Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Aquaculture is one of the fastest growing food producing sectors in the world. Over the past few years, aquaculture research has focused on improving rearing protocols and standards for the culture of aquatic organisms. Probiotics are gaining increasing interest as an alternative to antibiotics to improve animal health and welfare. The effects of probiotics on the physiological and biochemical development of the digestive tract of commercially raised Argyrosomus japonicus (dusky kob) larvae were investigated. Two probiotic treatments were compared to a control where the standard rearing protocol was applied. The growth of the larvae and histological development of the digestive tract was studied. The specific enzyme activity of key digestive enzymes was determined. Amylase, trypsin, pepsin, alkaline phosphatase, aminopeptidase N and leucine-alanine peptidase were assayed. The mean growth of the control group of larvae differs from the CSIR and BactoSafe treatment groups (P = <0.001). There were no differences in the histological development between the control and two treatments. The histology did indicate a slight delay in development of the digestive tract when compared to previous studies on dusky kob. No significant differences were observed between the control and treatment groups for any of the enzyme assays. The effect of probiotics on the development of the digestive system of dusky kob larvae could not be definitively described as it was not determined to what extent the probiotics had established in the gut. What the study did conclude was that the enzyme assays need to be refined in order to determine the optimal reaction conditions required for the determination of specific enzyme activity in commercially raised dusky kob. / AFRIKAANSE OPSOMMING: Akwakultuur is een van die vinnigste groeiende voedsel produserende sektore in die wêreld. Oor die laaste aantal jare het akwakultuur navorsing gefokus op die verbetering van grootmaak protokolle en standaarde vir die cultuur van akwatise organismes So het die belangstelling in pro-biotika, as alternatief tot antibiotika ten einde die gesondheid en welsyn van diere te verhoog, vermeerder. Die effekte van pro-biotika op die fisiologies en biochemiese ontwikkeling van die spysverteringskanaal van kommersieel geproduseer Argyrosomus japonicus larwes was ondersoek. Twee probiotiese behandelings is vergelyk met ʼn kontrole (standaard grootmaak protokol). Die groei van die larwes en die histologiese ontwikkeling van die spysverteringskanaal is ondersoek. Die spesifieke ensiem aktiwiteite van die sleutel verteringsensieme was ook bepaal. Amilase, tripsien, pepsien, alkaliese fosfatase, aminopeptidase N en leusien-alanien peptidase was ondersoek. Die gemiddelde groei van die kontrole groep was effe hoër as die van die ander twee behandelings. Daar was geen verskil in histologie van die groepe nie maar die tempo van ontwikkeling vir alle behandelinge blyk stadiger te wees as die wat in vorige studies vir A. japonicus rapporteer is. Geen betekenisvolle verskille is opgemerk tussen die kontrole en die behandelingsgroepe vir enige van die ensiem analises nie. Die invloed van die probiotika op die ontwikkeling van die spysverteringskanaal van die larwes kon nie onomwonde beskryf word nie aangesien die vestiging van die pro-biotika in die spysverteringkanaal nie omskryf is nie. Wat wel gevind was, is dat die analitiese tegnieke rakende die ensieme verfyn moet word ten einde die optimale reaksie omgewings te bepaal wat dit sal moontlik maak om spesifieke ensiemaktiwiteite in die kommersieel geproduseerde A. japonicus te bepaal.

In the present study, the potential of low-melting point lipids, namely methyl palmitate (MP) and menhaden stearine (MS), were studied for delivery of water-soluble materials to fish larvae. Addition of the solid emulsifier, sorbitan monopalmitate (SMP) resulted in higher RE compared to the liquid emulsifier sorbitan sesquioleate (SSO). Additions of SMP were found to have a positive effect on the stability of lipid spray beads (LSB) at concentrations >10% (w/w) of lipid. LSB were shown to retain riboflavin with the highest RE when the lipid matrix was composed of a mixture of MP+10% SMP+1O% ethyl cellulose (w/w). Use of MP facilitated digestive breakdown of LSB by larvae of zebrafish, Brachydanio rerio, and glowlight tetra, Hemigrammus erythrozonus, as indicated by release of riboflavin from ingested LSB. LSB composed of MS performed better than LSB composed of MP when particulate glycine was incorporated within LSB. Highest retention efficiencies (RE) and delivery efficiencies (DE) were achieved by LSB composed of 100% MS. RE and DE of LSB were further improved when glycine was encapsulated as aqueous droplets rather than in a particulate form. The overall performance of LSB containing tyrosine showed that nutrients with similar water-solubilities to tyrosine can be very effectively delivered to early fish larvae. Visual observation indicated that LSB composed of 100% MS were broken down by larvae of clownfish, Amphiprion percula. Zein-bound particles (ZBP) were not efficient in delivering riboflavin to fish larvae due to high leaching rates. In an attempt to improve ZBP, we developed complex particles (CP) containing LSB incorporated in a dietary mixture bound by zein, to obtain a single particle type. The potential of LSB for delivery of free amino acids (FAA) was evaluated when LSB were incorporated within CP. RE and DE for tyrosine were significantly greater than those for alanine, glycine and serine. There was a significant inverse correlation between RE for FAA and their solubilities where FAA with low solubilites resulted in higher RE. Development of CP with high RE and DE for amino acids is an important step towards formulating a diet to allow early weaning of fish larvae onto artificial diets. / Graduation date: 2003

There is no abstract available for this thesis. / Department of Biology

In this study were evaluated the zootechnics, reproductive aspects and biochemical s parameters aspects of female catfishes fed with three lipids and proteins levels on diets. Two experiments were conducted, the first being held between July 15th and October 15th, 2008, followed by a period of 14 days to create the post-larvae. We used 66 females with 14 months old (weight between 465,1 and 690,3g). 18 females were slaughtered for evaluation of biochemical s and histological parameters and 54 were distributed on six 1m³-net cage, fed at 9 a.m. and 4 p.m., at ease, during 90 days, with pelletized rations containing 28, 34 and 40% of PB and 14% of total lipids. Twelve females were induced to spawn to reproductive evaluation (fertilization rate, egg s number, eggs and larvae s biometrics and prost-larvae s growth). At experiment I, the results indicated that the increase of protein s level at diet didn t influence the zootechnics, reproductive and biochemical s parameters, however the 28% of PB level was superior for the post-larvae s growth on the variables weight, length and weight versus survival in 14 days. The second experiment was performed between July 15th and October 15th, 2009, and we used the best diet of first experiment (28% of PB and 14% of lipids), settling the 8, 14 and 20% of lipids and 28% of PB levels. In this experiment was selected 93 females with 14 months old and weighting between 596,28 and 640,4g and 66 of which was distributed on six net cages and 27 was slaughtered for evaluation of biochemical s and histological parameters and the gonad's lipid profile. For both experiments were followed the same procedure, just adding, at the second, the evaluation of ovaries and muscles lipids profile. The results of experiment II also didn t show difference to the zootechnics and biochemical s parameters, but there was a linear increase in visceral fat index with the increased level of lipid in the diets. The fatty acids profile didn t differ between the treatments, but there was variation in concentration. The egg s diameter and area were significantly smaller to the 20% of lipids level, damaging the post-larvae s growth, survival and weight versus survival. The best reproductive s answers to catfishe s females were obtained with diets containing 28% of PB and between 8 and 14% of total lipids. / Neste estudo avaliaram-se os aspectos zootécnicos, reprodutivos e parâmetros bioquímicos de fêmeas de jundiá alimentadas com três níveis protéicos e lipídicos nas dietas. Foram conduzidos dois experimentos, sendo o primeiro realizado entre 15 de julho e 15 de outubro de 2008, seguindo-se um período de mais 14 dias para a criação das pós-larvas. Utilizou-se 66 fêmeas com 14 meses de idade (peso entre 465,1 e 690,3 g). Foram abatidas 18 fêmeas para avaliação dos parâmetros bioquímicos e histológicos e 54 foram distribuídas em seis tanques-rede de 1m3, alimentadas às 9 e 16 h, a vontade, durante 90 dias, com rações peletizadas contendo 28, 34 e 40 % de PB e 14 % de lipídio total. Doze fêmeas foram induzidas à desova para avaliação da reprodução (taxa de fecundação, número de ovos, biometria dos ovos e larvas e crescimento das pós-larvas). No experimento I, os resultados indicaram que o aumento do nível de proteína nas dietas não influenciou os parâmetros zootécnicos, bioquímicos e reprodutivos, no entanto o nível de 28 % de PB mostrou-se superior para o crescimento das pós-larvas nas variáveis peso médio, comprimento total e peso versus sobrevivência aos 14 dias (P>0,05). O segundo experimento foi realizado no período entre 15 de julho e 15 de outubro de 2009 e utilizou-se a melhor dieta do experimento I (28 % PB e 14 % de lipídio), fixando-se os níveis em 8, 14 e 20 % de lipídio e 28 % de PB. Neste experimento foram selecionadas 93 fêmeas com 14 meses de idade e peso entre 596,28 e 640,4 g e 66 foram distribuídas em seis tanques-rede e 27 foram abatidas para avaliação dos parâmetros bioquímicos, histológicos e perfil lipídico das gônadas. Para os dois experimentos seguiram-se os mesmos procedimentos, apenas acrescido, no segundo, da avaliação do perfil lipídico dos ovários e músculos. Os resultados do experimento II igualmente não se mostraram diferentes para os parâmetros zootécnicos e bioquímicos, porém houve aumento linear do índice de gordura visceral com o aumento do nível de lipídio nas dietas. O perfil de ácidos graxos não diferiu entre os tratamentos. O diâmetro e a área do ovo foram significativamente menores para o nível de 20 % de lipídio, prejudicando o crescimento, sobrevivência e peso versus sobrevivência das pós-larvas (P>0,05). As melhores respostas reprodutivas para fêmeas de jundiá foram obtidas com as dietas contendo 28 % de PB e entre 8 e 14 % de lipídio total.

This study was prompted by the need to remedy the situation that existed with respect to the poor status of our knowledge regarding the ichthyoplankton assemblage of the nearshore region along the south-east Cape coast of South Africa. The first chapter provides a brief introduction to the field of ichthyoplankton research and includes a summary of the status of research in southern Africa and an explanation of early life history terminology. The selection of all sample sites, times and strategies is also outlined. The study area along the south-east Cape coast with respect to its location, climate and physical oceanography is described in the second chapter, as is the gear used, bongo nets and an RMT1x6. A sampling protocol for the use of bongos from a small ski-boat, and the RMT from the research vessels, and for the handling and processing of samples was established. The selection of Middlebank as the main monthly sampling site within the Tsitsikamma National Park (TNP) was based on taxonomic diversity as well as logistical and safety constraints. The effect of mesh size and time of sampling with bongo nets on the catchability of ichthyoplankton was investigated in chapter three. Most data was accumulated during Sea Fisheries research cruises, with additional collections coming from the National Parks vessel. Although the differences were not significant, the 505 μ mesh nets captured larger larvae, with catches comprising higher percentages of flexion and postflexion larvae. Larval concentration and size were consistently greater in samples from periods of reduced light intensity, but significant differences were the exception. It was decided that sampling with 505 μ mesh nets during daylight would provide a representative sample of the available ichthyoplankton assemblage, while at the same time being the most practical and least time consuming with respect to handling, clogging and backflushing. In chapter four, the early life history stages of thiny of the seventy-five taxa sampled are described, reflecting the paucity of information which existed on the ichthyoplankton of the nearshore zone in the south-east Cape. These descriptions are seen as an important contribution towards any future research efforts in the region, but as many of these descriptions are based on few or single specimens, it is realised that the description of egg and larval stages will be an ongoing process. Based upon the data collected during this study, an ichthyoplankton species checklist was established in chapter five. Seventy-five taxa of fish larvae were identified to either family, genus or species level. A number of squid para-larvae were also encountered. Similarities and discrepancies with a previous survey in the region are presented. The temporal distribution of eggs and larvae between August 1993 and October 1996 was established, and the spatial distribution of ichthyoplankton along an offshore transect was determined between January 1995 and May 1996. Only 7 species from Middlebank and twelve from all stations combined displayed seasonal trends, with most of these being prevalent during winter months. Egg production, both over Middlebank and from all stations combined, appeared to be consistent, with no seasonal trends. Based upon the results from the offshore transect samples, it would appear that a single ichthyoplankton assemblage exists from Storms River out to fifteen nautical miles. Although a variety of statistical methods were applied to the data during this study, low egg and larval concentrations and a low sampling frequency meant that results had to be interpreted carefully. Chapter six describes the preliminary investigation into the vertical distribution of eggs and larvae. During two research cruises, discrete depth sampling using an RMT1x6 net was performed, with the majority of samples being accompanied by physical data provided by a CTD rosette sampler. No definite patterns could be seen as larval concentrations were low, and the short time scale did not allow for the identification of any diel migratory patterns. The relationship between total larvae and the physical environment was poor. The only possible relationship was that between plankton volume and total egg and total larval concentrations. The TNP may play an important role in the conservation of reef fish and the seeding of nearby fishing grounds through the export of pelagic eggs and larvae. Chapter seven describes a preliminary investigation into the dispersal potential of ichthyoplankton from the TNP. Based upon longshore currents determined from drogues, ADCP vectors and current meter readings, it was clear that if larvae were passive drifters, the potential for their dispersal from the TNP did exist. This pilot study showed that future work should concentrate not only on the oceanographic aspects, but on behavioural aspects of larvae which may enhance or retard dispersal. In the final discussion, it is emphasised that while this study went a long way to increasing our knowledge of the nearshore ichthyoplankton community, the true picture of the temporal and spatial dynamics of the species assemblage may only be revealed once more intensive sampling has been performed. The resolution of the early life history stages of the sparids and the identification of eggs to species level are seen as priorities for the near future. A complete species checklist for the TNP is provided based upon previous surveys (both on adult and larval fishes), this work and personal observations. A total of 171 species of fish from 70 families were identified, illustrating that the eggs and larvae of many species in the TNP have yet to be sampled. A brief description of the collaborative effort which is envisaged for the TNP over the next few years is provided.

Malpighian tubules of A. dorsalis mosquito larvae, studied in vitro, actively transported magnesium at high rates against concentration gradients as large as 16-fold and transepithelial potential gradients of approximately -l5mV. Fluid secretion rates, determined over 90 minute periods, in the presence and absence of cAMP, indicated that A. dorsalis tubules were viable and had secretion rates of the same magnitude as those reported for A. taeniorhynchus tubules. Having characterized the in vitro preparation of Malpighian tubules, the main hypothesis that Mg²⁺ transport is driven predominately by counter transport with Na⁺ was tested. This hypothesis was not supported by kinetic, Na-substitution, or inhibitor studies. Kinetic and Bumetanide studies suggest backflux of K drives J mg; however, this was not consistently found in other studies. / Science, Faculty of / Zoology, Department of / Graduate

Food waste in the waste stream is becoming an important aspect of integrated waste management systems. Current efforts are composting and animal feeding. However, these food waste disposal practices rely on slow thermodynamic processes of composting or finding farmers with domestic animals capable of consuming the food wastes. Bioconversion, a potential alternative, is a waste management practice that converts food waste to insect larval biomass and organic residue. This project uses a native and common non-pest insect in Texas, the black soldier fly, which processes large quantities of food wastes, as well as animal wastes and sewage in its larval stage. The goal of this research is to facilitate the identification and development of the practical parameters of bioconversion methods at a large cafeteria. Three major factors were selected to evaluate the practicality of a bioconversion system: (1) the biological constraints on the species; (2) the economic costs and benefits for the local community; (3) the perception of and interaction between the public and management agencies with respect to the bioconversion process. Results indicate that bioconversion is feasible on all levels. Larvae tolerate and consume food waste as well as used cooking grease, reducing the overall waste volume by 30-70% in a series of experiments, with an average reduction of 50%. The economical benefits are reduced collection costs and profit from the sale of pupae as a feedstuff, which could amount to as much as $1,200 per month under optimal conditions. Social acceptance is possible, but requires education of the public, specifically targeting school children. Potential impediments to social acceptance include historical attitudes and ignorance, which could be overcome through effective educational efforts.

This study is concerned with description of larval stages of Pagurus granosimanus, P. hemphilli and P. hirsutiusculus. All three are found intertidally in Northern California. Descriptions are based on laboratory raised zoea and glaucothoe.

Escape behavior is the critical output of rapid sensorimotor processing in the brain that allows animals to sense danger and avoid it. The circuit structures and mechanisms that underlie escape are still under investigation. Drosophila larvae are an advantageous system for studying the neuromuscular circuitry of escape behavior. When threatened with harmful mechanical touch, heat, or light, larvae perform C-shaped bending and lateral rolling, followed by rapid forward crawling. The sensory input and neural circuitry that promotes escape in the larva have been extensively characterized, but we do not understand how bending and rolling motor programs are generated by the larval neuromuscular system. This work identifies the movement patterns, muscle activities, and motor circuit features that drive escape behavior. High-speed imaging approaches reveal that larvae select between four distinct, interchangeable patterns of escape rolling, and that each pattern consists of synchronous rotations of every segment as the larva rotates. Investigating electron microscopic reconstructions of premotor and motor neurons elucidates premotor to motor connectivity patterns that could underlie sequential muscle activity that circumnavigates the larva and propels synchronous rotation along the whole body. Volumetric Swept Confocally-Aligned Planar Excitation (SCAPE) microscopy uncovers that, unlike larval crawling, a well-studied form of larval locomotion that is driven by bilaterally symmetric peristaltic waves of muscle activity, the muscle activity during bending and rolling occurs in a circumferential sequence that is synchronous along the larva’s segments. Muscles neighboring the dorsal and ventral midlines of the larva demonstrate left-right symmetric activity during rolling, and ventral muscles appear to drive the propulsion. Shifts in magnitude of left-right symmetric activity in midline muscles allow the larva to transition from initial escape bending into escape rolling. Preliminary computational predictions of PMN activities confirm the likely necessity of strong ventral muscle coactivity for driving escape. Probing specific PMNs during rolling demonstrates robustness of circuits controlling escape and requires further investigation, alongside the role that sensory feedback could play in this behavior. Altogether, these data reveal a new circuit organization and motor activity pattern that underlie the coordination of muscles during an escape sequence. Future work could reveal circuit components necessary for escape, including the mechanistic basis for action selection, behavioral maintenance, and behavioral flexibility.

Black-fly larvae, and mosquito larvae and pupae, are shown to select certain temperature ranges when given a choice in a linear gradient. Larval age has little effect on the temperature selected, but pupae are tolerant of higher temperatures than larvae. The significance of this observation is discussed. The temperature selected is affected by the previous thermal history of the insect, although acclimation to the ambient temperature may be rapid. The final selected temperature of fourth-instar Aedes aegypti larvae was determined. Rearing temperature has a profound effect on the thermal resistance of Aedes aegypti exposed to high temperatures. / Thesis / Master of Science (MS)