Discriminative Response to Animal, But Not Plant, Chemicals by an Insectivorous, Actively Foraging Lizard, Scincella lateralis, and Differential Response to Surface and Internal Prey Cues

Responses by the insectivorous, actively foraging scincid lizard, Scincella lateralis, to chemical cues from a plant food favored by herbivorous lizards, its ability to discriminate prey chemicals from control substances, and its relative response to internal and surface prey chemicals were studied experimentally. We presented chemical cues to the lizards on cotton swabs and recorded their tongue-flicks and biting attacks on the swabs. The lizards exhibited significantly greater tongue-flick rates and biting frequencies to prey surface cues than to plant surface chemicals from romaine lettuce, diluted cologne (pungency control), and deionized water. Responses to the plant stimuli did not differ from those to the two control stimuli, in contrast with strong responses to the same plant cues by herbivores. This finding provides the first information suggesting that chemosensory response may be adapted to diet, with responsiveness to plant stimuli evolving de novo in herbivores. Biting and tongue-flicking responses were significantly greater to cricket chemicals than to all other stimuli, among which there were no differences. Thus, the lizards are capable of prey chemical discrimination, which may be ubiquitous among actively foraging lizards. The lizards exhibited more frequent biting and higher tongue-flick rates to internal than surface prey chemicals. Although different methods of stimulus preparation are appropriate for different purposes, we conclude that prey surface chemicals available to foraging lizards are most desirable for studies bearing on location and identification of prey.     

Responses to major categories of food chemicals by the lizard Podarcis lilfordi

Many lizards are capable of identifying food using only chemical cues from food surfaces, but almost nothing is known about the types of compounds that are effective stimuli. We experimentally studied lingual and biting responses by a lacertid lizard, Podarcis lilfordi, to single representatives of three major categories of food chemicals, sucrose as a carbohydrate, pure pork fat as a mixture of lipids, and bovine gamma globulin as a protein. In 60-sec trials in which stimuli were presented on cotton swabs, the lizards detected all three stimuli, exhibiting more tongue-flicks, licks, or bites, or a greater tongue-flick attack score (TFAS; overall measure of response strength to prey stimuli) than to deionized water. The initial response to all stimuli was tongue-flicking, but the lizards discriminated among the types of chemical stimuli. After preliminary tongue-flicks, the lizards responded to sucrose solutions by licking at high rates, to pure pork fat by biting, and to protein by a combination of additional tongue-flicks and biting. Biting is a feeding response to prey or solid plant material. Licking is a feeding response to sugars in nectar or ripe fruit. Its frequency increased with sucrose concentration. Our data suggest that lizards can identify several types of chemicals associated with food and direct feeding attempts to sources of such chemicals in the absence of visual cues.     

Responses to prey chemicals by a lacertid lizard,Podarcis muralis: Prey chemical discrimination and poststrike elevation in tongue-flick rate

The ability to discriminate prey chemicals from control substances and the presence of a poststrike elevation in tongue-flicking (PETF) rate are experimentally demonstrated in the lacertid lizard,Podarcis muralis, The tongue-flick attack score, a composite index of response strength, was significantly higher in response to integumental chemicals from cricket than to cologne or distilled water. The cricket chemicals additionally elicited a significantly greater rate of tongue-flicking and higher proportion of attacks by the lizards than did control stimuli. PETF combined with apparent searching movements strongly suggest the presence of strike-induced chemosensory searching (SICS). Experimental evidence indicates that both PETF and SICS occur in insectivorous representatives of three families of actively foraging autarchoglossan lizards, suggesting their widespread occurrence in such lizards. The adaptive roles of chemosensory behavior in the foraging behavior of P.Muralis are discussed. It is proposed that these lizards may form chemical search images and that PETF and SICS may have been present in the lacertilian ancestors of snakes.     

