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Research at AUT's School of Science is focused on key scientific issues with regional and global significance. The common theme connecting all research areas is sustainability – in the broadest sense as it relates to environmental and human health. Our research is closely allied to teaching and learning opportunities at undergraduate and postgraduate level within the school.
Research is organised in three thematic areas:
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Browsing School of Science by Author "Alfaro, AC"
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- ItemDifferential Expression of Novel Metabolic and Immunological Biomarkers in Oysters Challenged With a Virulent Strain of OsHV-1(Elsevier, 2017-04) Young, T; Kesarcodi-Watson, A; Alfaro, AC; Merien, F; Nguyen, TV; Mae, H; Le, DV; Villas-Bôas, SEarly lifestages of the Pacific oyster (Crassostrea gigas) are highly susceptible to infection by OsHV-1 μVar, but little information exists regarding metabolic or pathophysiological responses of larval hosts. Using a metabolomics approach, we identified a range of metabolic and immunological responses in oyster larvae exposed to OsHV-1 μVar; some of which have not previously been reported in molluscs. Multivariate analyses of entire metabolite profiles were able to separate infected from non-infected larvae. Correlation analysis revealed the presence of major perturbations in the underlying biochemical networks and secondary pathway analysis of functionally-related metabolites identified a number of prospective pathways differentially regulated in virus-exposed larvae. These results provide new insights into the pathogenic mechanisms of OsHV-1 infection in oyster larvae, which may be applied to develop disease mitigation strategies and/or as new phenotypic information for selective breeding programmes aiming to enhance viral resistance.
- ItemDual Analysis of Virus-host Interactions: The Case of Ostreid Herpesvirus 1 and the Cupped Oyster Crassostrea Gigas(Libertas Academica, 2019) Rosani, U; Young, T; Bai, CM; Alfaro, AC; Venier, PDual analyses of the interactions between Ostreid herpesvirus 1 (OsHV-1) and the bivalve Crassostrea gigas during infection can unveil events critical to the onset and progression of this viral disease and can provide novel strategies for mitigating and preventing oyster mortality. Among the currently used “omics” technologies, dual transcriptomics (dual RNA-seq) coupled with the analysis of viral DNA in the host tissues has greatly advanced the knowledge of genes and pathways mostly contributing to host defense responses, expression profiles of annotated and unknown OsHV-1 open reading frames (ORFs), and viral genome variability. In addition to dual RNA-seq, proteomics and metabolomics analyses have the potential to add complementary information, needed to understand how a malacoherpesvirus can redirect and exploit the vital processes of its host. This review explores our current knowledge of “omics” technologies in the study of host-pathogen interactions and highlights relevant applications of these fields of expertise to the complex case of C gigas infections by OsHV-1, which currently threaten the mollusk production sector worldwide.
- ItemEffect of Neuroactive Compounds on the Settlement of Mussel (Perna Canaliculus) Larvae(Elsevier, 2011) Young, T; Alfaro, AC; Robertson, JHerein, we present the first laboratory study on the effects of pharmacologically active compounds on larval settlement of the green-lipped mussel, Perna canaliculus. Competent hatchery-reared larvae were exposed to seawater containing excess K+ in the form of KCl and K2SO4 and the neurotransmitters -aminobutyric acid (GABA) and acetylcholine. Both KCl and K2SO4 were identified as active inducers of larval settlement with maximum inductions occurring after exposures to 10 and 7.5 mM, respectively. Peak settlement response to KCl was higher (>64%) than that achieved with K2SO4 (>41%). GABA did not induce larval settlement and displayed toxic and settlement inhibitive effects at 10-4 and 10-3 M. Acetylcholine induced larval settlement (>49%) at 10-4 M with minimal acute toxic effects (LC < 10%). To gain insight into the class of acetylcholine receptors involved, atropine was used to block the muscarinic-type receptors. Atropine treatment alone did not inhibit settlement compared to control assays, indicating that muscarinic-type receptors are not involved in settlement behavior. Furthermore, results showed that atropine did not significantly decrease acetylcholine induced settlement responses, which suggests an active role of the nicotinic-type receptors in the biochemical pathways of mussel settlement. Results of this study provide new insights on the mechanism of settlement behavior in P. canaliculus, which may have direct application to the growing New Zealand aquaculture industry.
- ItemEffects of Insect Meal and Grape Marc in the Nutritional Profile, Growth, and Digestibility of Juvenile New Zealand Farmed Abalone(Springer Science and Business Media LLC, 2023-08-21) Bullon, N; Seyfoddin, A; Hamid, N; Manivannan, M; Alfaro, ACGenerally, one of the most significant bottlenecks of land-based abalone aquaculture is the high cost of the feed, which is associated with the use of wild fish stocks to produce fish meal. Fish meal is a key ingredient used in aquaculture feeds due to its nutritional profile and palatability. Alternative ingredients, such as insect meal and grape marc, are potential candidates to be included in aquafeeds due to their suitable nutritional profile and more sustainable production. This study aimed to evaluate the effect of insect meal and grape marc on growth and nutritional profile using abalone as an animal model in a feeding trial for 165 days. Proximate analyses were used to identify nutritional variations in abalone tissue and faecal matter, and liquid chromatography-mass spectrometry and gas chromatography mass-spectrometry analyses were utilised to characterise amino acid and fatty acid composition. Results showed a 95% survival for all treatments. The inclusion of insect meal and grape marc did not affect the protein proportions of abalone tissues, but differences were found in the carbohydrate and lipid proportions. The inclusion of insect meal and grape marc significantly affected levels of amino acids L-histidine, L-methionine, and L-phenylalanine, and fatty acids oleic acid, linoleaidic acid, palmitic acid, palmitoleic acid, and α-linolenic suggesting a correlation between the feed source and fatty acid tissue composition. This work provides promising results for future optimisation of abalone diets including more affordable and sustainable alternative ingredients.
- ItemFaunal composition within algal mats and adjacent habitats in Likuri, Fiji Islands(Marine Biological Association of the United Kingdom/Cambridge University Press, 2009) Alfaro, AC; Zemke White, WL; Nainoca, WThe faunal composition within three mono-specific algal habitats was investigated at Likuri Island, southern Viti Levu, Fiji Islands. Gracilaria maramae was the dominant alga within algal drift mat, seagrass bed, and rocky substrate habitats at the study site. This algal species exhibits two distinctive morphologies depending on whether it is attached or loose-lying. When attached to seagrass blades or rocky substrates, this alga has long straight branches stemming from a single holdfast, while detached individuals develop curled tendrils that re-attach to adjacent substrates. Re-attachment behaviour and high growth rates result in a dense mat of drift algae, which provides a suitable micro-habitat for macro-invertebrates. The sources of algal fragments that contribute to the algal mat appear to be nearby seagrass beds and rocky substrates, where this species may settle directly from spores. Storm events may detach these algae, although pulling experiments showed that the attachment to rocky substrates is 5 times stronger than the attachment to seagrass blades. Results from the macrofaunal samples indicate that the loose-lying algal mat habitat had the highest abundance and biodiversity of organisms, followed by the seagrass bed, and then the rocky substrate habitat. The ability of loose G. maramae fragments to re-attach, along with their high growth rate, may provide a unique micro-habitat for highly abundant and diverse faunal assemblages, which in turn may sustain adjacent near-shore communities. This study highlights the ecological importance of floating algal mats to coastal ecosystems, which should be considered in future management strategies throughout the Fiji Islands.
- ItemHistopathological Investigation of Four Populations of Abalone (Haliotis iris) Exhibiting Divergent Growth Performance(Elsevier BV, 2023-12-14) Copedo, JS; Webb, SC; Ragg, NLC; Venter, L; Alfaro, ACThe black-foot abalone (pāua), Haliotis iris, is a unique and valuable species to New Zealand with cultural importance for Māori. Abalone are marine gastropods that can display a high level of phenotypic variation, including slow-growing or ‘stunted’ variants. This investigation focused on identifying factors that are associated with growth performance, with particular interest in the slow-growing variants. Tissue alterations in H. iris were examined using histopathological techniques, in relation to growth performance, contrasting populations classified by commercial harvesters as ‘stunted’ (i.e., slow-growing) and ‘non-stunted’ (i.e., fast-growing) from four sites around the Chatham Islands (New Zealand). Ten adults and 10 sub-adults were collected from each of the four sites and prepared for histological assessment of condition, tissue alterations, presence of food and presence of parasites. The gut epithelium connective tissue, digestive gland, gill lamellae and right kidney tissues all displayed signs of structural differences between the slow-growing and fast-growing populations. Overall, several factors appear to be correlated to growth performance. The individuals from slow-growing populations were observed to have more degraded macroalgal fragments in the midgut, increased numbers of ceroid granules in multiple tissues, as well as increased prevalence of birefringent mineral crystals and haplosporidian-like parasites in the right kidney. The histopathological approaches presented here complement anecdotal field observations of reduced seaweed availability and increased sand incursion at slow-growing sites, while providing an insight into the health of individual abalone and sub-populations. The approaches described here will ultimately help elucidate the drivers behind variable growth performance which, in turn, supports fisheries management decisions and future surveillance programs.
- ItemIdentification of Candidate Biomarkers for Quality Assessment of Hatchery-reared Mussel Larvae Via GC/MS-based Metabolomics(Taylor and Francis Ltd, 2015) Young, T; Alfaro, AC; Villas-Bôas, STo ensure environmental and economic sustainability of future aquaculture growth, large-scale hatchery production of mollusc larvae is required. However, variation in larval quality currently limits potential maximum yields. Identification of biomarkers which reflect the immediate physiological condition of larvae during hatchery production could help monitor and determine causes of variation. Metabolomics is well-suited to this task due to its capacity for providing an instantaneous snapshot of the physiology of an organism through analysis of its metabolite profile. As a test, we applied GC/MS-based metabolomics for this purpose. Using a variety of univariate and multivariate feature selection methods, we identified four metabolite–metabolite ratios involving levels of succinate, glycine, alanine, pyroglutamate and myristic acid as candidate biomarkers for assessing mussel larval quality. These metabolites are known to have roles in energy metabolism, osmotic regulation, immune function and cell–cell communication. We anticipate that further investigation of these metabolites and their associated biochemical pathways will yield a more complete understanding of the factors responsible for larval production variability.
- ItemInduction of Settlement in Larvae of the Mussel Mytilus Galloprovincialis Using Neuroactive Compounds(Elsevier, 2012-05-21) Young, T; Sánchez-Lazo, C; Martínez-Pita, I; Alfaro, ACWe investigated the effect on Mytilus galloprovincialis larval settlement, as well as the toxicity, of serial concentrations in filtered seawater of acetylcholine (AC), γ-aminobutiric acid (GABA); 3-isobutyl-1-methylxanthine (IBMX); and the potassium ion in the form of potassium chloride (KCl) and potassium sulfate (K2SO4). All the substances assayed induced larval settlement and peak responses were above 90% in exposures to 10− 2 mol L− 1 (M) AC, 10− 4 and 10− 5 M epinephrine, 10− 3 M GABA and 20, 30 and 40 mM KCl. The optimal concentration of K+ varied depending on the anionic component of the compound assayed, and peak settlement response to KCl was higher (100%) than that achieved with K2SO4 (69.7%). The estimated LC50 of the compounds assayed ranged from 9.4 × 10− 6 M (GABA) to 3.1 × 10− 2 M (KCl). GABA, IBMX and K2SO4 treatments displayed toxic effects in all the active concentrations. In contrast, AC 10− 5 M, epinephrine 10− 4 and 10− 5 M and KCl 20 mM treatments enhanced larval settlement without an acute short-term effect on mortality. These results provide new insights on the molecular mechanisms controlling settlement in M. galloprovincialis larvae, and yield promising outcomes for the mussel industry to find a reliable method to enhance larval settlement in hatcheries.
