摘要:

In this paper we describe the behaviour of the symbiotic bacteria ofBlattella germanicaandPeriplaneta americanaduring embryo development using transmission and scanning electron microscopy. InBlattella germanica, the bacteria are transferred by endocytosis to the egg cell and are sited in its peripheral cytoplasm; thence they begin to internalize in the yolk, using cytoskeletic structures which are probably only synthesized at this particular phase of their migration. In the 6–7‐day‐old embryo, the bacteria are in close contact with the vitellophages scattered in the yolk, where some of them appear to be in a degenerative phase. InPeriplaneta americana, after the internalization of the bacteria, there is the formation of the mycetome which appears to be made up of a syncytial envelope, probably formed by the vitellophages, that contains a ball of symbionts of considerable number. During development, there is a progressive decline in the bacterial population, caused by complex lytic processes which take place inside the mycetome. In embryos aged more than 17 days, the mycetome tends to regress, while there are many bacteriocytes present. A hypothesis for interpreting this phenomenon is that the embryo may use the bacteria as nutrients. It cannot, however, be excluded that the formation of the mycetome may be the expression of a cellular immune process.

ISSN:1125-0003    

DOI:10.1080/11250009609356100

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The morphology and the immunohistochemistry of the caudal neurosecretory system ofDicentrarchus labraxwere analysed after the fish acclimatation to fresh water. Two different sized neurosecretory cells have been identified in seawater‐acclimated fish and denoted as anterior and posterior cells. The two types of cells share similar patterns and intensities of immunoreactivity with urotensin I and urotensin II antisera. Posterior neurosecretory cells decreased in size in freshwater‐acclimated specimens, whereas anterior cells did not show changes. Urophyses of seawater‐ and freshwater‐acclimated fish reacted with both antisera. Immunohistochemistry of the urophysis did not provide evidence for a significant difference in the activity of the caudal neurosecretory system between seawater‐ and freshwater‐acclimated fish. However, on a morphological basis it was possible to suggest that the caudal neurosecretory system of the sea bass is involved in the hyper‐osmoregulation.

ISSN:1125-0003    

DOI:10.1080/11250009609356101

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Genetic variation in larvae and imagines of three species of Heptageniidae from central Italy,Ecdyonurussp.(venosusgroup),Elec‐trogena grandiae(Belfiore, 1981), andElectrogena lateralis(Curtis, 1834) was studied by starch‐gel electrophoresis. Thirteen enzyme systems were analysed for a total of 20 loci (Aat, Ada, Adk‐1, Adk‐2, Ck‐1, Ck‐2, Est‐1, Est‐2, α‐Gpdh, Gpi, La‐1, La‐2, Mdh‐1, Mdh‐2, Me‐1, Me‐2, Mpi, Pap, Pgm‐1, Pgm‐2), 15 of which were expressed in adults and 16 in the larvae. Only 11 loci (Aat, Ada, Est‐2, Gpi, La‐2, Mdh‐1, Me‐2, Mpi, Pap, Pgm‐1, Pgm‐2) were shared by larvae and adults. Observed heterozygosities were always lower than expected values; higher values were observed in larvae than in adults. Fixation indices and genetic distances were higher in the adults; however, the two genera were better discriminated using the larval samples. In conclusion, comparisons using larvae and adults simultaneously should be avoided, and absolute values of genetic identities and genetic distances to assess systematic levels have to be considered with caution, since they can vary from one developmental stage to another.

ISSN:1125-0003    

DOI:10.1080/11250009609356102

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Genetic variation was investigated among different populations of the European woodcock(Scolopax rusticola), using random amplification of polymorphic DNA (RAPD). Thirty‐nine ethanol‐preserved livers of bagged woodcock were used from three different sites: Harg (Uppsala, Sweden) 17 individuals, Alessandria (northern Italy) 14 individuals, Sinop Peninsula (Black Sea, Turkey) 8 individuals. DNA extracted from livers was amplified by PCR using 10‐mer primers (Kit A, Operon Technologies), and amplification products were revealed by electrophoresis on agarose gel containing ethidium bromide. A total of 7 primers out of the 20 tested were selected and a total of 71 bands were scored for band‐sharing analyses. Bands were firstly considered as presence‐absence characters which allowed a pairwise similarity matrix and an UPGMA dendrogram to be built. The latter showed a clustering of samples from Turkey leading to their almost complete separation from those of Sweden, while the samples from Italy showed affinities both to the Turkish and Swedish ones. Bands were also treated as dominant markers of mendelian loci with two alleles, yielding allele frequencies, genetic diversity and genetic distances. Average within‐population diversity Hwwas higher than between‐populations diversity HB, i.e., there was a low differentiation among populations (FST= 0.14). Non‐metric measures of genetic distances (Nei, Nei modified by Hillis, Nei jackknifed) as well as metric measures (Rogers, Wright, Cavalli‐Sforza & Edwards) indicated that the two most divergent groups were those of Sweden and Turkey, while Italian samples were more similar to the former than to the latter. The RAPD genetic patterns obtained agree with bird allozyme data, although genetic distances are higher. In addition, RAPD data are consistent with woodcock migration routes. Hence RAPD markers seem to provide reliable indices of bird genetic diversity, and the method is proposed as a support for the development of bird management plans.

ISSN:1125-0003    

DOI:10.1080/11250009609356103

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The chromosome complement of the African creek ratDesmomys harringtoni(sin.Pelomys harringtoni)is described. The diploid number is 52 and the autosomal Fundamental Number is 72. C‐ and G‐banding patterns were studied and the Nucleolus Organizer Regions were located by silver method. The findings are discussed within the karyological context of the related genus,Pelomys.

ISSN:1125-0003    

DOI:10.1080/11250009609356104

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Consecutive underwater mappings of specimens of the calcareous spongeClathrina cerebrumwere performed within a plastic quadrat (1 m‐side) fixed to a cliff wall of the Portofino Promontory (Ligurian Sea, Italy) at a depth of 4 m. The typical clathrate forms ofC. cerebrumwere present only during the cold season (from autumn to spring). In summer, species survival depends upon minute forms that represent a successful strategy for withstanding the heat crisis. Investigations carried out with scanning electron microscopy allowed two types of minute forms to be distinguished: type A, which shows the same architecture as the clathrate sponges, and type B, with characteristic quadriradial symmetry. The morphology of both forms is consistent with their different origin: by fragmentation (type A) and by sexual reproduction (type B). Comparative analysis revealed variations in the dimensional range of the porocyte openings. These findings support the hypothesis that the dynamics of water flow differs between clathrate and minute forms.

ISSN:1125-0003    

DOI:10.1080/11250009609356105

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The effects on animals feeding on resistant plants of widespread use of herbicides were studied. Aphids of the speciesSipha (Rungsia) maydisPasserini (Chaitophoridae) andSchizaphis graminumRondani (Aphididae), which feed on phloem sap of corn(Zea maysL.), were used as test‐organisms. Atrazine, an herbicide that acts via root absorption, is toxic to aphids, and this effect is manifest rather rapidly. In both aphid species was found rather severe tissue damage, which could be responsible for the death of animals. The most striking damage occurred in the digestive apparatus.

ISSN:1125-0003    

DOI:10.1080/11250009609356106

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper discusses the use of the ultrasound detector in research on bats, and introduces a system for analysing the bats’ sounds and identifying them from recorded calls. It also deals with the ‘ornithological approach’ by ‘ear identification’ pointing out the limitations and general problems of the acoustic method. The system proposes a standardizing of data collection when studying Chiroptera with an ultrasound detector.

ISSN:1125-0003    

DOI:10.1080/11250009609356107

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We studied the geographical variation of song in tawny owls, comparing temporal and frequency measures of the ≪hoot≫ in two races of the species (English and Italian) and in both adjacent and distant populations within each race. We found the two races differed significantly in five of the 13 parameters considered, duration of the second note, lowest frequency of the first note, and frequency modulation amplitude being the most important variables; Italian and English hoots were discriminated with a high success rate (86.7%). The seven populations also differed significantly from each other, particularly in the lowest frequency, but the overall rate of correct classification was lower (78.2%). Microgeographic variations between adjacent populations occurred in both countries: in general, the frequency measures varied through populations according to the habitat, being higher in open farmland and lower in dense woodland or urban habitats. A mosaic pattern of culturally transmitted hoot variations was therefore recognized, which might suggest the existence of dialects in the tawny owls.

ISSN:1125-0003    

DOI:10.1080/11250009609356108

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Osteological investigations of the Rivers Sava and Danube sampling of the bighead gobyNeogobius kessleriskull, pectoral girdle, and gill cover (50 characters) revealed values for some descriptive statistics parameters different from those obtained for the Dnjepar estuary population. Sexual dimorphism was not detected for any character. Certain characters of skull, suboperculum, praemaxilla, and hyomandibular were significantly different in particular length classes. Allometry was not detected. Multivariate analysis revealed that morphology of the biggest specimens is rather different from that of smaller ones. Overall, the results were consistent with a direct morphological formation through the bighead goby ontogeny. It was suggested that great variability in size classes, especially in the largest one, weakens their clear separation, and that the size component has a strong influence on the head skeleton shape.

ISSN:1125-0003    

DOI:10.1080/11250009609356109

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor