Thesis (MSc (Genetics))--University of Pretoria, 2005. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Group-living, within the Hymenoptera, is restricted to taxa in which females return to their nests repeatedly with food for their offspring (multiple provisioning), increasing the opportunities for helping (e.g. by guarding the nest). Some solitary wasps provide only one large prey item per cell (single provisioning). <i>Ammophila sabulosa</i> (Sphecidae) females provision half of their cells singly and half multiply. The costs and benefits of these two alternatives are compared in terms of : a. Total weight of prey (caterpillars) provided. b. Time taken to capture and transport prey. c. The probability of intraspecific theft of prey from cells. d. The incidence of parasitism by miltogrammine flies. There is no evidence that either strategy is more successful than the other. An advantage of flexible provisioning is suggested by a study of <i>Anoplius viaticus</i> (Pompilidae), females of which provision all cells singly with spiders. Despite provisioning prey of a smaller size range than does <i>Ammophila</i>, total prey weight in <i>Anoplius</i> cells is more variable and dependent upon seasonal changes in prey availability. <i>Ammophila</i> females steal caterpillars from each others' nests, and both they and <i>Anoplius</i> females brood-parasitize cells of conspecifics. Intraspecific parasitism as an alternative nesting strategy is discussed and compared with work on other solitary wasps. Patterns of resource utilization are documented for the guild of spider-hunting pompilid wasps at one site. Data were collected on : a. Microhabitat utilization. b. Seasonal occurrence. c. Female size distributions. d. Prey species and sizes. Observed patterns of utilization and overlap are compared with 'neutral' models of guild structure in which various aspects of the species x resources utilized matrix are randomized. Some of the results are consistent with the idea that interspecific competition has partly determined pompilid guild structure, but problems of methodology and interpretation are discussed.

No description available.

No description available.

No description available.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 159-165).

Branched actin networks play an important role in cellular processes ranging from cell motility, endocytosis, and adhesion. The Actin-related protein 2/3 (Arp2/3) complex nucleates actin branches from the sides of existing actin filaments. Arp2/3 complex is highly regulated and requires association with ATP, actin monomers, actin filaments and a class of proteins called nucleation promoting factors (NPFs) to undergo an activating conformational change where the actin-related subunits, Arp2 and Arp3, arrange into a filament-like conformation that templates a new actin branch. While some progress has been made, the individual roles of each of these factors on the activating conformational change is poorly understood. In addition, it is still unclear how Arp2/3 complex is held in its inactive state, which is vital for understanding how activation occurs. In this dissertation, we dissect key interfaces in Arp2/3 complex that are responsible for holding it in an inactive state, and specifically evaluate the roles of ATP and WASP, the canonical NPF, in the activating conformational change of Arp2/3 complex. In chapter II, we investigated the contacts made between the Arp2 and Arp3 subunits in their inactive state, and the role of ATP in stimulating the active conformation. We found that two key interfaces, the αE/αF loop in Arp2 and the C-terminus of Arp3, a conserved extension not present in actin, are vital for holding Arp2/3 complex in its autoinhibited state. Evaluation of the role of ATP demonstrated that binding of ATP is required for the activating conformational change and displaces the Arp3 C-terminus, an important step in destabilization of the inactive state. In chapter III, we investigated the mechanism of WASP-induced conformational changes using an engineered crosslinking assay that only forms crosslinks when Arp2/3 is in its active conformation. We discovered that many WASP-related proteins are capable of stimulating this conformational change through a mechanism that involves displacement of the Arp3 C-terminus. Interestingly, purified Arp2/3 complex crosslinked in the active conformation was hyperactive compared to WASP-mediated activation, demonstrating that WASP activation limits nucleation and that actin monomer delivery is not required for nucleation. This dissertation contains unpublished co-authored material.