- ItemItaconic Acid Inhibits Growth of a Pathogenic Marine Vibrio Strain: A Metabolomics Approach(Nature Publishing Group, 2019) Nguyen, TV; Alfaro, AC; Young, T; Green, S; Zarate, E; Merien, FThe antimicrobial role of itaconic acid (ITA) has been recently discovered in mammalian cells. In our previous studies, we discovered that marine molluscs biosynthesise substantial quantities of ITA when exposed to marine pathogens, but its antimicrobial function to Vibrio bacteria is currently unknown. Thus, in this study, we used an untargeted gas chromatography–mass spectrometry (GC-MS) platform to identify metabolic changes of Vibrio sp. DO1 (V. corallyliticus/neptunius-like isolate) caused by ITA exposure. Vibrio sp. DO1 was cultured in Luria-Bertani broth supplemented with 3 mM sodium acetate and with different concentrations of ITA (0, 3 and 6 mM) for 24 h. The results showed that ITA completely inhibited Vibrio sp. growth at 6 mM and partially inhibited the bacterial growth at 3 mM. A principal component analysis (PCA) revealed a clear separation between metabolite profiles of Vibrio sp. DO1 in the 3 mM ITA treatment and the control, which were different in 25 metabolites. Among the altered metabolites, the accumulation of glyoxylic acid and other metabolites in glyoxylate cycle (cis-aconitic acid, isocitric acid and fumaric acid) together with the increase of isocitrate lyase (ICL) activity in the 3 mM ITA treatment compared to the control suggest that ITA inhibited Vibrio sp. growth via disruption of central carbon metabolism.
- ItemLeaf Stable Isotope and Nutrient Status of Temperate Mangroves As Ecological Indicators to Assess Anthropogenic Activity and Recovery From Eutrophication(Frontiers Research Foundation, 2016-12) Gritcan, I; Duxbury, M; Leuzinger, S; Alfaro, ACWe measured nitrogen stable isotope values (δ15N), and total phosphorus (%P) and total nitrogen (%N) contents in leaves of the temperate mangrove (Avicennia marina sp. australasica) from three coastal ecosystems exposed to various levels of human impact (Manukau, high; Mangawhai, low; and Waitemata, intermediate) in northern New Zealand. We measured δ15N values around 10‰ in environments where the major terrestrial water inputs are sewage. The highest average total nitrogen contents and δ15N values were found in the Auckland city region (Manukau Harbour) at 2.2%N and 9.9‰, respectively. The lowest values were found in Mangawhai Harbour, situated about 80 km north of Auckland city, at 2.0%N and 5.2‰, respectively. In the Waitemata Harbour, also located in Auckland city but with less exposure to human derived sewage inputs, both parameters were intermediate, at 2.1%N and 6.4‰. Total phosphorus contents did not vary significantly. Additionally, analysis of historical mangrove leaf herbarium samples obtained from the Auckland War Memorial Museum indicated that a reduction in both leaf total nitrogen and δ15N content has occurred over the past 100 years in Auckland’s harbors. Collectively, these results suggest that anthropogenically derived nitrogen has had a significant impact on mangrove nutrient status in Auckland harbors over the last 100 years. The observed decrease in nitrogenous nutrients probably occurred due to sewage system improvements. We suggest that mangrove plant physiological response to nutrient excess could be used as an indicator of long-term eutrophication trends. Monitoring leaf nutrient status in mangroves can be used to assess environmental stress (sewage, eutrophication) on coastal ecosystems heavily impacted by human activities. Moreover, nitrogen and phosphorus leaf contents can be used to assess levels of available nutrients in the surrounding environments.
- ItemMapping the Green-Lipped Mussel (Perna canaliculus) Microbiome: A Multi-Tissue Analysis of Bacterial and Fungal Diversity(Springer, 2022) Li, S; Young, T; Archer, S; Lee, K; Sharma, S; Alfaro, ACPoor health and mortality events of the commercially important and endemic New Zealand green-lipped mussel (Perna canaliculus) pose a threat to its industry. Despite the known importance of microbiomes to animal health and environmental resilience, the host-associated microbiome is unexplored in this species. We conducted the first baseline characterization of bacteria and fungi within key host tissues (gills, haemolymph, digestive gland, and stomach) using high-throughput amplicon sequencing of 16S rRNA gene and ITS1 region for bacteria and fungi, respectively. Tissue types displayed distinctive bacterial profiles, consistent among individuals, that were dominated by phyla which reflect (1) a fluid exchange between the circulatory system (gills and haemolymph) and surrounding aqueous environment and (2) a highly diverse digestive system (digestive gland and stomach) microbiota. Gammaproteobacteria and Campylobacterota were mostly identified in the gill tissue and haemolymph, and were also found in high abundance in seawater. Digestive gland and stomach tissues were dominated by common gut bacterial phyla, such as Firmicutes, Cyanobacteria, Proteobacteria, and Bacteroidota, which reflects the selectivity of the digestive system and food-based influences. Other major notable taxa included the family Spirochaetaceae, and genera Endozoicomonas, Psychrilyobacter, Moritella and Poseidonibacter, which were highly variable among tissue types and samples. More than 50% of fungal amplicon sequence variants (ASVs) were unclassified beyond the phylum level, which reflects the lack of studies with marine fungi. However, the majority of those identified were assigned to the phylum Ascomycota. The findings from this work provide the first insight into healthy tissue microbiomes of P. canaliculus and is of central importance to understanding the effect of environmental changes on farmed mussels at the microbial level.
- ItemMetabolic Profiling of Mussel Larvae: Effect of Handling and Culture Conditions(Springer, 2015) Young, T; Alfaro, AC; Villas-Bôas, SGGas chromatography mass spectroscopy was applied to characterize the metabolic profiles of hatchery-reared mussel (Perna canaliculus) larvae before and after a prolonged handling and water exchange process, and to investigate the effect of culture conditions. A decrease in succinate and an increase in alanine were observed after the water exchange, which indicated alterations in energy production and osmotic balance. However, these variations were subtle and it is unlikely that the water exchange practice had any lasting negative effects on larval physiology and performance. Multivariate pattern recognition tools (hierarchical clustering, principal component analysis and projection to latent squares discriminant analysis) were used to assess metabolite variations in larvae reared in low-density static and high-density flow through systems and to construct a culture condition classification model. Twelve metabolites contributed most towards the model, which indicated differences in energy, protein and lipid metabolism. The clear group separations were not represented by observable variations in morphological traits. This suggests that growth performance is metabolically buffered through an adaptive physiological mechanism to provide similar developmental characteristics under these conditions.
- ItemMetabolomic Strategies for Aquaculture Research: A Primer(Wiley-Blackwell, 2016) Young, T; Alfaro, ACMetabolomics is a fast-evolving field that provides qualitative and quantitative analyses of metabolites within cells, tissues or biofluids. Recent applications of metabolomics approaches in aquaculture research have highlighted the huge potential for solving problems within all aspects of the production line, from hatchery production to post-harvest quality control. To assist with the growing application of metabolomics in aquaculture research, this contribution provides a review of techniques and steps necessary to conduct metabolomics research, from experimental design to data interpretation. Specifically, we target scientists who are new to the field of metabolomics, and we offer simple, but comprehensive steps and strategies to conduct this type of research. We conclude this primer with some advice on how to access relevant expertise and facilities for metabolomics-based aquaculture research.
