摘要:

The cement gland is a secreting organ located at the anterior end of the larva of anuran Amphibia. It is a highly conserved structure even if it has different shapes in the different species. The morphology and the histology of the cement glands of seven species are analysed:Xenopus laevis, Discoglossus sardus, Bufo bufo, Bufo viridis, Rana esculenta, Rana latasteiandHyla intermedia. XCGandXAGare genes specifically expressed in the cement gland ofXenopus laevisand can be used as markers to identify cement gland territory. By Northern analysis and whole mount’in situ’hybridization, the expressions of these genes are tested in the studied species, the presence of homolog transcripts is detected in all the species, exceptDiscoglossus sardus.Histological and molecular analysis show a substantial uniformity among the different types of adhesive organs. On the basis of the preliminary results obtained, some phylogenetic relations are inferred according to a recent phylogenetic tree based on molecular characters. The results seem to agree with the hypothesis that Pipi‐dae, to whichXenopus laevisbelongs, are nearer to Neobatrachia than to Archeobatrachia.

ISSN:1125-0003    

DOI:10.1080/11250000009356287

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The pleuro‐abdominal connectives (PACs) inAplysia fasciata(Poiret) observed at EM showed irregular compartments in which different calibre fibres were intermingled with abundant glia laminae. The estimated total numbers of axons were 1388 in the left and 1832 in the right PAC, with similar size distribution. Co2+backfills were applied to the severed PACs to highlight the populations of central neurones projecting into these nerves from either side. After left abdominal PAC stump backfills, an average of 51.5 ipsilateral and 9.2 contralateral neurones were stained; correspondingly, right PAC backfills yielded 32.5 and 13.1 neurones. Aided by a preliminary examination of the abdominal ganglion ofA. fasciata, a comparison withA. californicawas carried out and correspondences of neurones and clusters were proposed. In all, the stained abdominal neurones outnumbered the ones described as projecting into the PACs inA. californica, and a part appeared as newly identified. Backfills applied to pleural left or right PAC stump stained less numerous neurones, all ipsilateral, in the pleural ganglion (average 30.6 and 16.5, respectively) and pedal ganglion (3.3 and 3.9). Many stained fibres could not be traced to a soma; although often crossing the ganglia and entering a peripheral nerve, they appeared to assure long‐distance connections with the periphery.

ISSN:1125-0003    

DOI:10.1080/11250000009356288

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The structure of the optic nerve ofHydromantes genei,was investigated by confocal laser scanning microscopy and by the Cajal‐De Castro method. This nerve appears to be composed of un‐myelinated fibres, which is a rare case in amphibians. In view of this and the fact that it contains a relatively small number of nervous fibres, the optic nerve ofH. genei,in comparison with other species of Plethodontidae, can be considered a structure with a low level of complication.Key words: Optic nerve structure ‐ Confocal microscopy ‐Morphology ‐ Amphibia ‐ Anatomy.(Received 21 July 1999 – Accepted 30 August 1999)

ISSN:1125-0003    

DOI:10.1080/11250000009356289

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The grass goby,Zosterisessor ophiocephalus, breeds in dark underground reproductive burrows excavated by the male in the intertidal muddy area of seagrass meadows. The present study under laboratory conditions, describes the behaviour exhibited by both male and female grass gobies during breeding. The most common behaviours displayed by the male involved physical contact with the female (e.g., prodding, tail beating), whereas the female mostly reacted by performing behaviours related to body and/or fin oscillations. The most frequent behavioural sequences performed were tail beating and prodding by the male, followed by female body arching and dorsal fin oscillations, and the latter followed in turn by male tail beating and prodding. Both sequences occurred with the highest frequency during courtship. A statistical analysis of the behavioural sequences indicated that the most significant ones were prodding by the male followed by female body arching, and the latter followed in turn by male prodding. Both sequences were performed with the highest significance during courtship. In addition, prodding the female was the most significant behaviour performed by the male both during courtship and spawning. Behaviours such as prodding and tail beating cause physical contact between the male and the female, whereas a female's body and fin oscillation induces water vibrations around the fish. Hence, behaviours related to a mechanical stimulation of the partner appear to play a fundamental role during breeding in the grass goby. Such behavioural patterns may have evolved because they are particularly effective in the grass goby's breeding environment, i.e. the dark burrows excavated in the muddy seagrass beds where the visual communicative channel results of little use.

ISSN:1125-0003    

DOI:10.1080/11250000009356290

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The ultrastructure of the Malpighian tubules of the final instar nymph of the mayflyBaetis rhodaniis described. Numerous Malpighian tubules enter the alimentary canal at the transition from midgut to hindgut. Each of them is made up of a cylindrical distal portion and a proximal narrow duct emptying into the gut. At the junction between the two regions, the cylindrical portion enlarges and curves, to continue into the thin duct. The wall of the cylindrical portion consists of primary cells characterized by typical features of the secretory/absorbing epithelia. These cells show a large polytene nucleus, an apical microvillated border, a high number of mitochondria and basal infoldings. The narrow duct is formed of large cells joined by highly convoluted junctions, and their cytoplasm is filled with electron‐translucent vesicles. The apical border of the cells of narrow duct lacks microvilli but bears several finger‐like extensions. Each narrow duct empties into a canal interposed between groups of gut epithelial cells, which constitute the transition area between midgut and hindgut. The Malpighian tubules ofB. rhodanirepresent an ancestral condition and their structural arrangement provides important information for tracing mayfly evolutionary trends.

ISSN:1125-0003    

DOI:10.1080/11250000009356291

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Carp liver contains a glutathione S‐transferase isoenzyme which uses as best substrates l‐chloro‐2,4‐dinitrobenzene (CDNB) and cumene hydroperoxide, thus showing selenium‐independent glutathione peroxidase activity. This isoenzyme accounts for about 15% of the total activity with CDNB and does not bind to the affinity matrix of hexyl‐S‐glutathione Sepharose 6B. It has been partially purified by ionic exchange and gel filtration chromatographies and isoelectric focusing. The purified enzyme is an acidic protein of 55 kDa of relative molecular mass and has an isoelectric point at pH 5.4. Values of Km have been measured for both CDNB and reduced glutathione (GSH) substrates. The best substrates are CDNB and cumene hydroperoxide, followed by ethacrynic acid and 1,2‐epoxy‐3‐(p‐nitrophenoxy)‐propane. Hydrogen peroxide and 1,2‐dichloro‐4‐nitrobenzene are not substrates and trans‐4‐phenyl‐3‐buten‐2‐one is a very poor one. Among several glutathione S‐transferase inhibitors used, cibacron blue and rose bengal are the strongest; the herbicides, 5‐amino‐4‐chloro‐2‐phenyl‐3(2H)‐pyridazinone (Pyrazon), 2,4‐dichlorophe‐noxyacetic acid (2,4‐D), and 2‐(2‐methyl‐4‐chlorophenoxy) pro‐pionic acid (MCPA) are less effective.

ISSN:1125-0003    

DOI:10.1080/11250000009356292

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Xfinis aKrüppel‐type zinc finger protein characterized by the highest number of zinc finger motives (37) found to date. An interesting feature of this protein is the cytoplasmic location, coupled byin vitroRNA binding activity: both these properties may suggest a role forXfinin RNA metabolism. As the corresponding mRNA, the protein product ofXfinis part of the maternal store inXenopusand is present throughout embryogenesis. We usedin situhybridization to establish the expression pattern ofXfinin developmental stages. We show here that it is expressed evenly throughout gastrula and neurula stages embryos, while in later stages its transcripts are mainly enriched in the endoderm. In addition, we performed somein vivoperturbation experiments. We found that overexpression ofXfinby injection of synthetic mRNA in earlyXenopusembryos causes disruption of posterior development; also,Xfinoverexpression inhibits the normal expression of the pan‐mesodermal markerXbra.

ISSN:1125-0003    

DOI:10.1080/11250000009356293

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Eleven enzymes were analysed in seven tissues (heart, muscle, liver, kidney, gills, gut, and lung) of the Australian lungfish with the aim of identifying the distribution in an extant sarcopterygian fish and of comparing this distribution to patterns previously described in actinopterygian fishes and other vertebrates. Some enzymes (G6PDH, GPI, LDH, MDH, and SOD) were found to be present in all the tissues studied, while the others were found to be tissue specific. Similarities in expressed loci and/or tissue specificity with other vertebrates were found for several enzymes (ADH, FBALD, GAPDH, G3PDH, G6PDH, PGM and SOD). Differences were observed in the other enzymes: in ALP (due to the absence of an intestinal specific form typical of fish, amphibians, reptiles, or birds); in GPI and MDH (due to the tissue expression in Australian lungfish also present in other primitive fish species). Furthermore the LDH‐B4 was active only in the heart and kidney, while the LDH‐A4 form was dominant in all tissues. Moreover, a thirdLDH‐C*gene was expressed in the liver and kidney. Overall, comparison with other previously described vertebrates shows that the tissue expressions of several enzymes are relatively conservative, while others have changed markedly in this primitive dipnoan species.

ISSN:1125-0003    

DOI:10.1080/11250000009356294

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Two groups of eight long‐eared owls,Asio otus, and eight tawny owls,Strix aluco, which entered a Rehabilitation Centre as nestlings, were studied. When more than 60 days old they were released to the wild. The aim of this study concerns the analysis of their behaviour immediately after release and their adaptation to natural life. The owls were radio‐tagged and followed continuously, also with direct observation, until they disappeared from the area or died. The long‐eared owls, released in an agricultural area with scattered woods, were reluctant to fly frequently and remained mostly in thick vegetation along stream banks or very close to the release pen itself. Nevertheless, they progressively enlarged their home range in a matter of days. Half of them disappeared from the study area within 11 days; three others died in a few days, apparently from starvation, while the last owl was rescued because it fell into a stream. In contrast, the tawny owls had a much better survival rate, as only one out of the eight died because it was preyed on in the early days. The birds remained in the area for a longer time, constantly within the woods, and flew more often. They, too, enlarged their home range but only until day 10, when there was a contraction in size. Thus, inexperienced hand‐reared owlets are able to survive in the wild, but the possibility to cope with the new environment varies greatly between species, possibly due to environmental characteristics.

ISSN:1125-0003    

DOI:10.1080/11250000009356295

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Roost occupancy and behaviour at evening departure were studied in long‐eared owls (Asio otus) at a large winter roost in the southern suburbs of the city of Milan, northern Italy. The number of roosting owls was strongly correlated with decreasing daylength, while it was weakly negatively correlated with temperature. Hence changes in photoperiod can be considered among the proximate factors promoting the winter aggregation of long‐eared owls. Behaviour at departure was influenced by cloud cover: birds departed earlier, and departures were at a higher altitude and less concentrated, with covered sky than with clear sky; the reasons for these behavioural differences remain unclear. Directions of departure showed that owls do not use the urban area for hunting, as no birds were observed flying towards the city, consistently with dietary data.

ISSN:1125-0003    

DOI:10.1080/11250000009356296

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor