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241.
Dental microwear in relation to changes in the direction of mastication during the evolution of Myodonta (Rodentia,Mammalia) 总被引:2,自引:1,他引:1
Observations of dental microwear are used to analyse the correlation between changes in molar tooth crown morphology and the
direction of masticatory movement during the evolution of Myodonta (Rodentia, Mammalia). The studied sample includes 36 specimens
representing both superfamilies of Myodonta (Muroidea and Dipodoidea) spanning 16 dipodoid and 9 muroid species. Microscopic
scratches on occlusal surfaces resulting from contact between opposite teeth during mastication are analysed. Using these
features, we determine the direction of masticatory movements. Microwear patterns display diverse orientations among Dipodoidea:
oblique in Sicistinae, Euchoreutinae and Zapodinae, propalinal in Dipodinae and intermediary in Allactaginae. Similarly, Muroidea
exhibit the following orientations: oblique in Cricetinae and propalinal in Arvicolinae, Cricetomyinae, Gerbillinae and Murinae.
These various chewing types illustrate different evolutionary grades within the superfamilies. Acquisition of the antero-posterior
masticatory movement in Dipodoidea is related to flattening of the molar occlusal surface. However, in some muroid subfamilies,
this direction of mastication is associated with low-crowned and cuspidate molars (Cricetomyinae, Murinae). 相似文献
242.
In holometabolous insects, pupation site selection behaviour has large consequences for survival. Here, we investigated the
combined effects of temperature and parasitism by the parasitoid Asobara tabida on larval pupation behaviour in two of its main Drosophila sp. hosts differing in their climate origin. We found that larvae of Drosophila melanogaster—a species with a (sub)tropical origin—placed at 25°C pupated higher in rearing jars than those placed at 15°C. The opposite
pattern was observed for Drosophila subobscura larvae—a species from temperate regions—which pupated lower, i.e. on or near the substrate at 25°C, than those placed at
15°C. When placed at 25°C, parasitized larvae of both species pupated closer to the substrate than unparasitized ones. Moreover,
the Drosophila larvae that had been exposed and probably stung by A. tabida, but were not parasitized, pupated lower than the control unparasitized larvae. These results provide new insights of host
behaviour manipulation by A. tabida larvae. 相似文献
243.
Firmat C Gomes Rodrigues H Hutterer R Rando JC Alcover JA Michaux J 《Die Naturwissenschaften》2011,98(1):33-37
Malpaisomys insularis is a mouse-like rodent endemic to the eastern Canary Islands. It became extinct during the fourteenth century. It was a remarkable
species living under hyperarid conditions. A dental microwear analysis was performed in order to determine its former diet.
The elevated number of fine scratches found in Malpaisomys molars suggests that it consumed a significant part of Poaceae, grass consumption leaving the most distinctive features on
dental wear facets. A graminivorous diet with a high amount of abrasive items is in agreement with the broad teeth of Malpaisomys, considered as adapted to grass consumption. However, in the absence of potential competitors over its native range, it is
likely that Malpaisomys also foraged on dicots to meet higher nutrient and energetic requirements. The ecology of Malpaisomys is discussed from these results in the context of the desertic climatic conditions of the eastern Canary Islands and with
a special concern on its small body size in contrast to other large-sized island murine species such as the giant rats of
the central Canary Islands. 相似文献
244.
245.
Bourgeois W Romain AC Nicolas J Stuetz RM 《Journal of environmental monitoring : JEM》2003,5(6):852-860
Continuous, in situ monitoring of air, water and land quality is fundamental to most environmental applications. Low cost and non-invasive chemical sensor arrays provide a suitable technique for in situ monitoring. Their ability and performance under realistic conditions is discussed in this paper. Published studies report promising results despite a number of limitations that are associated with both the technology itself and its application in ever changing ambient conditions. Early investigations include the analysis of single substances as well as odour and wastewater organic load monitoring. Reported applications typically highlight the sensitivity of the currently available sensors to changes in temperature, humidity and flow rate. Two types of approaches are recommended to deal with these effects: either working under fixed experimental conditions or measuring the external parameters to numerically compensate for their change. The main challenge associated with the use of non-specific sensor arrays lies in establishing a relationship between the measured multivariate signals and the standards metrics that are traditionally used for quality assessment of gas mixtures. For instance, odour monitoring requires calibration against olfactometric measurements while investigations of wastewater samples still need to be correlated with organic pollution parameters such as BOD, COD or TOC. On the other hand, results obtained in the field have demonstrated how sensor arrays can be readily used as simple alarm devices or as early warning systems based on a general air/water quality index. 相似文献
246.
Environmental Modeling & Assessment - This paper investigates whether economic development is impeded by binding national emission standards to control climate change. We develop a simple model... 相似文献