Derek A. Jackson

Colour and odour drive fruit selection and seed dispersal by mouse lemurs

Animals and fruiting plants are involved in a complex set of interactions, with animals relying on fruiting trees as food resources, and fruiting trees relying on animals for seed dispersal. This interdependence shapes fruit signals such as colour and odour, to increase fruit detectability, and animal sensory systems, such as colour vision and olfaction to facilitate food identification and selection. Despite the ecological and evolutionary importance of plant-animal interactions for shaping animal sensory adaptations and plant characteristics, the details of the relationship are poorly understood. Here we examine the role of fruit chromaticity, luminance and odour on seed dispersal by mouse lemurs. We show that both fruit colour and odour significantly predict fruit consumption and seed dispersal by Microcebus ravelobensis and M. murinus. Our study is the first to quantify and examine the role of bimodal fruit signals on seed dispersal in light of the sensory abilities of the disperser.

Environmental properties of pentafluorosulfanyl compounds: Physical properties and photodegradation

The pentafluorosulfanyl (SF5) functional group was investigated from an environmental perspective to ascertain its physical properties and photolytic fate. Five aromatic probe compounds were compared with their trifluoromethyl analogs. Water solubilities for SF5 compounds ranged from 78 mg/L to 2.4 g/L. Octanol-water partitioning coefficients ranged from log K(OW) = 2.9 to 3.6, all of which were approximately 0.5 to 0.6 log units more hydrophobic than their trifluoromethyl analogs. The direct photolytic fate of SF5 compounds was studied, and the SF5 group was found to completely degrade using actinic radiation with hourly half-lives. The reaction was followed by high-performance liquid chromatography with a UV-visible detector, 19F nuclear magnetic resonance spectroscopy, and high-resolution mass spectrometry. It was found that five equivalents of fluoride were released to form a benzenesulfonate as a final product of photodegradation. Finally, an SF5 analog of fluometuron, a potentially new herbicide, was synthesized and likewise photolyzed. The present study provides the first evidence that pentafluorosulfanyl can degrade under mild, environmentally relevant conditions.

Polyfluorinated amides as a historical PFCA source by electrochemical fluorination of alkyl sulfonyl fluorides.

Polyfluorinated amides (PFAMs) are a class of compounds produced as byproducts of polyfluorinated sulfonamide synthesis by electrochemical fluorination (ECF). We measured four PFAM derivatives of perfluorooctanoic acid (PFOA) in a wide range of compounds, experimental materials, and commercial products synthesized by ECF. Initial screening was performed using headspace solid phase microextraction gas chromatography mass spectrometry (SPME-GC-MS), and quantification using in-house synthesized standards was accomplished with GC-MS using positive chemical ionization. Two monosubstituted PFAMs, N-methylperfluorooctanamide (MeFOA) and N-ethylperfluorooctanamide (EtFOA), were detected in the majority of materials that were analyzed. Two disubstituted PFAMs, N-methyl-N-(2-hydroxyethyl)perfluorooctanamide (MeFOAE) and N-ethyl-N-(2-hydroxyethyl)perfluorooctanamide (EtFOAE), were not detected in any sample, likely because they were never synthesized. The concentrations of PFAMs in the sulfonamide compounds under study ranged from 12 to 6736 μg/g, suggesting their historical importance as PFCA precursors. In each case, branched isomers for PFAMs were detected, providing further support for their link to an ECF source. A hydrolysis study performed at pH 8.5 showed no degradation of EtFOA to PFOA after 8 days due to the stability of the amide bond. The environmental fate of PFAMs is suggested to be volatilization to the atmosphere followed by oxidation by hydroxyl radical with a predicted lifetime of 3-20 days. Subsequent PFAM exposure to biota will likely lead to enzymatic hydrolysis of the amide linkage to give a PFCA. Human exposure to PFAMs may have contributed to the presence of branched PFOA isomers in blood by serving as an indirect source. The decline in PFOA concentrations in human blood is consistent with a significant drop in PFAM production concurrent with the POSF phase-out in 2000-2001.

Atmospheric oxidation of polyfluorinated amides: historical source of perfluorinated carboxylic acids to the environment.