Orientador: Sulene Noriko Shima / Banca: Edilberto Giannotti / Banca: Sidnei Mateus / Resumo: As vespas são um excelente modelo para se tentar compreender a evolução do comportamento social nos Hymenoptera. A biologia e a organização social das vespas eussociais primitivas, em especial o gênero Mischocyttarus, são pouco conhecidas, apesar da grande diversidade de espécies desse gênero nos trópicos. Com o objetivo de identificar os mecanismos envolvidos na regulação social de Mischocyttarus cerberus styx, foram coletadas 6 colônias com histórico comportamental das fêmeas conhecidas, para a análise da morfofisiologia dos indivíduos, no Câmpus da Unesp de Rio Claro, SP. Foi verificado que a dinâmica hierárquica desta espécie é regulada através de uma estratégia que relaciona comportamento de manutenção da colônia ao gasto energético diferencial. Os indivíduos mais dominantes tendem a permanecer mais tempo no ninho, construir mais células e apresentam balanço energético positivo. Através desses mecanismos, a hierarquia é regulada de forma dinâmica, de maneira a permitir que qualquer indivíduo possa ocupar diferentes papéis dentro da colônia, uma vez que, como verificado, os adultos demonstram capacidades reprodutivas similares e não apresentam diferenças morfológicas significativas entre as castas. A determinação das suas funções na colônia dependerá, portanto, das estratégias comportamentais acima descritas / Abstract: The wasps are an excellent model to try itself to understand the evolution of the social behavior in the Hymenoptera. The biology and the social organization of the primitive eusociais wasps, in special the Mischocyttarus genus, little is known, although the great diversity of species of this genus are in the tropics. The objective of this work is identify to the involved mechanisms in the social regulation of Mischocyttarus cerberus styx, had been collected 6 colonies with behavior description of the known females, for the analysis of the morfophysiology of the individuals, in the Campus of the UNESP - Rio Claro, SP. It was verified that the hierarchic dynamics of this species is regulated through a strategy behavior of maintenance of the colony and the distinguishing energy expense. The individuals most dominant tend to remain more time in the nest, to construct more cells and present positive energy balance. Through these mechanisms, the hierarchy is regulated of dynamic form, way to allow that any individual can inside occupy different works in the colony, in such a way, the adults demonstrate similar reproductive capacities and they do not present significant morphologic differences between the cast ones. The determination of its functions in the colony will depend, therefore, of above described the behavior strategies / Mestre

Made available in DSpace on 2014-06-11T19:30:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-30Bitstream added on 2014-06-13T18:40:13Z : No. of bitstreams: 1 silva_rm_me_rcla.pdf: 1162202 bytes, checksum: 846ac38f3ba6ac45f0a1d9d936aaad33 (MD5) / Universidade Estadual Paulista (UNESP) / As vespas são um excelente modelo para se tentar compreender a evolução do comportamento social nos Hymenoptera. A biologia e a organização social das vespas eussociais primitivas, em especial o gênero Mischocyttarus, são pouco conhecidas, apesar da grande diversidade de espécies desse gênero nos trópicos. Com o objetivo de identificar os mecanismos envolvidos na regulação social de Mischocyttarus cerberus styx, foram coletadas 6 colônias com histórico comportamental das fêmeas conhecidas, para a análise da morfofisiologia dos indivíduos, no Câmpus da Unesp de Rio Claro, SP. Foi verificado que a dinâmica hierárquica desta espécie é regulada através de uma estratégia que relaciona comportamento de manutenção da colônia ao gasto energético diferencial. Os indivíduos mais dominantes tendem a permanecer mais tempo no ninho, construir mais células e apresentam balanço energético positivo. Através desses mecanismos, a hierarquia é regulada de forma dinâmica, de maneira a permitir que qualquer indivíduo possa ocupar diferentes papéis dentro da colônia, uma vez que, como verificado, os adultos demonstram capacidades reprodutivas similares e não apresentam diferenças morfológicas significativas entre as castas. A determinação das suas funções na colônia dependerá, portanto, das estratégias comportamentais acima descritas / The wasps are an excellent model to try itself to understand the evolution of the social behavior in the Hymenoptera. The biology and the social organization of the primitive eusociais wasps, in special the Mischocyttarus genus, little is known, although the great diversity of species of this genus are in the tropics. The objective of this work is identify to the involved mechanisms in the social regulation of Mischocyttarus cerberus styx, had been collected 6 colonies with behavior description of the known females, for the analysis of the morfophysiology of the individuals, in the Campus of the UNESP - Rio Claro, SP. It was verified that the hierarchic dynamics of this species is regulated through a strategy behavior of maintenance of the colony and the distinguishing energy expense. The individuals most dominant tend to remain more time in the nest, to construct more cells and present positive energy balance. Through these mechanisms, the hierarchy is regulated of dynamic form, way to allow that any individual can inside occupy different works in the colony, in such a way, the adults demonstrate similar reproductive capacities and they do not present significant morphologic differences between the cast ones. The determination of its functions in the colony will depend, therefore, of above described the behavior strategies

No description available.