No description available.

No description available.

No description available.

Pomacea canaliculata es un gasterópodo de agua dulce perteneciente a la familia Ampullariidae (Architaenioglossa, Caenogastropoda), cuyo rango de distribución natural abarca desde el sur de Brasil hasta el sur Bonaerense. Se lo considera uno de los 100 peores invasores a escala global debido a su voracidad, altas tasas reproductivas y alta plasticidad en su ciclo vital. El objetivo principal de este trabajo de tesis fue estudiar la norma de reacción de diversas características del ciclo vital de P. canaliculata frente a la disponibilidad trófica. Específicamente se estudió cómo afectan distintos niveles de disponibilidad trófica constantes, el crecimiento, la talla y la edad a la que alcanzan la madurez, la cantidad de recursos que destinan a la reproducción y la forma de su conchilla. Finalmente, se estudió el efecto de una interrupción abrupta en la alimentación sobre la reproducción, el crecimiento y la supervivencia. Los resultados mostraron una superioridad en los parámetros específicos de ingestión y eficiencia de crecimiento de las hembras respecto de los machos y en los juveniles respecto de los adultos. P. canaliculata puede completar normalmente su ciclo vital bajo un amplio rango de disponibilidades tróficas. Frente a distintas disponibilidades tróficas la estrategia de las hembras fue madurar a distintas edades y a una talla semejante, mientras que en los machos fue madurar a edades semejantes pero a tallas muy distintas. La disponibilidad trófica no afectó el éxito reproductivo de los machos, mientras que en las hembras las restricciones en la disponibilidad trófica provocaron descensos, principalmente en el número de huevos. En caracoles en reproducción, un corte abrupto de la alimentación redujo la supervivencia más en machos que en hembras, y produjo una caída en el número de cópulas y de puestas. Un efecto maternal en el cual el vigor de la progenie de hembras que crecieron con baja disponibilidad trófica se incrementa respecto de las hembras sin restricciones alimentarias parece indicar una estrategia adaptativa transgeneracional. La forma de la conchilla parece cambiar en algún grado con la disponibilidad trófica pero sin ningún patrón claro y monótono; el dimorfismo sexual no parece verse alterado por la disponibilidad trófica. Aparecen indicios que sugieren que el contenido de nitratos del agua y la materia orgánica del sustrato en ambientes naturales tienen relación con parámetros poblacionales como la densidad de puestas y la talla máxima de P. canaliculata; por el contrario, los iones inorgánicos y los factores fisicoquímicos analizados no mostraron relación con éstos. La estrategia evolutiva de Pomacea canaliculata frente a la disponibilidad trófica parece basarse en una alta plasticidad de su ciclo vital, abarcando el crecimiento, la maduración y el esfuerzo reproductivo, así como en un alto grado de diferenciación sexual en estas características. / Pomacea canaliculata is a freshwater snail belonging to the family Ampullariidae (Architaenioglossa, Caenogastropoda) whose natural range extends from Southern Brazil to Southern Pampas in Argentina. It has been nominated as one of the 100 worst invaders at a global scale, owing to its voracious feeding habits, high reproductive rates and plastic life history traits. The main aim of this Thesis was to study the reaction norms to trophic availability of several life history traits in P. canaliculata. Specifically, the way in which growth, age and size at maturity, reproductive effort and shell shape are affected by different chronic levels of trophic availability was investigated. In addition, the effect of an abrupt shortage of food on reproduction, growth and survivorship was investigated. The results obtained showed higher values of specific parameters of ingestion and growth efficiency in females than in males and in juvenile snails relative to adults. P. canaliculata is able to complete its life cycle under a wide range of trophic availability. Confronted with different trophic availabilities, the strategy of females was to mature at different ages but always at almost the same size, whereas for males it was to mature at the same age but at very different sizes. Trophic availability did not affect the reproductive success of males while for females restricted trophic availabilities caused a drop mainly in the number of eggs laid. For snails which were already in reproductive state, an abrupt shortage of food reduced the survivorship of males in a higher degree than in females and a drop in the number of copulations and egg masses laid. A maternal effect, in which the progeny of females grown under low trophic availabilities showed a higher vigor than those from females fed ad libitum, suggests a transgeneration adaptive strategy. Shell shape seems to be affected by trophic availability though without producing a clear and monotonous pattern; sexual dimorphism seems not to be affected by trophic availability. The nitrate content of water and the organic matter of sediments seem to be related to demographic parameters of P. canaliculata, like density of egg masses and maximum sizes; on the other hand, inorganic ions and physicochemical variables did not show any relation with them. The evolutionary strategy of Pomacea canaliculata relative to trophic availability seems to be based on a high plasticity in life history, including growth, maturity and reproductive effort, and on a high degree of sexual differentiation in these traits.

O Estado da Bahia corresponde 35% da área total do nordeste brasileiro, abrangendo 417 municípios. Vários espécimes de moluscos terrestres e dulciaquícolas na coleção de Malacologia do Museu de Zoologia da Universidade de São Paulo (MZSP, São Paulo, Brasil) foram coletados em municípios pertencentes a mesorregião Centro-Sul Baiano, a maior do estado. Contudo, cidades como Condeúba, Cordeiros, Mortugaba e Piripá permanecem sem registros, não só na coleção do MZSP, mas inclusive na literatura. A importância da diversidade de moluscos terrestres no Centro-Sul Baiano pode estar ligada ao fato da região incluir a fronteira entre três biomas brasileiros, Caatinga, Cerrado e Floresta Estacional Decídua. Trabalhos recentes realizados em áreas próximas aos municípios em questão, evidenciaram um número surpreendente de novos registros e novos táxons, o que justificaria um maior esforço pelo levantamento faunístico e conservação dos ambientes de Cerrado e Caatinga, que sofrem constante degradação. Assim, o presente estudo teve como objetivo central realizar o levantamento da malacofauna terrestre e dulcícola da mesorregião do Centro-Sul Baiano, usando dados da literatura, material histórico da coleção do MZSP, novas coletas, e a realização da sinopse taxonômica do material obtido. O levantamento resultou em 23 espécies de gastrópodes para os quatro municípios supracitados, das quais 95% evidenciaram novos registros. Exemplares das espécies Megalobulimus conicus e M. oblongus coletados, também foram estudados anatomicamente, revelando diferenças significativas entre as espécies. / Bahia state accounts for 35% of the total area of northeastern Brazil, including 417 municipalities. Several specimens of terrestrial and freshwater molluscs in the malacology collection of the Museum of Zoology of the University of São Paulo (MZSP, São Paulo, Brazil) were collected in municipalities belonging to the Central-South region of Bahia, the largest in the state. However, cities such as Condeúba, Cordeiros, Mortugaba and Piripá lack specific records, not only in the MZSP collection, but also in the literature. The importance of the diversity of terrestrial molluscs in the Center-South of Bahia may be related to the fact that the region includes the border between three Brazilian biomes, Caatinga, Cerrado and Atlantic Forest. Recent works carried out in areas close to the municipalities in question have revealed a surprising number of new records and new taxa, which would justify a greater effort for faunal surveys and the conservation of Cerrado and Caatinga environments, which suffer constant degradation. Thus, the present study aimed at surveying the terrestrial and freshwater malacofauna of the Center-South of Bahia, using data from the literature, historical material from the MZSP collection, new sampling, and the taxonomic study of the material obtained. The survey resulted in 23 species of gastropods for the four municipalities mentioned above, of which 95% are new records for the region. Specimens of Megalobulimus conicus and M. oblongus collected were also studied anatomically, revealing significant differences between species.

Thesis (Ph. D.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 215-251).

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 152-172). Description: xiv, 172 leaves : ill. ; 29 cm.

Inadequate information of the nutritive physiology and the dietary requirements of abalone are the principle factors that currently limit the development of a formulated feed for the commercial culture of Haliotis midae. The need to develop a method to determine apparent digestibility co-efficient's for abalone in order to facilitate further applied nutritional research was identified. Animals between 50 and 80 mm were collected from natural stocks along the east Cape coast of South Africa at Port Alfred and Great Fish point, and acclimated to laboratory conditions. Initial trials demonstrated that H. midae accepted and preferred a semi-purified diet to the seaweed Plocamium corallorhiza, one of the main components of it's natural diet. A technique of determining apparent digestibility co-efficient's (ADC) using the indirect method with chromic oxide as an inert marker was developed. Digestibility trials yielded higher dry matter (DMADC) and crude protein apparent digestibility co-efficient's (CPADC) for the semi-purified diet than for two species of algae, Gelidium amanzii and P. corallorhiza (83.7% and 95.6%, 70.7% and 80.0%, and 29.9% and 57.3% respectively). The ability of the animals to utilize terrestrial animal and plant ingredients efficiently makes it feasible to use conventional feed ingredients in formulated feeds for H. midae. Trials to determine the effect of different temperatures (15°C, 18°C and 22°C) on DMADC and CPADC of the semipurified diet showed that peak digestibility occurred at 18°C. There was also a positive relationship between temperature and consumption rate. Although no enzyme studies with H. midae have been conducted, the peak ADC's at 18°C is attributed to an increase in enzyme activity at this temperature. Transit time, an inverse function of temperature and consumption, is considered to be responsible for the decrease in the ADC' s at 22°C in conjunction with a possible decrease in enzyme activity at this temperature. A photoperiod trial to investigate the effect of darkness on DMADC and CPADC of the semi-purified diet revealed that digestive efficiency decreased with increasing hours of darkness. There was also a positive relationship between duration of darkness and the rate of consumption. The decrease in ADC's is attributed to decreased transit times as the duration of darkness increased . The contribution of this project to the understanding of abalone nutrition, the development of a formulated abalone feed and systems design for abalone farms is discussed.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Ecology and Biodiversity / Doctoral / Doctor of Philosophy