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121.
Heike Kappes Kurt Jordaens Frederik Hendrickx Jean-Pierre Maelfait Luc Lens Thierry Backeljau 《Landscape Ecology》2009,24(5):685-697
Habitat fragmentation is a major cause for species loss, but its effect on invertebrates with low active dispersal power,
like terrestrial gastropods, has rarely been studied. Such species can not cross a hostile habitat matrix, for which the predictions
of island theory, such as positive relations between species richness and patch size, should apply. In order to test this
prediction, we studied gastropod species diversity by assessing gastropod assemblage characteristics from 35 sites in 19 fragments
of deciduous old-growth forests in the Lower Rhine Embayment, Germany. Assemblages differed between larger (≥700 ha) and smaller
forests (<400 ha), those of large forests held a higher percentage of forest species. Although α-diversity was similar between
the two forest size classes, small forests often comprised matrix species, resulting in a higher β-diversity. Edge effects
on the species richness of matrix species were noticeable up to 250 m into the forest. Hierarchical partitioning revealed
that distance to disturbances (external edge, internal edges like roads) explained most assemblage variables, whereas forest
size and woodland cover within a 1 km radius from the sites explained only a few assemblage variables. Densities of two forest-associated
species, Discus rotundatus and Arion fuscus, decreased with forest size. Yet, forest size was positively correlated with richness of typical forest species and densities
of Limax cinereoniger. The latter species seems to need forests of >1,000 ha, i.e., well above the size of most fragments. In conclusion, the prediction
is valid only for forest species. The response to fragmentation is species specific and seems to depend on habitat specialization
and macroclimatic conditions.
Jean-Pierre Maelfait: Deceased. 相似文献
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Liesbet Ledeganck Kaatje Kromhout Koen Chiers Elke Van der Vekens Luc Van Ham Sofie F.M. Bhatti Ine Cornelis 《Veterinary radiology & ultrasound》2023,64(2):E10-E13
A 9-month-old male entire Doberman Pinscher presented with acute onset of severe cervical hyperesthesia after a fall. Neurological examination revealed a normal gait with low head carriage and severe cervical hyperesthesia. A CT scan of the cervical vertebral column revealed the presence of a comminuted fracture at the dorsomedial aspect of the right occipital condyle and sclerosis of the underlying bone. Medical management was initiated consisting of an external bandage, strict rest, and pain medication. Due to the lack of clinical improvement, the dog was euthanized 2 months after diagnosis. Histopathology of the lesion was compatible with a healing fracture. 相似文献
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Esterase-mediated bifenthrin resistance in a multiresistant strain of the two-spotted spider mite, Tetranychus urticae 总被引:2,自引:0,他引:2
A field-collected multiresistant strain of Tetranychus urticae Koch exhibiting high resistance to bifenthrin was investigated in comparison with a susceptible laboratory strain. The esterase inhibitor S,S,S-tributyl-phosphorotrithioate (DEF) was able strongly to synergise bifenthrin toxicity in the resistant strain. Optimal conditions for determining esterase activities in T. urticae were determined, and a higher esterase activity towards several artificial substrates was found in this resistant strain, which had a preference for hydrolysing 4-nitrophenyl butyrate. Bifenthrin was able to bind the active centres of T. urticae esterases in vitro, as was determined after competition experiments by a Dixon plot, revealing a higher affinity of bifenthrin in the resistant strain. Bifenthrin-hydrolysing activity in the resistant and susceptible strains was examined in vitro and quantified with gas chromatography. A 7.2-fold higher metabolising rate was found in the resistant strain. 相似文献
130.
Comparison of the ability of the three endogenous GnRHs to stimulate release of follicle-stimulating hormone and luteinizing hormone in chickens 总被引:2,自引:0,他引:2
Proudman JA Scanes CG Johannsen SA Berghman LR Camp MJ 《Domestic animal endocrinology》2006,31(2):141-153
It is well established that GnRH can stimulate the release of LH and FSH in mammals. Two GnRHs have been found in the chicken hypothalamus, cGnRH-I and -II. There is controversy as to whether either peptide can stimulate release of FSH in birds. The present studies compared the ability of cGnRH-I and -II to stimulate the release of FSH and LH in chickens. Lamprey (l) GnRH-III may be a specific-releasing factor for FSH, as it selectively stimulates FSH release in rodents and cattle, and has been detected in the hypothalamus of rodents, sparrows and chickens. Therefore, the ability of lGnRH-III to stimulate LH and FSH release was also examined. In our first experiment, the effects of cGnRH-I and -II were studied using 17-week prepubertal females. Intravenous injection of cGnRH-II at 1 and 10 microg/kg BW significantly increased LH secretion more than did cGnRH-I. Neither peptide significantly increased plasma FSH levels. In our second study, we administered cGnRH-I, -II or lGnRH-III to mature males maintained on a short photoperiod. cGnRH-II was again more potent than cGnRH-I in stimulating LH release, while lGnRH-III produced a modest LH rise. No GnRH peptide provided specific or potent stimulus to FSH secretion, although the high dose of cGnRH-II modestly enhanced FSH levels in the adult male (P < 0.05). Our results are not consistent with the view that lGnRH-III is a specific FSH-releasing hormone across multiple classes of vertebrates. We conclude that the mechanism by which independent release of FSH occurs in chickens remains unresolved. 相似文献