Polyfluorinated amides (PFAMs) are a class of fluorinated compounds which were produced as unintentional byproducts in the electrochemical fluorination process used for polyfluorinated sulfonamide synthesis in 1947-2002. To investigate the historical potential of PFAMs as an atmospheric perfluorinated acid (PFCA) source we studied N-ethylperfluorobutyramide (EtFBA) as a surrogate for longer chained PFAMs. Smog chamber relative rate techniques were used to measure bimolecular rate coefficients for reactions of EtFBA with chlorine atoms and hydroxyl radicals. It was found kCl = (2.08 ± 0.15) × 10(-11) cm(3) molecule(-1) s(-1) and kOH = (2.65 ± 0.50) × 10(-12) cm(3) molecule(-1) s(-1) and the atmospheric lifetime of EtFBA with respect to reaction with OH was estimated to be approximately 4.4 days. Offline sampling with both GC-MS and LC-MS/MS techniques was used to determine the products and hence a plausible pathway of atmospheric oxidation of EtFBA. Three primary oxidation products were observed by GC-MS, the N-dealkylation product C3F7C(O)NH2 and two carbonyl products, probably C3F7C(O)N(H)C(O)CH3 and C3F7C(O)N(H)CH2CHO. These primary products react further to give perfluorocarboxylic acids (PFCAs) as detected by LC-MS/MS, suggesting that eight carbon PFAMs were a historical source of PFCAs to remote regions, including the Canadian Arctic.

Enzymatic kinetic parameters for polyfluorinated alkyl phosphate hydrolysis by alkaline phosphatase.

The hydrolysis kinetics of three polyfluorinated alkyl phosphate monoesters (monoPAPs), differing in fluorinated chain length, were measured using bovine intestinal alkaline phosphatase to catalyze the reaction. Kinetic values were also measured for analogous hydrogenated phosphate monoesters to elucidate the effects of the fluorinated chain on the rate of enzymatic hydrolysis. Michaelis constants (K(m)) were obtained by a competition kinetics technique in the presence of p-nitrophenyl phosphate (PNPP) using UV-vis spectroscopy. Compared with K(m) (PNPP), Michaelis constants for monoPAPs ranged from 0.9 to 2.1 compared with hydrogenated phosphates, which ranged from 4.0 to 13.0. Apparent bimolecular rate constants (k(cat)/K(m)) were determined by monitoring rates of product alcohol formation at low substrate concentrations using gas chromatography-mass spectrometry. The experimental values for k(cat)/K(m) averaged as 1.1 × 10(7) M(-1) s(-1) for monoPAPs compared with 3.8 × 10(5) M(-1) s(-1) for hexyl phosphate. This suggests that the electron-withdrawing nature of the fluorinated chain enhanced the alcohol leaving group ability. The results were used in a simple model to suggest that monoPAPs in a typical mammalian digestive tract would hydrolyze in approximately 100 s, supporting a previous study that showed its absence after a dosing study in rats.

Atmospheric Degradation of Perfluoro-2-methyl-3-pentanone: Photolysis, Hydrolysis and Hydration

Perfluorinated carboxylic acids are widely distributed in the environment, including remote regions, but their sources are not well understood. Perfluoropropionic acid (PFPrA, CF(3)CF(2)C(O)OH) has been observed in rainwater but the observed amounts can not be explained by currently known degradation pathways. Smog chamber studies were performed to assess the potential of photolysis of perfluoro-2-methyl-3-pentanone (PFMP, CF(3)CF(2)C(O)CF(CF(3))(2)), a commonly used fire-fighting fluid, to contribute to the observed PFPrA loadings. The photolysis of PFMP gives CF(3)CF(2)C·(O) and ·CF(CF(3))(2) radicals. A small (0.6%) but discernible yield of PFPrA was observed in smog chamber experiments by liquid chromatography-mass spectrometry offline chamber samples. The Tropospheric Ultraviolet-Visible (TUV) model was used to estimate an atmospheric lifetime of PFMP with respect to photolysis of 4-14 days depending on latitude and time of year. PFMP can undergo hydrolysis to produce PFPrA and CF(3)CFHCF(3) (HFC-227ea) in a manner analogous to the Haloform reaction. The rate of hydrolysis was measured using (19)F NMR at two different pHs and was too slow to be of importance in the atmosphere. Hydration of PFMP to give a geminal diol was investigated computationally using density functional theory. It was determined that hydration is not an important environmental fate of PFMP. The atmospheric fate of PFMP seems to be direct photolysis which, under low NO(x) conditions, gives PFPrA in a small yield. PFMP degradation contributes to, but does not appear to be the major source of, PFPrA observed in rainwater.

