摘要:

Karyotypic analysis was performed in two male specimens of Sphiggurus villosus collected in the Atlantic Forest of Rio de Janeiro State, Brazil. The observed 2n = 42 / FN = 76 karyotype was similar to those of other Erethizontidae such as Erethizon dorsatum and Sphiggurus vestitus and to hystricomorph rodents like Myocastor coypus. Current karyotypic data showed that two species of the genus Coendou share the same diploid and fundamental numbers (2n = 74 / FN = 82) but 3 Sphiggurus species differ in diploid number while sharing the same fundamental number.

ISSN:0165-0521    

DOI:10.1076/0165-0521(200008)35:2;1-9;FT081

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In a transition zone between Andean forests and Patagonian steppe, local populations of five sympatric species of sigmodontine rodents (Abrothrix longipilis, A. xanthorhinus, Eligmodontia morgani, Oligoryzomys longicaudatus, Reithrodon auritus) were examined for their microhabitat use. The study area represents a herbaceous steppe with sparse bushes. Over a four-year period, monthly samples were obtained by baited traps. The vegetation cover at each trapsite was monitored. The capture frequency in a particular microhabitat turned out to be strongly correlated with the local vegetation cover. This result is interpreted as a species-specific selection at a fine spatial scale of those microsites which resemble the characteristic environment in the area of main biogeographic occurrence of each of the rodents. The data on preferential microhabitat use might gather importance considering that two of these sigmodontine species are Hantavirus reservoirs.

ISSN:0165-0521    

DOI:10.1076/0165-0521(200008)35:2;1-9;FT085

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The diet of Crested Bobwhite (Colinus cristatus, Phasianidae) in a non-flooded savanna located in central-eastern Venezuela was studied. Food items obtained from crops were sorted, counted, and identified mostly to species level. Birds are omnivorous and their diets comprised mostly seeds, some invertebrates, and green vegetation; besides, they consumed snail shells during the breeding season. Seeds dominated in the diet during most of the year but the relative use of seeds, invertebrates, and green vegetation changed seasonally. Some management guidelines in order to increase the abundance of this important game bird in neotropical savannas are proposed.

ISSN:0165-0521    

DOI:10.1076/0165-0521(200008)35:2;1-9;FT091

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Seasonal parameters of infection by the nematode Contracaecum rudolphii in the Neotropic cormorant Phalacrocorax brasilianus (Phalacrocoracidae) and their relation with feeding and infection in fishes from River Valdivia, Chile, were determined. The prevalences of infection in birds were similar during seasons, whereas mean intensity and percentages of adult gravid females were higher in spring and summer, respectively. For fishes no seasonal differences were found in infection. Cormorant diet varied seasonally in relation to fish prey consumed and this can be related to seasonal differences in infection parameters of birds. The high infection in birds should be considered as a potential risk for salmoniculture.

ISSN:0165-0521    

DOI:10.1076/0165-0521(200008)35:2;1-9;FT101

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The symphoretic relationship between a species of Nanocladius (Plecopteracoluthus) (Diptera, Chironomidae) and Kempnyia tijucana (Plecoptera, Perlidae) is recorded and described for the first time from southeastern Brazil. About 31% of the collected perlids were hosts of the chironomid larvae. The entire larval cycle of N. (Plecopteracoluthus) sp. may be completed on a single instar of K. tijucana and the larval position on the host varied according to the stage of development of the chironomid, apparently being constant for young and old instars.

ISSN:0165-0521    

DOI:10.1076/0165-0521(200008)35:2;1-9;FT109

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

About 9,000 individuals of sap-sucking and leaf-chewing insects, representing 345 species, were collected from 10,000 seedlings belonging to 5 rainforest tree species in an unlogged forest in Guyana. For the 40 most common species, it was possible to estimate their host specificity, diurnal activity, seasonal distribution, spatial aggregation, abundance and body weight. Most species were generalists but more specialised species tended to show a higher spatial aggregation, a more restricted diurnal activity and a higher seasonality. Although insect abundance was highest at the onset of the long wet season in May, seasonal amplitude was not pronounced. The combined effects of host and rainfall explained 14.5% of the total variance in insect seasonality, which was poorly explained by the leaf production of seedlings. The spatial distribution of insects was often aggregated and, overall, explained by host effect, production of young foliage, number of conspecific trees within a radius of 50m, and number of dead seedlings at each collecting station. However, these variables explained only 7% of the variance in spatial distribution. The lack of notable influence of leaf production and other important variables recorded at the collecting stations suggests that the seedlings represent a marginal food resource for most of the insect species collected.

ISSN:0165-0521    

DOI:10.1076/0165-0521(200008)35:2;1-9;FT115

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The mounds of ant nests have been characterized as structures that facilitate the colonization of habitats subject to extreme temperatures. My objective was to investigate the importance of the mound of Acromyrmex lobicornis (Formicidae, Attini) in this process. In the most climatically rigorous environment that this ant genus lives (northwestern Patagonia), I determined (1) the temperature range within Acromyrmex lobicornis nest-mounds, (2) the influence of mound damages on the mortality or abandonment rate of Acromyrmex lobicornis nests, and (3) compared, from the existing literature, the distribution limits between the species of Acromyrmex that do and do not construct mounds. The mounds of A. lobicornis function as 'thermal buffers' by diminishing the effects of external thermal variations, and previous mound damage increased mortality or abandonment only of colonies with nest mounds constructed on bare ground. Mounds constructed on tussock plants increased their diameter faster and recovered better from perturbations. This may be due to the structural support of plant stems facilitating repair. At a larger scale, the species of Acromyrmex with mounds have more southerly range limits than species that do not construct mounds, indicating an important function of this nest structure for the colonization of temperate environments.

ISSN:0165-0521    

DOI:10.1076/0165-0521(200008)35:2;1-9;FT131

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Numbers of described families, genera, and species (as well as estimations of existing species) are given for all taxa which represent the Arachnida and Myriapoda world-wide and in Amazonia.

ISSN:0165-0521    

DOI:10.1076/0165-0521(200008)35:2;1-9;FT139

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The complete larval development of the shallow-water Caribbean porcellanid crab, Petrolisthes politus (Gray, 1831), is described and illustrated from specimens reared in the laboratory. Petrolisthes politus hatches as a prezoea, which persist for less than 90 minutes, and then molts through two subsequent zoeal stages, which are completed in 6 to 7 and 14 to 16 days, respectively, before the megalopal stage is reached. From a total of about 2000 zoeae that were cultured, only two reached the megalopal stage. The two megalopae survived for up to 5 days but did not molt to the first crab stage. The zoeae of P. politus are compared with those of Petrolisthes rufescens (Heller, 1861), Petrolisthes lamarckii (Leach, 1820), Petrolisthes carinipes (Heller, 1861), Petrolisthes coccineus (Owen 1839) and Petrolisthes pubescens (Stimpson, 1858), which were hitherto the only species having bifid lateral spines on the telson of the first zoeal stage.

ISSN:0165-0521    

DOI:10.1076/0165-0521(200008)35:2;1-9;FT143

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A new rotifer is described and figured based on females taken from Comprida lagoon, Rio de Janeiro State, in southeastern Brazil. This new animal belongs to the Genus Macrochaetus which includes several species recorded in South America. A key to species of the Genus Macrochaetus of the Neotropical Region is presented.

ISSN:0165-0521    

DOI:10.1076/0165-0521(200008)35:2;1-9;FT157

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor