Feeding responses to solanaceous allelochemicals by larvae of the tobacco hornworm, Manduca sexta

Feeding responses of the oligophagous tobacco hornworm to allelochemicals prevalent in their host plants were determined in food choice-tests using filter paper discs laced with a test solution or water (control). Six solanaceous alkaloids, tomatine, tomatidine, solanine, solanocapsine, atropine and nicotine, were tested and only tomatine and solanocapsine were found to influence preference behavior. Solanocapsine (5 mM) deters feeding whereas tomatine (1 mM) stimulates feeding slightly. No synergistic effect of either tomatine or tomatidine with sucrose was found.The responses to tomatine are affected by previous feeding experience. Tomatine slightly stimulates feeding in larvae reared on tomato (Lycopersicon esculentum), but slightly deters feeding in larvae reared on Jerusalem cherry (Solanum pseudocapsicum). Such induced preference is absent for the other alkaloids tested, which indicates that these alkaloids do not by themselves induce preferences for the plants containing them.The non-alkaloid allelochemicals, chlorogenic acid, rutin, and 2-tridecanone also influenced food choice behavior. Chlorogenic acid is slightly stimulatory at its natural concentration (1mM), but strongly deterrent at higher concentrations. Rutin stimulates feeding in a concentration-dependent manner. Its activity must be due to the glycosylated structure, because both the aglycone (quercetin) and the sugar moiety (rutinose) are neutral. Removal of the glucose part of rutin, as in quercitrin, results in feeding deterrent activity. 2-Tridecanone is neutral at its concentration in cultivated tomato (1 mM), but strongly deterrent and toxic at higher concentrations. Preference behavior is not affected by solanesol, GABA, and a mixture of host plant compounds stimulatory for anothe solanaceous-specific feeder, the Colorado potato beetle (Leptinotarsa decemlineata).We conclude that the prevalent solanaceous alkaloids and other allelochemicals tested do not play important roles in food selection of the tobacco hornworm, although some may make small contributions.

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Résumé Des experiences de choix de chenilles oligophages de M. sexta ont été réalisees avec des disques de papier filtre imbiles d'eau ou de solutions des substances allélochimiques dominantes dans les plantes consommées. Sur les six alcaloïdes de solanées examinés: tomatine, tomatidine, solanine, solanocapsine, atropine et nicotine, seuls la tomatine et la solanocapsine ont influé sur le choix; la solanocapsine (5 mM) empêche la prise de nourriture, tandis que la tomatine (1 mM) la stimule légèrement. Aucun effet synergique de la tomatine ou de la tomatidine n'a été observé en présence de sucrose.La réponse à la tomatine est modifiée par la prise de nourriture antérieure. Elle stimule légèrement l'alimentation de chenilles élevées sur tomates (Lycopersicon esculentum), mais dissuade légèrement les chenilles élevées sur Solanum pseudocapsicum. II n'y a pas d'action induite semblable avec les autres alcalïdes examinés, ce qui indique que ces alcaloïdes ne peuvent pas induire par eux-mêmes de préférences pour les plantes qui les contiennent.Des substances allélochimiques non-alcaloïdes: acide chlorogénique, rutine, et 2-tridécanone, influent aussi sur le comportement de choix alimentaire. L'acide chlorogénique est légèrement stimulant à sa concentration naturelle (1 mM), mais fortement dissuasif aux concentrations supérieures. La rutine stimule la prise de nourriture en fonction de sa concentration. Son activité doit être due à sa structure glucosylate, puisqu'aussi bien l'aglycone (quercitine) que la moiteé sucrée (rutinose) sont neutres. La suppression de la partie glucose de la rutine, comme dans le cas de la quercitine, a un effet dissuasif. A sa concentration dans la tomate cultivée (1 mM), le 2-tridécanone est neutre, mais il est fortement dissuasif et toxique à des concentrations supérieures.Le comportement de choix n'est pas modifié par le solanésol, le GABA, et par un mélange de composés végétaux stimulant un consommateur spécifique de solanées, comme le doryphore (Leptinotarsa decemlineata).Nous pouvons conclure que les principaux alcaloïdes et autres substances allélochimiques des solanées que nous avons examinés n'interviennent pas d'une façon importante, mais peuvent avoir une influence secondaire, dans les choix alimentaires de Manduca sexta.

     

Ant eating behavior of mountain gorillas

Eleven cases of feeding on driver ants (Dorylus sp.) by mountain gorillas (Gorilla gorilla beringei) are described. Ant eating provides the gorillas with more animal protein and other nutrients per unit feeding time than do other forms of insectivory that contribute to their diet, but it is so rare that it is unlikely to be of real nutritional significance. Gorillas obtain ants with their hands and do not use tools. Immature individuals (except infants) ate more ants than did adult females, and silverbacks were not seen to eat ants. These differences are more likely to reflect differences in individual taste and interest in novelty than differences in nutritional strategy. Not all gorillas in the Virungas population eat ants. Intra-population variability may be ecologically contingent, but ant eating appears to be a socially acquired and transmitted taste.     

Host plant recognition in monophagous weevils: specificity in feeding responses of Ceutorhynchus constrictus and the variable effect of sinigrin

Host plant relations of the monophagous weevil Ceutorhynchus constrictus Marsh. (Coleoptera: Curculionidae: Ceutorhynchinae) feeding on garlic mustard, Alliaria petiolata (Bieb.) Cavara & Grande (Cruciferae) were studied in the laboratory. Most other crucifers were rejected in choice tests using garlic mustard as a reference plant, but Brassica nigra, Sinapis alba and Thlaspi arvense were as acceptable as the host plant. Flowering plants of Descurainia sophia were acceptable while young plants of this species were not. The most important feeding stimulants in extracts of garlic mustard were uncharged, water soluble compounds. The most abundant glucosinolate in garlic mustard, sinigrin, was a feeding stimulant, too. However, the feeding stimulatory activity of sinigrin was only expressed in the presence of still unidentified uncharged compounds from garlic mustard leaves. Host plant relations in monophagous crucifer-feeding insects is discussed in relation to the distinctness of glucosinolate patterns found in their host plants.

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Zusammenfassung Ceutorhynchus constrictus Marsh. (Coleoptera: Chrysomelidae: Ceutorhynchinae) ist ein monophager Rüsselkäfer, der an Knoblauchhederich frisst. Das Wirtswahl-Verhalten dieses Käfers ist im Labor untersucht worden. Die meisten Crucifiren waren im Wahlversuche nicht akzeptiert, wenn Knoblauchhederich als Vergleichspflanze vorhanden war. Von Brassica nigra, Sinapis alba, und Thlaspi arvense wurden im Vergleich gleiche Mengen verzehrt wie von der Wirtspflanze. Blühende Descurainia sophia Pflanzen wurden, im Gegensatz zu Jungpflanzen der gleichen Art, angenommen. Die wichtichsten Phagostimulanten in Extrakten von Knoblauchhederich-Blättern waren ungeladene, wasserlösliche Substanzen. Das häufigste Glukosinolat im Knoblauchhederich, Sinigrin, war auch ein Phagostimulant. Doch war die phagostimulierende Wirkung von Sinigrin nur in Kombinationen mit noch nicht identifizierten, ungeladenen Substanzen aus Knoblauchhederich-Blätter nachweisbar. Wirtspfanzen-Beziehungen von monophagen Insekten werden diskutiert im Zusammenhang mit der Eigenart des Glukosinolat-Inhaltes ihrer Wirtspflanzen.

     

Trace elements in human parotid saliva

Although various proteins and some electrolytes have been measured in human saliva, little systematic data about the major and minor elemental components of this body fluid have been obtained. In order to obtain such data, concentrations of C, Na, P, Cl, K, Ca, Sc, Cr, Fe, Co, Zn, Se, Br, Rb, Sb, I, and Cs in human parotid saliva were measured by instrumental nuclear methods. The data obtained confirmed the relative lack of Zn in saliva of patients with hypogeusia (decreased taste acuity) and suggested that concentrations of Na, Cl, Br, and Ca followed the order: normals > hypogeusia > hyposmia (decreased smell acuity). To compare concentrations of elements in saliva with those in blood and urine, absolute concentrations were normalized to that of Na through the use of a concept called an enrichment factor. On this basis, parotid saliva is relatively depleted in Se, Zn, and Fe and enriched for most other elements relative to blood plasma indicating that the fluid is not simply a transudate of blood plasma. Using this same technique, saliva composition was found more similar to urine than blood plasma, being relatively depleted in Se, Cs, and Co, being enriched in I, Br, and Cr and having about the same relative concentrations of P, Cl, Zn, Fe, Ca, K, and Rb. As the total body concentrations of many of the enriched elements in saliva are extremely small, their enrichment in saliva suggests special roles for these elements in the oral cavity. Because of its accessibility, ease of collection, and interaction with some body constituents, saliva represents a useful, albeit neglected, tool in the diagnosis of some physiological and pathological changes in body function and in understanding important aspects of trace metal metabolism.     

Odor, taste, and flavor perception of some flavoring agents

Psychophysical functions for the odor, taste, and flavor offive common flavorings were obtained by the method of magnitudeestimation. The stimuli included three simple compounds (vanillin,piperonal, and benzaldehyde) and two complex ones (natural vanillaextract and artificial almond essence). The odor intensity ofall the flavorings grew much less rapidly with concentrationthan did taste intensity. The growth of flavor for the complexsubstances and piperonal behaved very much like taste. For vanillinand benzaldehyde, the flavor functions resembled taste functionsat high concentrations but showed a tendency to flatten at lowerconcentrations. These findings implied that, at least for someflavorings, the growth of flavor reflects the most salient featureon the particular concentration range studied. At low concentrationsodor seems to be the most important feature and so flavor functionsare generally flat, but at high concentrations taste becomesthe salient feature and so flavor functions steepen.     

Ionic basis of methacholine-induced shrinkage of dissociated eccrine clear cells

Summary Apical membrane currents were recorded from the taste pore of single taste buds maintained in the tongue of the rat, using a novel approach. Under a dissection microscope, the 150-m opening of a saline-filled glass pipette was positioned onto single fungiform papillae, while the mucosal surface outside the pipette was kept dry. Electrical responses of receptor cells to chemical stimuli, delivered from the pipette, were recorded through the pipette while the cells remained undamaged in their natural environment. We observed monophasic transient currents of 10-msec duration and 10–100 pA amplitude, apparently driven by action potentials arising spontaneously in the receptor cells. When perfusing the pipette with a solution of increased Na but unchanged Cl concentration, a stationary inward current (from pipette to taste cell) of 50–900 pA developed and the collective spike rate of the receptor cells increased. At a mucosal Na concentration of 250mm, the maximal collective spike rate of a bud was in the range of 6–10 sec^–1. In a phasic/tonic response, the high initial rate was followed by an adaptive decrease to 0.5–2 sec^–1. Buds of pure phasic response were also observed. Amiloride (30 m) present in the pipette solution reversibly and completely blocked the increase in spike rate induced by mucosal Na. Amiloride also decreased reversibly the stationary current which depended on the presence of mucosal Na (inhibition constant near 1 m). During washout of amiloride, spike amplitudes were first small, then increased, but always remained smaller than the amiloride-blockable stationary current of the bud. This is understandable since the stationary current of a bud arises from a multitude of taste cells, while each current spike is presumably generated by just one taste cell. We suggest that, in a Na-sensitive receptor cell, (i) the apical amiloride-blockable Na inward current serves as a generator current causing cell depolarization and firing of action potentials, and (ii) each current spike recorded from the taste pore arises mainly from a modulation of the apical Na inward current of this cell, because the action potential generated by the taste cell will transiently decrease or abolish the driving force for the apical Na inward current. The transients are indicators of receptor cell action potentials, which appear to be physiological responses of taste cellsin situ.     

Consistency statistics and genetic parameters for taste panel assessed meat quality traits and their relationship with carcass quality traits in a commercial population of Angus-sired beef cattle

Sensory traits, such as juiciness and tenderness, are known to be important to the consumer and thus will influence their consumption of meat, specifically beef. These traits are difficult to measure and often require the use of taste panels to assess the complex parameters involved in the eating experience. Such panels are potentially a large source of measurement error, which may reduce the effectiveness of breeding programmes based on the data they generate. The aim of this study was to assess the quality of such taste panel-derived sensory traits as well as calculating genetic parameters and residual correlations for these traits along with a further set of traditional carcass quality traits. The study examined a sample of 443 Aberdeen Angus-cross animals collected from 14 breeder-finisher farms throughout Scotland. To assess the quality of the taste panel measurements, three consistency statistics were calculated: (i) panel-member consistency, i.e. the extent to which an individual panel member varied in their scoring for a given trait over the period of the experiment; (ii) repeatability, i.e. the consistency with which an individual panel member was able to score a trait on repeated samples from the same animal; and (iii) reproducibility, i.e. the extent to which taste panel members agreed with each other when scoring a trait. These consistency statistics were moderately high, particularly for panel-member consistency and reproducibility, with values ranging from 0.48 to 0.81 and 0.43 to 0.73 respectively. Estimated heritabilities were low for most of the sensory taste-panel-evaluated traits where the maximum value was 0.16 for overall liking. Residual correlations were high between many of the closely related sensory traits, although few significant correlations were found between the carcass quality data and meat quality traits.     

Role of BDNF in the taste system

Neurotrophins are a family of proteins that regulate neural survival, development, function and plasticity in the central and the peripheral nervous system. There are four neurotrophins： NGF, BDNF, NT-3 and NT-4. Among them, BDNF is mostly studied in the taste system due to its high expression. Recent studies have shown BDNF play an important role in the developmental and mature taste system, by regulating survival of taste cells and geniculate ganglion neurons, and maintaining and guiding taste nerve innervations. These studies imply BDNF has great potentialities for therapeutic usage to enhance sensory regeneration following nerve injury, with aging, and in some neurodegenerative diseases.     

棉铃虫幼虫对人类呈味物质的取食反应

利用叶碟法在室内测定了棉铃虫对人类酸、甜、苦、咸4种基本呈味物质和麻、辣味2种植物提取物的取食反应。正交试验结果表明,棉铃虫幼虫对用甜味、苦味和辣味物质(蔗糖、奎宁和辣椒提取物)处理过的烟叶取食选择率较高,对这3种呈味物质表现出有较好的适应性;而幼虫对咸味、酸味和麻味物质(氯化钠、柠檬酸和花椒提取物)处理过的烟叶取食量较少,这3种呈味物质表现出较强的拒食活性。在选择性条件下,幼虫的取食量与花椒提取物剂量显著相关;而在非选择性条件下,幼虫的取食量与氯化钠剂量显著相关。     

Fish tongues–surface fine structures and ecological considerations

The surface structures of the tongues of Dissostichus mawsoni, Trematomus bemacchii, f. borchgrevinki (Nototheniidae), Stemoptyx diaphana (Sternoptychidae), Diretmus sp. (Diretmidae), Cataetyx memorabilis (Ophidiidae), Photoblepharon palpebratus (Anomalopidae), Carapus mourlani (Carapidae) and Salmo gairdneri (Salmonidae) were investigated with the scanning electron microscope. The aim of the study was to test the theory that the degree to which gustatory receptors are developed morphologically in different species of fishes is related to the environment, and in particular to the variey of food present in the latter. It was found that in the two mesopelagic species, S. diaphana and Diretmus sp., taste receptors were poorly developed, but in the benthic deep-water fish C. memorabilii , which lives off South West Africa in a biologically rich environment, well-developed taste receptors occurred in large numbers. The three Antarctic species studied had similar tongue surface structures with rather well developed papillae of a moderate density. Photoblepharon palpebratus , in spite of its small tongue, possessed a large number of taste buds on elevated ridges; Carapus mourlani , however, had only very few obvious receptors and is thought to be a poor taster. Undoubtedly the highest degree of taste receptor development is found in the freshwater trout Salmo gairdneri. The results support the hypothesis that taste receptor development and the variety of food types preseni in a fish's environment are correlated.