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141.
The macroinvertebrate fauna of littoral and bottom substrata as a tool for biotypology of Frisian waters 总被引:1,自引:0,他引:1
T. H. L. Claassen 《Aquatic Ecology》1987,21(2):181-191
During a biotypological research of surface waters in the province of Friesland, The Netherlands, the macroinvertebrate fauna was sampled, both from the littoral and bottom substrata. Results of this investigation in different types of water on 60 and 55 stations in 1981 and 1982, respectively, are presented. The species richness in the littoral samples exceeded that of the bottom samples, and the samples per station had relatively few species in common. Even in many cases the most abundant taxon was a different one in both samples of the same spot. With multivariate analysis of the data sets from bottom, littoral and total samples a fairly good resemblance was found between these data sets. It is concluded that the semi-quantitative processing of macroinvertebrate fauna data leads to reliable results. One can use one sample per station, wherein different substrata are combined. Distinct clusters were recognized in more extreme environmental conditions such as brackish and acid waters. With the help of the macroinvertebrate fauna the other types of water could not easily be differentiated. 相似文献
142.
The effects of long term browsing on growth and morphology of P. atlantica trees and P. palaestina shrubs, and on the colonization of these hosts by their respective gall-inducing aphid guilds, were studied in natural vegetation
pastures in Israel. To simulate apical dominance release by browsing, trees and shrubs were pruned and observed one year later.
P. atlantica responded strongly to browsing, producing a crown of dense and sharp dry branches and thorn-like shoots, and pruning, compensating
or overcompensating for the lost biomass in the studied morphological variables. Morphological responses of P. palaestina were less evident: we found no compensation in most variables. Three species of aphids produced more galls on browsed than
on control shoots of P. atlantica. Two species induced more galls on pruned shoots. The five aphid species on P. palaestina colonized browsed and unbrowsed shoots equally, and produced fewer galls on pruned shoots. The role of apical dominance in
architectural responses of trees and shrubs to browsing and pruning, as related to resource availability and timing, is discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
143.
Tobias L. Kordsmeyer John Hunt David A. Puts Julia Ostner Lars Penke 《Evolution and human behavior》2018,39(4):424-436
Recent evidence suggests that in sexual selection on human males, intrasexual competition plays a larger role than female choice. In a sample of men (N?=?164), we sought to provide further evidence on the effects of men's physical dominance and sexual attractiveness on mating success and hence in sexual selection. Objective measures and subjective ratings of male sexually dimorphic traits purportedly under sexual selection (height, vocal and facial masculinity, upper body size from 3D scans, physical strength, and baseline testosterone) and observer perceptions of physical dominance and sexual attractiveness based on self-presentation video recordings were assessed and associated with mating success (sociosexual behaviour and number of potential conceptions) in a partly longitudinal design. Results from structural equation models and selection analyses revealed that physical dominance, but not sexual attractiveness, predicted mating success. Physical dominance mediated associations of upper body size, physical strength, as well as vocal and facial physical dominance and attractiveness with mating success. These findings thus suggest a greater importance of intrasexual competition than female choice in human male sexual selection. 相似文献
144.
145.
P. Slurink 《Human Evolution》1993,8(4):265-273
In contrast to many other models of human evolution the “balance of power” theory of Alexander has a clear answer to the question
why a runaway selection process for unique social and moral capacities occurred in our ancestry only and not in other species:
“ecological dominance” is hypothesized to have diminished the effects of “extrinsic” forces of natural selection such that
withinspecies, intergroup competition increased (Alexander, 1989). Alexander seems to be wrong, however, in his claim that
already the common HUCHIBO (Humans, Chimps, Bonobo's)-ancestor has crossed the ecological dominance barrier. In this paper
an adapted version of Alexander's model is presented and several different ways are proposed to make this adapted version
testable. A preliminary survey of the available paleontological and paleoecological data suggests that there is some evidence
of a less vulnerable position towards predators in earlyHomo and that there are clear signs related to a crossing of the ecological dominance barrier inHomo sapiens sapiens. 相似文献
146.
Mating behavior of the Hog-badger (Arctonyx collaris) was recorded on 463 videos (totally 8053 s) taken with auto-trigger cameras between March 13 and May 13, 2017 in Jiangxi Wuyishan. Males followed and guarded the females for several hours before mating. One mounting behavior, and three mating behaviors were observed from 01:55 to 08:49 on April 18. The durations of mating behaviors lasted for 731s, 1690s and 1494s, respectively. Based on these observations, we found: 1) mating behavior was controlled by the female, including obvious sexual solicitations; 2) females can mate more than one time within one estrous cycle; 3) quickly and repeatedly pumping and inserting behavior was observed in male during mating. 相似文献
147.
《Tissue & cell》2016,48(6):588-595
In the present study, we examined the morphology of cilia and expression of the dynein intermediate chain 2 (DNAI2) in the oviduct of non-obese diabetic (NOD) mice. Results obtained with immunohistochemistry showed that DNAI2 expression was reduced in oviducts of diabetic NOD (dNOD) mice, as compared to that observed in the normoglycemic NOD (cNOD) group, especially in the acyclic dNOD mice. Oviductal cilia of dNOD mice appeared to be reduced in number. Results obtained with Western blot analysis revealed that the expression of DNAI2 protein was significantly less in oviducts of dNOD mice as compared to that of cNOD mice corroborating the results obtained with immunohistochemistry. Electron microscopic examination and quantitative imaging of thin sections of Epon-embedded oviducts of both dNOD and cNOD mice confirmed the reduction of the number of cilia in the oviduct of the dNOD group which also displayed aberrant axonemal ultrastructure, including disorganization of the axoneme and alteration of microtubule doublets into singlets as well as disruption of the plasma membrane in many cilia. Taken together, the present findings suggest that structural alterations of oviductal cilia in female diabetic NOD mice might be detrimental to the normal function of these particular cell structures in gamete transport. 相似文献
148.
149.
To determine a possible mechanism causing male and female sterility in Cryptomeria japonica male and female cones were collected from a C. japonica, tree, ShinDai2, that lacks pollen release and fertile seeds and specimens were processed to examine the development of pollen
and female gametophytes using light microscopy and field emission scanning electron microscopy. Pre-meiotic development proceeded
normally, but the formation of aberrant meiotic products was observed in cones of both sexes. In sterile microsporangia, heterogeneous
microspore populations ranging from monads to polyads gave rise to mature pollen grains of non-uniform size. These pollen
grains were covered with an amorphous layer and adhered to each other. In addition, they remained in the microsporangia and
were not released even after the onset of pollen dissemination from fertile trees. In the ovules of sterile female cones,
megaspores with abnormal shapes, numbers, and sizes formed, and the development of female gametophytes was arrested at the
free nuclear or archegonium formation stages. These gametophytes collapsed, and no fertile embryo was generated. Results indicate
that meiotic defects are important in the sterility mechanism. 相似文献
150.
Antier D Carswell HV Brosnan MJ Hamilton CA Macrae IM Groves S Jardine E Reid JL Dominiczak AE 《Free radical research》2004,38(2):177-183
Hypertension, aging and a range of neurodegenerative diseases are associated with increased oxidative damage. The present study examined whether superoxide (O2•-) levels in brain are increased during aging in female rats, and the role of superoxide dismutase (SOD) and oestrogen in regulating O2•- levels.
Young adult (3 month) and old (11 month) female spontaneously hypertensive stroke prone rats (SHRSP) and normotensive Wistar-Kyoto rats (WKY) were studied. O2•- levels were measured in brain homogenates by lucigenin chemiluminescence and SOD expression by Western blotting. Ageing significantly increased brain O2•- levels in WKY (cortex +216%, hippocampus +320%, striatum +225%) and to a greater extent in SHRSP (cortex +540%, hippocampus +580%, striatum +533%). Older SHRSP showed a decline in cortical Cu/Zn SOD expression compared to young adult SHRSP. Oestrogen did not attenuate O2•- levels.
The results show a significant age-dependent increase in brain O2•- levels which is exaggerated in SHRSP. The excess cortical O2•- levels in the SHRSP may be associated with a down-regulation of Cu/Zn SOD but are not related to a decrease in oestrogen. 相似文献
Young adult (3 month) and old (11 month) female spontaneously hypertensive stroke prone rats (SHRSP) and normotensive Wistar-Kyoto rats (WKY) were studied. O2•- levels were measured in brain homogenates by lucigenin chemiluminescence and SOD expression by Western blotting. Ageing significantly increased brain O2•- levels in WKY (cortex +216%, hippocampus +320%, striatum +225%) and to a greater extent in SHRSP (cortex +540%, hippocampus +580%, striatum +533%). Older SHRSP showed a decline in cortical Cu/Zn SOD expression compared to young adult SHRSP. Oestrogen did not attenuate O2•- levels.
The results show a significant age-dependent increase in brain O2•- levels which is exaggerated in SHRSP. The excess cortical O2•- levels in the SHRSP may be associated with a down-regulation of Cu/Zn SOD but are not related to a decrease in oestrogen. 相似文献