摘要:

Changes in skeletal structure occurring in differently sized specimens of two species ofTethya (T. aurantiumandT. citrina)were studied. In the two species, differences in sponge consistency were found to be affected by their radial strongyloxeas skeleton and by aster sheets reinforcing their collagenous ectosomes. InT. aurantium,body enlargement was enhanced by the production of new megasters, while inT. citrinaa proliferation of strongyloxea bundles accompanied its growth. These differences are related to the different ecological strategies of the two species. In both species, strongyloxea length was clearly related to individual size.

ISSN:1125-0003    

DOI:10.1080/11250000009356318

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The histological analysis of the fat bodies, gonads, and prothoracic gland of both sexes ofBlattella germanica,carried out throughout their adult life, revealed different fates of these structure in the two sexes. In the males, the prothoracic gland and the fat bodies showed a precocious alteration while the testicular morphology was preserved until two months of adult life. In the females, instead, the prothoracic gland persisted slightly longer and the fat body and ovary do not show alterations until after two months of adult life. Moreover, while the histological alterations found in the males were uniformly diffused, in females the occurrence of alterations was scattered in the fat body lobes and ovarioles. The amount of bacteriocytes was initially higher in females than in males; later, however, bacteriocytes decreased precociously in males, whereas in females they decreased only after the synthesis phase of vitellogenins. Such synthesis could be ascribed not only to the fat bodies, but also to the bacteriocytic component. The numerical decrease of bacteriocytes in both sexes is due to cellular degeneration with consequent loss of the symbiotic complement. We suggest that the preservation, over time, of the fat body morphology and of the bacteriocytic component in the female can be attributed to the synthesis of ecdysteroids, which are initially secreted by the prothoracic gland and later by the ovaries.

ISSN:1125-0003    

DOI:10.1080/11250000009356319

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Lectin peanut aglutinin histochemistry was used to elucidate histogenesis of septa and valves in mouse heart morphogenesis. Soon after the proliferation of mesenchyme cells in endocardial cushions, lectin peanut aglutinin was found to recognise a glyco‐protein of about 65 kDa, which is part of a fibrous network present in the extracellular matrix of endocardial cushions. During a later stage of morphogenesis, both atrioventricular and spiral septa were positive to peanut aglutinin, while interatrial septa were not labelled. At the completion of morphogenesis, septa showed a marked decrease of peanut aglutinin positivity, in concomitance with extended fenestrations of the septal tissue; however, valve leaflets were still positive to the lectin. Thus, lectin peanut aglutinin appears to be a reliable marker of endocardial cushion‐derived tissues during valvuloseptal morphogenesis.

ISSN:1125-0003    

DOI:10.1080/11250000009356320

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The present paper describes the annual variations in plasma concentrations and thyroid and hepatic contents of thyroid hormones, as well as the activity of hepatic 5'‐T4 ORD (type II) monodeiodinase, in the male lizard,Podarcis sicula,during two consecutive years. Plasma concentration of T4 was low in winter and increased in March, reaching maximal levels in May‐June; plasma levels of T3 varied throughout the year, reaching minimum values in December and February. The thyroid content of T3 was high between March and July; the T4 content followed a similar seasonal pattern and showed a minimum in January and a maximum in July. Low hepatic contents of T3 and T4 were found in winter, increasing rapidly after spring to reach maximal values in July‐October. Moreover, the maximal activity of hepatic 5'‐T4 ORD (type II) monodeiodinase was observed in May and June‐July. Minimal activity was detected in winter and in October‐November. Plasma TSH levels were high between March and July and low from November to January.

ISSN:1125-0003    

DOI:10.1080/11250000009356321

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A preliminary study on nucleolus organizer region polymorphism was carried out in a Sicilian population ofLebias fasciatausing several staining techniques (Ag‐staining, CMA3‐staining, and FISH). Intrapopulation polymorphism of the number and size of the rDNA loci was found. A maximum of six NORs was found, involving four chromosome pairs both in homozygotic and het‐erozygotic conditions. Duplication of NORs was also detected.

ISSN:1125-0003    

DOI:10.1080/11250000009356322

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Using a polyclonal antibody raised against purified phenoloxidase from the colonial ascidianBotryllus schlossen,we studied its distribution among haemocytes and its intracellular location. The enzyme is present inside granular amoebocytes and morula cells, thus confirming the close relationship between the two cell types, as suggested by previous histochemical and histoenzymatic analysis. Immunocytochemistry in both light and electron microscopy shows that phenoloxidase is located inside the vacuoles of moru‐la cells, known to be the effectors of the rejection reaction.

ISSN:1125-0003    

DOI:10.1080/11250000009356323

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A genetic variability assessment of five samples of the sand gobyKnipowitschia panizzaefrom Adriatic lagoons revealed the presence of two phosphoglucomutase loci suitable for population genetics studies. Previous biochemical investigations on the same species referred phosphoglucomutase data only to a single structural locus. The differential tissue expression of this enzyme system was tested in the eye, liver, mature ovary, and epiaxial muscle by starch gel electrophoresis. In particular, good electromorph resolution in the muscle and liver tissues was observed. Early expression during ontogenesis was demonstrated through the analysis of individuals of different age classes. Different levels of observed heterozygosity were found at thePGM‐1*(0.043–0.095) andPGM‐2@*0.355–0.576) loci in the five analysed samples.

ISSN:1125-0003    

DOI:10.1080/11250000009356324

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This research represents the first description of stridulations produced by the different castes (gynes, males, workers) of the harvesting antsMessor minorandM. wasmanni.Further information on the stridulatory, sounds produced byM. capitatusandM. structorare also given; The sounds produced by the examined samples (n= 103) of the genusMessor arehomogenous in their acoustic structure and consist of long sequences of pulse‐trains organized in two subunits. They are characterized by pulses with opposite phase produced by rapidly raising and lowering the gaster, so as to cause a series of ridges to rub against a scraper. For all samples of the tested species, the maximum frequency values lie within the ultrasonic range (> 18–20 kHz) and vary between 41 and 98 kHz. This is the first recording of ultrasounds produced by ants of the genusMessor.Hence, the range of frequencies involved in sound production by these species is considerably wider than previously known. Moreover, the description and comparison of several acoustical parameters show some caste‐dependent differences and similarities among the examined samples. The possible functional role of stridulations emitted by the different castes of these species is also discussed.

ISSN:1125-0003    

DOI:10.1080/11250000009356325

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Very few studies have addressed the effect of protection on macrozoobenthos in marine protected areas, and particularly for sites in the Mediterranean Sea. In the present study, the molluscan assemblages associated with photophilic algal communities of the Marine Reserve of Ustica Island, were investigated. A survey was carried out along transects from 1 to 15 m in depth, during the spring of 1996 at three different sites, subjected to different levels of reserve protection. Species richness and number of individuals reflected the level of protection, and both variables were significantly higher in the integral (most heavily protected) part of the reserve compared with the less well protected buffer areas. Species diversity values showed no correlation with the level of protection. The results reported here do not agree with previous findings on the ‘reserve effect’ involving large‐sized macrozoo‐benthic species. However, the data reported, together with a study on polychaetes from the same study sites, and visual census observations concerning the fish assemblage of the island may support the hypothesis that protection of piscivore and macrocar‐nivore species within the integral reserve suppresses populations of small‐sized microcarnivorous fish species, allowing ‘prey‐release’ of small benthic invertebrates.

ISSN:1125-0003    

DOI:10.1080/11250000009356326

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Sampling campaigns were carried out in 1976 and in 1989 in the Sacca degli Scardovari, a brackish lagoon in the Po Delta (upper Adriatic Sea). By means of different methods (i.e., average taxonomic distinctness index, conventional diversity measures, and non‐parametric multivariate analysis), changes in benthic community structure were investigated. In the 13‐year period, the southern area of the lagoon underwent a marinization process. A quite strong environmental gradient along its main N‐S axis was then found. Multivariate analysis was the most powerful tool for the assessment of benthic community changes, revealing community patterns that univariate measures of diversity were unable to detect. Relevant information on the taxonomic structure of the community was given by the distinctness index, but this did not prove sensitive to environmental changes, probably due to the characteristics of the studied environment.

ISSN:1125-0003    

DOI:10.1080/11250000009356327

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor