Adaptations in allopatric populations of Triakis megalopterus isolated by the Benguela Current: steps towards understanding evolutionary processes affecting regional biodiversity
- Authors: Soekoe, Michelle
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5389 , http://hdl.handle.net/10962/d1021264
- Description: This study was initiated to gain a better understanding of evolution and adaptation of elasmobranchs by investigating how a putative biogeographic barrier, the Benguela Current, had influenced populations of a demersal shark species, Triakis megalopterus. It was hypothesized that the Benguela Current formed a biogeographic barrier in the distribution of T. megalopterus and was responsible for the divergence between South African (SA) and Angolan (AN) populations. Since elasmobranchs are generally characterized by a slow rate of evolutionary change and conservative morphology and life history traits, it was hypothesized that there would be limited genetic, morphological and life history divergence between the populations. Both mtDNA Control Region (mtCR) and microsatellites (nDNA) were used to assess population connectivity and structure of T. megalopterus. The mtCR predominantly showed a northern (Angola, AN, and Namibia, NA) versus southern (Western Cape, WC, and Eastern Cape, EC) Benguela subsystem arrangement. This suggested that the formation of the Benguela Current had an influence on the genetic structure of T. megalopterus during the early Pleistocene. The nDNA, however, showed a distinct transoceanic, Atlantic (AN, NA, WC) versus Indian Ocean (EC) arrangement, and this was attributed to the more recent exposure of the Agulhas Bank and reduced rocky shore habitat during the glaciations of the late Pleistocene. Traditional morphological analyses on full body and tooth morphology were used to assess phenotypic plasticity and/or adaptability of T. megalopterus. A novel method of geometric morphology, with potential for non-lethal application, was developed and tested to examine interpopulation divergence in shape. Traditional morphometrics showed significant divergence between populations and this variation was congruous with the mtCR haplotypes. However, the divergence in the truss variables was not concomitant to the haplotypes and suggested that differences in shape may be attributed to phenotypic plasticity. There was limited divergence in the tooth morphology between populations. The divergence in several morphological characters associated with swimming speed and manoeuvrability may be attributed to both habitat structure and dominant prey in the different biogeographic zones. The diet of T. megalopterus consisted primarily of crustaceans, teleosts and molluscs. The significant variation in the diet between populations suggested a generalist tooth configuration and broad trophic adaptability. There was significant divergence in the interpopulation life history parameters. The AN population had the fastest growth, smallest size at maturity, and shortest longevity. Individuals in the EC population had the youngest age at maturity, while the WC population had the earliest parturition. This divergence may be attributed to the contrasting thermal regimes in the three biogeographic regions and the dissimilar exploitation rates of the three populations. The results of this thesis demonstrated that a combination of the formation of the Benguela Current and sea level change most likely contributed to vicariance of three populations of T. megalopterus. The significant interpopulation morphological and life history divergence appeared to be both phenotypic and genetic, and suggested that contrasting environmental drivers can result in relatively rapid change in elasmobranchs.
- Full Text:
- Date Issued: 2016
- Authors: Soekoe, Michelle
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5389 , http://hdl.handle.net/10962/d1021264
- Description: This study was initiated to gain a better understanding of evolution and adaptation of elasmobranchs by investigating how a putative biogeographic barrier, the Benguela Current, had influenced populations of a demersal shark species, Triakis megalopterus. It was hypothesized that the Benguela Current formed a biogeographic barrier in the distribution of T. megalopterus and was responsible for the divergence between South African (SA) and Angolan (AN) populations. Since elasmobranchs are generally characterized by a slow rate of evolutionary change and conservative morphology and life history traits, it was hypothesized that there would be limited genetic, morphological and life history divergence between the populations. Both mtDNA Control Region (mtCR) and microsatellites (nDNA) were used to assess population connectivity and structure of T. megalopterus. The mtCR predominantly showed a northern (Angola, AN, and Namibia, NA) versus southern (Western Cape, WC, and Eastern Cape, EC) Benguela subsystem arrangement. This suggested that the formation of the Benguela Current had an influence on the genetic structure of T. megalopterus during the early Pleistocene. The nDNA, however, showed a distinct transoceanic, Atlantic (AN, NA, WC) versus Indian Ocean (EC) arrangement, and this was attributed to the more recent exposure of the Agulhas Bank and reduced rocky shore habitat during the glaciations of the late Pleistocene. Traditional morphological analyses on full body and tooth morphology were used to assess phenotypic plasticity and/or adaptability of T. megalopterus. A novel method of geometric morphology, with potential for non-lethal application, was developed and tested to examine interpopulation divergence in shape. Traditional morphometrics showed significant divergence between populations and this variation was congruous with the mtCR haplotypes. However, the divergence in the truss variables was not concomitant to the haplotypes and suggested that differences in shape may be attributed to phenotypic plasticity. There was limited divergence in the tooth morphology between populations. The divergence in several morphological characters associated with swimming speed and manoeuvrability may be attributed to both habitat structure and dominant prey in the different biogeographic zones. The diet of T. megalopterus consisted primarily of crustaceans, teleosts and molluscs. The significant variation in the diet between populations suggested a generalist tooth configuration and broad trophic adaptability. There was significant divergence in the interpopulation life history parameters. The AN population had the fastest growth, smallest size at maturity, and shortest longevity. Individuals in the EC population had the youngest age at maturity, while the WC population had the earliest parturition. This divergence may be attributed to the contrasting thermal regimes in the three biogeographic regions and the dissimilar exploitation rates of the three populations. The results of this thesis demonstrated that a combination of the formation of the Benguela Current and sea level change most likely contributed to vicariance of three populations of T. megalopterus. The significant interpopulation morphological and life history divergence appeared to be both phenotypic and genetic, and suggested that contrasting environmental drivers can result in relatively rapid change in elasmobranchs.
- Full Text:
- Date Issued: 2016
An evaluation of sampling and statistical methods for long-term monitoring of subtidal reef fishes : a case study of Tsitsikamma National Park marine protected area
- Authors: Parker, Denham
- Date: 2016
- Subjects: Reef fishes -- South Africa -- Monitoring , Tsitsikamma National Park (South Africa)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5385 , http://hdl.handle.net/10962/d1019991
- Description: Tsitsikamma National Park (TNP) possesses the oldest (established 1954), and one of the largest (350 km2) ‘no-take’ marine protected areas (MPA) in South Africa. A long-term monitoring (LTM) programme to observe the subtidal reef fishes in the TNP MPA was established in 2007. To date, 243 angling replicates have been completed, and a total of 2,751 fish belonging to 41 different species have been caught and released. In an era of unprecedented global biodiversity loss, data that can be used to monitor ecosystems and gauge changes in biodiversity through time are essential. This thesis aims to improve the methodological and statistical processes currently available for LTM of subtidal reef fish by providing an evaluation of the TNP MPA LTM programme. Angling data revealed definitive spatial structuring, in the form of spatial autocorrelation, and a shift in viewing spatial dependency as a statistical obstacle to a source of ecological information created a new avenue of data inference. Species-specific distribution maps identified localized habitat as the main predictor variable for species abundance, emphasizing the need for accurate a priori bathymetric information for subtidal monitoring. ‘Random forest’ analyses confirmed spatial variables are more important than temporal variables in predicting species abundance. The effectiveness of Generalized Linear Mixed Models (GAMMs) to account for spatial autocorrelation was highlighted, and evidence that disregarding spatial dependencies in temporal analyses can produce erroneous results was illustrated in the case of dageraad (Chrysoblephus cristiceps). Correlograms indicated that the current sampling strategy produced spatially redundant data and the sampling unit size (150 m2) could be doubled to optimize sampling. Temporal analyses demonstrated that after 50 years of ‘no take’ protection the TNP MPA ichthyofauna exhibits a high level of stability. Species-specific size structure was also found to be highly stable. Dageraad was the only species to exhibit a definitive temporal trend in their size structure, which was attributed to recruitment variation and the possibility that large individuals may migrate out of the study area. The inadequacy of angling as a method for monitoring a broad spectrum of the fish species was highlighted, particularly due to its selectivity towards large predators. As a result, a new sampling technique known as Stereo Baited Remote Underwater Videos (stereo-BRUVs) was introduced to the LTM programme in 2013. Stereo-BRUVs enabled sampling of 2640 fish belonging to 52 different species, from 57 samples collected in less than two years. A comparison of the sampling methods concluded that, compared to angling, stereo-BRUVs provide a superior technique that can survey a significantly larger proportion of the ichthyofauna with minimal length-selectivity biases. In addition, stereo-BRUVs possess a higher statistical power to detect changes in population abundance. However, a potential bias in the form of ‘hyperstability’ in sites with unusually high fish densities was identified as a possible flaw when using stereo-BRUVs. In an attempt to provide a more rigorous method evaluation, simulation testing was employed to assess the ability of angling and stereo-BRUVs to accurately describe a decreasing population. The advantage of this approach is that the simulated population abundances are known, so that each sampling method can be tested in terms of how well it tracks known abundance trends. The study established that stereo- BRUVs provided more accurate data when describing a distinct population decline of roman (Chrysoblephus laticeps) over 10- and 20-year periods. In addition, spawner-biomass was found to be a more accurate population estimate than relative abundance estimates (CPUE and MaxN) due to the inclusion of population size structure information, highlighting the importance of length-frequency data. The study illustrated that an evaluation framework that utilizes simulation testing has the potential to optimize LTM sampling procedures by addressing a number of methodological questions. This includes developing a procedure that aligns data collected from different sampling methods by applying correction factors, thus ensuring LTM programmes are able to adapt sampling strategies without losing data continuity.
- Full Text:
- Date Issued: 2016
- Authors: Parker, Denham
- Date: 2016
- Subjects: Reef fishes -- South Africa -- Monitoring , Tsitsikamma National Park (South Africa)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5385 , http://hdl.handle.net/10962/d1019991
- Description: Tsitsikamma National Park (TNP) possesses the oldest (established 1954), and one of the largest (350 km2) ‘no-take’ marine protected areas (MPA) in South Africa. A long-term monitoring (LTM) programme to observe the subtidal reef fishes in the TNP MPA was established in 2007. To date, 243 angling replicates have been completed, and a total of 2,751 fish belonging to 41 different species have been caught and released. In an era of unprecedented global biodiversity loss, data that can be used to monitor ecosystems and gauge changes in biodiversity through time are essential. This thesis aims to improve the methodological and statistical processes currently available for LTM of subtidal reef fish by providing an evaluation of the TNP MPA LTM programme. Angling data revealed definitive spatial structuring, in the form of spatial autocorrelation, and a shift in viewing spatial dependency as a statistical obstacle to a source of ecological information created a new avenue of data inference. Species-specific distribution maps identified localized habitat as the main predictor variable for species abundance, emphasizing the need for accurate a priori bathymetric information for subtidal monitoring. ‘Random forest’ analyses confirmed spatial variables are more important than temporal variables in predicting species abundance. The effectiveness of Generalized Linear Mixed Models (GAMMs) to account for spatial autocorrelation was highlighted, and evidence that disregarding spatial dependencies in temporal analyses can produce erroneous results was illustrated in the case of dageraad (Chrysoblephus cristiceps). Correlograms indicated that the current sampling strategy produced spatially redundant data and the sampling unit size (150 m2) could be doubled to optimize sampling. Temporal analyses demonstrated that after 50 years of ‘no take’ protection the TNP MPA ichthyofauna exhibits a high level of stability. Species-specific size structure was also found to be highly stable. Dageraad was the only species to exhibit a definitive temporal trend in their size structure, which was attributed to recruitment variation and the possibility that large individuals may migrate out of the study area. The inadequacy of angling as a method for monitoring a broad spectrum of the fish species was highlighted, particularly due to its selectivity towards large predators. As a result, a new sampling technique known as Stereo Baited Remote Underwater Videos (stereo-BRUVs) was introduced to the LTM programme in 2013. Stereo-BRUVs enabled sampling of 2640 fish belonging to 52 different species, from 57 samples collected in less than two years. A comparison of the sampling methods concluded that, compared to angling, stereo-BRUVs provide a superior technique that can survey a significantly larger proportion of the ichthyofauna with minimal length-selectivity biases. In addition, stereo-BRUVs possess a higher statistical power to detect changes in population abundance. However, a potential bias in the form of ‘hyperstability’ in sites with unusually high fish densities was identified as a possible flaw when using stereo-BRUVs. In an attempt to provide a more rigorous method evaluation, simulation testing was employed to assess the ability of angling and stereo-BRUVs to accurately describe a decreasing population. The advantage of this approach is that the simulated population abundances are known, so that each sampling method can be tested in terms of how well it tracks known abundance trends. The study established that stereo- BRUVs provided more accurate data when describing a distinct population decline of roman (Chrysoblephus laticeps) over 10- and 20-year periods. In addition, spawner-biomass was found to be a more accurate population estimate than relative abundance estimates (CPUE and MaxN) due to the inclusion of population size structure information, highlighting the importance of length-frequency data. The study illustrated that an evaluation framework that utilizes simulation testing has the potential to optimize LTM sampling procedures by addressing a number of methodological questions. This includes developing a procedure that aligns data collected from different sampling methods by applying correction factors, thus ensuring LTM programmes are able to adapt sampling strategies without losing data continuity.
- Full Text:
- Date Issued: 2016
The effect of kelp supplementation in formulated feed on the production performance and gut microbiota of South African abalone (Haliotis midae)
- Authors: Nel, Aldi
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/899 , vital:20001
- Description: Formulated feeds with a relatively low (< 5 % of dry mass) kelp (Ecklonia maxima) inclusion level are widely used on commercial abalone (Haliotis midae) farms in South Africa. Although the use of kelp, a major constituent of the natural diet of H. midae, as a dietary supplement is considered to enhance abalone growth and feed utilisation, there are no published studies which quantify the effects of kelp inclusion in formulated feeds. Furthermore, the physiological mechanisms by which kelp supplementation may positively influence abalone digestive physiology and growth are largely unknown. As the kelp supplement is comprised mostly of soluble fibres and abalone gut bacteria associated with macroalgae (and its fibrous polysaccharides) are known to play a key role in digestion, it was hypothesised that the kelp supplement influences the gut-bacterial community profiles of cultured abalone through prebiotic and other metabolic effects. The present thesis thus examined the effect of kelp supplementation on the performance of abalone (Haliotis midae) fed formulated feeds and explored the influence of a kelp supplement on the abalone gut microbiota and its function in the gastrointestinal tract. The key hypotheses of the study were that kelp supplementation in formulated feed: 1) enhances abalone growth; 2) causes a shift in abalone gut-bacterial community composition through a prebiotic-like effect; 3) may induce changes in crop morphology as a result of potential bacterial-associated increases in volatile short-chain fatty acids, and 4) alters digestive enzyme activities in the abalone gut through changes in bacterial-derived (exogenous) digestive enzymes. The growth-promoting efficacy of low-level kelp supplementation was tested by feeding isonitrogenous and isoenergetic experimental feeds containing 0.00 – 3.54 % kelp (dry mass) to sub-adult abalone (~43 mm shell length) for eight months under commercial farm conditions. The growth trial established that kelp supplementation (0.44 – 3.54 % of dry mass) promoted faster growth and improved feed conversion and protein efficiency ratios in cultured abalone compared to abalone fed the non-supplemented control diet, while there were no significant differences in growth for abalone fed the different kelp-supplemented diets (0.44, 0.88, 1.76 and 3.54 % of dry mass). Feed conversion and protein efficiency ratios displayed significant correlations with kelp level in the range of 0.00 – 3.54 % dry mass, and it is therefore recommended that kelp be included in the formulated feeds of cultured South African abalone at a rate of up to 3.54 % of dry mass. A kelp-supplemented (0.88 % dry weight inclusion) feed was fed to abalone under farm conditions to compare gut physiological parameters (crop morphology, digestive enzyme activities and the gut microbiota) in abalone against that of abalone fed an isonitrogenous and isoenergetic non-supplemented control feed. To establish if the observed higher abalone growth rates were related to improved gastrointestinal tract epithelium activity and integrity, as reflected by epithelial cell growth in response to potential changes in bacterial-derived short-chain fatty acid production, crop epithelial morphology was compared between abalone fed the kelp-supplemented and control feeds. Kelp supplementation did not induce any observable changes in crop epithelial cell height for farm-reared sub-adult abalone fed the experimental diets on-farm for seven weeks. This was attributed to the similar macronutrient compositions of kelp-supplemented and control diets and/ or the common diet history of experimental abalone from weaning to the initiation of the experiment. Digestive enzyme activity was compared between abalone fed a kelp-supplemented and a control feed during an on-farm feeding trial with sub-adult abalone. Gut samples were collected after seven weeks and colorimetric enzyme assays were performed for the polysaccharide-degrading enzymes amylase, alginate lyase, laminarinase and fucoidanase, and for acid protease, trypsin and chymotrypsin activity. Amylase and alginate lyase activities were relatively high, compared to the other enzymes. Polysaccharidase and acid protease activity levels did not differ significantly between abalone fed kelp-supplemented and control feeds, but a greater variability in enzyme activity levels was observed in abalone fed the control diet. It was hypothesised that this might be due to the kelp supplement promoting a more stable and less opportunistic gut-bacterial community than the control diet. Pooled gut samples of abalone fed the kelp-supplemented diet were used for proteomic analyses to identify the composition of enzyme proteins of both endogenous and exogenous origin in the abalone digestive system. The key polysaccharidases and proteases in the gut samples of kelp-supplemented formulated feed-fed abalone were all of abalone origin, whereas the bacterial enzymes were of the types that form part of intermediate reactions in metabolic pathways. The results suggested that bacterial enzymes play a different role to abalone endogenous enzymes in the digestion of formulated feed. While abalone enzymes appear to be the main degraders of carbohydrate and protein macromolecules, the profile of exogenous enzymes suggests that they perform bioconversions of smaller organic compounds. The profiles of gut-bacterial communities of farm-reared sub-adult abalone fed kelpsupplemented and control feeds on-farm for seven weeks were analysed with metagenomic pyrosequencing and DGGE analyses, using 16S rDNA-targeted amplified DNA. The results indicated a shift in gut-bacterial composition with a higher abundance of Mollicutes in abalone fed kelp-supplemented feed compared to those fed the control feed. DGGE band patterns displayed a greater within-group similarity in gut bacteria for abalone fed the kelpsupplemented diet and the presence of unique and variable bands for bacteria in the guts of abalone fed the control diet. It was concluded that when cultured abalone are fed kelpsupplemented formulated feeds, more stable gut bacterial communities are present compared to a more opportunistic gut-bacterial community in abalone fed non-supplemented feeds, and that the observed increase in Mollicutes could reflect the restoration of the abalone gut microbiota to a more natural state. The novel application of proteomics to abalone nutrition in the present study demonstrated that gut-bacterial enzymes may form part of many different metabolic pathways and suggests that the metabolism of the gut microbiota serves as an extension of the abalone’s digestive metabolism. Future studies should quantify the contribution of commensal gut-bacteria to cultured abalone nutrition by employing metabolomic studies to characterize the utilisation of bacterial-derived metabolites by the abalone host.
- Full Text:
- Date Issued: 2016
- Authors: Nel, Aldi
- Date: 2016
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/899 , vital:20001
- Description: Formulated feeds with a relatively low (< 5 % of dry mass) kelp (Ecklonia maxima) inclusion level are widely used on commercial abalone (Haliotis midae) farms in South Africa. Although the use of kelp, a major constituent of the natural diet of H. midae, as a dietary supplement is considered to enhance abalone growth and feed utilisation, there are no published studies which quantify the effects of kelp inclusion in formulated feeds. Furthermore, the physiological mechanisms by which kelp supplementation may positively influence abalone digestive physiology and growth are largely unknown. As the kelp supplement is comprised mostly of soluble fibres and abalone gut bacteria associated with macroalgae (and its fibrous polysaccharides) are known to play a key role in digestion, it was hypothesised that the kelp supplement influences the gut-bacterial community profiles of cultured abalone through prebiotic and other metabolic effects. The present thesis thus examined the effect of kelp supplementation on the performance of abalone (Haliotis midae) fed formulated feeds and explored the influence of a kelp supplement on the abalone gut microbiota and its function in the gastrointestinal tract. The key hypotheses of the study were that kelp supplementation in formulated feed: 1) enhances abalone growth; 2) causes a shift in abalone gut-bacterial community composition through a prebiotic-like effect; 3) may induce changes in crop morphology as a result of potential bacterial-associated increases in volatile short-chain fatty acids, and 4) alters digestive enzyme activities in the abalone gut through changes in bacterial-derived (exogenous) digestive enzymes. The growth-promoting efficacy of low-level kelp supplementation was tested by feeding isonitrogenous and isoenergetic experimental feeds containing 0.00 – 3.54 % kelp (dry mass) to sub-adult abalone (~43 mm shell length) for eight months under commercial farm conditions. The growth trial established that kelp supplementation (0.44 – 3.54 % of dry mass) promoted faster growth and improved feed conversion and protein efficiency ratios in cultured abalone compared to abalone fed the non-supplemented control diet, while there were no significant differences in growth for abalone fed the different kelp-supplemented diets (0.44, 0.88, 1.76 and 3.54 % of dry mass). Feed conversion and protein efficiency ratios displayed significant correlations with kelp level in the range of 0.00 – 3.54 % dry mass, and it is therefore recommended that kelp be included in the formulated feeds of cultured South African abalone at a rate of up to 3.54 % of dry mass. A kelp-supplemented (0.88 % dry weight inclusion) feed was fed to abalone under farm conditions to compare gut physiological parameters (crop morphology, digestive enzyme activities and the gut microbiota) in abalone against that of abalone fed an isonitrogenous and isoenergetic non-supplemented control feed. To establish if the observed higher abalone growth rates were related to improved gastrointestinal tract epithelium activity and integrity, as reflected by epithelial cell growth in response to potential changes in bacterial-derived short-chain fatty acid production, crop epithelial morphology was compared between abalone fed the kelp-supplemented and control feeds. Kelp supplementation did not induce any observable changes in crop epithelial cell height for farm-reared sub-adult abalone fed the experimental diets on-farm for seven weeks. This was attributed to the similar macronutrient compositions of kelp-supplemented and control diets and/ or the common diet history of experimental abalone from weaning to the initiation of the experiment. Digestive enzyme activity was compared between abalone fed a kelp-supplemented and a control feed during an on-farm feeding trial with sub-adult abalone. Gut samples were collected after seven weeks and colorimetric enzyme assays were performed for the polysaccharide-degrading enzymes amylase, alginate lyase, laminarinase and fucoidanase, and for acid protease, trypsin and chymotrypsin activity. Amylase and alginate lyase activities were relatively high, compared to the other enzymes. Polysaccharidase and acid protease activity levels did not differ significantly between abalone fed kelp-supplemented and control feeds, but a greater variability in enzyme activity levels was observed in abalone fed the control diet. It was hypothesised that this might be due to the kelp supplement promoting a more stable and less opportunistic gut-bacterial community than the control diet. Pooled gut samples of abalone fed the kelp-supplemented diet were used for proteomic analyses to identify the composition of enzyme proteins of both endogenous and exogenous origin in the abalone digestive system. The key polysaccharidases and proteases in the gut samples of kelp-supplemented formulated feed-fed abalone were all of abalone origin, whereas the bacterial enzymes were of the types that form part of intermediate reactions in metabolic pathways. The results suggested that bacterial enzymes play a different role to abalone endogenous enzymes in the digestion of formulated feed. While abalone enzymes appear to be the main degraders of carbohydrate and protein macromolecules, the profile of exogenous enzymes suggests that they perform bioconversions of smaller organic compounds. The profiles of gut-bacterial communities of farm-reared sub-adult abalone fed kelpsupplemented and control feeds on-farm for seven weeks were analysed with metagenomic pyrosequencing and DGGE analyses, using 16S rDNA-targeted amplified DNA. The results indicated a shift in gut-bacterial composition with a higher abundance of Mollicutes in abalone fed kelp-supplemented feed compared to those fed the control feed. DGGE band patterns displayed a greater within-group similarity in gut bacteria for abalone fed the kelpsupplemented diet and the presence of unique and variable bands for bacteria in the guts of abalone fed the control diet. It was concluded that when cultured abalone are fed kelpsupplemented formulated feeds, more stable gut bacterial communities are present compared to a more opportunistic gut-bacterial community in abalone fed non-supplemented feeds, and that the observed increase in Mollicutes could reflect the restoration of the abalone gut microbiota to a more natural state. The novel application of proteomics to abalone nutrition in the present study demonstrated that gut-bacterial enzymes may form part of many different metabolic pathways and suggests that the metabolism of the gut microbiota serves as an extension of the abalone’s digestive metabolism. Future studies should quantify the contribution of commensal gut-bacteria to cultured abalone nutrition by employing metabolomic studies to characterize the utilisation of bacterial-derived metabolites by the abalone host.
- Full Text:
- Date Issued: 2016
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