978 resultados para Xu, Zechun, 1787-1858.


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All the larval stages of the hermit crab Pagurus brevidactylus were studied in the laboratory, with special emphasis on external morphology and on the duration of each stage. The larvae were kept in individual containers, with water of 35 salinity and fed on nauplii of Artemia salina; room temperature was maintained at 24±1ºC. The post-embryonic development includes four stages of zoea and one of megalopa. All the larval stages are drawn and described in detail.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The leg exocrine gland was examined in two species of Neotropical termites. Scanning microscopy studies showed a set of pores on the ventral surface of the first and second tarsomeres in all legs of Serritermes serrifer. In Heterotermes tenuis these pores are present on a sunken plate in all castes. To date, this gland has been observed only in Rhinotermitid species. The presence of leg exocrine gland provides additional evidence supporting a close phylogenetic relationship between the Serritermitidae and Rhinotermitidae.

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The internal structure of three nests of Atta laevigata was studied in Botucatu city, São Paulo State, Brazil. Two nests were excavated through the opening of trenches and one was cement-moulded to enable a better view of the internal structures. The three nests presented a similar structure, with the depths and number of chambers varying as a function of the loose soil area of the nests. The number of chambers ranged from 1149 to 7864, reaching as deep as 7 m underground. Chamber volume ranged from 0.03 to 511. The foraging tunnels extended as far as 70m from the loose soil region. The nests of this species are the deepest within the genus Atta and have the highest number of chambers.

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The larval development of Pachygrapsus gracilis was studied in the laboratory under conditions of 25-degrees-C temperature and 20, 24, 28, 32 and 34 parts per thousand salinity. The objective of the study was to characterize the plankton phase of life of this species.

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Acquired immunity of horses to larvae, nymphs and adults of the Amblyomma cajennense tick was evaluated through three consecutive experimental infestations of tick-bite naive hosts. Data from these infestations were compared to those from field-sensitized horses and donkeys. It was observed that tick-bite naive horses developed a low level of resistance after two infestations as shown by a significant decrease in larval yield and a tendency for lower engorged weight of nymphs during third infestation. Ticks fed on field-sensitized horses had a similar biological performance to that observed on the third infestation of tick-bite naive horses but the mean engorged nymph weight was significantly lower than that of the first infestation from tick-bite naive horses. Donkeys presented the strongest resistance with significantly lower engorged weights of all instars and of the egg mass compared to the first infestation of tick-bite naive horses. Donkeys also displayed a significantly higher resistance than field-sensitized horses as demonstrated by significantly lower egg mass weights. Overall these results indicate that donkeys but not horses maintain a strong resistance to A. cajennense ticks. The importance of these findings in relation to vectoring of tick-borne diseases is discussed. (C) 2003 Elsevier B.V. All rights reserved.

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P>The Cayenne tick Amblyomma cajennense infests preferably horses in its adult form but other mammal species in its immature stages and is the main vector of Rickettsia rickettsii, the Brazilian spotted fever pathogen. As wooless lambs are often raised on pasture together with horses, an experiment was performed to investigate their possible acquisition of resistance to A. cajennense after experimental infestations. Seven naive wooless lambs were infested thrice at 60 days interval with immature and adult instars of A. cajennense from a laboratory colony, the tick biotic potential being determined and biopsies of tick bite lesions taken to investigate the inflammatory cell component. Nearly 100% of larvae died in all infestations, while nymphs and adults fed normally throughout re-infestations. Microscopic features of adult tick bite lesions revealed predominance of neutrophils (38%) and eosinophils (36.8%), respectively, in the first and second infestations. In the third infestation, 43.6% of MN cells were found and about 31% of eosinophils. on the other hand, nymph bite lesions revealed in all infestations a predominance of eosinophils, increasing from 36% in the first infestation to 50.5% in the third one. It is concluded that wooless lambs present remarkable innate resistance against larvae of A. cajennense, but marked susceptibility to the other tick instars despite the migration of great number of eosinophils to the tick lesion.

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A new characid species, Hemigrammus taphorni, is described from the Río Caura drainage, Venezuela. The new species is distinguished from its congeners by characters related to its color pattern, number of scale rows below the lateral line, teeth morphology, and dorsal-fin length. A brief discussion about the putative relationships of H. taphorni is provided. Copyright © 2007 Magnolia Press.

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The aim of this study was to discuss aspects of the diet of Serrasalmus maculatus. Fish were collected using gill nets, whose lengths measured 100 m and mesh diameters varied from 3 to 8 cm. A total of 107 individuals were collected. Their length varied from 62 to 210 mm. They were mainly represented by female and immature individuals. No individual was caught in temperatures below 21°C. Four feeding item categories were observed: fish muscle pieces, parts of fish fins, plant fragments, and insects. Comparisons made among individual length classes revealed some significant differences within stomach consumed contents. Individuals whose length exceeded 165 mm consumed only parts of fish muscles and plants. The food availability in the environment and the class lengths amplitude may, however, have influenced the results, in which ontogenetic differences should not be precisely observed.

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The present note reports the first record for Brazil of the cicada Zammara smaragdula Walker, 1858 (Hemiptera, Cicadidae, Zammarini). This new record brings the number of reported Cicadidae species for Brazil to 153, including three species in the genus Zammara. © 2011 Check List and Authors.

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Four colonies of the ant Pachycondyla striata were used to analyze the specie behavioral repertoire. Forty-six behavioral acts were recorded in laboratory. Here, we present the record the division of labor between the castes and the temporal polyethism of monomorphic workers. The queens carried out many of the behavioral traits recorded in this work however; they performed them less frequently compared to the worker. The workers activity involved chasing and feeding on fresh insects and usingthem to nourish larvae besides laying eggs in the C-posture, an activity also performed by queens, which is similar to that of wasps of the subfamily Stenogastrinae. The young workers were involved in activities of brood care, sexuate care, and nest maintenance, and the older workers were involved in defense, exploration, and foraging. © 2012 Adolfo da Silva-Melo and Edilberto Giannotti.