摘要:

An inheritable mechanism of sex‐ratio distortion, causing a conspicuous, variable and unpredictable excess of males, has been recently observed in a field population ofMusca domestica.The cause of this sex‐ratio distortion, named Non‐Mendelian‐Sex‐Ratio (NMSR), is always strictly associated with a male determinant on autosome 3 (MIII). NMRS causes a gametic selection, whereby the sperms carrying NMSR are advantaged during zygote formation. Therefore, the progeny consists mainly of males due to the association withMIII.

ISSN:0373-4137    

DOI:10.1080/11250008909355631

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

At the end of spermiogenesis inChalcides ocellatus tiliguguthe acrosomal complex is constituted by a homogeneous anterior cap derived from the acrosomal vesicle and by a paracrystalline posterior cap that arises from nuclear membrane proliferation. During the spermiogenetic process, the spherical nucleus becomes elongated and cylindrical in shape, and assumes a homogeneous appearance because its chromatine condenses. At the onset of spermatid elongation, a set of microtubules appears as a helix surrounding the nucleus. At the end of elongation, the microtubules become parallel to the main axis of the nucleus. From the early stage of spermiogenesis, the two centrioles (proximal and distal) and the flagellum are situated at the posterior pole of the nucleus. The two centrioles are encircled by the dense connecting piece, which is continuous with the nine accessory fibers surrounding the flagellum. At a later stage, the mitochondria form the mitochondrial sheath and four rings of electron‐dense material. In the first portion of the flagellum, between mitochondria and accessory fibers, a fibrous helix encircles the entire length of the flagellum. The spermatozoa mature completely eliminating their cytoplasm in the epididymal duct.

ISSN:0373-4137    

DOI:10.1080/11250008909355632

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The spatial distribution of microfilaments during the first phases of gastrulation in theDrosophila melanogasterembryo was observed in whole mounts using rhodamine‐labelled phalloidin (Rh‐phalloidin). At the beginning of gastrulation, bright fluorescence lined the bases of the blastoderm cells. Fluorescence was most marked at the apices of the cells which constitute the cephalic and ventral furrows. At this time no fluorescence was observed at the bases of the anterior and posterior blastoderm cells. Very bright staining was observed at the apices of the cells constituting the wall of the forming amnio‐proctodeal invagination. The possible relationship between microfilament distribution and gastrulation inDrosophilais also discussed.

ISSN:0373-4137    

DOI:10.1080/11250008909355633

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Zoothamnium intermediumwas found attached to the exoskeleton of planktonic crustaceans, most of which were copepodsAcartia clausi.It formed branching colonies that consisted of zooids characterized by: 1) a bell‐like shape; 2) peristomial cilia that formed a single haplokinety raised above a double polykinety; and 3) unbranched annular striae, regularly distanced from each other by about 0.5μm, around the zooid circumference. Fully developed colonies contained also several roundish zooids that were identified as potential motile stages. In addition to colony members, free‐swimming dimorphic individuals were also occasionally observed: one type showed long trochal cilia and a scopula with a central area containing numerous protuberances; the other was characterized by short, stumpy cilia and a scopula endowed with a central finger‐like process surrounded by a pleated wrap. These free‐swimming individuals were tentatively identified as the microgamont and telotroch stage ofZoothamnium intermedium, respectively.

ISSN:0373-4137    

DOI:10.1080/11250008909355634

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A recent study carried out in this laboratory revealed differences in oestrous cycling between individually housed female mice that had been reared from 19 days to 4.5 months of age in single‐sex groups of 30 or reared in single‐sex littermate groups of four with the mother. The present experiment assessed whether prior housing and social conditions have long‐term consequences on oestrous cycling in female mice. Prior rearing conditions influence oestrous cycling in female mice, but their influence may be modulated by the subsequent housing and social conditions.

ISSN:0373-4137    

DOI:10.1080/11250008909355635

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A total of 213 males and 234 females of the tiger‐beetleCephalota circumdata leonschaeferi(Cassola) were individually colour marked in the three years of study (1984, 1985, 1986). The maximum number of days in which marked individuals were resighted was 37. These tiger‐beetles dispersed within a radius of 30 m from their respective marking places. Re‐sightings were rare beyond this dis tance; one individual was observed at about 100 m from its marking place. The ground temperature proved to be a key‐factor influencing the activity and viability of the population; optimal ground temperature ranged between 32–33°C as to number of individuals present, but a temperature of 34–35°C determined the greatest number of matings. A negative influence onC. c. leonschaeferisurvival and activity was exerted by cloudy and, particularly, rainy weather. Wind force influenced the habitat selection: an increase of wind force generated a greater use of terrain without vegetation(Salicornia).Apparently the increased hunting success of these beetles in open ground at wind force 3–4 (Beaufort scale) determined the habitat selection. Males proved significantly more active than females by covering greater daily distances. Both sexes showed two peaks of activity in the early morning and in the afternoon, but they were inactive in the central hours of the day, when the ground temperatures were beyond 36–37°C.

ISSN:0373-4137    

DOI:10.1080/11250008909355636

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Relative indices (MOT = the average number of birds counted during the trips in the breeding season; ITA = the average number of birds encountered per hour during the trips in the breeding season) were used to monitor the rock‐partridge breeding population in four areas of Sicily. Statistical analysis of variance demonstrated that the indices are unbiased estimators of the populations under study. The Anova Model II results showed that sampling means were obtained by studying populations of different densities in the chosen areas. The reason for this difference is due to the different habitat structure and mainly to the presence‐absence of hunting protection. Post‐breeding relative indices (MOTpb = the average number of birds encountered during the trips in the post‐breeding season; MIB = the average number of birds gathered in coveys) were also useful in population monitoring. Data on breeding biology show a medium productivity rate (ratio juveniles/adults) of the population. Pair‐forming starts in February, egg‐laying occurs from March to June, while chicks are present from June to September; average clutch size is 12 eggs. The seasonal development of calling activity through different time bands is also reported.

ISSN:0373-4137    

DOI:10.1080/11250008909355637

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This study concerns the composition and distribution of the microzoobenthos in Lake Suviana (Tusco‐Emilian Apennines) with particular attention to the Protozoa. The microfauna, sampled monthly from October 1986 to September 1987, in two stations of this man‐made lake, was composed of nine zoological groups. Ciliophora, comprising 45 taxa, was the most important group and their maximum density was 358 ind. cm‐2in the profundal zone of the lake. Rhizopoda became the predominant group in November reaching a peak of 2097 ind. cm‐2due prevalently to the growth ofCochliopodium granulatum.Other groups, such as Nematoda and Rotifera, were also abundant in some periods. Moreover, there was a low number of species and individuals of the ciliate taxocoenosis of Lake Suviana in comparison with other lakes.

ISSN:0373-4137    

DOI:10.1080/11250008909355638

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

About 2000 earthworm specimens, collected during 1987–1988 in 50 localities of North‐Western Turkey, are described and classified. They belong to 51 species, 14 of which have not previously been described. For some new species it has been necessary to institute the new genusHealyellawhich is closely related to the genusSpermophorodrilusBouché; both these genera are included in the new lumbricid subfamily Spermophorodrilinae, characterized by a peculiar pattern of copulating. Six other new species, some of which show curious morphological traits, are included in the genusDendrobaena,and one in the genusAllolobophora.

ISSN:0373-4137    

DOI:10.1080/11250008909355639

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0373-4137    

DOI:10.1080/11250008909355640

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor