摘要:

Haeckel distinguished between ≪Phylogenie≫ and ≪Ontogenie≫, as opposed to ≪Phylogenese≫ and ≪Ontogenese≫. The former concepts are supposed to deal with the history of phyletic and biontic (i.e. individual) development, respectively, while the latter are concerned with the mechanisms of these processes. Haeckel's terminological distinction can no longer be upheld, ≪phylogeny≫ and ≪phylogenesis≫ are currently used as synonyms, and the same holds for the other pair of words.

ISSN:0373-4137    

DOI:10.1080/11250008709355584

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Unlike other gyrinid species, the chorionic surface ofDineutes horniis covered with blunt conical projections. The micropylar region consists of a stalk‐like structure in the center of a depression. Internally the chorion consists of an exo‐ and endo‐chorion. The outer chorion has large spaces and is composed of a laminated and porous material, whereas the inner chorion is made‐up of a thick granulated layer and a thin electron‐dense layer. The vitelline membrane has an electron‐dense upper surface and spherical, vesicular‐like structures that are dispersed throughout the membrane.

ISSN:0373-4137    

DOI:10.1080/11250008709355585

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The surface modifications which follow the migration of the nuclei in the periplasm during stage 9 and 10 were studied in the earlyDrosophilaembryo by scanning electron microscopy. Anti‐tubulin immunofluorescence microscopy was also used to observe the changes in microtubule organization during the cap cycle 10. Cap formation occurs in three steps. First the caps enlarge and flatten, then a bilobed structure forms and finally the daughter caps become round and separate. The phenomenon of cap formation is related to the presence of actin and tubulin networks.

ISSN:0373-4137    

DOI:10.1080/11250008709355586

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Two cuticles are secreted at different times over the epidermal cells during the embryonic development ofCeratitis capitata.The first cuticle, 12–14 nm thick, appears in 12–13 hr old embryos at the beginning of gastrulation when the posterior midgut invagination occurs. This cuticle corresponds to the ≪embryonic envelope≫ or ≪atypical cuticle≫ of previous authors. The second cuticle, which becomes the first larval cuticle, appears 38–40 hr after egg deposition. The first phase of larval cuticle secretion occurs when mor‐phogenetic movements cease. This cuticle consists of three layers: cuticulin, epicuticle and endocuticle. Freeze‐fracture replicas show intramembrane clusters of particles associated with the P‐face of the membrane in correspondence with the short protuberances of the epidermal cell apex.

ISSN:0373-4137    

DOI:10.1080/11250008709355587

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The chorionic surface ofBelostoma lutariumcan be divided into three distinct morphological regions. The basal area contains the hydropyle which has a filamentous central core and long excrescences surrounding the core. The medial area is composed of polygons that have indistinct ridges which makes demarcation not as well defined as on the apical cap area. Each medial polygon has twelve to twenty‐one areopyles. The apical cap area has polygons with distinct ridges and is covered with a plastron network. There are six to eight micropyles in a semi‐circle on a raised portion of the apical end. The aeropyles in this region are situated at the junction of several polygons and they contain an inner meshwork. The internal structure of the chorion consists of porous layers and spaces.

ISSN:0373-4137    

DOI:10.1080/11250008709355588

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Morphological changes in the gonads of the freshwater gobyPadogobius martensifrom March to October were examined. Histological analysis showed that this species has a ≪group synchronous≫ ovary and, therefore, it can spawn more than once during a breeding season. Furthermore, the species, similar to most gobies of temperate freshwaters, shows a distinct seasonality in reproductivity and has a relatively short breeding season. Associated with the testis are glandular structures similar in morphology to the ≪sperm‐duct glands≫ described in a number of gobies. They grow enormously only during spermiogenesis and exhibit apocrine secretion. A role of these structures could be secretion of sex actractant substances.

ISSN:0373-4137    

DOI:10.1080/11250008709355589

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Sixty‐two species have been recorded in autumn‐winter in 11 selected habitats of Northern Tuscany (Italy). Riparian woodland and olive orchard supported the highest number of bird species. The interhabitat similarity is higher in woody habitats than in open habitats. The specific inter‐monthly stability and the habitat breadth are positively correlated (p < .001). In woodlands the residents are dominant whereas in farmlands the partial and transalpine migrants are dominant. The patchy structure of habitats and the abundance of resources are probable factors responsible for the low intercategory overlap.

ISSN:0373-4137    

DOI:10.1080/11250008709355590

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Plasma luteinizing hormone (LH) levels in migratory male chaffinches exposed to natural lighting in northern Italy were seasonally high during May and June. In birds held on a fixed short day length of 8 hr light: 16 hr darkness from February to July, plasma LH levels increased slowly reaching a low plateau in July. The seasonal fall in plasma LH levels in June was not reversed by transferring the birds to continuous light in October and February: the larger increase was observed in February. It was concluded that the initiation of breeding may involve an underlying Autonomous increase in reproductive function, and that breeding is terminated by the development of absolute as opposed to relative long day refractoriness.

ISSN:0373-4137    

DOI:10.1080/11250008709355591

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Weight and other body measurements of crested porcupines captured in the Maremma Natural Park, central Italy, were compared between the sexes. The weights and body lengths of females were significantly greater than those of males (P < 0.05). A stepwise discriminant analysis showed that 802 of the females (N = 10) and 85.7% of the males (N = 14) were classified correctly by the discriminant function, which was correlated most highly with body length and weight. Body length proved the best single variable for differentiating between the sexes. The larger size of females is discussed in relation to the reproductive and life‐history strategies of the crested porcupine. The distribution and quality of food resources is suggested as the factor responsible for the evolution of sexual size dimorphism in favour of females in the crested porcupine.

ISSN:0373-4137    

DOI:10.1080/11250008709355592

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The profundal macrobenthos of a regulated lake (Lake Canterno, Central Italy) was investigated to provide information on the structure and composition of this community in a lake long subject to wide fluctuations of the water level and to the influence of domestic sewage. Pollution‐tolerant forms constituted most of the total macrobenthos. It is suggested that large water movements (water level drawdown and hypolimnical drawoff), by producing a marked environmental instability, and eutrophication phenomena (e.g.deoxygenation), account for: a) high abundances of mobile fauna(Dero digitata, ProcladiusandChaoborus flavicans),especially at the station close to the water outlet; and b) high abundances of mud‐dwelling fauna (Tubificidae andChironomus plumosus)in the stations far from the water outlet. Diversity was negatively affected by mobile form percentages, and positively influenced by mud‐dwelling fauna percentages. Lastly, behavioural indicators are suggested to be useful markers with which to monitor environmental stress in lakes.

ISSN:0373-4137    

DOI:10.1080/11250008709355593

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor