Role of olfaction and vision in homing behaviour of black rockfish Sebastes inermis

How fish find their original habitat and natal home remains an unsolved riddle of animal behaviour. Despite extensive efforts to study the homing behaviour of diadromous fish, relatively little attention has been paid to that of non-diadromous marine fish. Among these, most rockfish of the genus Sebastes exhibit homing ability and/or a strong fidelity to their habitats. However, how these rockfish detect the homeward direction has not been clarified. The goal of the present research was to investigate the sensory mechanisms involved in the homing behaviour of the black rockfish Sebastes inermis, using acoustic telemetry. Vision-blocked or olfactory-ablated rockfish were released in natural waters and their homing behaviours compared with those of intact or control individuals. Blind rockfish showed homing from both inside and outside their habitat. The time taken by blind fish to reach their home habitat was not significantly different from that of the control fish. In contrast, most olfactory-ablated fish did not successfully reach their original habitat. Our results indicate that black rockfish predominantly use the olfactory sense in their homing behaviour.     

大壁虎与嗅觉相关的学习记忆

壁虎科动物鼻腔较大,化学感觉系统发达,类似于对化学信息敏感的舌端游离的蜥蜴目动物（Malan,1946),并且嗅黏膜面积很大,感觉器神经元多,嗅神经系统十分完善（Gabe and Saint,1976).     

The effect of hormone therapy on olfactory sensitivity is dependent on apolipoprotein E genotype

Patients with Alzheimer's disease (AD) show a deficit in olfactory threshold sensitivity. The Apolipoprotein E (ApoE) 4 allele is associated with increased risk of AD and earlier symptom onset. Hormone therapy (HT) may exert neuroprotective effects on brain areas affected by AD. The current study investigated the effect of HT on performance on an olfactory threshold test in 4 positive and 4 negative non-hysterectomized, non-demented, elderly females and AD patients. Among the non-demented participants, 4 positive females who had received HT performed 1) significantly better than those without HT, and 2) at levels similar to those of 4 negative females. In contrast, those without HT who were 4 positive performed significantly worse than those who were 4 negative. HT had no effect on performance in AD patients regardless of 4 status. These results suggest that HT may offer protection against loss of olfactory function in 4 positive individuals in preclinical stages of AD. Future research is warranted in order to investigate further the neuroprotective role of HT on sensory and cognitive functions in non-demented aging individuals.     

The influence of ethanol on feeding in the frugivorous yellow-vented bulbul (Pycnonotus xanthopygos)

The sugars in fleshy fruits provide a rich source of energy to frugivorous animals. However, these carbohydrates also serve as a substrate for alcoholic fermentation by yeasts, ethanol being the main by-product of this process. Ethanol ingestion via frugivory thus occurs in a diverse assemblage of invertebrate and vertebrate taxa, including numerous species of birds. We tested the roles of ethanol as an odor cue for resource location by adult yellow-vented bulbuls (Pycnonotus xanthopygos) and as a possible appetite stimulant in feeding trials with artificial food. We hypothesized (1) that the odor of ethanol does not serve as a food-locating cue in diurnal frugivorous passerine birds, and predicted that the choice of food source and the mass of food eaten by such birds will not be influenced by the odor of ethanol. We further hypothesized (2) that food intake in passerine birds is affected by ingestion of ethanol according to its concentration [EtOH], and predicted that food intake will follow a bell-shaped curve in relation to [EtOH]. In accord with hypothesis (1) and its prediction, we found that the odor of ethanol did not affect food preferences, in either ethanol-naïve or ethanol-experienced yellow-vented bulbuls, when presented at concentrations found in naturally ripe fruit (0.0–1.0%); this suggests that the odor of ethanol is not a food-locating cue for the bulbuls. Hypothesis (2) was partially supported, namely at low [EtOH] (0–3%), food intake was constant and at high [EtOH] (3%) food intake decreased, following only the right half of the predicted bell-shaped response. Ethanol-naïve birds showed no preference towards any [EtOH] presented in two-way choice trials. However, daily food intake in ethanol-experienced bulbuls in single option trials decreased by an average of 36% when the artificial food contained the highest tested concentration of ethanol (3.0%). We suggest that decreasing food intake when food ethanol concentration is relatively high may be a means of avoiding intoxication and is related to the ethanol-metabolizing ability of the bird.     

Predation risk assessment by olfactory and visual cues in a coral reef fish

Assessment of predation risk is vital for the success of an individual. Primary cues for the assessment include visual and olfactory stimuli, but the relative importance of these sources of information for risk assessment has seldom been assessed for marine fishes. This study examined the importance of visual and chemical cues in assessing risk for the star goby, Asterropteryx semipunctatus. Visual and chemical cue intensities were used that were indicative of a high threat situation. The behavioural response elicited by both the visual cues of a predator (the rock cod, Cephalopholis boenak) and the chemical alarm cues from conspecifics were similar in magnitude, with responses including a decrease in feeding strikes and moves. A bobbing behaviour was exhibited when the predator was visible and not when only exposed to the chemical alarm cue. When visual and chemical cues were presented together they yielded a stronger antipredator response than when gobies were exposed solely to conspecific alarm cues. This suggests additivity of risk assessment information at the levels of threat used, however, the goby’s response is also likely to depend on the environmental and social context of the predator–prey encounter. This study highlights the importance of chemical cues in the assessment of predation risk for a coral reef fish.     

犬蝠对不同浓度香蕉汁的选择

为了解犬蝠的嗅觉灵敏度,我们以6 只成年犬蝠对不同浓度的成熟香蕉汁和纯水对照的选择倾向和取食时间各进行了连续5 个夜晚的室内观察。香蕉汁的浓度分别为100% (120 g),50% (60 g 香蕉汁和60 g 纯水),25% (30 g 香蕉汁和90 g 纯水),12. 5% (15 g 香蕉汁和105 g 纯水);另取纯水(W)与熟烂的香蕉汁(OR)各120 g 作为对照。将以上食物和对照随机注入不同的容器内,观察犬蝠对不同浓度的香蕉汁、熟烂香蕉汁和纯水的选择。结果表明,犬蝠对纯成熟香蕉汁的选择性最强,取食次数和取食量均最高,而停留时间也最长;说明犬蝠具有分辨不同浓度的气味差异。我们推测犬蝠在野外觅食时可能优先取食成熟水果。     

Influence of blood meal on the responsiveness of olfactory receptor neurons in antennal sensilla trichodea of the yellow fever mosquito, Aedes aegypti

In female Aedes aegypti L. mosquitoes, a blood meal induces physiological and behavioral changes. Previous studies have shown that olfactory receptor neurons (ORNs) housed in grooved peg sensilla on the antennae of Ae. aegypti down-regulate their sensitivity to lactic acid, a key component driving host-seeking behavior, which correlates with observed changes in the host-seeking behavior of this species. In the present study, we performed electrophysiological recordings from the most abundant antennal sensillum type, sensilla trichodea. Our results indicate that the response spectra of ORNs contained within most trichoid sensilla do not change in response to blood feeding. However, we observe an increase in sensitivity to primarily indole and phenolic compounds in neurons housed within four of the five functional types of short blunt tipped II trichoid sensilla, both at 24 and 72 h post-blood feeding, which was more pronounced at 24 h than 72 h. Furthermore, sensitivity to undecanone, acetic acid and propionic acid was observed to increase 72 h post-blood meal. Considering the timing of these changes, we believe that these neurons may be involved in driving the orientation behavior of female mosquitoes to oviposition sites, which are known to release these compounds.