web. Our results continue to build evidence for the coevolution of behavioral (web building), ecological (web microhabitat) and biomaterial (silk biomechanics) traits that combined allow C. darwini to occupy a unique niche among spiders

Till death (or an intruder) do us part: intrasexual-competition in a monogamous Primate

Polygynous animals are often highly dimorphic, and show large sex-differences in the degree of intra-sexual competition and aggression, which is associated with biased operational sex ratios (OSR). For socially monogamous, sexually monomorphic species, this relationship is less clear. Among mammals, pair-living has sometimes been assumed to imply equal OSR and low frequency, low intensity intra-sexual competition; even when high rates of intra-sexual competition and selection, in both sexes, have been theoretically predicted and described for various taxa. Owl monkeys are one of a few socially monogamous primates. Using long-term demographic and morphological data from 18 groups, we show that male and female owl monkeys experience intense intra-sexual competition and aggression from solitary floaters. Pair-mates are regularly replaced by intruding floaters (27 female and 23 male replacements in 149 group-years), with negative effects on the reproductive success of both partners. Individuals with only one partner during their life produced 25% more offspring per decade of tenure than those with two or more partners. The termination of the pair-bond is initiated by the floater, and sometimes has fatal consequences for the expelled adult. The existence of floaters and the sporadic, but intense aggression between them and residents suggest that it can be misleading to assume an equal OSR in socially monogamous species based solely on group composition. Instead, we suggest that sexual selection models must assume not equal, but flexible, context-specific, OSR in monogamous species.Wenner-Gren Foundation, L.S.B. Leakey Foundation, the National Geographic Society, National Science Foundation (BCS- 0621020), the University of Pennsylvania Research Foundation and the Zoological Society of San Diego, German Science Foundation (HU 1746-2/1

Gelechiidae Moths Are Capable of Chemically Dissolving the Pollen of Their Host Plants: First Documented Sporopollenin Breakdown by an Animal

Background: Many insects feed on pollen surface lipids and contents accessible through the germination pores. Pollen walls, however, are not broken down because they consist of sporopollenin and are highly resistant to physical and enzymatic damage. Here we report that certain Microlepidoptera chemically dissolve pollen grains with exudates from their mouthparts. Methodology/Principal Findings: Field observations and experiments in tropical China revealed that two species of Deltophora (Gelechioidea) are the exclusive pollinators of two species of Phyllanthus (Phyllanthaceae) on which their larvae develop and from which the adults take pollen and nectar. DNA sequences placed the moths and plants phylogenetically and confirmed that larvae were those of the pollinating moths; molecular clock dating suggests that the moth clade is younger than the plant clade. Captive moths with pollen on their mouthparts after 2-3 days of starvation no longer carried intact grains, and SEM photographs showed exine fragments on their proboscises. GC-MS revealed cis-b-ocimene as the dominant volatile in leaves and flowers, but GC-MS analyses of proboscis extracts failed to reveal an obvious sporopollenindissolving compound. A candidate is ethanolamine, which occurs in insect hemolymphs and is used to dissolve sporopollenin by palynologists. Conclusions/Significance: This is the first report of any insect and indeed any animal chemically dissolving pollen

Postcopulatory sexual selection

The female reproductive tract is where competition between the sperm of different males takes place, aided and abetted by the female herself. Intense postcopulatory sexual selection fosters inter-sexual conflict and drives rapid evolutionary change to generate a startling diversity of morphological, behavioural and physiological adaptations. We identify three main issues that should be resolved to advance our understanding of postcopulatory sexual selection. We need to determine the genetic basis of different male fertility traits and female traits that mediate sperm selection; identify the genes or genomic regions that control these traits; and establish the coevolutionary trajectory of sexes

Support for maternal manipulation of developmental nutrition in a facultatively eusocial bee, Megalopta genalis (Halictidae)

Developmental maternal effects are a potentially important source of phenotypic variation, but they can be difficult to distinguish from other environmental factors. This is an important distinction within the context of social evolution, because if variation in offspring helping behavior is due to maternal manipulation, social selection may act on maternal phenotypes, as well as those of offspring. Factors correlated with social castes have been linked to variation in developmental nutrition, which might provide opportunity for females to manipulate the social behavior of their offspring. Megalopta genalis is a mass-provisioning facultatively eusocial sweat bee for which production of males and females in social and solitary nests is concurrent and asynchronous. Female offspring may become either gynes (reproductive dispersers) or workers (non-reproductive helpers). We predicted that if maternal manipulation plays a role in M. genalis caste determination, investment in daughters should vary more than for sons. The mass and protein content of pollen stores provided to female offspring varied significantly more than those of males, but volume and sugar content did not. Sugar content varied more among female eggs in social nests than in solitary nests. Provisions were larger, with higher nutrient content, for female eggs and in social nests. Adult females and males show different patterns of allometry, and their investment ratio ranged from 1.23 to 1.69. Adult body weight varied more for females than males, possibly reflecting increased variation in maternal investment in female offspring. These differences are consistent with a role for maternal manipulation in the social plasticity observed in M. genalis