Sensory integration during foraging: the importance of fruit hardness, colour, and odour to brown lemurs

Animal reliance on fruit signals, such as hardness, colour, and odour, during foraging is poorly understood. Here, we present data on fruit foraging behaviour and efficiency (rate of fruit ingestion) of three groups of wild, frugivorous brown lemurs (Eulemur fulvus, N = 29 individuals) in Ankarafantsika National Park, Madagascar. We quantify fruit hardness using a modified force gauge, fruit colour using spectroscopy, and fruit odour using volatile organic compound (VOC) sampling with gas chromatography-mass spectrometry. We relate lemur foraging behaviour to fruit traits by calculating touching, visual inspection, and sniffing indices and relate lemur foraging efficiency to fruit traits by calculating acceptance indices. The use of different sensory modalities by lemurs is marginally predicted in one case by fruit traits—fruits with higher overall smell signals are sniffed less than fruits with lower overall smell signals. When controlling for all fruit traits, fruit size is the only significant predictor of fruit foraging efficiency—lemurs forage more rapidly on smaller fruits relative to larger fruits.

It’s Not Easy Being Blue: Are There Olfactory and Visual Trade-Offs in Plant Signalling?

Understanding the signals used by plants to attract seed disperses is a pervasive quest in evolutionary and sensory biology. Fruit size, colour, and odour variation have long been discussed in the controversial context of dispersal syndromes targeting olfactory-oriented versus visually-oriented foragers. Trade-offs in signal investment could impose important physiological constraints on plants, yet have been largely ignored. Here, we measure the reflectance and volatile organic compounds of a community of Malagasy plants and our results indicate that extant plant signals may represent a trade-off between olfactory and chromatic signals. Blue pigments are the most visually-effective – blue is a colour that is visually salient to all known seed dispersing animals within the study system. Additionally, plants with blue-reflecting fruits are less odiferous than plants that reflect primarily in other regions of the colour spectrum.

Fruit Ripening Signals and Cues in a Madagascan Dry Forest: Haptic Indicators Reliably Indicate Fruit Ripeness to Dichromatic Lemurs

Fruit ripeness can be indicated through changes in chromaticity, luminance, odor, hardness, and size to attract seed dispersing animals. We quantified these attributes for both ripe and unripe fruits of 31 lemur-dispersed plant species in Ankarafantsika National Park, a tropical dry forest in northwestern Madagascar. We used spectroscopy, gas-chromatography mass-spectrometry, and a modified force gauge to quantify chromaticity, luminance, odor, and hardness. We compared these traits between unripe and ripe fruits of each species to determine which traits reliably indicate fruit ripeness across species. Overall, ripe fruits were significantly heavier and softer than unripe fruits. Ripe fruits were not more chromatically-conspicuous or odiferous relative to unripe fruits, nor were ripe fruits more conspicuous in the luminance channel. Contrary to expectation, our findings indicate that, in this particular system, plant-lemur interactions may be strongly mediated by haptic traits, such as fruit hardness, which are consistent and reliable indicators of fruit ripeness. Despite the potential importance of haptic indicators of fruit ripeness, they are underrepresented in the literature on sensory ecology.

Response to Comment on "Atmospheric degradation of perfluoro-2-methyl-3-pentanone: photolysis, hydrolysis, and hydration".

Perfluorinated carboxylic acids (PFCAs) are ubiquitous in biotic and abiotic environments. Longer-chain (>C8) PFCAs are bioaccumulative and have attracted substantial research interest. Precipitation measurements by Scott et al. have demonstrated that short-chain PFCAs, notably trifluoroacetic acid (TFA) and perfluoropropionic acid (PFPrA), dominate the PFCA profile. Although these smaller compounds are not expected to bioaccumulate and are not believed to represent a threat to ecosystems, their source is unclear and requires study. Thermolysis of fluoropolymers has been suggested as a potential source of TFA observed in rainwater. Other sources of TFA include the atmospheric oxidation of hydrofluorocarbons and polyfluorinated compounds. Small yields of PFPrA have been proposed from thermolysis of fluoropolymers and atmospheric oxidation of fluorotelomer alcohols but do not explain the levels of PFPrA observed in precipitation. Perfluoro-2-methyl-3-pentanone (PFMP) is a fire protection fluid, marketed as Novec 1230 by 3M. It is a replacement for chlorofluorocarbons (CFCs) and Halons, which deplete stratospheric ozone. The atmospheric lifetime of PFMP from previous work seems to be determined by photolysis and is approximately 1 week. PFMP does not contribute to stratospheric ozone depletion and has a negligible global warming potential. The major photolysis products are CF3C(O)F and COF2. 10 The atmospheric fate of CF3C(O)F is hydrolysis to yield TFA. It is possible that chemistry in remote environments following the photolysis of PFMP would give small yields of PFPrA or isoperfluorobutanoic acid (i-PFBA) via reactions of the corresponding perfluoroacyl radicals with HO2 radicals. 12,13