Pheromonal Discrimination of Sex by Male and Female Leopard Geckos (Eublepharis macularius)

The ability of male and female Eublepharis macularius to discriminate among pheromones of males and females and a blank control was investigated. Stimuli were presented on ceramic tiles in the animal's home cages. Males tongue-flicked at significantly lower rates in response to male stimuli than to female and control stimuli. Males also performed aggressive behaviors toward male, but not female or control, stimuli, and tail vibrations toward female, but not male or control, stimuli. Mean tongue-flick rates by females did not differ significantly among conditions. Discrimination of male pheromones by females was demonstrated by greater performance of labial-licking and chin-rubbing in response to male stimuli than to either female or control stimuli.     

Correspondence Between Diet and Food Chemical Discriminations by Omnivorous Geckos (Rhacodactylus)

Chemosensory responses to food are correlated with geographic variation in diet of some colubrid snakes, but the influence of diet on chemosensory behavior has not been established generally in snakes or lizards. Most lizards are generalist predators of small animals, making it difficult to study effects of diet, but herbivory and omnivory have evolved in several lineages, providing an excellent opportunity to study the effects of dietary change on chemosensory behavior. Based on ecological considerations, I argue that inclusion of plants in the diet of lizards that evolved from ambush foragers lacking prey chemical discrimination might be expected to evolve responsiveness to plant food chemicals. If animal prey also are retained in the diet, then responsiveness to prey chemicals should evolve as well. I experimentally studied tongue-flicking and biting responses by omnivorous geckos of the genus Rhacodactylus to chemical stimuli from plant and animal foods and control substances presented on cotton swabs. The lizards exhibited significantly greater responses to plant stimuli than to control stimuli. One of two species tested responded strongly to cricket chemicals, but the other showed no significant response to mouse surface chemical stimuli. The results support the hypothesis that dietary shifts induce corresponding changes in chemosensory response, but establishment of correlated evolution between diet and food chemical discriminations in lizards will require study of many herbivores/omnivores and insectivores as controls.     

Production and Predator-Induced Release of Volatile Chemicals by the Plant Bug Lygus hesperus

Both sexes of adult western tarnished plant bug, Lygus hesperus Knight (Heteroptera: Miridae), released three volatile chemicals in relatively large amounts when attacked by ants (Pogonomyrmex rugosus and Solenopsis xyloni) or when grabbed by forceps, as determined by solid-phase microextraction (SPME) and gas chromatography–mass spectrometry (GC–MS). The relative amounts of the volatile compounds, hexyl butyrate, (E)-4-oxo-2-hexenal, and (E)-2-hexenyl butyrate, absorbed by SPME as a percentage of the largest were 100%, 44%, and 4%, respectively, from females, and 83%, 37%, and 3% from males. Both ant species were repelled by the defensive discharges (confirmed by SPME) when the ants attacked L. hesperus adults. Sexually mature L. hesperus were individually extracted in pentane to quantify the mean amounts of hexyl butyrate (14.9 μg/female; 10.3 μg/male), (E)-4-oxo-2-hexenal (2.7 μg/female; 3.1 μg/male), and (E)-2-hexenyl butyrate (1.2 μg/female; 0.6 μg/male). (E)-4-Oxo-2-hexenal was unstable in solvent when in contact with a macerated adult, but relatively stable when the solution was decanted within minutes. The production of the three major volatile components began soon after the emergence of the adult and amounts increased for about 5–10 d with little or no increase thereafter. Minor additional constituents were cross-correlated in many cases with the three major ones. A cost of defensive secretion is suggested for females but not for males, because heavier females produced more volatile compounds than lighter females. The initial discharge percentage, defined as the proportion of volatile compounds initially present that is discharged to defend against predation was estimated at about 50% in males and 70% in females. Newly eclosed adults did not produce volatile chemicals until 2 d after molting.     

A Resistant Predator and Its Toxic Prey: Persistence of Newt Toxin Leads to Poisonous (Not Venomous) Snakes

The common garter snake (Thamnophis sirtalis) preys upon the rough-skinned newt (Taricha granulosa), which contains the neurotoxin tetrodotoxin (TTX) in the skin. TTX is toxic, large quantities are present in a newt, and highly resistant snakes have the ability to ingest multiple newts; subsequently snakes harbor significant amounts of active toxin in their own tissues after consuming a newt. Snakes harbor TTX in the liver for 1 mo or more after consuming just one newt, and at least 7 wk after consuming a diet of newts. Three weeks after eating one newt, snakes contained an average of 42 microg of TTX in the liver. This amount could severely incapacitate or kill avian predators, and mammalian predators may be negatively affected as well.     

Olfactory Reactions of the Twelve-Spotted Lady Beetle, Coleomegilla maculata and the Green Lacewing, Chrysoperla carnea to Semiochemicals Released from Their Prey and Host Plant: Electroantennogram and Behavioral Responses

Electroantennograms (EAGs) were recorded from two predatory insect species, the twelve-spotted lady beetle, Coleomegilla maculata and the green lacewing, Chrysoperla carnea in response to semiochemicals emitted from one of their prey species, the pea aphid Acyrthosiphon pisum and their host plant. EAG responses were also recorded from C. maculata in response to extracts from individuals of the opposite sex and to extracts from an herbaceous plant, catnip Nepeta cataria. Extracts of catnip and two sex pheromone components of aphids, (4aS,7S,7aR)-nepetalactone and (1R,4aS,7S,7aR)-nepetalactol, elicited significant EAG responses from the antennae of both predatory species. Of 10 corn volatile compounds tested, C. carnea adults responded most strongly to 2-phenylethanol and (E)--farnesene. A significant difference in EAG response to extracts of corn leaf collections was observed between male and female C. carnea. In C. maculata, significant EAG responses were elicited by most of the tested corn volatile compounds, except -pinene and (E)-2-hexenal. The highest EAG responses were observed in response to (E)--farnesene, -terpineol, 2-phenylethanol, and -caryophyllene. Sexual differences in EAG responses of C. maculata were only found in response to 1-octen-3-ol. Male antennae of C. maculata produced significant EAG responses to extracts from conspecific females, but not to males, which indicates that some chemicals from females could be involved in sexual communication. A significant EAG response also was recorded in response to the extracts of fluids produced during reflex bleeding. Male and female antennae of both species exhibited similar dose–response curves to most of the selected compounds, although female C. maculata antennae exhibited higher thresholds in response to several compounds including -terpineol, (Z)-3-hexenol, and (4aS,7S,7aR)-nepetalactone. Field tests showed that 2-phenylethanol was highly attractive to both sexes of the two investigated species. Only C. maculata was attracted to traps baited with -terpineol.     

Attraction of the Larval Predator Elater ferrugineus to the Sex Pheromone of Its Prey, Osmoderma eremita, and Its Implication for Conservation Biology

Elater ferrugineus is a threatened click beetle inhabiting old hollow trees. Its larvae consume larvae of other saproxylic insects including the threatened scarab beetle Osmoderma eremita. Recently, (R)-(+)-gamma-decalactone was identified as a male-produced sex pheromone of O. eremita. Here we present evidence that E. ferrugineus adults use this odor as a kairomone for location of their prey. In field trapping experiments, significantly more trapping events of E. ferrugineus beetles were observed in Lindgren funnel traps baited with (R)-(+)-gamma-decalactone than in control traps (20 vs. 1, respectively). Analyses of headspace collections from E. ferrugineus beetles indicate that the predator itself does not produce the substance. Both sexes were attracted to the prey pheromone. suggesting that E. ferrugineus males use the odor as an indirect cue for location of mates or of the tree hollows, which make up their habitat. When compared to pitfall traps, the Lindgren system was significantly more effective in trapping E. ferragineus, and no difference could be established for O. eremita, showing the high potential to use odor-based systems to catch both species. We suggest that (R)-(+)-gamma-decalactone could be used as a master signal in monitoring programs for these vulnerable beetle species. which are both regarded as indicators of the associated insect fauna of the threatened habitat of old hollow trees.     

