摘要:

Zosterisessor ophiocephalusis a large, nest guarding goby which breeds within horizontal burrows excavated by males in the muddy bottom of the coastal shallow, brackish waters of the Italian northern Adriatic. Females spawn their eggs attaching them to the downhang‐ingZosterasp. roots. The present study reports the first successful attempt of rearing this species under laboratory conditions from fer tilized eggs to bottom dwelling juveniles. We describe embryonic and larval development in order to identify age stages and diagnostic features to be compared with other Mediterranean goby species. Lar val behaviour is also observed. Embryonic development is com pleted within 8 d at 18° C. At hatching, the yolk‐sac larva is positive phototactic, has an open mouth and visible swimbladder. The first exogenous feeding on rotifers occurs at day 2 post‐hatching, while yolk sac absorption and the negative phototaxis are at day 4. Defined patterns of melanophore distribution characterize and differentiate the yolk sac stage from equivalent ones reported for other Medi terranean species. Larvae metamorphose into juveniles at day 13 when all the fins appear. They feed onArtemiaand show an in creased growth rate. At day 26, the juvenile bodies become com pressed dorso‐ventrally. The juveniles shift to benthic habits and can be fed on artificial feed pellets. At day 82, the final body shape and colour patterns are acquired and territorial behaviour is displayed.

ISSN:1125-0003    

DOI:10.1080/11250009709356197

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The previtellogenetic stages of oogenesis were analysed at the morphocytological level in three species of Nototheniidae and two of Channichthyidae collected in the Ross Sea near the Terra Nova Sound. The aim was to determine whether specific adaptations have occurred in these Antarctic species in response to the particularly severe environmental conditions of their habitat. The data obtained indicate that the previtellogenetic stages of oogenesis in all five species are similar to those observed in other fishes and vertebrates. The observations also reveal the existence in the oocyte cytoplasm of large inclusions of ribonucleoprotein showing a peculiar ultrastructural organization. This finding reinforces the hypothesis that the process of adaptation of notothenioids to the Antarctic seas has involved predominantly ecological diversification.

ISSN:1125-0003    

DOI:10.1080/11250009709356198

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A biochemical‐genetic analysis was carried out on five samples of three species ofLeuciscus, to verify the genetic divergence between PadanianL. cephalusandL. souffiaand to unravel the taxonomic status of aLeuciscuspopulation preliminarly reported asLeuciscussp., collected from the Adriatic drainage basins and morphologically related toL. lucumonis, a recently described taxon of the Tyrrhenian basins. Both isozymic data on 25 loci and total protein analyses identifiedLeuciscussp. asL. lucumonisand showed the high genetic divergence and polymorphism ofL. souffiawith respect toL. cephalusandL. lucumonis. This study confirms thatL. lucumonisis a valid species that inhabits also Adriatic drainage basins and provides conclusive evidence that it is not originated by hybridization. In addition, genetic data fully support the hypothesis of a sharp divergence ofL. souffiafrom congeneric taxa.

ISSN:1125-0003    

DOI:10.1080/11250009709356199

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

InTriturus carnifex, the mechanism of respiratory compensation which regulates the quantity of circulating erythrocytes according to the environmental conditions is already active in larvae at Glücksohn's stage LXI. Larvae anesthetized with chlorbutol and kept at 27° C for 25 min show red blood cell (RBC) counts slightly below 70 000/mm3and hematocrit values around 17, while those kept at 6° C for 100 min ‐ the time necessary for the heart to beat the same number of times as at the former temperature ‐ show significantly lower values (P < 0.01): about 40 000 RBC/mm3and a hematocrit of 11. The percentage mass and histology of the spleens removed from specimens frozen in liquid nitrogen immediately after testing show that this organ is the site where excess erythrocytes are stored. Tests at 18° C show that, though the voluntary movements of the anesthetized larvae are completely blocked, their gills still move rhythmically, which prevents them from going into hypoxia in stagnant water as, instead, occurs in adults.

ISSN:1125-0003    

DOI:10.1080/11250009709356200

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The aim of the research presented here was to determine whether low concentrations (1 μg/ml) of a highly specific microtubule depolymerizing agent, nocodazole (NOC), affects the meiosis ac tivation process in conjugating pairs of the ciliated protozoanBlepharisma japonicum. In order to identify and quantify differen ces in meiosis, both NOC treated and untreated coeval pairs were stained and examined for their meiotic phases. A clear‐cut delay in the progression of meiosis in treated pairs was found. The findings indicate that NOC reversibly inhibits meiosis induction and that treated pairs need both continuous cell union and a period of recovery in order to progress through meiosis after NOC is with drawn. These results suggest that cytoplasmic microtubule dynamics may be involved in the meiotic activation processs ofBlepharismaconjugating pairs.

