摘要:

Lead nitrate administration dramatically modified liver cells and sinusoids assayed by scanning and transmission electron microscopy. Hepatocytes became more roundish and many apoptot‐ic cells were visible both inside the parenchyma and in the sinusoidal lumen. Many of the those free in the sinusoids, probably derives from Kupffer cells, since their number was apparently reduced and some showed nuclear chromatin condensation. The remaining healthy Kupffer cells were often observed present beneath the endothelial wall into the space of Disse or between the disconnected hepatocytes. Except for scarce signs of apoptosis and a reduced number of fenestrae that were sometimes observed, the endothelial lining cells appeared almost healthy. At the longer times following treatment, further modifications of the liver were described: the presence of fribrotic materials, many sinusoids destroyed and enlarged spaces between hepatocytes.

ISSN:1125-0003    

DOI:10.1080/11250009809386737

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The skin and gill epithelia ofHeteropneustes fossilishave been shown to possess specific patterns of immunoreactivity for the an‐tisera against a set of calcium‐binding proteins such as calmod‐ulin, parvalbumin, S‐100 protein, and calbindin D28K. In the epidermis, both the more superficial cells and the club cells reacted positively for all the calcium‐binding proteins tested, except for calbindin D28K in the former and for parvalbumin in the latter. As in the club cells of the epidermis, also in the gill all the calcium‐binding protein antisera, except anti‐parvalbumin, appear to stain neuroendocrine cells scattered throughout these epithelia. The co‐localization of a serotonin reactivity in the S‐100 protein positive cells confirms the qualification of these branchial cells as being of the neuroendocrine type.

ISSN:1125-0003    

DOI:10.1080/11250009809386738

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The conduction properties of the I and II spinal nerves from the Mediterranean fishTrachurus trachurus,permanently adapted to a template environment, were studied. These nerves have two types of fibres, myelinic and unmyelinic, correlated with two classes of extracellular compound action potentials, characterised by fast (14 m/s) and slow (3.5 m/s) conduction velocities, as measured at 18° C. The conduction of the nerve impulses is tetrodotoxin sensitive (Kd= 22 nM). The temperature dependence of the conduction velocity is bimodal, changing its slope at about 22° C. The Q10above 22° C is 1.39 ± 0.02, while below 22° C it is 1.87 ± 0.02. These data will be useful for comparisons with other species adapted to extreme environments.

ISSN:1125-0003    

DOI:10.1080/11250009809386739

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Simultaneous hermaphroditism and brooding were observed in the solitary coralBalanophyllia europaeaat Calafuria (Leghorn, Italy), in a phase of its reproductive cycle. This is the first report of hermaphroditism inBalanophyllia.Individuals of different sizes were collected in April 1997 and reared in laboratory for two months. Histological analysis showed the presence of immature and mature clusters of male gametes, vitellogenic oocytes and embryos at different stages of development. Early stages of embryogenesis were observed. Periblastulae were found free in the coelenteron. Developing embryos, already colonised by zoo‐xanthellae, were localised in the interseptal spaces or in the mesenteries.

ISSN:1125-0003    

DOI:10.1080/11250009809386740

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The stridulatory organ of four ant species of the genusMessorwas investigated by a SEM analysis providing the first report on the presence and morphological characteristics of this organ in all casres ofM. minorandM. wasmanni.Gynes, males and workers ofM. capitatusas well as gynes and workers ofM. structorwere examined and further information on their stridulatory organ were collected. In the studied species the file orpars stridensoccurs mid‐dorsally on the fourth abdominal segment, a position regarded as typical of Formicidae. The size and the general outline of the file vary with the caste and the species. The scraper orplectrumis represented by a thickened portion of the posterior margin of the third abdominal tergite lying over the file. Several morphological parameters were measured and a comparison both within and between the species was made. The possible role of acoustical communication in the social organization of these ants was also discussed.