Foraging Behavior and Microhabitat Use by Spiny Mice, Acomys cahirinus and A. russatus, in the Presence of Blanford's Fox (Vulpes cana) Odor

We investigated the responses of common and golden spiny mice (Acomys cahirinus and A. russatus, respectively) to the fecal odor of Blanford's fox (Vulpes cana), a predator of Acomys, which overlaps in habitat use with the mice. Neither species of mouse showed a significant response to the presence of fox odor compared with the presence of the fecal odor of a local herbivore (Nubian ibex, Capra ibex nubia). One explanation is that the impact of predation from V. cana may be sufficiently low that the cost of avoidance, in terms of missed feeding opportunities, conveys little selective advantage. Alternatively, fecal odor may not provide a focused cue of immediate danger for spiny mice. The diurnal A. russatus showed a stronger (near significant) response than the nocturnal A. cahirinus to fecal odor of this nocturnal predator. This may be a legacy of the underlying nocturnal activity rhythm of A. russatus or may indicate a generally more cautious response to predator odors, as A. russatus has a much stronger preference for sheltered microhabitats than A. cahirinus.     

Olfactory Reception of Conspecific Aggregation Pheromone and Plant Odors by Nymphs of the Predator, Podisus maculiventris

Olfactory reception of 23 odorants, including plant volatiles and male-produced aggregation pheromone, by third and fifth instars of the spined soldier bug (SSB) Podisus maculiventris was investigated by using electroantennograms (EAGs). Both nymphal stages were sensitive to male-produced aggregation pheromone components (E)-2-hexenal, benzyl alcohol, and -terpineol. The plant volatile, (E)-2-hexen-1-ol (a chemical known to be released by plants in response to prey feeding over the short-term), elicited the largest EAGs of all volatiles tested. While third instars were sensitive to nonanal, only fifth instars responded to both nonanal and (±)-linalool, both compounds released systemically by plants in response to feeding by potential prey. Antennal extirpation experiments showed that sensilla responsive to hexan-1-ol, (E)-2-hexenal, and -terpineol are situated mainly on the terminal antennal segment. The results support the hypothesis that P. maculiventris nymphs use both plant volatiles and pheromone components in locating potential prey and other behaviors.     

A rapid,automated method for the determination ofcis andtrans content of fats and oils by fourier transform infrared spectroscopy

A rapid Fourier transform infrared (FTIR) method was developed to simultaneously determine percentcis andtrans content of edible fats and oils. A generalized, industrial sample-handling platform/accessory was designed for handling both fats and oils and was incorporated into an FTIR spectrometer. The system was calibrated to predict thecis andtrans content of edible oils by using pure triglycerides as standards and partial least squares as the chemometric approach. The efficacy of the calibration was assessed by triglyceride standard addition, by mixing of oils with varyingcis/trans contents, and by analyzing fats and oils of known iodine value. Each of the approaches verified that the FTIR method measured thecis andtrans content in a reproducible (±0.7%) manner, with the measured accuracies being 1.5% for standard addition and 2.5% for the chemically analyzed samples. Comparisons also were made to the conventional American Oil Chemists’ Society (AOCS) method for the determination oftrans isomers by IR spectroscopy. The FTIR-partial least squares approach worked well over a wide range oftrans contents, including those between 0 and 15%. The sample-handling accessory designed for this application is robust, flexible, and easy to use, being particularly suited for quality-control applications. In addition, the analysis was automated by programming the spectrometer in Visual Basic (Windows), to provide a simple, prompt-based user interface and to allow an operator to carry outcis/trans analyses without any knowledge of FTIR spectroscopy. A typical analysis requires less than two minutes per sample. The derived calibration is transferable between instruments, eliminating the need for recalibration. The integrated analytical system provides a sound basis for the implementation of FTIR methods in place of a variety of AOCS wet chemical methods when analytical speed, cost, and environmental concerns are issues.     

Variation in cardenolide content of the lygaeid bugs,Oncopeltus fasciatus andLygaeus kalmii kalmii and of their milkweed hosts (Asclepias spp.) in central California

A colorimetric assay was used to quantify the amount of cardenolides in the lygaeid bugsOncopeltus fasciatus andLygaeus kalmii kalmii and their milkweed host plants (Asclepias spp.) in central California. The cardenolide content of individual insects, determined in microgram equivalents of digitoxin, varied from zero to over 300 g per insect. Sources of variation of cardenolide content in the insects include interspecific and intraspecific differences in the content of the host plant species and also differences in the content of plant organs on which insects were feeding. This last source of variability may explain temporal variation in the cardenolide content of the insects. Adults ofO. fasciatus, which migrate into California in the late spring and early summer, and adults ofL. k. kalmii, which emerge from winter hibernacula in the early spring, contained small to immeasureable amounts of cardenolides. The colonization pattern ofO. fasciatus on species ofAsclepias in north central California suggests that this species does not maximize its opportunities to sequester large quantities of cardenolides from potential hosts. The emetic potential of lygaeids in California to vertebrate predators is briefly discussed.     

Behavioral and cardiac responses of the rabbit,Oryctolagus cuniculus,to chemical fractions from anal gland

Unrestrained rabbits, 2–3 months old and nestlings, were exposed to the odors of the acid-neutral, acid, neutral, and basic fractions of the anal gland of male rabbits. The acid-neutral, acid, and neutral fractions elicited the strongest response in the form of avoidance. The heart rates of the nestlings were monitored using a radio telemetry technique. Statistically significant lowering of the heart rate and an increase in variability occurred on exposure to the fractions. The extent of the changes varied consistently in relation to a given odor, being greatest for the acid and neutral fractions. The results indicate the usefulness of heart-rate monitoring as a tool in the study of the perception of odors by animals.     

Soldier frontal glands of the termiteMacrotermes subhyalinus: Morphology,chemical composition,and use in defense

Soldiers of the East African fungus-growing termiteMacrotermes subhyalinus (Rambur) (Termitidae: Macrotermitinae) employ both mechanical and chemical defenses. Soldiers release a chemical secretion composed of long-chain saturated and monounsaturated hydrocarbons into wounds inflicted by their powerful mandibles. Chemical analysis of the secretion shows the paraffin fraction to consist primarily ofn-tricosane,n-pentacosane, 3- and 5-methylpentacosane, and 5-methylheptacosane. The major oleflns were identified as (Z)-9-heptacosene and (Z)-9-nonacosene. The secretion originates from the frontal glands of both major and minor soldiers; however, the hypertrophied gland of the major soldiers contains 500-fold more secretion than that of the minor soldiers. This secretion appears to impair the healing of wounds in test ants, and thus could represent a valuable supplement to the mechanical defense mechanism.     

Olfactory behavior and receptor potentials of the khapra beetleTrogoderma granarium (Coleoptera: Dermestidae) induced by the major components of its sex pheromone,certain analogues,and fatty acid esters

On the basis of the antennal receptor potentials and the extent of attraction and copulation induced in unmated male khapra beetles, (Z)- and (E)-14-methyl-8-hexadecenal were recognized as the most important components of the pheromone system of femaleTrogoderma granarium (Everts), and were named (Z)- and (E)-trogodermal. Air blown over 10^–5 to 10^–4 g of (Z)-trogodermal produced receptor potentials equivalent to that elicited by one virgin femaleT.granarium, while 10^–2 g of (Z)-trogodermal was required to cause complete attraction and copulation of unmated males. (Z)-Trogodermal was about 10 times more active than (E)-trogodermal. (Z)-8-Hexadecenal was 10^–2 times less effective than (Z)-trogodermal in causing attraction and 10⁴ time less active in stimulating copulation. (Z)- and (E)-14-methyl-8-hexadecen-1-ol and methyl (Z)- and (E)-14-methyl-8-hexadecenoate displayed a relatively low activity for unmated male khapra beetles. Methyl and ethyl oleate, ethyl linoleate, ethyl palmitate, and ethyl stearate were less effective than (Z)-trogodermal by 6–8 orders of magnitude and are nonspecific attractants. The intensity of response to a particular compound was consistent when assessed by the essential components of mating behavior: receptor potentials, attraction, and copulation.     