ISSN:1125-0003    

DOI:10.1080/11250009709356201

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The present paper deals with the genetic relationships between the two oldest Italian fallow deer populations (Castelporziano and San Rossore) in order to investigate their origin, and to verify their status and variability in the light of the genetic consequences of human selection through historical times. The analysis, performed using the RAPD fingerprinting technique, confirms the low variability of the San Rossore fallow deer, and reveals the Castelporziano population characterised by an unexpected higher rate of variability.

ISSN:1125-0003    

DOI:10.1080/11250009709356202

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Polyacrylamide gel electrophoresis was used to assess genetic variability and differentiation at 40 gene loci in 102 roe deer from five sampling sites in the province of Siena, central Italy. Eight loci proved to be polymorphic in at least one population. Averaged over populations, values of expected heterozygosity (mean He = 0.044, SD = 0.007) and the proportion of polymorphic loci (mean P = 0.135, SD = 0.028) were as high as those found for roe deer of southern and central Europe. In spite of a moderately high level of gene flow between sites (Nm = 4.7), the existence of some degree of genetic structuring in the whole population of Siena could be demonstrated. Demographic events (i.e., restocking, bottlenecks), rather than genetic isolation were explained to be responsible for the differences in allele frequencies found among populations. The allochthonous origin of roe deer living on Mount Amiata could be proved by genetic data. The results are discussed in the light of historical and demographic information on this species in the province.

ISSN:1125-0003    

DOI:10.1080/11250009709356203

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Pied flycatchers were tested twice at sunset under a clear sky, a clear sky with moon, and under artificial overcast conditions. The mean spring direction was W‐NW, with a higher westward bias than in previous tests performed in complete darkness. The activity of single tests was high but their directionality was low, with an inverse correlation between activity and directionality. Under clear skies (with or without moon) the distribution of birds performing a test for the first or second time was not different, with high consistency of individual birds, while in overcast conditions second tests shifted southwards, seemingly a phototactic reaction. Under clear skies (with and without moon), in the second test individual vector lengths increased and there was no correlation between individual activity and vector value, indicating an improvement of the perform ance; in contrast, in second overcast tests vectors tended to decrease and the negative correlation activity/vector was significant. So, although the mean direction was not different from the clear sky, the individual performance was worse in overcast conditions, probably due to a decrease in motivation to migrate during prolonged overcast conditions.

ISSN:1125-0003    

DOI:10.1080/11250009709356204

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The species assemblages of benthic ciliates from two adjacent locations at a sandy shore of the Ligurian Sea (Italy) are examined and compared. The environmental conditions are very similar, ex cept that one location is more exposed to hydrodynamic disturban ce than the other. Sediment samples (168 sandy samples from each station) for the identification and enumeration of ciliates were collected following a multifactorial sampling design under three dif ferent conditions: (1) a moderately perturbed spring‐ summer period; (2) an unusual one‐month‐long calm in spring; (3) an autumn‐winter period. Both stations showed a rich and well‐structured ciliate microcommunity. During the spring‐summer period, charac terized by highest ciliate density, 42 species, belonging to 27 genera, and 33 species belonging to 18 genera were found at the sheltered and exposed station, respectively. During this period, the exposed station harbours only a sub‐set of the ciliate assemblage living in the sheltered one. The two ciliate communities differ significantly in abundance, species diversity, and patch frequency with the sheltered station yielding higher values. All such differences disap pear after a month of calm conditions and during the autumn‐winter period.

ISSN:1125-0003    

DOI:10.1080/11250009709356205

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A study was undertaken to define the benthic populations, the environmental‐ecological variability and trophic aspects according to the functional feeding groups in the upper reaches of the Nera River, a tributary of the Tiber, in central Italy. A total of 12 681 individuals was collected and 83 taxa were identified; 11 proved to be endemic for Italy, 7 of them typical of the central Apennines. The greatest number of taxa (58), and the highest values of diversity were recorded at the lowest sampling station, 37 km from the source. A dendrogram constructed by the UPGMA method based on values of similarity revealed two main clusters, one identified withcrenon(at the source) and the other withrhithron(the downstream stations) fluvial typology. Correspondence analysis on the environmental matrix parameters confirmed this finding. Taxa abundance was evaluated by grouping the individuals collected into classes using semi‐quantitative sampling. The results of trophic‐functional analysis, calculated on the basis of the estimated abundance and tested with statistical methods, agreed with fauna composition analysis clusters for the filtering collector and shredder categories. The zonal and clinal patterns reveal that there may be a weak upstream to downstream gradient within a single fluvial zone and almost discontinuity in contiguous tracts when the abiotic gradient changes suddenly.

ISSN:1125-0003    

DOI:10.1080/11250009709356206

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor