排序方式: 共有28条查询结果,搜索用时 46 毫秒
1.
山茶科系统发育诠释:Ⅸ.山茶属的原始特征及其演化趋向 总被引:3,自引:0,他引:3
讨论和比较了关于山茶属演化趋向的两种观点,认为根据现存种类及目前发现的化石资料,花无梗,苞被不分化为苞片和萼片,代表了山茶属的原始特征;而花梗伸长,引起了苞萼分化,苞片在花梗上疏离,宿存,脱落或减少,演化出更加进步的类群;而苞被保持不分化,多数状态下也可能在花和果等方面得到演化,体现了系统发育和个体发育在山茶属内次级分类群中并不一致 相似文献
2.
《Journal of Natural History》2012,46(23-24):1569-1611
Differentiation of external morphology of Oribatella Banks, 1895 was investigated, in light of the ontogeny of O. quadricornuta (Michael, 1880), O. superbula (Berlese,1904) and O. calcarata (CL Koch, 1835) studied here for the first time, and that of the other species from the literature. The pattern of gastronotal setae in larvae is similar, except for lack of seta h 3 in O. nortoni Behan-Pelletier, 2011, while that of nymphs and adults is differentiated. The nymphs of most species have 15 pairs of gastronotal setae, but those of O. metzi Behan-Pelletier, 2011 and most nymphs of O. calcarata have 13 pairs. The nymphs of most species carry the exuvial scalps of previous instars on apical parts of gastronotal setae da, while setae dm and dp, located under these scalps, are subjected to translocation, reduction in size or loss. In O. berlesei (Michael, 1898), O. nortoni, O. quadricornuta and O. sexdentata Berlese, 1916 pair dp takes a more lateral position, compared with the larvae, in O. superbula and O. canadensis Behan-Pelletier and Eamer, 2010 it is reduced in size (in the latter species pair dm is also reduced), while O. metzi loses setae dm and dp. In contrast, the nymphs of O. calcarata do not carry the scalps, and usually lose setae c 1 and dm. The adults of all species lose setae c 1, c 3 and d-series, compared with the tritonymph, and only 10 pairs of notogastral setae remain (c 2, l-, h- and p-series), but O. quadricornuta and O. calcarata rarely retain seta c 3 unilaterally, which indicates the order of setal loss in Oribatella according to Shaldybina (1972). 相似文献
3.
Summary Cytosolic estrogen and androgen receptors and membrane prolactin-binding sites in the male adrenal glands showed a definite pattern during sexual development. The level of sexual steroid receptors paralleled adrenal growth, whereas prolactin binding reached its maximum value in mature rats.Lüthy, I. A., Predoctoral Fellow from the Consejo Nacional de Investigaciones Cientificas y Técnicas and Calandra, R. S., Research Career Awardee from the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.Acknowledgments. We would like to thank Mrs D. Bas and Mrs D. B. Destéfano for the skillful technical assistance and the secretarial work, respectively. This work was partially supported by the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET), and the Comisión Nacional de Energía Atómica. 相似文献
4.
We examined levels of melatonin in the pineal, eyes and plasma over a 24 h period during development in the altricial zebra finch. Beginning as early as 2 days after hatching there was a distinct 24 h rhythm in melatonin in the pineal and plasma. Beginning at day seven after hatching there was also a 24 h rhythm present in the eyes. In the pineal and eyes the amplitude of the 24 h rhythm increased with age. In contrast, the amplitude of the plasma melatonin rhythm at 2 days was already within the range of adults and did not increase with age. These results confirm and expand earlier findings in the European starling and parallel those from precocial birds indicating that the circadian system is already competent at or shortly after hatching even in atricial birds. 相似文献
5.
6.