Basic investigation of the chemical deactivation of V2O5/WO3-TiO2 SCR catalysts by potassium,calcium, and phosphate

Topics in Catalysis - The influence of the combustion products of different lubrication oil additives and impurities in fuel or urea solution on the activity and selectivity of V2O5/WO3-TiO2...     

Selective reduction of NOx by hydrogen and methane in natural gas stationary sources over alumina-supported Pd, Co and Co/Pd catalysts: Part A. On the effect of palladium precursors and catalyst pre-treatment

The aim of the present work is to study the selective reduction of NO_x from natural gas sources. The unburned methane can be used as reductant. Another reductant such as hydrogen can be created in situ, using a microreformer. The results suggest that the NO_x are reduced by H₂ at low temperature, when methane is not activated and at higher temperature the methane is then the main reductant. However, the catalytic behaviour depends on the metal precursor and the catalyst treatment. The most prominent result is obtained on the palladium catalyst prepared from Pd(NH₃)₄(NO₃)₂ precursor. Comparing the reduction and the calcination step in the course of catalyst preparation, one can conclude that calcination lead to the higher activity in deNO_x, since reduced catalysts are oxidized during the deNO_x process.     

Growth response,yield and yield components of upland cotton (Gossypium hirsutum L) as affected by rates and time of nitrogen application in the Nigerian savannah

Effects of rate and time of nitrogen fertilization on growth, yield and yield components of upland cotton (Gossypium hirsutum L) were studied in two years (1975–76). Four rates of nitrogen application (0, 26, 52 and 78 kg ha^–1) timed at 3 or 8 weeks after sowing were compared. Seed cotton yield components increased significantly with increased N application at least up to 52 kg N ha^–1, with yield increases between 49% and 73%. Seed cotton yield was influenced by treatments mainly through boll number. Both crop growth rate and fruiting were enhanced by nitrogen fertilization. Applying N at 8 weeks (flowering) favoured yield only slightly over that at 3 weeks (thinning), but improved crop growth and fruiting by about 64% and 24%, respectively. There were significant N rate × time interactions in favour of fertilization at flowering. Applying 52 kg N ha^–1 at 8 weeks seems best for cotton in the Nigerian savannah.     

Inter- and intrapopulation variation of the pheromone,ipsdienol produced by male pine engravers,Ips pini (Say) (Coleoptera: Scolytidae)

We determined the chirality of ipsdienol in individual male pine engravers,Ips pini (Say), from New York, California, and two localities in British Columbia (BC). Both quantity and chirality of ipsdienol varied significantly between and within populations ofI. pini. Beetles from California and southeastern BC produced primarily (R)-(–)-ipsdienol with mean ratios of (S)-(+) : (R)-(–) of 9 : 91 and 11 : 89, respectively, while beetles from New York produced primarily (S)-(+)-ipsdienol with a mean (S)-(+) : (R)-(–) ratio of 57 : 43. A population from southwestern BC was unlike any other known western population, producing primarily (S)-(+)-ipsdienol with a mean (S)-(+) : (R)-(–) ratio of 66 : 34. In contrast to the unimodal chirality profiles for ipsdienol production in populations from California and southeastern BC, the profiles of the populations from southwestern BC and New York were bimodal, with a common mode at approximately 44 : 56 (S)-(+) : (R)-(–). Bimodality in the profiles of ipsdienol chirality in two populations ofI. pini and remarkably high levels of intrapopulation variation in pheromone chirality in all four populations suggest that evolutionary change in pheromone channels of communication could occur, possibly in response to artificial selection pressures such as mass trapping.