Cadmium (Cd) is a toxic metal known to accumulate in and have adverse effects on the olfactory systems of fish. The objective of this project was to investigate the effect of cadmium on zebrafish larvae, specifically the effects on the olfactory system at cellular and functional levels. Zebrafish larvae (72 hours post fertilization) were exposed to sublethal concentrations of cadmium (0.5, 1, 5, and 10 µM) for 96 h. Whole-body cadmium accumulation during this exposure period as quantified using GFAAS (graphite furnace atomic absorption spectroscopy) was found to increase with both exposure length and concentration. Using a transgenic strain of hsp70/eGFP (heat shock protein 70/enhanced green fluorescent protein reporter gene) zebrafish, dose-dependent induction of the heat shock response was observed in the olfactory epithelium. Expression of hsp70/eGFP in the olfactory epithelium was a highly sensitive biomarker for the effects of cadmium in the olfactory system with a lowest observed effects concentration (LOEC) of 0.5 µM Cd. Strong induction of the transgenic reporter gene correlated closely with cell death (LOEC of 5 µM Cd) and histological alterations (LOEC of 1 µM Cd) in the olfactory epithelium of zebrafish larvae following cadmium exposure. Additionally, loss of sensory cilia from the surface of the olfactory epithelium was observed in larvae exposed to 5 and 10 µM Cd. Furthermore, behaviour tests to assess olfactory function revealed sensory deficits, likely due in part to the cadmium-induced degeneration of the olfactory epithelium (p<0.05 for 1 µM; p<0.001 for 5 and 10 µM Cd). <p>To determine if cadmium was entering the cells of the olfactory epithelium by acting as a calcium (Ca) antagonist, zebrafish larvae were co-exposed to 1, 5, or 10 µM Cd with 1 or 5 mM Ca for 96 h. Whole-body cadmium accumulation as quantified using ICP-MS (inductively coupled plasma mass spectrometry) was decreased in larvae co-exposed to cadmium and calcium. Additionally, induction of the heat shock response was reduced in the presence of increasing calcium co-treatment. These ameliorating effects of calcium were further revealed in cell death and histological analyses of the olfactory epithelium. Also, larvae co-exposed to cadmium and calcium exhibited greater olfactory sensory function compared to larvae exposed to cadmium only. Significant increases in aversion response were observed in larvae exposed to 5 µM Cd with 1 and 5 mM Ca (p<0.05). These results indicate that cadmium gains entry to the olfactory epithelium via calcium uptake systems, wherein it causes damage to the olfactory system and can lead to sensory impairment.

Graduation date: 1992

Cadmium (Cd) is a toxic metal known to accumulate in and have adverse effects on the olfactory systems of fish. The objective of this project was to investigate the effect of cadmium on zebrafish larvae, specifically the effects on the olfactory system at cellular and functional levels. Zebrafish larvae (72 hours post fertilization) were exposed to sublethal concentrations of cadmium (0.5, 1, 5, and 10 µM) for 96 h. Whole-body cadmium accumulation during this exposure period as quantified using GFAAS (graphite furnace atomic absorption spectroscopy) was found to increase with both exposure length and concentration. Using a transgenic strain of hsp70/eGFP (heat shock protein 70/enhanced green fluorescent protein reporter gene) zebrafish, dose-dependent induction of the heat shock response was observed in the olfactory epithelium. Expression of hsp70/eGFP in the olfactory epithelium was a highly sensitive biomarker for the effects of cadmium in the olfactory system with a lowest observed effects concentration (LOEC) of 0.5 µM Cd. Strong induction of the transgenic reporter gene correlated closely with cell death (LOEC of 5 µM Cd) and histological alterations (LOEC of 1 µM Cd) in the olfactory epithelium of zebrafish larvae following cadmium exposure. Additionally, loss of sensory cilia from the surface of the olfactory epithelium was observed in larvae exposed to 5 and 10 µM Cd. Furthermore, behaviour tests to assess olfactory function revealed sensory deficits, likely due in part to the cadmium-induced degeneration of the olfactory epithelium (p<0.05 for 1 µM; p<0.001 for 5 and 10 µM Cd). <p>To determine if cadmium was entering the cells of the olfactory epithelium by acting as a calcium (Ca) antagonist, zebrafish larvae were co-exposed to 1, 5, or 10 µM Cd with 1 or 5 mM Ca for 96 h. Whole-body cadmium accumulation as quantified using ICP-MS (inductively coupled plasma mass spectrometry) was decreased in larvae co-exposed to cadmium and calcium. Additionally, induction of the heat shock response was reduced in the presence of increasing calcium co-treatment. These ameliorating effects of calcium were further revealed in cell death and histological analyses of the olfactory epithelium. Also, larvae co-exposed to cadmium and calcium exhibited greater olfactory sensory function compared to larvae exposed to cadmium only. Significant increases in aversion response were observed in larvae exposed to 5 µM Cd with 1 and 5 mM Ca (p<0.05). These results indicate that cadmium gains entry to the olfactory epithelium via calcium uptake systems, wherein it causes damage to the olfactory system and can lead to sensory impairment.

This study was based on samples taken from 7 cruises between February 2004 and November 2004 and intended to investigate the effects of hydrographic conditions on the spatiotemporal variations of fish larvae assemblage in the waters surrounding Taiwan. The cold, low salinity, and nutrient-rich waters were usually found in the seas northwest of Taiwan in winter, probably due to the invasion of China Coastal Current (CCC). While the dominance of warm and saline waters in the Taiwan Strait in summer and in the waters south and east of Taiwan throughout the year implied that the waters of these areas might be controlled by Kuroshio Current (KC) and South China Sea Waters. In total, 622 fish larvae taxa belonging to 295 genera and 138 families were identified by this study with an overall mean abundance of 760.52 ¡Ó 75.63 ind./1000m3. No significant difference in abundance was found among seasons. The 10 predominant taxa, which constituted 32% of the total number of fish larvae, were Engraulis japonicus, Benthosema pterotum, Scomber japonicus, Vinciguerria nimbaria, Encrasicholina punctifer, Sigmops gracilis, Auxis sp., Trichiurus lepturus, Bleekeria mitsukurii, and Maurolicus sp.. The distribution patterns of fish larvae showed a close relationship with the water masses, higher abundance and lower species richness of fish larvae were always found in the northwestern and northern waters of Taiwan where the CCC prevails, and lower abundance and higher species diversity were present in the eastern waters of Taiwan where the KC dominates. Results of cluster analysis distinguished three station groups, the western, transitional, and eastern groups, and the distribution patterns of these station groups were also corresponded with hydrographic conditions. Furthermore, two seasonal groups of fish larvae assemblages were also recognized, spring-summer group and autumn-winter group. Results of correlation coefficients showed that total abundance of fish larvae and the most dominant taxa were positively related to zooplankton abundance but negatively related to phytoplankton abundance, and suggested that food source might be a key factor to determine the abundance and distribution of fish larvae in the waters surrounding Taiwan. Results of indicator species analysis designated Engraulis japonicus the indicator species of the CCC, and Vinciguerria nimbaria, Maurolicus sp., and Sigmops gracilis the indicator species of the KC.

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Bruchid pests are of considerable economic importance, infesting legume seeds and pods in fields and stores, predominately in the semi-arid tropics. One of the foremost bruchid pests"Callosobruchus maculatus is a niche generalist in that it can infest seeds whilst within pods or when loose. It exhibits a much greater degree of polyphagy than its wild relatives, perhaps partly due to behavioural plasticity. As their larvae are restricted to a single seed, resources available for growth are directly related to egg distribution by the ovipositing female. Host selection is a complex process and involves host finding, recognition (which may occur before or after contact with the plant), and host acceptance which is manifested as contact inspection behaviour and culminates in oviposition. Numerous factors influence these processes including the nature of host chemistry and the presence of conspecific epideictic pheromones. The purpose of this study was to investigate the factors which modulate the tendency to oviposit and oviposition behaviour itself. 2 The oviposition behaviour of newly emerged beetles was recorded on several seeds that vary in their attractiveness as hosts. The behavioural repertoire and the stereotypical sequences that characterise the acceptance or rejection of a host were recorded on pristine and egg laden seeds. These sequences were used to construct flow charts of transitions between the most common behaviours. Several indicators of a host's acceptahility were identified and quantified, including the duration of selected key behaviours. The combination of behaviours exhibited, their position in the transitional matrix and their respective durations, indicated the relative acceptability of the host seeds studied, and provided information on how the different sense organs have complementary roles in the process of host acceptance. This demonstrated that the perception of primary host and conspecific stimuli which influence host acceptance is undertaken by the palps and., to a lesser extent, by the antennae. The study of oviposition behaviour in conjunction with studies on the course of oviposition over extended periods on real and artificial hosts provided the tools by which the chemical bases of host acceptance could be investigated. Host seed extracts were screened for their ability to influence behaviour, and some of the active components were identified as a number of commonly occurring fatty acids. These same fatty acids have been shown to stimulate egg laying, and in different proportions and concentrations, to deter oviposition both as components of a conspecific oviposition deterrent pheromone, and as components of vegetable oils added to stored seeds as a protectant

No description available.

No description available.

Exposure of fourth instar Aedes aegypti larvae to graded concentrations of the entomopathogenic cercariae of the digenean Plagiorchis elegans, induced fundamental changes in the partitioning of time among a number of major behavioural activities. In the absence of the parasite, swimming, breathing and feeding remained stable over time. Grooming was rarely observed. In the presence of cercariae, larvae increased grooming 26-fold. Concomitantly, feeding was reduced to 33% of control values. Times spent swimming and breathing remained unchanged. The increase in grooming activity was attributable to the attachment of cercariae to the surface of the mosquito larvae, but was independent of infection. Grooming reduced cercarial penetration. Seventy-five percent of cercariae were lost to predation by larvae, but their caloric value was insignificant and failed to compensate for the loss of feeding time due to grooming. The findings are discussed in the context of their impact on larval growth, development and survival.

Cercariae of the digenean Plagiorchis elegans cause high levels of morbidity and mortality among larvae of Aedes aegypti . The impact of this parasite on the larval population dynamics of the experimental host as mediated through intraspecific competition, egg hatchability and ovipositional preference was assessed by calculating the probability of pre-imagos to develop from one stage to the next, or to die within consecutive 24 h intervals. Attractiveness of the water to ovipositing females in a dynamic larval population was not affected by exposure to the parasite, but varied significantly over time, regardless of food abundance. In optimally fed populations, these changes were positively correlated with pupal production, but were not affected by early instar development. Most of the entomopathogenic effects of the parasite were expressed in the pupal stage. Thus, exposure to the parasite significantly reduced adult emergence, but did not greatly impair pre-imago development. Nonetheless, exposure to various levels of the parasite significantly increased mortality of all larval stages. Suboptimally fed larval populations displayed severely impaired development and produced few adults. Exposure to P. elegans increased adult production slightly, suggesting depensatory mortality. In nutritionally stressed populations, no correlation was found between biomass and ovipositional preference, but attractiveness of the water was significantly increased by the removal of individuals by pupation or mortality. Egg hatchability was not significantly affected by population structure, but varied with the nutrient content of the water. This study provides new insight into the use of parasites as agents in the biological control of mosquitoes.