- ItemNeurophysiological Control of Swimming Behaviour, Attachment and Metamorphosis in Black-footed Abalone (Haliotis Iris) Larvae(Taylor and Francis, 2014) Alfaro, AC; Young, T; Bowden, KExperiments were conducted to test the effect of a range of chemicals on larval responses in swimming behaviour, attachment and metamorphosis of the black-footed abalone (Haliotis iris). The effect of antibiotics on larval survival was first tested within negative (filtered seawater) and positive (GABA at 10−5, 10−4 and 10−3 mol L−1) control assays over 3 days. This experiment corroborated the effectiveness of using antibiotics to improve survival of larvae without obvious synergistic interactions with the GABA inducer or confounding effects of potential bacterial interactions. Chemical treatments (acetylcholine, potassium chloride, dopamine and glutamine) were then tested at various concentrations for their ability to modulate swimming behaviour and induce larval attachment and metamorphosis over 14 days. Generally, larval state shifted from swimming to attached, and from attached to metamorphosed, in the control and treatments over time. However, the peak percentage of attached and metamorphosed larvae varied in time among chemicals and concentrations. While overall percent metamorphosis was minimally enhanced after 14 days of exposure to some chemical treatments at certain concentrations, all treatments displayed significant capacities to down-regulate larval swimming and induce early attachment and metamorphosis. Mortality was recorded throughout the duration of the experiment, and was generally low (<20%) across controls and most treatments for exposures of less than 12 days. Interpretations of specific results from this study are used to elucidate neurophysiological control of larval activities for this abalone species. Comparisons with other marine invertebrates highlight the specificities of chemical cues and endogenous regulatory mechanisms across relatively closely related taxa.
- ItemNutritional and Metabolomic Changes of Juvenile Farmed Abalone (Haliotis iris) in New Zealand(Hindawi Limited, 2023-01-01) Bullon, N; Seyfoddin, A; Dezfooli, SM; Young, T; Alfaro, ACSeasonal variations play a crucial role in the physiology, immune responses, and nutritional profile of aquatic animals. Unpredictable water temperature fluctuations, especially those caused by climate change, may negatively affect feed consumption and growth of cultured organisms, such as abalone. In addition, metabolic and nutritional changes across different seasons may have significant effects on aquaculture production. This study aimed to investigate biochemical and metabolic alterations in healthy abalone (Haliotis iris) during 1 year of grow out in a land-based farm in New Zealand. Proximate analyses were used to identify nutritional variations in whole animal tissues, and a gas chromatography–mass spectrometry-based metabolomics approach was used to identify metabolic changes in adductor muscle of abalone during different seasons in the 1-year sampling period. Results showed that protein content was higher in warmer months compared with colder months, whereas lipid, ash, and carbohydrate contents remained generally constant throughout the year. Metabolic profile fluctuations indicated higher amounts of glutamic acid, glutathione, methionine, lysine, serine, tyrosine, and glycine in January and March compared with October and July, indicating possible amino acid breakdown and collagen degradation due to warmer temperatures. Although the proximate analyses findings revealed no signs of nutritional deficiencies in abalone among seasons, the metabolic profiles suggested possible thermal stress during summer months. This study provides a foundation for further nutritional studies to optimise seasonal diets for farmed Haliotis iris and highlights the need to monitor thermal stress effects, especially during summer and/or heatwave events.
- ItemPerkinsus olseni and Other Parasites and Abnormal Tissue Structures in New Zealand Greenshell™ Mussels (Perna canaliculus) Across Different Seasons(Springer Science and Business Media LLC, 2022-10-19) Muznebin, F; Alfaro, AC; Webb, SCThe New Zealand Greenshell™ mussel (Perna canaliculus) supports the largest aquaculture industry in the country. However, summer mortality events and potential disease outbreaks may threaten the growth of this industry. As an approach to gauging potential threats through the seasons, a detailed histopathological examination was conducted on 256 adult cultured mussels collected from a farm between April 2018 to September 2019, which covered the austral autumn, winter, spring and summer seasons. Histological sections followed by confirmatory in situ hybridization (ISH) resulted in the identification of Perkinsus olseni at an overall prevalence of 56%. Other parasites and pathogens were identified by histology: apicomplexan parasite X (APX) (78%), copepods (Pseudomyicola spinosus or Lichomolgus uncus) (1%), Microsporidium rapuae (1%), intracellular microcolonies of bacteria (IMCs) (2%) and bacilli and cocci bacteria (4%) in gills, mantle, gonads, digestive epithelium and digestive tubules. There was a significant association between P. olseni and APX infection in mussels. This is the first report on seasonal variations of P. olseni and APX in New Zealand Greenshell™ mussel. There was a significant association between seasons and the presence of P. olseni and APX in mussels. A significant positive association between the brown material accumulation and parasites (P. olseni and APX) and between haemocytosis and P. olseni infections were recorded. A significant association between presence of parasites and health condition (healthy and unhealthy) of mussels was observed. Moreover, a significant association between digestive tubule deterioration (large lumen, with a thin epithelial wall) and P. olseni infection was noted. Therefore, this study provides information regarding the infections of potential parasites and pathogens for the first time in P. canaliculus, their seasonal variations and host-parasite interactions within a commercial farm.
- ItemPractical Fertilization Procedure and Embryonic Development of the New Zealand Geoduck Clam (Panopea Zelandica)(Marine Biological Association of the United Kingdom 2016, 2016-12-19) Le, DV; Young, T; Alfaro, AC; Ragg, NLC; Hilton, Z; Watts, E; King, NCopyright © Marine Biological Association of the United Kingdom 2016Cultivation of the geoduck Panopea zelandica (Quoy & Gaimard, 1835) requires knowledge on embryonic development to produce spat in hatcheries. This study investigated the development of P. zelandica embryos at 15°C and 35 ppt and the optimal sperm:egg ratios for fertilization under hatchery conditions. Panopea zelandica broodstock were induced to spawn by serotonin injection. Sperm and eggs were collected and fertilization was conducted at sperm:egg ratios of: 50:1, 100:1, 500:1, 1000:1 and 10,000:1 over 40 min. The optimal sperm:egg ratio was <500:1 and the normal embryo yield at 3 and 18 h post-fertilization (hpf) ranged from 83–96%. Panopea zelandica eggs (~80 μm diameter) developed the first and second polar bodies within 15–20 and 50–55 min post-fertilization, respectively. The blastula appeared at ~8 hpf, including the XR and XL cells and the presumptive shell field depression. Gastrulation occurred at 12–18 hpf with organic material apparent at the shell field depression. The mid-stage trochophore, which appeared at around 35 hpf had an apical plate with an apical tuft. The shell field spread to form the periostracum, which expanded and folded into right and left segments covering the late trochophore. The early D-stage veliger appeared at 45 hpf with the soft body being enclosed by two valves and the appearance of the velum. These observations will serve as the basis for future analyses of P. zelandica embryogenesis and for optimization of commercial production of D-veliger larvae.
- ItemPutative Involvement of Adrenergic Receptors in Regulation of Mussel (Perna Canaliculus) Larval Settlement(Taylor and Francis Ltd., 2015) Young, T; Alfaro, AC; Sánchez-Lazo, C; Robertson, JAbstract: Settlement responses were investigated for mussel (Perna canaliculus) larvae after exposure to catecholamines and their precursor metabolites. Settlement and mortality assays were conducted in Petri plates with chemical treatments (L-phenylalanine, L-tyrosine, L-DOPA, dopamine hydrochloride and epinephrine at various concentrations) and controls. The proteinogenic amino acids L-phenylalanine and L-tyrosine were both effective inducers (~65%) of larval settlement at 10−5 mol l−1 compared with controls (4%). Exposure of larvae to L-DOPA, dopamine and epinephrine resulted in maximum settlement induction (50, 60 and 51%, respectively) at 10−5 mol l−1. Larval mortalities were low (comparable to controls) across all concentrations of L-phenylalanine and L-tyrosine treatments, whereas high mortalities (>60%) were observed for L-DOPA, dopamine and epinephrine at concentrations ≥ 10−4 mol l−1. Our results indicate that P. canaliculus larval settlement is under endogenous regulation by a catecholaminergic mechanism. Furthermore, the inductive effects of all tested metabolites in the epinephrine biosynthesis pathway point to a putative involvement of adrenergic-type receptors in the regulation of larval settlement in this mussel species.
- ItemShowcasing Metabolomic Applications in Aquaculture: A Review(John Wiley & Sons, 2016) Young, T; Alfaro, ACAquaculture production is currently challenged to meet the growing demands for seafood protein throughout the world. To achieve this growth in an efficient, safe and sustainable manner, novel tools and applications will need to be incorporated at each step of the production line. A variety of ‘omics’ (e.g. transcriptomics, proteomics, metabolomics) applications have already begun to emerge in aquaculture research with extreme success. A promising new ‘omics’ approach is metabolomics, which aims to use metabolite profiles to identify biomarkers indicative of physiological responses of living samples (e.g. whole organism, tissues, cells) to environmental or culture conditions. One of the benefits of this approach is that it uses a broad scan of biological conditions to identify often unexpected problem or risk areas upon which to focus management attention. In this contribution, we have selected relevant research examples to showcase the applications of metabolomics in aquaculture in four major areas: hatchery production, nutrition and diet, disease and immunology, and post-harvest quality control. The novelty of this approach is highlighted by the fact that we cite the majority of published papers in this field, and they are all recent (within the last decade) contributions.
- ItemThe Effect of Simulated Marine Heatwaves on Green-Lipped Mussels, Perna canaliculus: A Near-Natural Experimental Approach(Elsevier BV, 2023-09-04) Venter, L; Alfaro, AC; Ragg, NLC; Delorme, NJ; Ericson, JAMarine heatwaves (MHW) are projected for the foreseeable future, affecting aquaculture species, such as the New Zealand green-lipped mussel (Perna canaliculus). Thermal stress alters mussel physiology highlighting the adaptive capacity that allows survival in the face of heatwaves. Within this study, adult mussels were subjected to three different seawater temperature regimes: 1) low (sustained 18 °C), 2) medium MHW (18–24 °C, using a +1 °C per week ramp) and 3) high MHW (18–24 °C, using a +2 °C per week ramp). Sampling was performed over 11 weeks to establish the effects of temperature on P. canaliculus survival, condition, specific immune response parameters, and the haemolymph metabolome. A transient 25.5–26.5 °C exposure resulted in 61 % mortality, with surviving animals showing a metabolic adjustment within aerobic energy production, enabling the activation of molecular defence mechanisms. Utilisation of immune functions were seen within the cytology results where temperature stress affected the percentage of superoxide-positive haemocytes and haemocyte counts. From the metabolomics results an increase in antioxidant metabolites were seen in the high MHW survivors, possibly to counteract molecular damage. In the high MHW exposure group, mussels utilised anaerobic metabolism in conjunction with aerobic metabolism to produce energy, to uphold biological functions and survival. The effect of exposure time was mainly seen on very long-, and long chain fatty acids, with increases observed at weeks seven and eight. These changes were likely due to the membrane storage functions of fatty acids, with decreases at week eleven attributed to energy metabolism functions. This study supports the use of integrated analytical tools to investigate the response of marine organisms to heatwaves. Indeed, specific metabolic pathways and cellular markers are now highlighted for future investigations aimed at targeted measures. This research contributes to a larger program aimed to identify resilient mussel traits and support aquaculture management.