《Journal of Natural History》2012,46(30):2815-2860
The stalk morphology of the deep‐sea stalked crinoid Guillecrinus changes a lot from juvenile to adult. As a result of its unusual morphology among the extant crinoids, its taxonomic and phylogenetic affinities remain unsettled. Distinctive morphological changes characterize the various growth stages in stalked crinoids. We conduct and discuss a detailed ontogenetic analysis of the stalk of the two species (Guillecrinus neocaledonicus and G. reunionensis) of this Indo‐Pacific genus, which was observed in its environment during submersible dives off New Caledonia. Analyses examined (1) morphological changes, (2) the degree of change in morphology, (3) architectural constraints, and (4) the functional constraints related to environmental factors. The relations between three levels of integration were examined: the ossicle (columnal), the stalk, and the complete individual. The changes in level of organization were estimated. The analysis reveals that the external stalk morphology of Guillecrinus goes from a pronounced xenomorphic type in juveniles, characterized by diversified columnal articulations, which provide the proximal and distal part of the stalk with a considerable degree of flexibility, to a dominant homeomorphic type in adults, characterized by columnal articulations which allow little or no movement. This ontogenetic change through a mosaic of heterochronic developments corresponds with a change in the hydrodynamic environment, from a turbulent to a laminar water flow, and from nutritional contraints. The extensive development of deep ligament fossae in adults and in the distal stalk of juveniles corresponds to a relatively low allocation of energy to the skeleton, rather than a functional necessity. Proximal columnals in juvenile Guillecrinus display characteristics of adult Hyocrinidae. Distal columnals exhibit the typical morphology observed in Bourgueticrinina. Juveniles stages of both proximal and distal columnals show a high degree of specialization (derived characters). Well‐supported classifications have typically placed the Bourgueticrinina and the Hyocrinidae in two very dissimilar groups. Specific characteristics from the three very different families Bathycrinidae, Guillecrinidae and Hyocrinidae appear to be expressed either separately (Hyocrinus or Bathycrinus) or together (Guillecrinus). Their expression appears to depend on functional and environmental constraints. The transformation of columnals from juvenile to adult shows the important role of hypermorphic processes. However, no evidence of phylogenetic recapitulation was observed. Does the evidence presented here support or disprove current taxonomic interrelationships? How does morphology relate to ontogeny? Is heterochrony involved? 相似文献
7.
Many agamid lizards are known to show sexual dimorphism in body shape, colour and ornamentation or a combination of these traits. Adult males of Salea horsfieldii have a discontinuous dorsal crest at the nuchal region, which is a sexually dimorphic character. However, there is no information about the age or size at which this dimorphic ornamentation develops and if the species exhibits sexual shape dimorphism (SShD). The authors studied the morphology of S. horsfieldii and found that its ornamentation is an ontogenetically stable character present in all males, including juveniles. Seven morphological characters were measured to determine if they exhibited SShD at adult and juvenile stages. Analysis of covariance was used to identify differences in morphology between sexes. The results show that only adults exhibited SShD, but not juveniles. Adult males had larger head and foot lengths in comparison to females of the same size. Larger head length in adult males is a sexual fitness trait, which increases bite-force during intra-sexual combats. Although the presence of sexually dimorphic ornamentation right from the juvenile stage is rare in agamids, S. horsfieldii is an exception . The role of sexually dimorphic ornamentation at juvenile stages remains unknown and requires further investigation. 相似文献
8.
《Journal of Natural History》2012,46(15-16):951-971
The larva, nymphal stages and adult of Hydrozetes longisetosus sp. nov. are described and illustrated, and the relationship of this species with the other European species of Hydrozetes is investigated. This species was first found at the edge of a forest lake, Dury 3, in the Tuchola Forest (Poland). Subsequently, we studied specimens that had been collected in 1976 by Dr H.M. Engelmann 40 km north of Görlitz Niederspree (Germany). Many adults of this species have three setae of the c‐series, which is rare in Hydrozetes and is considered a primitive character. Most adults have two pairs of p‐series setae, which is not common in Brachypylina and is unique among European Hydrozetes. The nymphal stages have many long setae in the marginal part of the gastronotum (whole l‐ and h‐series and seta p 1), and some or all long setae of the c‐ and d‐series, which is unique among European Hydrozetes. In H. longisetosus neotrichy occurs in the h‐series, as in H. parisiensis Grandjean, 1948. Therefore, the former species is closely related to the latter, and also to H. lacustris (Michael, 1882) and H. octosetosus Willmann, 1932, which rarely retain all the c‐series setae in the adults. 相似文献
9.
A. Marrero J. M. Martin M. A. Pérez A. Rodríguez C. M. Yanes 《Cellular and molecular life sciences : CMLS》1987,43(8):927-928
Summary Giant mitochondria were observed in the perikarya and dendrites of Purkinje cells in the developing cerebellar cortex of the lizardGallotia galloti at sevral stages previous to hatching. Such mitochondria are absent from the adult cerebellum.4 December 1986The authors would like to thank Prof. L. Puelles (Murcia University) for his critical assistance and the Edafology Department of La Laguna University for facilities offered, specially for the use of the electron microscope. This work has been pertially suported by a CAICYT research grant No. 909-2. 相似文献
10.
紫外线对果蝇生长发育和表型变异的影响 总被引:3,自引:0,他引:3
对紫外线照射黄身果蝇进行了研究.结果表明:紫外线照射能够极显著地降低果蝇的寿命,使果蝇成蝇的存活时间比对照组降低66.31%~83.96%;能够抑制果蝇的产卵量,并降低卵的成活率;影响子代的个体发育,使子二代个体重量减少12.08%.紫外线照射还能影响当代或子代的行为性状,引起果蝇子代的表型变化.随着照射时间的延长和照射频率的增加,其伤害作用明显增加. 相似文献