ISSN:1125-0003    

DOI:10.1080/11250009809386741

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This preliminary note describes experiments aimed at setting up a new test for memory, utilizingGracula religiosabirds, a species known to learn several sentences and repeat them easily and with a human‐like voice. Present results reflect the recognized very poor amnestic activity of buspirone, and the strong ability of alprazolam to disrupt both direct and conditioned vocal responses of birds. Brand names: Axoren (= Buspirone); Xanax (= Alprazolam).

ISSN:1125-0003    

DOI:10.1080/11250009809386742

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

To analyse the possible relationship between some ecological variables parameters and trends (r or K tendency) in the reproductive strategy of Palearctic birds, female size was plotted against egg size and other parameters such as clutch‐size or fledging age for the western Palearctic bird families, and the differences were calculated between the values expected according to a purely arithmetic relationship and those actually found. It appears that, apart from some extreme cases of adaptation to peculiar life styles, the key factors that account for the position of the various bird families within a positive or negative residual with respect to the arithmetic values are food and nest type.

ISSN:1125-0003    

DOI:10.1080/11250009809386743

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Food habits of the royal python (Python regius)were studied in some localities of southeastern Nigeria by means both of faeces analysis and forced regurgitation of living individuals. Female pythons were significantly longer than the males. Both sexes preyed exclusively upon birds and mammals, but there were significant intersexual differences in terms of dietary, composition. Males preyed more frequently upon birds (70.2% of the total number of prey items) whereas females preyed more frequently upon mammals (66.7% of the total number of prey items). There was an apparent ontogenetic change in the diet of both sexes: specimens shorter than 70 cm total length preyed almost exclusively upon small sized birds (nestlings and immature), whereas the longer specimens (> 100 cm total length) preyed almost entirely upon small mammals. We suggest that the two sexes are different in terms of their main natural history traits (males being more arboreal than females), and that this behavioural difference can explain the observed intersexual differences in dietary composition.

ISSN:1125-0003    

DOI:10.1080/11250009809386744

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The reproductive condition ofEmys orbicularisfemales (presence or absence of oviductal eggs) was studied by palpation and radiography in a coastal population of central Italy (Tuscany). Forty‐nine females were recaptured at least twice during the reproductive period in 1997; 15 of them were found without eggs, 29 reproduced at least once, and 5 reproduced twice. The period of egg retention was estimated to be three to four weeks, and the time between two depositions about 34 days (n= 5). Despite the small sample of females reproducing twice, there is a significant tendency regarding a positive correlation between frequency of reproduction and female body size, within the study population. Reproductive females were bigger than females found without eggs; in addition, carapace length increased significantly in females found zero, one and two times with eggs. A comparison with preliminary data from northern populations ofE. orbicularis,lead to the hypothesis that the annual clutch frequency could be negatively related to latitude, the model of this relationship should be still a matter of discussion.

ISSN:1125-0003    

DOI:10.1080/11250009809386745

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The ciliate communities, living in different habitats of Lake Massaciuccoli and its marshland, were studied from June 1992 to July 1993. Ninety‐three species were identified and their relative abundance and biomasses evaluated, both at the surface and at the bottom levels of four different stations (placed in the lake close to the shore of Piaggetta, Burlamacca canal, Collettore canal, and in one small shallow pond called Chiaro). The most interesting results are: (a) the great biodiversity of the ciliate communities found in Lake Massaciuccoli likely depends upon the wide range of different microhabitats available for these communities and present in the four stations chosen; (b) the communities of the Piaggetta and Burlamacca stations are similar to each other, mainly characterized in their seasonal dynamics at the surface level (open water); (c) the communities of the Collettore and the Chiaro stations are typical of shallow waters, characterized by very large amounts of organic debris on the bottom, as shown by the rich populations of filter‐feeders and thigmotactic species which, in turn, constitute a goodpabulumfor the carnivorous species; (d) the major peaks of specimens density and biomass values were found during autumn 1992 and in early spring 1993.

ISSN:1125-0003    

DOI:10.1080/11250009809386746

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor