摘要:

The ultrastructure of the spore wall ofEncephalitozoon cuniculiwas studied using thin sections, freeze‐fracture and quick‐freezing deep‐etching techniques. The exospore was found to be very complex and to consist of three layers: an outer spiny layer, an intermediate electronlucent lamina and an inner fibrous layer. The intermediate lamina and the inner fibrous layer apparently are fibrillar. The spore wall is known to be chitinous and its fine structural appearance shows some structural similarities to other chitin containing structures.

ISSN:1125-0003    

DOI:10.1080/11250009709356166

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Gigaseals were obtained from enzymatically dissociated epithelial cells ofHydra vulgaris, and resting potentials were recorded in the whole‐cell configuration. These results were obtained in spite of hard difficulties of applying patch‐clamp techniques in the whole‐cell configuration toHydracells. These difficulties are principally inherent to the fact thatHydralives in a low ionic strength medium. It will be now possible to apply patch‐clamp techniques to the study ofHydraextraocular photoreception.

ISSN:1125-0003    

DOI:10.1080/11250009709356167

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A comparative survey of sensory organs (mainly visual) of 35 species of crustaceans (Mysidacea, Stomatopoda and Decapoda) was initiated in the SE Gulf of California, Mexico, an enclosed sea which has been well studied for its physical conditions and the taxonomy of crustacean species. The purpose of this survey was to study how the perceptive capacities are conditioned by the signals arriving from their environment. Studied species were sampled from terrestrial, intertidal, subtidal and deep sea habitats. Our data indicate that down to 200 m there seems to be not much difference of skewing patterns in stomatopods. Eyes are adapted to local conditions. In crabs and stomatopods, ommatidia are aligned in a vertical array along the longer axis of the eye. Visual fields of ommatidia overlap. This could emphasize, for instance, the horizontal motion of vertical edges. Deep‐sea crustaceans still have eyes, but in the same habitat species with apparently functional eyes occur together with species with strongly reduced eyes. When eyes are reduced, nervous structures are still observable but not ommatidia. Almost all species studied have extra‐organs in the eye. These are mechano‐(crabs) or chemo‐ (deep‐sea crustaceans) receptors or else organs which seem to have a specific (e.g. adaptation) visual task (shrimps). All extra‐organs have small ganglia and nerves contacting the visual ganglia on their way towards the brain.

ISSN:1125-0003    

DOI:10.1080/11250009709356168

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The genetic differences in 32 populations ofHydropsychebelonging to nine species distributed in Sicily, and central and southern Italy were assayed by horizontal starch gel electrophoresis. Larval specimens were examined. Twelve enzyme loci were assayed and allele frequencies, variability parameters, and Nei's genetic distance were calculated. The percentage of polymorphic loci ranged from 8.3 to 50.0%, the mean number of alleles per locus from 1.1 to 1.8, and the mean observed heterozygosity from 0.009 to 0.123. Nei's genetic distances values between conspecific populations ranged from 0 to 0.096; in the comparison between populations from Sicily and Calabria,H. doehlerihad the highest values. Only forH. spiritoithere were differences among the Sicilian populations. From genetic distance data, a dendrogram was obtained. At interspecific level, the values of genetic distance between conspecific populations ranged from 0.201{H. spiritoi ‐ H. gereckei)to 1.135(H. dinarica ‐ H. klefbecki). Genetic data were in agreement with morphological data.

ISSN:1125-0003    

DOI:10.1080/11250009709356169

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Genetic variation in samples of the endemicCrocidura siculaliving in Sicily and in two surrounding small islands, Marettimo and Ustica, was analysed by Random Amplified Polymorphic DNA fingerprinting (RAPD) and compared to morphometrics and external phenotypes. Molecular variation in the random sample of 99 DNA fragments of the Ustica shrews, showing.a melanic fur and a size‐shape variation in skull morphometrics, is of comparable size to that of the of northwestern and northeastern samples Sicily (Tufanio and Madonie). In the Marettimo shrews, bicoloured (grey and white) animals like those coming from Sicily and presenting a significant reduction in body‐size and skull morphometrics, molecular differentiation is higher than in those of the other locations, and characterizes this geographic population. Considering the paleogeographic records, it is hypothesized that the Marettimo shrews must have been isolated longer from the mother‐island; whereas for the Ustica shrews, a more recent arrival/isolations presumed. The RAPD results proved to be consistent with this reconstruction of theC. siculabiogeography. The Marettimo population, as opposed to that of Ustica, can thus be considered ‘one step further’ on the road of the speciation process. Melanism in the more recently isolated Ustica population does not parallel genetic differentiation and could emerge as an answer to the very strong selection and ecological adaptation in that volcanic insular environment. In any case, each population living in these two small islands off Sicily shows an independent evolutive divergence.

ISSN:1125-0003    

DOI:10.1080/11250009709356170

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Several newly‐mated females of the European slave‐making antPolyergus rufescensusually participate in slave raids and penetrate together the same target colony. This fact could result in a pleometrotic colony foundation. In the laboratory, two newly‐mated females ofP. rufescenswere introduced simultaneously into queenright artificial colonies ofFormica cunicularia, the slave species present in the natal dulotic nest. The experiments were carried out using artificial colonies of two kinds: ‘simple’ (a nest connected with a foraging arena) and ‘complex’ (a simple colony connected with an empty nest serving as a flight‐chamber). In both cases, the two parasitic females never cooperated in attacking and killing theFormicaqueen. In fact, only one of the two was able to obtain adoption by the resident workers, the other being killed by them. Egg‐laying by the usurping queens was observed the following spring, and in the summer new mixed colonies developed: this is the ultimate criterion for looking upon colony foundation by the parasite as successful. In our experiments, pleometrosis did not occur and the dependent mode of colony foundation typical ofP. rufescensled to a primary monogyny.

ISSN:1125-0003    

DOI:10.1080/11250009709356171

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We characterized the trophic niche of two syntopic owl species, barn owl(Tyto alba)and little owl(Athene noctua), which inhabit rice field and water‐meadow habitats of northern Italy. Small mammals were the most important prey category for barn owls with 84% of prey, while invertebrates (primarily insects) accounted for approximately 55% of little owl prey. Small mammals were the staple food of both predators in terms of relative biomass of prey. Barn owls preyed upon larger rodent species (common rats, water voles), whereas little owls concentrated their hunting pressure on wood mice, a medium‐sized rodent. Mean weight of small mammals ingested by barn owls (37.7 g) was considerably greater than that by little owls (22.3 g). Dietary width was significantly greater in little owl than barn owl diet (2.2vs1.4), although the reverse was true for that of width in relation to small mammal prey (8.5 for barn owlsvs4.7 for little owls). Niche overlap was considerably high (GO = 0.94), but not complete.

ISSN:1125-0003    

DOI:10.1080/11250009709356172

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Data obtained in three‐year field study on a Mediterranean prey‐predators community in central Italy are discussed. In particular, the aim of this paper was to test whether some parameters linkedto themorphology, phylogenesis and habitat preferences of a given potential prey could affect its predatory exposure. Eight predator species belonging to two different guilds (snakes and owls) were found at the study area, while ten preyed small mammal taxa were recognized in predator diets. One of the main factors emerging from this study was the great importance of body mass similarity in assessing the degree of overlap of predatory exposure between two small mammal taxa. On the contrary, the phylogenetic relationship between prey was of very little importance, probably because each phylogenetic group is composed by different potential prey species living in different habitats. In conclusion, due to the apparent lack of importance in the overlap of habitat preferences between the various prey in the overlapping of their predatory exposure, it could be stressed that the body mass similarity can be said to play the most relevant role in determining the overlap of predator community, exerciting a selective pressure on two different preyed taxa, and their effective predation risk.

ISSN:1125-0003    

DOI:10.1080/11250009709356173

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A new species of the genusClionaGrant is described from the Ionian Sea (Eastern Mediterranean).Cliona parenzanisp. n. is characterized by an encrusting or massive shape and a spiculation consisting of robust tylostyles, together with spiny and smooth‐spirasters. The new species is very close to the group of related speciesC. nigricans(Schmidt),C. viridis(Schmidt), andC. copiosaSara from which it mainly differs by the occurrence of reduced spirasters that lost their spines.

ISSN:1125-0003    

DOI:10.1080/11250009709356174

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Two monocelidid species from eastern Australia are described.Necia boreoceloidesn. sp. is characterized by an extremely elongated, adhesive tail, and further distinguished from the only known congeneric species by details of the reproductive system. A Gondwanian origin of the genusNeciais proposed.Pseudomonocelis hoplitesn. sp. differs from congeneric species by the presence of an accessory organ provided with a stylet. The definition of the genusPseudomonocelisis accordingly modified.

ISSN:1125-0003    

DOI:10.1080/11250009709356175

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor