Preliminary observations on predator/prey relationships between chaetognaths and copepods in the Java sea

There is evidence that copepods undertake vertical migrations in shallow waters off the north coast of Java. They aggregate at the surface of the sea at dawn and dusk but sink to deeper levels in the middle of the day. Chaetognaths feed on copepods and tend to occur in areas which are rich in their prey. They do not however follow them on vertical migrations during daylight.     

Olfactory receptors and odour coding

The first step of olfactory detection involves interactions between odorant molecules and neuronal protein receptors. Odour coding results from the combinatory activation of a set of receptors and rests on their clonal expression and olfactory neurone connexion, which lead to formation of a specific sensory map in the cortex. This system, sufficient to discriminate myriads of odorants with a mere 350 different receptors, allows humans to smell molecules that are not natural (new cooking flavours, synthetic chemicals...). The extreme olfactory genome diversity explains the absence of odour semantics. Olfactory receptors are also involved in cellular chemotaxis.     

Olfactory experience modifies the effect of odour on feeding behaviour in a goal-related manner

Natural food odours elicit different behavioural responses in snails. The tentacle carries an olfactory organ, and it either protracts toward a stimulating carrot odour or retraces in a startle-like fashion away from a cucumber odour. The tentacle retraction to cucumber was still present after the snails were fed cucumber during inter-trial periods. Also, snails without any food experience displayed a longer latency to the first bite of cucumber than of carrot and rejected cucumber more often. After tasting these foods, the latency to carrot was not affected while the latency to and number of rejections of cucumber decreased. These results suggest that initial repulsive features of food odour can be only partially compensated by olfactory learning and feeding experience. In the present study, we demonstrated that an invertebrate can be repulsed or attracted by the same natural odour at the same time and that these behavioural responses are likely aimed at achieving different physiologically relevant goals.     

Abdominal odours of young,low-ranking European rabbit mothers are less attractive to pups: an experiment with animals living under natural breeding conditions

Lactating rabbit females (Oryctolagus cuniculus) emit abdominal, ventral odour cues that are involved in guiding the pups to the nipples. We tested the impact of the females’ social rank and age on the emission of this odour signal; both factors are highly collinear in wild rabbits and we did not aim to disentangle them in our study. We predicted that the abdominal odours of young, low-ranking females, which are usually more stressed and have a comparatively lower body condition, should be less attractive to pups than those of older, high-ranking females. For the experiment, we caught females from a population of wild-type European rabbits living in a large field enclosure. Pairs of adult females were placed in boxes with wire-mesh floor fixed over an arena with three rabbit pups aged 4–7 days old. First, we evaluated the effectiveness of our two-choice design by testing lactating females (LF) against non-lactating (NLF) controls (n = 17 pairs). In accordance with recent studies, the pups showed a clear preference for lactating females by means of a higher exploration time and more local searching under the ventral region of these females. In a second experiment, the pups chose between lactating 1-year-old, low-ranking females (Y/LRF) and older, high-ranking females (O/HRF) (n = 10 pairs). These latter assays suggested a comparatively lower attractiveness of Y/LRF females to pups searching for milk. Although the pups showed no significant preference in exploration behaviour, they preferably directed local searching events to the abdominal region of O/HRF females. In conclusion, our study suggests that mother–offspring chemosensory communication is modified by the mother’s age and social rank, i.e., by a complex of factors that are strongly linked in rabbit females in the wild.     

Wood ash for application in municipal biowaste composting

This study aimed to clarify the impacts of pH control by wood ash amendment on biowaste composting processes. To achieve this, fresh source separated municipal biowaste was mixed with low doses (2-8% wt/vol) of wood ash and processed in a pilot and large-scale composting systems. The results indicated a correlation between a low initial pH and delay in the early rise of the process temperature. Wood ash elevated the composting temperatures and pH, and stimulated the mineralisation both in the pilot scale and the industrial large-scale processes. According to the results addition of amounts of 4-8% wood ash is sufficient for efficient biowaste composting process and yields a safe end product. However, to minimise the environmental risk for heavy metal contamination, and meet the criteria for the limit values of the impurities in wood ash, strict quality control of the applied wood ashes should be implemented.     

New units for indoor air quality: decicarbdiox and decitvoc

Abstract Two new units are proposed for the evaluation of indoor air quality using the decibel concept, which give a much better approximation of the human perception of odour intensity, compared to the CO₂ and total volatile organic compounds (TVOC) concentration scales: the decicarbdiox and the devitvoc. On the psychophysical scale according to Yaglou, the weakest odour that can be detected by the human smell sensors is equal to one, and corresponds to the lower limit of percentage dissatisfaction (PD) of 5.8%. It is equivalent to: (1) a CO₂ threshold concentration of 485 ppm – 0 dB (odour CO₂) – 0 dCd (decicarbdiox), and (2) a TVOC threshold concentration of 50 μg m⁻³– 0 dB (odour TVOC) – 0 dTv (decitvoc). The upper limit is determined by the initial value of toxicity: (1) CO₂– 15,000 ppm – 134 dCd, and (2) TVOC – 25,000 g/m⁻³– 135 dTv. Optimal pollutant values (corresponding to PD=20%) and admissible values (PD=30%) for unadapted and adapted persons are calculated. Long-term tolerable values (determining the sick building syndrome range) and short-term tolerable values (the beginning of the toxic range) are also stated. The same system used to evaluate noise can be used to evaluate air quality. Additionally, the contribution of the individual constituents (at present acoustic and odour) to the overall quality of the environment can be ascertained. The new units dCd and dTv can express an increase or decrease in air contamination, e.g. by the use of air cleaners, new building materials etc. The proposed system of using dCd and dTv is compatible with BSR/ASHRAE 62–1989 R which can be used to determine the required volume of fresh air for ventilation by an improved method, which takes into account different levels of required indoor air quality. Received: 21 January 1998 / Revised: 20 May 1998 / Accepted: 30 September 1998     

Experimental manipulation of predation risk and food quality: effect on grazing behaviour in a central-place foraging herbivore

The relative importance of predation risk and food quality on spatial grazing pressure and activity patterns was tested in a central-place foraging herbivore: the European rabbit. Rabbits grazed less with increasing distance from their burrows into adjacent grassland, thereby creating a gradient of increasing vegetation height and plant biomass and decreasing plant nutrient concentration. When nitrogen concentration was experimentally increased by 150% through fertilizing and mowing, rabbits visited these plots four times more frequently than the untreated control plots. Addition of predator scent (mink pellets) did not result in different patch use by rabbits. The combined addition of fertilizer and mink pellets had the same effect as addition of fertilizer alone. However, the mink pellets changed the temporal activity pattern of rabbits as measured with infrared detectors. Rabbits were predominantly nocturnal but shifted their activities to the day when mink pellets were added, resulting in equal activities during night and day. We conclude that rabbits are sensitive to perceived predation risk, but that this does not influence their spatial grazing pressure. A selection for the highest food quality on the other hand can explain the observed natural rabbit grazing gradient. Food quality was highest close to the burrows, therefore rabbits selecting for high quality food should forage most intensely close to the burrows and only move further away for higher quality items or when the vegetation close to their burrows is depleted. Through intensive grazing close to the burrows rabbits facilitated for themselves either through stimulating fresh protein rich re-growth or the return of nutrients through faeces or both. This is in contrast with central-place foraging theory where intense feeding close to the burrow is assumed to lead to reduced food resources.     

Temporal and sexual variation of leaf-produced pollinator-attracting odours in the dwarf palm

Information on intra-specific variation in pollinator-attracting floral traits provides clues to selective pressures imposed by pollinators. However, these traits also reflect constraints related to floral phenology or morphology. The specific weevil pollinator Derelomus chamaeropsis of the dioecious Mediterranean dwarf palm Chamaerops humilis is attracted by volatile compounds that leaves, and not flowers, release during anthesis. Production of these olfactory cues is thus probably not constrained by any other floral function. This provides the opportunity to study variation of a floral trait that is not produced by a floral organ. We studied volatile compounds emitted by leaves of 12 individual C. humilis over the whole flowering season. The quantity of volatile compounds emitted by leaves reached a maximum when plants required pollinator visits. The relationship between odour emission and floral phenology was slightly different between male and female plants, probably reflecting differences in the exact time at which females and males benefit from pollinator visitation. Male plants produced higher quantities of volatile compounds than females. Odour composition was highly variable among individuals but did not differ between male and female plants. In this system, female C. humilis are pollinated by deceit and pollinators should be selected to avoid visiting them. The absence of sexual difference in blend composition may thus prevent pollinators from discriminating between male and female plants.An erratum to this article can be found at